Welcome to the IRaP 2002 Online Review

Please rate each abstract carefully and push 'Submit' at the bottom of the page.


Abstracts for Oral Presentation
Topic #1 - Ions, electrons, photons: interactions with polymers
#013
THE EFFECTS OF ADDTIVES ON THERMAL STABILITY OF ELECTRON BEAM CROSS-LINKED (POLYETHYLENE -VINYLACETATE) BLEND IN HOT WATER

S. Hassanpour, F. Khoylou, E. Jabbarzadeh. Gamma Irradiation Center, Atomic Energy Organization of Iran, Tehran ,I. R. Iran

Now a days electron beam irradiation has a wide verity of applications in wires, pipes, cable coating and modification of the polymers[1] and blending is a well-known method of modifying the properties of polymers. As it is reported, mechanical properties of irradiated polyethylene improve with the addition of ethylene- vinyl acetate copolymer[2]. In the pervious research work the thermal oxidation of electron beam irradiated LD/EVA blends without any additive in hot water was investigated [3]. In this work LD/EVA blend mixed with additives was exposed to electron beam radiation. The effects of a hindered Amin antioxidant, Chimmasorb 944 and two trifunctional monomers, Triallyoxy-1, 3,5-Triazine and 2-ethyl 2- (Hydroxymethyl) 1,3 Propandiol Trimethacrylate on its properties after irradiation and thermal aging in hot water were investigated. After irradiation the gel fraction increased up to 70%. In addition, irradiated samples showed noticeable changes in mechanical properties and elongation at break. From the results of the thermal aging procedure, Chimmasorb 944 showed a convenient influence on the increasing of the polymer blend thermal stability due to having a quite slow migration to the surface of the specimens. Furthermore, it appeared that the two trifunctional monomers have different thermal stability after long time immersion in hot water.

References:
[1] Cheremisinoff , Nicholas P.Advanced polymer processing operations.Noyes Publications, USA.1998
[2] Sharif j.et al. Radiation effects on LDPE/EVA blends, Radiat. Physics and Chem. 58, 191-195.(2000)
[3] Hassanpour S. et al Thermal degradation of electron beam crosslinked (polyethylene -vinylacetate ) blends in hot water.In press.
Review score for abstract #013:
Comments:

#015
OBSERVATION OF HEAVY-ION TRACKS IN POLYIMIDE BY MEANS OF HIGH-RESOLUTION SCANNING ELECTRON MICROSCOPY

S. Abu Saleh and Y. Eyal. Department of Chemistry, Technion, Israel Institute of Technology, Haifa 32000, Israel

Employing HRSEM (high-resolution scanning electron microscopy), we determined the etching radius of seven-year old latent tracks created in a polyimide foil (Kapton, procured from Du Pont) by charge-equilibrated 1.79 GeV U ions. Sections of the irradiated foil were subjected to 0, 20, 40 s, 1, 2, 3, 4, and 5 min etching treatments in a NaOCl solution at 60 &Mac176;C, and then were examined uncoated by HRSEM. Nanometric etch pits have been clearly identified on all 40-s and longer-time etched surfaces. Typical HRSEM images are displayed in Fig. 1. Mean pit sizes and standard deviations are displayed in Fig. 2. The dispersion in the track diameter can be attributed to four factors: Dispersion in the charge states of the projectile ions, dispersion in the ions stopping power, inhomogeneity of the polymer density, and fluctuations in the etching yield. The data can be explained by a simple etching model that takes into account the finite radial extension of the primary track core. Assuming isotropic etching of undamaged material at velocity VB, and enhanced etching velocity, VT, along the track, the pit diameter is given by Dpit(t) = Dlatent + 2 tanf(VT-VB)t. Here, t is the etching time, Dlatent is the diameter of the latent track, and tanf = VB/(VT2-VB2)1/2, where 2f is the pit cone angle. Extrapolation of the data to t = 0 (Fig. 2) gives Dlatent = 6.9 ± 1.4 nm.
The extracted Dlatent matches the mean core diameter of few-week old latent tracks, 8.1 ± 1.7 nm, as determined by transmission electron microscopy [1]. This experiment involved high-energy Au and Pb projectiles. The stopping powers of the projectiles in the latter and present experiments, controlled primarily by electronic processes, are estimated to be ~16 and ~18 keV/nm, respectively. Three important conclusions emerge. First, the track region that manifests itself by a highly-elevated chemical reactivity coincides with the primary structurally-altered region of the track. There is no evidence for enhanced chemical reactivity outside the track core. Second, chemical equilibration processes in the track are very slow. Third, there is no indication for any significant instability in the track size with time.



[1] Y. Eyal and G. Khattib, Nucl. Instr. and Meth. B 156 (1999) 183-190.
Review score for abstract #015:
Comments:

#016
A RADIOCHROMIC FILM DOSIMETER FOR USE IN GAMMA AND ELECTRON BEAM RADIATION DOSIMETRY

A. Akhavan, M. Sohrabpour. Gamma Irradiation Center, Atomic Energy Organization of Iran, Iran.

Radiochromic film dosimeters are often preferred over liquid and other types of dosimeters for routine dosimetry for a number of reasons such as, ease of handling and read out, raggedness, long shelf life post irradiation, stability of response and coverage of wide dose ranges [1,2]. A new radiochromic film dosimeter, called GIC-79, has been investigated for its use as a routine dosimeter in radiation processing. This film has a colour change from pale blue to dark blue after exposure. Gamma and electron beam response of the film was studied spectrophotometrically at 630 nm (major absorption band) over the dose range from 1 to 70 kGy. The present study investigates the response of the film at different environmental conditions that are encountered during commercial irradiation facilities. In addition the effect of dose rate on dosimeter performance as well as the post irradiation stability at different storage conditions have been also discussed [3,4].

Refrences
[1] McLaughlin W. L., Boyd A. W., Chadwick K. H., McDonald J. C. and Miller A. (1989) Dosimetry for radiation processing. Taylor & Francis, London.
[2] Humpherys K. C. and Kantz A. D. (1977) Radiochromic: a radiation monitoring system. Radiat. Phys. Chem. 9,737.
[3] Bishop W. P., et al (1973) Poly(halostyrene) thin film dosimeters for high doses. Rev. Sci. Instr. 44, 443-452.
[4] McLaughlin W. L.et al (1995) Temperature and relative humidity dependence of radiochromic film dosimeter response to gamma and electron radiation. Radiat. Phys. Chem. 46, No. 4-6, pp.1227-1233

Review score for abstract #016:
Comments:

#032
A method to determine the opening process for pores of latent ion tracks in polymer using electrolytic etching

V.R.Oganessian1, V.V.Trofimov1, J.Vetter2, M.Danziger3, B.Dörschel4, D.Hermsdorf4

1 – Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research, 141980 Dubna, Russia
2 – Gesellschaft für Schwerionenforschung, 642491 Darmstadt, Germany
3 – Fraktal AG, 06484 Quedlinburg, Germany
4 – Institut für Strahlenschutzphysik, TU Dresden, 01062 Dresden, Germany

Up to this time, most of works did not paid enough attention to detailed process of electrolytic chemical etching for single heavy ion tracks as the object in array of many tracks in polymer films. It is not easy due to very high values of electric resistance in the very first moments of pore opening. Here we tried to analyze samples with low particle fluencies up to 3.7·107 ions/cm2. In our researching polyethyleneterephthalate (PETP) Hostaphan films with the thickness 20_m were used. They were irradiated by Bi ions with the energy of 11.4 MeV/nucleon at accelerator in GSI. Using optimized etching conditions, computer program and LabView model we got interesting results those are in good agreement with theory and model. Detailed graphics of increasing conductivity of the etched single tracks beginning from breakthrough up to the next pore opening as a function of time and quantity of opened pores proved preliminary assumes and calculations. Thus "track-by-track" method was developed and can be used effectively for conductometric and graphic description of sequent pores appearance.
Review score for abstract #032:
Comments:

#043
Radiation grafting of different monomers onto PP foils irradiated with a 25 MeV proton beam

Ruben Mazzei, Daniel Tadey, Eduardo Smolko and Carmelo Rocco. Comisión Nacional de Energía Atómica, Centro Atómico Ezeiza, Unidad de Aplicaciones Tecnológicas y Agropecuarias, División de Aplicaciones Industriales de las Radiaciones Ionizantes, Laboratorio de Polímeros, Pbro. Juan Gonzales Y Aragón 15, Ezeiza, C.P. 1802AYA, Pcia de Buenos Aires, Argentina.

ABSTRACT

The radiation induced graft polymerisation is a known method to obtain new materials. Until recently only conventional radiation sources, such as 60Co and electron beams were used. Moreover, part of the damage induced in polymer by heavy ion can produce active sites (peroxides and hidroperoxides) useful to initiate grafting reactions.
Polymer surface modification were obtained by grafting different monomers onto polypropylene films.
The damage induced in polypropylene (PP) by a 25 MeV proton beam was used to initiated grafting reactions by the peroxide method.
The present work gives the grafting yield of AAc, MMA and styrene as a function of proton fluency and dose.
The experimental points obtained by grafting PP foils were fitted with the equations deduced supposing the target theory.
Review score for abstract #043:
Comments:

#062
ION-BEAM ETCHING RATE AND STRUCTURAL MODIFICATION OF POLYMER FILMS DURING LOW ENERGY ION IRRADIATION

V. Zaporojtchenko, J. Zekonyte, J. Erichsen, F. Faupel. Faculty of Engineering, Christian-Albrechts-University of Kiel, Kaiserstr. 2, 24143 Kiel, Germany

Various polymers were sputtered with low Ar+ ion energy (0.5 – 5 keV) in order to determine their etching rate under these condition. Hydrocarbons, oxygenated, halogenated and nitrogen-containing glassy polymers with a varied range of the glass transition temperature (Tg ) were chosen. The polymer films of interest: polysterene (PS), poly(a-metylstyrene), polyethylene oxide (PEO), Teflon AF, fluorinated ethylene propylene (FEP), polybenzoxazole (PBO), bisphenol-A polycarbonate (BPA-PC), pyromellitic dianhydride-4,4-oxydianiline (PMDA-ODA), SiLK“, Nylon11, poly(methyl metacrylate) (PMMA) were prepared by spin coating or vapor deposition. The surface potential during the sputtering of thin (0.1-0.5 m) polymer films, as determined from the energy shift of C1s XPS line, was very small compared to the ion energy and thus has no influence on the etching rate. The etching rate was measured gravimetrically and also using a profilometer (Dektak 8000). At the same time the surface chemical modification was studied using x-ray photoelectron spectroscopy (XPS). The well known effects [1] (polymer degradation and cross-linking) associated with ion polymer interaction were observed in XPS spectra. Comparing the etching rate to various polymer properties few conclusions could be deduced. The chemical structure of polymers plays an important but not dominant role in etching process. Two different groups of polymers with significant difference in etching rate were found. In most cases the etching rate, calculated as the ratio between the sputter depth and sputter time (D/t) at a constant ion current density 4.5 ¥ 10-6 Acm-2 (measured with Faraday cup), was between 2 ¥ 10-3 – 5 ¥ 10-3 nm/s, being almost the same as for metals. The etching rate for PMMA was found 10 times higher and the rate for Teflon AF, FEP and Nylon was higher even by three orders of magnitude, than most of the other investigated polymers. This behavior seems to be associated with a different fraction of cross-linking in their chains. For example, PS is a typical cross-linking polymer and in FEP the chain scission dominates during ion bombardment. Cross-linking of polymers was verified by the surface glass transition temperature measurement using the method of the embedding of noble metal nanoclusters [2]. Significant effects of ion irradiation on Tg and chemical modification were observed at a fluence as low as 1013 ions/cm2. The correlation between the monomer yield obtained by thermal degradation of polymers and the etching rate was also observed. All these observed effects between the character of the polymer degradation and ion-beam etching rate are discussed.

References
[1] D. Briggs, "Surface analysis of polymers by XPS and static SIMS", Cambridge University Press, 1998.
[2] V. Zaporojtchenko, T. Strunskus, J. Erichsen, F. Faupel, Macromolecules 34(5), 1125-1127, (2001).
Review score for abstract #062:
Comments:

#068
RADIATION INDUCED PROCESSES IN THE CO-POLYMER, POLYETHYLENE-POLY(VINYL ALCOHOL)

B. H. Milosavljevic and J. K. Thomas[1], University of Notre Dame, Department of Chemistry and Biochemistry, Notre Dame, IN 46556-5670, USA

The co-polymer of polyethylene-poly(vinyl alcohol) containing 44 mole % polyethylene is important industrially [2]. Of particular importance is its commercial application as a packaging material following radiation processing. Radiation induced crosslinking of the co-polymer reduces water penetration, that causes undesirable lowering of the glass transition point. In turn, the latter increases oxygen penetration of the co-polymer and reduces its mechanical properties. To this end we have studied the radiation chemistry of the co-polymer by pulsed radiolysis (2 ns pulses of 0.4 MeV electrons), and by steady state 60Co g at 77 K. Fast spectroscopy and standard EPR techniques are used to elucidate the various chemical processes and modifications that take place in the co-polymer. These events are discussed in terms of the radiation chemistry of the pure component polyethylene PE [3], and poly(vinyl alcohol), PVA [4], which have been studied earlier by our techniques. A brief outline of the events established in the co-polymer are given below.
Fluorescence and absorption spectroscopy with the molecular probe pyrene show that the physical, polarity, etc., of the co-polymer are intermediate between those of PE and PVA as required for a random co-polymer, while phosphorescence studies show that the rigidity of the polymer is closer to that of PVA. High energy radiation develops excited states of guest molecules (pyrene) in hydrophobic PE but not in hydrophilic PVA or co-polymer. This is shown to be due to the rapid destruction of the positive hole in the latter two polymers by the OH groups. In radiolysis, the radical ions of guest molecules are developed in all three polymers but the radical cation is only developed in PE. The yields of these reactions are high with G values of the order of unity. In all three polymers the H atom adduct of the probe molecule is developed; in PE via radical reactions. but in PVA and co-polymers via reaction with a proton. Fast spectroscopy at room temperature identify a large yield (G = 2.0) of trapped electrons in the co-polymer, while low temperature ESR studies show that the a cation radical of the alcohol group is produced in agreement with the PVA studies [5].

References:

[1] Work supported by the National Science Foundation.
[2] W.E. Brown, Plastics in Food Packaging, Marcel Dekker Inc., New York, (1992)
[3] M. Biscoglio and J. K. Thomas, J. Phys. Chem. B., 104, 475-484 (2000)
[4] B. H. Milosavljevic and J. K. Thomas, Radiat. Phys. Chem., 62, 3-10 (2001)
[5] Zainuddin, David J. T. Hill and Tri T. Le, Radiat. Phys. Chem., 62, 283-291 (2001)
Review score for abstract #068:
Comments:

#082
SCISSION CROSS SECTIONS OF CHEMICAL BONDS INDUCED BY IONS IN A CELLULOSE NITRATE DETECTOR. EXPERIMENT AND SIMULATION.

R. BARILLON1, T. YAMAUCHI2. 1 IReS, Université Louis Pasteur (UMR 7500), F-67037 Strasbourg Cedex 2, France, 2 Kobe University of Mercantile Marine, 5-1-1 Fukaeminami, 658-0022 Kobe, Japan


This study attempts to find answers based on physical and chemical criteria that are the best suited for describing the formation of tracks induced by ions in plastic detectors. Only the area where the energy-loss is mainly governed by excitation and ionisation processes is studied.
A Cellulose nitrate detector (LR115) was irradiated with ions from proton to fluorine (H, Li, B, C, O, F) in the energy range 1-10 MeV/uma. Each irradiated sample consisted of a stack of several detectors (about 20 to 30) each 12 mm thick. So chemical damages were studied according to the energy lost in each detector. Broken bonds were identified and quantified using infrared spectroscopy. In the same time we develop the same approach as proposed by Katz R. for the nuclear emulsion response. This approach is based on the hit theory, where the hits are produced by the secondary electrons removed by the incoming ion. Using this approach, neglecting any differences in the initial electron energy spectra and in the temporal aspect of energy deposition, it is surprising to simulate, with the very same parameters, the chemical cross sections from protons to fluorine ions. This study must be carried on for higher energies and heavier ions and also for different polymers. But if such behaviour is confirmed, one can be able to propose new parameters for the ion track formation including the radiation chemistry of the detector.
Review score for abstract #082:
Comments:

#086
COMPARISON BETWEEN ELECTRON BEAM AND _ IRRADIATION ON POLY (VINYL CHLORIDE) FOR MEDICAL APPLICATIONS

(S. Baccaro+, V. Brunella*, A. Cecilia+, L. Costa*)

+ENEA, FIS/ION R. C. Casaccia, Via Anguillarese 301, 00060 S. Maria di Galeria (Rome), Italy
*Department of Chemistry, IFM, University of Turin, Via P. Giuria 7, 10125 Turin, Italy

High energy radiation is used in several fields for the production of new and modified polymers (radiation curing, cross-linking and grafting) and for biomaterials’ sterilisation.
Usually, the term "high energy radiation" indicates both electron beam and g radiation even if the process is rather different, in particular as far as regards dose-rate, source and plant. In this sense, it is very interesting to compare the effects induced in the material by electron beam or g radiation.
Among materials that can be studied, the Poly (Vinyl Chloride) represents an attractive and versatile polymer material to manufacture many vital single-use medical devices. This polymer is not very stable under high energy radiation and the process is not selective, because the radiation has enough energy to break off all the polymer bonds, consequently the irradiation process produces a large amount of radicals.
We have studied the effects on Poly (Vinyl Chloride) powders with and without additives, when the irradiation is performed in inert atmosphere and in presence of oxygen with electron beam and g radiation. The sterilisation dose is normally 25 kGy but we studied the effects at higher doses (25, 50, 100 and 150 kGy).
To investigate the modifications induced in the material by radiation treatments, we analysed the results obtained by FTIR, EPR, UV-Vis and GPC techniques.
The aim of this activity is focused on the possibility to employ the bremsstrahlung X-rays in the industrial applications, generated by stopping beam of accelerated electrons in metal targets.
Review score for abstract #086:
Comments:

#090
CROSSLINKING OF POLYMERS IN HEAVY ION TRACKS

H. Koizumi(1), M. Taguchi(2), Y. Kobayashi(2), T. Ichikawa(1). 1Division of Molecular Chemistry, Graduate School of Engineering, Hokkaido University, Kita-ku, Sapporo 060-8628, Japan. 2Takasaki Radiation Chemistry Research Establishment, Japan Atomic Energy Research Institute, 1233 Watanuki-machi, Takasaki, Japan.

Ion beams deposit energy along their tracks with high density. The high local dose in heavy ion tracks exceeds gelation dose of several crosslinking polymers [1-4]. A gel string is hence generated in each ion track [4,5]. This technique can be utilized for producing a nano-structure of polymers. We then examined gelation of polydimethylsiloxane irradiated with 204 MeV C ions, 306 MeV Ne ions, 256 MeV Ar ions. The insoluble residue of the irradiated polymers was separated with membrane filters. The weight of the insoluble residue is proportional to the number of irradiated ions. This result indicates formation of the gel strings. The gelation occurs in each ion tracks, and the weight of the insoluble residue is hence the products of the number of ion tracks and the weight of a gel string. This dependence is different from that for low-LET radiations. The gel fraction for g- or electron irradiated polymers zero at lower than a gelation dose. It abruptly increases at doses higher than the gelation dose and approaches unity. The weight of a gel string increases in proportion to the initial molecular weight of polydimethylsiloxane (Mn): the weights for 256 MeV Ar irradiated polydimethylsiloxane of Mn of 30,000, 60,000, 103,000, and 165,000 are 1.8x10-14 g, 3.6x10-14 g, 6.0x10-14 g, and 9.6 x10-14 g, respectively. It arises from an increase in the radius of the gel strings with increasing Mn. The gelation dose decreases with increasing Mn. The dose in an ion track decreases with increasing the distance from the center of the ion track, the area higher than the gelation dose in the ion tracks then increases with decreasing the gelation dose. The radius of the gel strings hence increases. The radii of the gel strings are estimated from the local dose distribution in the ion tracks [6] and the dose-yield relationship for low-LET radiation [7]. We assumed that the gelation in the ion tracks occurs with the same dose relationship for low-LET radiation. The weights of a gel string were calculated with the estimated radii and the ion range. The estimated weight agrees with the experimental values. The weight of a gel string also depends on the ion beams. It is ascribed to difference in local dose distribution in the ion tracks.

References
[1] Koizumi, H. et al., Nucl. Instrum. Meth. B132, 633-638 (1997).
[2] Koizumi, H. et al., Nucl. Instrum. Meth. B117, 431-435 (1996).
[3] Koizumi, H. et al., Appl. Radiat. Isot., 7, 1205-1209 (1996).
[4] Koizumi, H. et al., Nucl. Instrum. Meth. B179, 530-535 (2001).
[5] Koizumi, H. et al., TIARA Annual Report 1998, Japan Atomic Energy Research Institute, Takasaki, 1999, pp. 93-94.
[6] Chatterjee, A., Schaefer, H.J., Radiat. Environm. Biophys.,13, 215-227 (1976).
[7] Delides, C.G, Shepherd, I.W., Radiat. Phys. Chem.,10, 379-385 (1977).
Review score for abstract #090:
Comments:

#126
LET EFFECTS ON THE MOLECULAR EMISSION OF ALIPHATIC POLYMERS

V. Picq and E. Balanzat .CIRIL, CEA-CNRS-ISMRA,, BP 5133, 14070 Caen Cedex 5, France.

The release of small gaseous molecules is a general phenomenon of irradiated polymers. It is in some way the counterpart of the modification remaining in the film. Due to their high Linear Energy Transfer, LET, swift heavy ions induce a complex damage along their path. We show here that the release of small hydrocarbon molecules is especially sensitive to the LET of the impinging particles and is consequently very informative on the processes inducing ion tracks in polymers.
We have studied three full aliphatic polymers: polyethylene (PE), polypropylene (PP) and polybutene (PB). They mainly differ by the nature of the side group (none for PE, -CH3 for PP, -CH2CH3 for PB). Irradiations have been performed with particles of increasing LET: electron beams (LET = 3.5 10-3 MeV/mg/cm2) and different ion beams within a LET range from ª2 to ª 40 MeV/mg/cm2. We have developed an on-line detection of the gas release by infrared spectroscopy that has given accurate yields for the most hydrocarbon molecules formed.
Increasing LET induces a huge increase of the yields of hydrocarbon molecules. We can distinguish two LET domains. In the low LET range, the hydrocarbon emission is ruled by the side group departure; the yield is zero for PE, moderated for PP and PB and formed by methane and two carbon atom molecules in respectively PP and PB. Above a LET threshold at ª 5 MeV/mg/cm2, a chain fragmentation process is triggered. For the highest LET studied, the total hydrocarbon yields are very high. The mass loss due to the formation and escape of small hydrocarbon molecules can quantitatively explain the decrease of atomic density around the ion path that is characteristic of an ion track. Therefore we make evident that gas release is a crucial process in the track registration process.
After a LET transition zone, from the side group departure regime to the chain fragmentation regime, the composition of the gas mixture released stabilises with respect to LET, while the total gas yield always increases when increasing LET. So, at high LET, in each polymer, a typical gas mixture is formed probably in a radius around the ion path that increases when increasing LET.
Somme common features characterise the gas mixture released at high TEL. We could mention the predominance of highly unsaturated molecules and the high yield of acetylene and propadiene. Moreover, some molecules having the same chemical formula as propyne and propadiene show systematically very different yields. This indicates that some specific molecules have a much greater stability in the very chemically reactive zone of the core track and are consequently the favourite by-product of chemical reactions in this hot zone.
Finally, in PB we could quantify the relative stability of bonds involving secondary and tertiary carbons. For that, we have measured at low LET the yields of methane and of two carbon atom molecules.
Review score for abstract #126:
Comments:

#127
VERY LOW TEMPERATURE IRRADIATION OF ALIPHATIC POLYMERS:
ROLE OF RADICAL MIGRATION ON THE CREATION OF STABLE GROUPS

M. Mélot, Y. Ngono-Ravache, E. Balanzat. CIRIL, Unité mixte CEA-CNRS-ISMRA, BP 5133, 14070 Caen cedex 5, France

Even though the information obtained by very low temperature irradiations of polymers associated with an in-situ low temperature identification of stable modifications is unique (role of the radical motion on the creation of stable species), there are only a few experiments reported in the literature [1,2].
We have performed polymer irradiations at 8 K and 290 K. The samples irradiated at 8 K have been progressively annealed up to 290 K. The modifications were followed by in-situ infrared spectroscopy (FTIR). All the FTIR spectra were recorded at 8 K. Polyethylene films were irradiated with an oxygen ion beam at 13.6 MeV/amu. This low Linear Energy Transfer (LET) ion beam induces, at room temperature, effects comparable to those of classical electron or gamma irradiations [3]. We focus on the creation of two unsaturated groups: trans-vinylene and trans-trans diene.
Concerning the radiochemical yield (calculated at zero dose) of trans-vinylene groups, the yield decreases by a factor two when decreasing the irradiation temperature from 290 K to 8 K. Therefore only a half of the involved radicals leads to the formation of trans-vinylene groups by reacting close to their creation site (in-cage reactions). In the case of trans-trans diene groups, radical migration is imperative: the ratio G(8K)/G(290K) is close to zero.
The evolution with dose is markedly influenced by temperature. At room temperature the concentration of unsaturated groups tends to saturation when increasing dose. This is likely due to the destruction of the created groups by radiation. At 8 K, the reverse behaviour is observed: the creation rate increases with dose. This could be explained by an increase of radical-radical reactions due to the increase of radical concentration with dose. These results clearly demonstrate the crucial role of radical mobility in the room temperature destruction of the created unsaturations.
The evolution of infrared bands with annealing temperature shows different recovery stages. In some cases a clear anticorrelation is observed between the creation of stable groups and the disappearance of an infrared band that has appeared during irradiation at 8 K. This reveals the role of a single radical, identified by an infrared band, in the creation process.
Irradiation with a sulphur beam at 11.2 MeV/amu allows us to investigate the influence of the LET and hence of the radical concentration within the ion track.
When unsaturations pre-exist at a sufficient high concentration, radiation induces a destruction of these bonds instead of a supplementary creation. This is the case of EPDM (ethylene propylene 1-4 hexadiene copolymer). We studied the influence of temperature on this destruction process.

[1] D.C. Waterman, M. Dole, J. Phys. Chem. Vol74, N°9 1970
[2] D.C. Waterman, M. Dole, J. Phys. Chem. Vol75, N°26 1971
[3]E. Balanzat, N. Betz and S. Bouffard, Nucl. Instr. and Meth.B105 (1995) 46-54
Review score for abstract #127:
Comments:

Topic #2 - Plasmas, lasers and cluster beams: interactions with polymers
#044
SURFACE MODIFICATION OF ETHYLENE-CO-TETRAFLUOROETHYLENE (EFTE) BY PLASMAS

N. Inagaki. Laboratory of Polymer Chemistry, Faculty of Engineering, Shizuoka University, 3-5-1 Johoku, Hamamatsu, 432-8561 Japan; Phone & Fax, 81-53-478-1161; E-mail, tcninag@ipc.shizuoka.ac.jp

Plasma treatment is a useful technology for polymer surface modification. Once every poly-mer surface is exposed to plasma just for a few minutes, the exposed surface causes to be modified, for example, from hydrophobic to hydrophilic. Even polytetrafluoroethylene (PTFE) can easily be modified by plasma. Figure 1 shows contact angle of water on PTFE surfaces exposed to hydrogen and oxygen plasmas as a function of the exposure time. When PTFE surfaces are exposed to the hydrogen plasma only for 60s, the surfaces show a large decrease in water contact angle from 106 to 80 degrees. However, oxygen plasma cannot modify PTFE surfaces into so hydrophilic as the hydrogen plasma does. On the other hand, polyethylene (PE) surfaces are well modified into hydrophilic by both hydrogen and oxygen plasmas (Figure 1). Why is there difference in plasma susceptibility between PTFE and PE surfaces? If polymer surface containing both CF2-CF2 and CH2-CH2 components is exposed to oxygen or hydrogen plasma, can the oxygen plasma modify CH2-CH2 component alone on the polymer surface? Can the hydrogen plasma modify both CF2-CF2 and CH2-CH2 com-ponents on the polymer surface?
Ethylene-co-tetrafluoroethylene, ETFE, is an alternating copolymer of ethylene and tetrafluoroethylene. Physical and chemical properties of ETFE are similar to those of polytetrafluoroethylene and other fluoropolymers such as copolymers of tetrafluoroethylene and hexafluoropropylene, FEP; and of tetrafluoroethylene and perfluoro(alkyl vinyl ether), PFA. When ETFE surface is exposed to plasma, what modification will occur on the ETFE surface? Can CH2 components in the ETFE be selectively modified by oxygen plasma? Can hydrogen plasma modify homogeneously both CH2 and CF2 components in ETFE?
In this study, we have focused on what surface reactions occurred in exposing ETFE surface to plasmas such as hydrogen, oxygen, and argon plasmas. The exposed surfaces were characterized by contact angle measurement, XPS, and ATR FT-IR spectroscopy.
Review score for abstract #044:
Comments:

Topic #3 - Fundamental physical and chemical processes
#055
MEASUREMENTS OF FREE RADICALS IN X-IRRADIATED DIPHENYL METHANE AT 20 K

M. S. Jahan(1), D. W. Cooke(2), D. E. Thomas(1), M. Ridley(1), B. L. Bennett(2), E. B. Orler(2), D. A. Wrobleski(2), (1)Department of Physics, The University of Memphis, Memphis, TN 38152 USA. (2)Los Alamos National Laboratory, Los Alamos, NM 87545 USA

In previous work we have utilized electron spin resonance (ESR) and luminescence techniques to investigate radiation damage in MDI-based poly(ester urethane).1,2 Unfortunately, the complexity of the ESR spectra in this polymer has precluded unambiguous identification of the radiation-induced radicals, and has led us to examine the less complex model compound, diphenylmethane (DPM). In the present work we report the observation of free radicals in DPM measured at 20 K following x irradiation at the same temperature. The ESR spectrum of the putative DPM radical (-f-.CH-f-) exhibits characteristic features of an anisotropic powder-pattern radical having axial symmetry with g_ = 2.0313 and g^ = 2.0013. Additional weak lines in the spectrum suggest the presence of a second radical of very low concentration, characterized by a quintet of lines with hyperfine splitting approximately 2.1 mT. This radical is tentatively ascribed to an anionic species.

References
[1]. D. W. Cooke, R. E. Muenchausen, B. L. Bennett, E. B. Orler, D. A. Wrobleski, M. E. Smith, M. S. Jahan and D. E. Thomas, "Luminescence, Optical Absorption, and Electron Spin Resonance of an X-Irradiated Poly(ester urethane)," Radiat. Phys. Chem. 55, 1 (1999).

2. M. S. Jahan, M. C. King, J. M. Gray, D. W. Cooke, B. L. Bennett, E. B. Orler and D. A. Wrobleski, "Electron Spin Resonance of Radiation-Induced Oxidation in Poly (ester urethane) Containing Hard and Soft Segments," Polymer Reprints 42, 379 (2001).
Review score for abstract #055:
Comments:

#069
LOCALIZATION OF PRIMARY RADIATION-INDUCED EVENTS IN POLYMERS: POSITIVE HOLE MIGRATION AND TRAPPING

V. I. Feldman. Institute of Synthetic Polymeric Materials of RAS, 70 Profsoyuznaya Str. Moscow 117393 Russia and Karpov Institute of Physical Chemistry, 10 Vorontsovo Pole Str., Moscow 103064 Russia

Ionization of macromolecules is the basic primary physical event induced by high-energy radiation. This process appears to be insensitive to chemical or supermolecuar structure of the material. Meanwhile, localization of primary chemical events (e. g., formation of radicals) is often controlled by rather subtle effects (conformation, molecular packing, weak association, etc.)1,2. Early concepts of the role of "defects" in the radiation chemistry of polymers lacked solid experimental basis, which often resulted in misleading conclusions. Model investigations carried out in our laboratory3,4 suggest that specific mode of the chemical bond rupture in irradiated organic solids can be understood, to a large extent, on the basis of site-selective and matrix-sensitive reactivity of the primary ionized molecules. This implies key significance of positive hole localization. The present contribution gives a review of our recent studies of positive hole migration and trapping in model systems and macromolecules. The following aspects will be outlined:
1. Intrachain migration and delocalization: hole trapping in alkanes and conjugated systems.
2. Trap-to-trap hole transfer in aromatic systems: evidence for "fine tuning" effects.
3. Role of molecular packing: hole trapping at dimeric associates.
4. Effect of positive hole localization on radical yields and reaction kinetics in irradiated solid polymers.
In general, positive hole migration (as well as electron migration) is not limited by slow molecular motion in solids, so this process may be quite effective in the cases of low physical temperature (irradiation of polymers at cryogenic temperatures below 77 K) or low "structural temperature" (for rigid highly organized systems).
This work was supported by INTAS and the Russian Foundation for Basic Research (projects no. INTAS 2000-0093 and RFBR 00-03-32041).

1. V. I. Feldman, F. F. Sukhov and N. A. Slovokhotova. Polym. Sci. B. 36 (1994) 420.
2. V. I. Feldman. Appl. Radiat. Isot. 47 (1996) 1497.
3. V. I. Feldman. Radiat. Phys. Chem. 55 (1999) 565.
4. V. I. Feldman, F. F. Sukhov, A. Yu. Orlov and N. A. Shmakova. J. Phys. Chem. A. 104 (2000) 3792.
Review score for abstract #069:
Comments:

#123
NMR MEASUREMENTS OF RESIDUAL DIPOLAR COUPLINGS FOR LIFETIME ASSESSMENTS IN g-IRRADIATED SILICA-PDMS COMPOSITE MATERIALS*

Robert S. Maxwell(1), Bryan Balazs(1), William Sung(2). 1Chemistry and Materials Science Directorate, Lawrence Livermore National Laboratory, Livermore, CA USA, 2Honeywell FMT, Kansas City Plant, Kansas City, MO USA

We have measured changes in 1H NMR transverse relaxation times, residual dipolar couplings, and the mean squared fluctuations in the residual dipolar couplings, associated with cross-link density changes in a complex silica-filled PDPS/PDMS block copolymer composite material. The cross-links were induced by exposure of the composite material to g-radiation from a Co-60 source. We have detected 1H NMR responses from polymer chains directly interacting with the silica, network polymer chains not directly interacting with the silica, and non-network, low molecular weight chains and chain ends. The residual dipolar couplings change in a straight-forward manner with radiation and chemically induced cross-linking of the polymer network. The strength of the filler-polymer interaction was seen to affect only the residual dipolar couplings and the transverse relaxation times and not directly the mean squared fluctuations of the residual dipolar couplings. Dipolar Correlation Effect NMR shows direct evidence for surface adsorbed species, however, and has measured changes in the amount of surface adsorption due to irradiation. The results suggest that siloxane polymer cross-linking was preceded by an initial disruption of the hydrogen bond interaction between the polymer backbone and the silica silanol groups at the polymer/silica interface and that noticeable radiation induced cross-linking then occurs at dosages above 100 kGray. The changes in residual dipolar couplings have also been compared to changes in crosslink density directly measured by solvent swelling and in storage modulus measured by DMA. The work reported here shows that detailed characterization of the NMR relaxation processes under static conditions can provide important insight into the aging affects of ionizing radiation on complex polymer systems.

*This work was performed under the auspices of the U.S. Department of Energy by University of California Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48
Review score for abstract #123:
Comments:

#134
ON THE MECHANISM OF THE ELECTRON BEAM INDUCED POLYMERIZATION OF ALLYLUREA IN THE SOLID STATE

J. Luna-Carlos, A. Olivier, F. Cazaux and X. Coqueret. Laboratoire de chimie macromoléculaire - UPRESA CNRS 8009, Université des Sciences et Technologies de Lille, 59655 Villeneuve d'Ascq Cedex, France

In the frame of a program aiming at the development of biodegradable thermoplastics with improved physical properties, we have recently demonstrated that the electron beam (EB) irradiation of amorphous starch-allylurea mixtures is an efficient method for stabilizing the physical properties of blends including allylurea (AU) above its compatibility limit.1,2)

Simplified representation of allylurea grafting onto starch by EB-processing (AGU = anhydroglucose unit).
The reactivity of unsaturated monomers under ionizing radiation is generally strongly dependent on their physical state. AU is claimed to undergo gamma ray-induced polymerization in the crystalline state with formation of long chain polymer. Its reactivity in solution is considered to be poor, on the basis of low polymer yield after precipitation.3) We have monitored by various spectroscopic methods the reactivity of allyllurea EB-irradiated at room temperature in each of its two allotropic crystalline forms (monoclinic and tetragonal) and in amorphous mixtures, where AU is blended with starch or with model oligosaccharides. The conversion profiles indicated a much higher reactivity in the blend that in the pure crystals, thus encouraging the use of a radiation-induced process for achieving graft polymerization.4)
In order to gain a deeper insight into the grafting mechanism, amorphous mixtures of maltotriose and AU, as well as pure AU in the crystalline form, were irradiated with accelerated electrons and subsequently analyzed by MALDI mass spectrometry. Various initiation, transfer and termination mechanisms were evidenced from the detailed examination of the mass spectra. Those obtained from sugar-AU blends revealed the presence of short chain AU oligomers, free or grafted onto the oligosaccharide. Extensive hydrogen transfer from/to monomer is believed to cause short kinetic chain length. This peculiarity for the mechanism is consistent with the proportionality of AU conversion with radiation dose. In addition, these results afforded unambiguous evidence, at the molecular level, of the grafting of oligo-AU onto polysaccharides that competes efficiently with homopolymerization.

References
1. D. Ruckert, F. Cazaux, X. Coqueret, J. Appl. Polym. Sci. 73, 409-417 (1999)
2. A. Olivier, F. Cazaux, C. Gors, X. Coqueret, Biomacromolecules 1, 282-289 (2000)
3. A. Usanmaz, O. Ylmaz, Eur. Polym. J. 22, 657-660 (1986)
4. A. Olivier, F. Cazaux, X. Coqueret, Biomacromolecules 2, 1260-1266 (2001)
Review score for abstract #134:
Comments:

#136
ESR INVESTIGATIONS ON IRRADIATED POLYSTYRENE

M. Chipara, R. Benson (1), M. D. Chipara, J. R. Reyes (2)
Indiana University Cyclotron Facility, Bloomington, IN 47403, USA.
1 University of Tennessee, Knoxville, TN, USA.
2 Central University of Venezuela, Caracas, Venezuela.

Pure polystyrene, free of low molecular mass components, obtained by anionic polymerization was irradiated in air, at room temperature, by using a 60Co source, at a dose rate of about 0.5 MRads/hour, up to an integral dose of about 35 MRads. The ESR spectra of gamma-irradiated polystyrene were recorded by using a JES-ME-3X spectrometer, operating in the X band (ª9 GHz). A variable temperature accessory (JES-VT-3X) was used to investigate (in situ) the isothermal recombination of free radicals, in the temperature range 300 K &Mac184; 460 K. To estimate accurately the resonance line position and the double integral of the resonance spectrum, MgO: Mn2+ was used as field and intensity marker. As may be observed from Figure 1, at each temperature, the concentration of free radicals is decreasing with the storage time, due to recombination processes. The best fit of the isothermal recombination data was obtained assuming a combination of first and second order processes (see the solid line in Figure 1). It was noticed that the corresponding isothermal reaction rate constants associated to free radicals’ recombination, at different constant temperatures, present deviations from an Arrhenius-like dependence. This anomaly was assigned to the glass transition phenomenon. A model for the recombination of free radicals, within the glass transition temperature range, based on a free volume approach (compatible with Williams-Landel-Ferry equation) is proposed. The agreement between the predictions of the model and the temperature dependence of the isothermal reaction rates is good.

Review score for abstract #136:
Comments:

#023
Radiation-chemical Transformations in Epoxy Oligomers and Compositions on their Base.

V.P. Laricheva. Obninsk Branch, State Research Center "Karpov Institute of Physical Chemistry’, 249033 Obninsk, Kaluga Region, Russia

Epoxy oligomers are the most well known materials used in radiation and Space technology. Due to the presence of 2 functional groups in them the properties of epoxy composition can be greatly changed, including the change of their sensitivity to radiation.

The generalized literature and our own experimental data are given in the paper. It allows the author to propose the mechanisms of radiation-chemical transformations in epoxy oligomers and compositions in their base and also to give general recommendations on the prediction of radiation stability of epoxy composites and on the use of modified epoxy oligomers in the radiation technology.

It has been shown that what ever the type of the initial resin the same radiation-chemical transformations took place in them : the loss of the epoxy groups on radiation, the formation of the carbonyl and hydroxyl groups , the increase of molecular weight, the decrease of UV- transparency, the formation of steric structure.

The radiation yield of the loss of the epoxy groups is not large (3 / 100 eV), therefore using the radiation for cross-linking of nonmodified epoxy oligomers is not rational. The radiation stability of cured epoxy oligomers depends on the molecular weight of the initial oligomers.
Review score for abstract #023:
Comments:
Topic #4 - Surface and bulk modifications

#028
RADIATION GRAFTING OF N,NDIMETHYLAMINOETHYLMETHACRYLATE
AND 4-VINYLPYRIDINE ONTO POLYPROPYLENE BY THE TWO-STEP METHOD AND FROM THE BINARY MONOMERS MIXTURES

R. Aliev, E.Bucio, G. Burillo. Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Ciudad Universitaria, 04510, Mexico, D.F.

In recent years there has been increasing interest in developing novel polymeric liquid crystalline materials (1). It is known that homopolymers obtained from monomers, containing tertiary amino groups, such as N,N-dimethylaminoethylmethacrylate (DMAEMA) or 4-vinylpyridine (4-VP) form salts with several benzoic acid derivatives but these compounds often have poor mechanical properties. Therefore preliminary graft polymerization of these monomers onto mechanically durable polymer matrices is of practical interest. Moreover, the advantage in thermal properties of the polyDMAEMA-g-PE composition with derivative of benzoic acid over the polyDMAEMA contained this compound has been shown (2).
There are investigations on introduction of two modifying polymers in the starting ones by the two-step grafting or by the graft copolymerization from the binary monomers mixtures (3-9), but grafting of DMAEMA and 4-VP by these methods has never been investigated before.
In the present work, the radiation grafting of DMAEMA and 4-VP from the 50% monomers solutions in toluene and dichloroethane onto polypropylene (PP) films was carried by their mutual g-irradiation (first step). Effect of dose rate and solvents on the grafting efficiency was studied. Then, the grafting of DMAEMA or 4-VP from their solutions in toluene was performed onto PP modified preliminary with the other polymer: poly4-VP or polyDMAEMA (second step). It has been found that chemical structure of PP modified with the first grafted polymer affected the efficiency of the other monomer grafting by the second step. Different dependence of thickness and area of the modified films on the grafting value testify to predominant location of the grafted chains near the PP surface. Radiation grafting of DMAEMA and 4-VP from their binary mixtures in toluene onto PP films was also investigated. Dependence of the grafted copolymers composition on starting monomers mixtures was determined, and constants of copolymerization were calculated.

References:
1. Bazuin G.C. (1998) In: Mechanical and Thermophysical Properties of Polymer Liquid
Crystals. Brostow W., Ed.; Chapman & Hill, London; Chapter 3, p.59.
2. Burillo G. et al. (2000) J. Appl. Polym. Sci., 78, 972.
3. Kondo T. et al. (1998) J.Appl. Polym. Sci., 67, 2057.
4. Chen J. et al. (2000) Radiat. Phys. Chem., 59, 313.
5. El Salmawi K. et al. (1997) Polym. Int., 44, 181.
6. Dessouki A.M. et al. (1998) Polym Int., 45, 67.
7. Hegazy El-S.A. et al. (1999) Nucl. Instr. Meth., B, 151, 386.
8. Choi S.H., Nho Y.C. (2000) Radiat. Phys. Chem., 58, 157.
9. El-Naggar A.M. et al. (2001) Polym. Int., 50, 1082.
Review score for abstract #028:
Comments:

#096
DURABLE WATER REPELLENT CLOTHING BY PLASMA TREATMENT

D. Tessier, M. Filteau. Groupe CTT Group, Textile Technology Center, 3000 Boullé, Saint-Hyacinthe (Prov. Quebec), Canada, J2S 1H9.

Cold plasma technology is a versatile, environmentally friendly, energy cost effective, and promising tool for surface modification. Plasma treatments allow the tailoring of many surface properties for technical textiles such as : wettability, adhesion, wear or wash resistance, capillarity, moisture absorption, colorfastness, water and oil repellency, solvent/chemical resistance, anti-soiling, barrier to liquids, gas permselectivity, electrostatic dissipation and so forth.
Still environmentally hazardous fluoropolymer emulsions are applied for the preparation of so called conventional water repellent (WR) technical textiles. However, our work demonstrates that cold plasma process is very effective to obtain excellent WR ratings and durability to domestic washing. Aramid fabric, used in fire-fighter clothing, was treated in a semi-continuous low pressure plasma pilot line to confer a durable WR fabric. SEM analysis.revealed that a very thin coating, with a thickness varying between 0.2 –0.4 micron, was deposited. Spray test results were compared to conventional WR treated fabric and, as a result, after several washes ratings remains much higher for the plasma treated fabric. No change of rating is observed for the plasma treated fabric from initial to 5 washes; WR ratings remain excellent. Moreover, after 10 washes, WR rating stands relatively high even if some fabric degradation or fiber damage is observed.
Plasma treated fabric does not exhibit significant morphological difference from the original, non-treated fabric. Therefore, the hand feel is not changed and the breathability remains high after plasma treatment, which is important for the general comfort of the wearer.
Review score for abstract #096:
Comments:

#125
PLASMA TREATMENT OF POLYMERS FOR SURFACE AND ADHESION IMPROVEMENT

D. Hegemann, H. Brunner, C. Oehr. Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB, Nobelstrasse 12, 70569 Stuttgart, Germany

Polymers are distinguished by their low density, flexibility, ease of manufacture, and cost-effectiveness. However, their surface properties often do not meet the demands regarding scratch-resistance, wettability, biocompatibility, gas transmission, adhesion, or friction. Hence, an additional surface modification is required to achieve the desired properties, while maintaining the characteristics of the volume [1]. Primarily, a plasma treatment provides manifold possibilities to refine a polymer surface, enabled by the adjustment of parameters like gas flows, power, pressure, and treatment time.
Therefore, this work investigates the surface modification of different polymers (like PP, PET, PC, ABS, etc.) by plasma treatment. Radio frequency (13.56 MHz) was used to excite the plasma. Enabled by a confined gas discharge between symmetrical, plane parallel electrodes, a well-defined and homogeneous plasma results and plasma parameters can be varied in a wide range, e.g. very low up to high input powers. Depending on the gas composition and plasma conditions, ions, electrons, fast neutrals, radicals and VUV radiation contribute to the polymer treatment resulting in ablation, etching, activation and/or cross-linking. The surface modifications are analyzed using XPS, AFM, hardness, and contact angle measurements. The investigations aim for the improvement of wettability and adhesion, as well as for the reduction of friction of polymer surfaces. Aging effects are also regarded.
To improve the adhesion of plasma-deposited coatings, it was found that for polymer-like films a mild pretreatment is appropriate, whereas for hard coatings the film properties must be adapted on the polymers via interphase and film gradient [2].


References
[1] R. Li, L. Ye, Y.-W. Mai, Application of plasma technologies in fibre-reinforced polymer composites: a review of recent developments, Composites 28A, 73-86 (1997).
[2] D. Hegemann, H. Brunner, C. Oehr, Improving the adhesion of siloxane-based plasma coatings on polymers with defined wetting properties, will be published on Proc. 45th Annu. SVC Tech. Conf., Lake Buena Vista, FL 13-18 April 2002.
Review score for abstract #125:
Comments:

Topic #5 - Micro- and nanostructures
#010
PREPARATION OF THE METALLIC STRUCTURES ON THE BASIS OF POLYMER TRACK MEMBRANES AND THEIR APPLICATION TO NUCLEATE BOILING PROCESS

Akapjev G.N.(1), Shirkova V.V.(1), Shulz A.(2) 1 - JINR, Flerov Laboratory, Dubna, Russia 1 SDK-Technik GmbH, Gröpern 25, D-06484 Quedlinburg, Germany

The microgalvanic method for metal filling of etched ion tracks in organic foils is of particular interest for fabrication of micro- and nanosized structures. The metallic microstructures with high aspect ratio produced in ion track membranes are suitable for the investigation of heat transfer processes, especially the phenomena of the bubble nucleation in boiling processes. A heat transfer surface with good heat transfer characteristics is defined as a surface where a small temperature difference causes a large heat transfer from the surface material to the liquid. It is well-known that a porous boiling surface layer transfer to a boiling liquid large quantities of heat at much lower temperature differences than required in conventional heat exchange apparatus. Copper whiskers with a high aspect ratio and a density of 105 - 108 per cm2 form a "hairy" structure which produces boiling heat transfer coefficients many times as large as those obtained with conventional smooth surfaces.

Fig. 1: Heat transfer modeling.
Conjugate process involving conduction (liquid, metallic structure) and evaporation.
d is the height of the copper whiskers in the range of 10 – 100 µm.

Polycarbonate foils (LONZA) with different thicknesses were irradiated and etched to pore membranes. By the method of electrodeposition the pores were filled with deposited copper. Thereafter the host membrane was removed by etching with NaOH revealing metallic microstructures.

Fig.2: Suited microstructures to increase the heat transfer on nucleate boiling processes.
The electrochemical deposition of copper into the pores was performed in a CuSO4*5H2O + H2SO4 + H2O in a galvanostatis regime at room temperature.
The whiskers enlarge the smooth area (5–20) fold and form a surface with an extreme porosity. Good conditions for the production of vapour bubbles between the wiskers made it possible to significantly increase the boiling heat transfer coefficient.

Review score for abstract #010:
Comments:

#045
OXIDATIVE DEGRADATION OF CR-39 TRACK DETECTOR IN THE SURFACE REGION DURING GAMMA-IRRADIATION

T. Yamauchi(1), Y. Somaki(1), H. Nakai(1), K. Oda(1), T. Ikeda(2), H. Honda(2), S. Tagawa(2). 1Kobe University of Mercantile Maine, 658-0022 Kobe, Japan. 2The Institute of Scientific and Industrial Research, Osaka University, 567-0047 Ibaraki, Japan.

Because a CR-39 nuclear track detector has an excellent track registration characteristic, it is important to understand the latent track formation mechanics in it. Such knowledge will help us to develop the more sensitive and reliable track detectors. In order to know the latent track formation process in CR-39, we have been engaged in the investigations on the bulk etching property of gamma and high-energy electron beam irradiated CR-39. The examined total low-LET radiation doses were comparable to the doses in the track cores. We have found that the bulk etch-rate is dependent on the depth from the original surface [1,2], as well as the total absorbed dose and the dose-rate [3,4]. The damaged region was found to be limited near the surface and the depth of the region was dependent on the dose rate, and hardly on the total dose. On the other hand, the etching property in the deeper region was similar to that of in-vacuum irradiation. The observed dose-rate and depth dependence implies that the oxygen from the surroundings will take an important role in the formation of the damage that contributes to the enhancement of the bulk etch-rate. The damage depth-distribution has been calculated numerically based on the mass balance equation for the radicals, the active site by irradiation, and on the diffusion equation for the oxygen dissolved [5]. The experimentally ascertained depth-distribution and the dose-rate dependence were re-constructed well through the calculation, considering the natural radical decay and the surface resistance surface condition for the feed of the oxygen from the air. IR spectral study has been also made for ion and gamma irradiated CR-39. The newly generated CO2 gas shows directly the scission of the main chain [6]. The increase of the density of OH group should have a close relation to the damage that caused the bulk etch-rate enhancement [6,7].

References
[1] T. Yamauchi et al., Radiation Measurements 33, 189-192 (2001)
[2] T. Yamauchi et al., Radiation Measurements 34, 85-89 (2001)
[3] T. Yamauchi et al., Radiation Measurements 31, 121-126 (1999)
[4] K. Oda et al., Radiation Measurements 28, 85-88 (1997)
[5] S. Seguchi et al., Radiat. Phys. Chem. 17, 195-201 (1981)
[6] T. Yamauchi et al. Gamma-ray and ions irradiation effects on the optical property of VR-39 detector and their latent track size, Proc. The First International Symposium on Supercritical Water-cooled Reactors, Tokyo 6-9 November 2000.
[7] T. Yamauchi et al., Radiation Measurements 34, 69-73 (2001)
Review score for abstract #045:
Comments:

#046
TRACK CORE SIZE ESTIMATION IN CR-39 TRACK DEDECTOR USING ATOMIC FORCE MICROSCOPE AND UV-VISIBLE SPECTROMETER

T. Yamauchi(1), D. Mineyama(1), H. Nakai(1), K. Oda(1), N. Yasuda(2). 1Kobe University of Meracantile Maine, 658-0022 Kobe, Japan. 2Natoinal Institute of Radiological Science, Chiba 263-8555, Japan.

A CR-39 nuclear track detector has been well demonstrated to have an excellent track registration property and used widely in various fields by many authors. A few studies, however, have been performed to obtain the fundamental information on the radial track core size in the detectors [1,2]. In the present study two series of examinations have been made to estimate the track core radial size in CR-39 for light and heavy ions. In the first, the surface morphological observations on the heavy ion irradiated CR-39 were made carefully using Atomic Force Microscope (AFM) subsequent to the slight chemical etchings [3]. The track core radii were determined from the intersections of the extrapolated fitting lines for the growth curves of etch pit radius, plotting the radius as a function of the etching duration for C(8.5MeV), O(8.6MeV), Ne(41.5MeV) and Xe(104MeV) ions [4,5]. The core radii were found to be in the range between 3 and 4 nm and hardly dependent on the ion species. Because of the original surface roughness of the CR-39 sheets, it was difficult to distinguish the minute etch pits of light ions from them. In the second, UV-visible spectra of ion irradiated CR-39 were obtained as a function of the fluence. Based on the simple track over-lapping model, in which the latent track was assumed to have a cylindrical shape, the track core radii were evaluated for H(3.4MeV), He(5.1MeV), C(8.5MeV) and O(7.0MeV) ions. The obtained track core radii, rt, were summarized well in the following experimental formula that contains stopping power dE/dx in keV/µm as a parameter: rt = 0.159(dE/dx)0.39 (nm) [6,7]. Finally, the results both from AFM and UV-visible observations were compared and found to be concordant each other.

References
[1] P. Apel et al., Nuclear Instr. and Meth. B144, 468-474 (1998)
[2] W. Enge, Radiation Measurements 25, 11-26 (1995)
[3] N. Yasuda et al., Nuclear Instr. and Meth. B142, 111-116 (1998)
[4] N. Yasuda et al., Radiation Measurements 34, 45-49 (2001)
[5] T. Yamauchi et al., Subsurface layer in CR-39 plastic track detector where the bulk etch rate is enhanced, Radiation Measurements (in press)
[6] T. Yamauchi et al. KEK-Proceedings 99-8, 45-55 (1999)
[7] T. Yamauchi et al. Gamma-ray and ions irradiation effects on the optical property of VR-39 detector and their latent track size, Proc. The First International Symposium on Supercritical Water-cooled Reactors, Tokyo 6-9 November 2000.
Review score for abstract #046:
Comments:

#058
NANOCHANNELS IN TRACK ETCHED MEMBRANES OBSERVED BY SMALL ANGLE SCATTERING OF X-RAYS AND NEUTRONS

G. Pépy(1), A. Kuklin(2), 1LLB, CEA Saclay, 91191 Gif sur Yvette CEDEX, France 2FLNP, JINR, 141980 Dubna, Russia

Track membranes are thin polymer foils irradiated by heavy ions [1,2]. The defects created by the heavy ions are located along the ions trajectory, the track. It is possible to open channels by etching with a chemical agent, typically 0.25N NaOH at 80°C for polyethyleneterephtalate (PET) polymer foils.
We have prepared PET and PC (polycarbonate) track membranes. They were irradiated by Kr ions in Dubna or Kr and Xe ions in GANIL, at various energies.
The diffraction techniques, Small Angle X-ray scattering, SAXS, or neutron scattering, SANS, can give overall information about the geometry of the nanochannels. SAXS has been performed in the ESRF (Grenoble), SANS at the LLB (Saclay) and ILL (Grenoble).
As the nanochannels are strictly parallel, an excellent sample orientation is required to obtain interpretable spectra. For some samples shoulders due to the oscillations of the Bessel function (radial part of the channel shape Fourier transform) are easily seen in the scattered intensity [3].
Improvements in the PXY data treatment software [4] of SAS spectra allow
- to determine the channel diameter with its dispersion law,
- to demonstrate the existence of a wall thickness with a linearly varying density,
- and to assess the roughness [5].
PXY can also detect non cylindric shapes like single or double cones or spindles.
We shall report about the observations over a wide range of PET and PC samples and make a comparison of SAXS and SANS.

References :
1 - R. Spohr, Nuclear Instruments and methods, 173 (1980) 229-236
2 - D. Albrecht thesis, (1983), GSI report 83-13
3 – G. Pépy, A. Kuklin, Nuclear Instruments and methods in Physics Research B 185 (2001) 198-203
4 – http://www-llb.cea.fr/menl/softs.html
5 - G. Pépy, A. Kuklin, to be published.
Review score for abstract #058:
Comments:

#067
NANO-, MICRO- AND MACROSCOPIC HYDROGELS SYNTHESIZED BY RADIATION TECHNIQUE

J.M. Rosiak, I. Janik, S. Kadlubowski, M. Kozicki, P. Kujawa, P. Stasica, P. Ulanski. Institute of Applied Radiation Chemistry, Technical University of Lodz, Wroblewskiego 15, 93-590 Lodz, Poland

Radiation techniques, due to the additive-free initiation and easy process control, are very suitable tools for synthesis of hydrogels. In our group, a number of techniques have been elaborated allowing for targeted synthesis of gels of various size ranges, from internally crosslinked individual macromolecules, via microgels to macroscopic hydrogels [1].
While the general ability of a water-soluble polymer to undergo crosslinking is mainly a function of its chemical structure, the mode of crosslinking can be controlled by a proper selection of polymer concentration, type of irradiation (pulsed vs. continuous) and dose rate. Under high-dose pulse irradiation of dilute polymer solutions, crosslinks are almost solely formed between chain segments within single macromolecules (formation of nanogels) [2, 3], while at moderate dose rates and high concentrations intermolecular recombination prevails, leading either to microgels (below the gelation dose) or to the macroscopic, "wall-to-wall" gels.
Synthetic methods and properties of obtained products are optimized and adjusted with respect to particular biomedical applications (cf. [4]). Solutions of nanogels having suitable rheological properties are being tested as synovial fluid substitutes. Microgels, due to their short swelling time and high degree of swelling, are promising candidates to replace "dietary fiber" compositions used in slimming diets. When combined with a cationic compound, they form preparations able to bind fat and cholesterol. These materials are designed as food additives reducing the absorption of food fat and cholesterol from digestive tract. Macroscopic gels based on our technologies are used in drug release devices [5, 6] and wound dressings [7], the latter being produced on a large scale. Lab tests are on the way on two new hydrogel-based materials – a substitute of intervertebral disc nucleus and stimuli-sensitive membranes. When formation of a macroscopic, stimuli-sensitive gel is combined with grafting on a suitable porous support (e.g. an ion-track membrane), the products (composite membranes) of stimuli-regulated permeation properties are obtained.
Combined polymerization and crosslinking of multifunctional compounds was utilized to design two highly sensitive dosimetric systems for radiotherapy: a threshold dosimeter and a system to determine the three-dimensional dose distribution.

References

[1] J. M. Rosiak, P. Ulanski, Radiat.Phys.Chem. 55, 139-151 (1999).
[2] Ulanski P. et al., Radiat. Phys. Chem. 52, 289-294 (1998).
[3] Ulanski, P. et al., Radiat. Phys. Chem. 63, 533-537 (2002).
[4] Ulanski, P. et al., Polym. Adv. Technol. (2002) in press.
[5] Rosiak JM. et al., Med. Sci. Monit. 2, 78-79 (1996)
[6] J.M. Rosiak, J. Controlled Release 31, 9-19 (1994)
[7] J.M. Rosiak Hydrogel Dressings HDR. In: Radiation Effects on Polymers (Clough RL, Shalaby
SW – eds), ACS Symposium Series 475, 1991, American Chemical Society, Washington DC,
pp. 271-299.
Review score for abstract #067:
Comments:

#071
THERMO-SENSITIVE POLY(VINYL METHYL ETHER) HYDROGELS OF DIFFERENT DIMENSIONS FORMED BY HIGH ENERGY RADIATION

T. Schmidt and K.-F. Arndt. Institute of Physical Chemistry and Electrochemistry, Dresden University of Technology, D-01062 Dresden, Germany.

An aqueous solution of poly(vinyl methyl ether) (PVME) has a lower critical solution temperature (LCST) of 37 °C [1]. When an aqueous solution of PVME (above the overlap concentration) is irradiated with an electron beam or g-rays the solution is transformed into a hydrogel. The crosslinking mechanism is a radical process. Due to the formation of OH and H radicals in water, which attack the polymer chain and abstract hydrogen atoms, the radical is transferred to the macromolecule [2]. The combination of such radicals from different molecules leads to intermolecular crosslinking.
These hydrogels show the same thermo-sensitive behavior (phase transition) like the non-crosslinked polymer. Due to the transformation of a part of the electron energy in thermal energy the temperature of the polymer solution exceeds the phase transition temperature and a hydrogel with a porous structure is formed [3]. This sponge-like structure could be observed by field emission scanning electron microscopy (FESEM). We also have determined the radiation dose dependence of the gel content and the swelling degree in water. NMR relaxation experiments were used to calculate the content of dangling ends and the Mc-values in the dry, swollen and shrunken state.
Irradiation of dilute polymer solutions in water leads to intra- and intermolecular crosslinking and the formation of nanogels or microgels (depending on the homogeneity of the solution). The light scattering study of dilute PVME solutions showed that the PVME molecules are not homogeneously dissolved below the LCST. After heating above this temperature the aggregates collapse to spherical particles (soft spheres). Radiation crosslinking conserves the structure of PVME in the phase-separated state [4]. Static and dynamic light scattering were used to determine the dimension of the formed microgels (diameter in the range of 300-500 nm). Multimodal particle size distributions were found by analytical ultracentrifugation. The colloidal solution consists of crosslinked microgels and non-crosslinked polymer. The structure of the swollen and the shrunken microgel particles was characterized by FESEM, too. The microgels are spherical and porous. The influence of the molecular weight of PVME on the size of the microgels was analyzed by using branched PVME molecules. Irradiation of dilute solutions of PVME below the LCST forms branched molecules with higher molecular weights depending on the radiation dose.

References
[1] H. Schäfer-Soenen et al. Macromolecules 30, 410-416 (1997).
[2] I. Janik et al. Perkin Trans. 2, 2034-2040 and 2041-2048 (2000).
[3] K.-F. Arndt, T. Schmidt, H. Menge, Macromol. Symp. 64, 313-322 (2001).
[4] K.-F. Arndt, T. Schmidt, R. Reichelt, Polymer 42, 6785-6791 (2001).
Review score for abstract #071:
Comments:

Topic #6 - Stability of polymers to ionizing radiation
#087
LET EFFECTS OF NEUTRON IRRADIATED PLASTIC SCINTILLATORS

B. Bodmann, S. Göb, U. Holm. Institut für Experimentalphysik, Universität Hamburg, Luruper Chaussee 149, D-22761 Hamburg, Germany

Plastic scintillators often suffer radiation damage when used in the harsh environment of high energy physics detectors. Neutron and g backgrounds may induce additional absorption in the plastic material and destroy the fluors. Due to the high LET (linear energy transfer) of protons scattered by fast neutrons the neutron induced damage may be different from the g one for the same applied dose [1]. The high density of reactive intermediate species as e.g. radicals leads to an overlapping of spurs [2] along the path of the ionizing particle. As a consequence there are enhanced interactions between shortlived intermediates as e.g. the recombination of radicals and possibly other permanent damages than for g irradiation where the resulting electrons have a much smaller energy loss per path length. We have irradiated plastic scintillators with polystyrene (PS), polymethyl methacrylate (PMMA) and polyvinyltoluene (PVT) bases and the pure bases with neutrons of different spectra from fission reactors and a cyclotron via the 9Be(d,n) reaction and with g radiation from a 60Co source. The radiation induced additional optical absorption was measured in dependence on the time after irradiation. In parallel ESR studies of the radicals produced by the irradiation have been performed. For PMMA there are no clear differences in the permanent damage between n and g irradiation. The ESR spectrum of the initial damage can be understood as a sum of four radical spectra. Two radicals can explicitly be assigned to the annealing optical damage whereas there are no more radicals after total recovery. The annealing of the radicals is not only governed by O2 diffusion, but also by radical interaction. For PS there are strong wavelength dependent differences in optical damage for n and g irradiation. Three radicals are seen in the ESR spectrum where the benzyl radical is assigned to an optical absorption. The third radical only vanishes after the oxygen diffusion and the annealing of the optical damage has come to an end.

References

[1] B. Bodmann, U. Holm, Nucl. Instr. And Meth. B185 (2001)299-304.
[2] H. Kudoh et al., Radiat. Phys. Chem. 48 (1996)555-562.
Review score for abstract #087:
Comments:

#100
THE DAMAGING PROCESS IN IRRADIATED LIGHT GUIDES AND SCINTILLATING FIBERS

B. Bodmann, K. Wick, Ar. Ziegler, T. Zoufal. Institut fuer Experimentalphysik, University of Hamburg, Luruper Chaussee 149,D-22761 Hamburg, Germany

The kinetics of the oxidation process has been studied in commercial light guides (BCF-98, FL-51, GS218) and scintillating fibers (SCSF-38, SCSF-81, SCSF-81(Y7), BCF-12 and BCF-60). The irradiations were performed with X-rays in air at room temperature. In order to prevent recovery effects due to oxygen diffusion most radiation exposures were carried out at low doses so that the oxygen dissolved in the fiber was not consumed during irradiation. Optical measurements of transmission and fluorescence light yield were performed before, during and after irradiation, electron spin resonance (ESR) studies started a few minutes after the end of irradiation.
ESR measurements of PMMA (polymethyl methacrylate/GS218) showed that the primary radicals react in a very short time with oxygen and form peroxide radicals RO2 &Mac215; . These decay within hours via a bimolecular process. Similar results were derived from optical transmission spectra of the fiber FL-51 which has a PMMA core. Besides the well-known permanent absorption damage a very weak unstable absorption was detected in the UV part of the spectrum. Since it decreased with the identical time dependence as the ESR spectra, the absorption is attributed to peroxide radicals.
ESR studies of polystyrene (PS) showed no evidence that radicals survive in the presence of oxygen. On the other hand one can conclude from transmission spectra of PS (BCF-98) that the primary radicals (mainly benzyl radicals) are stable at very low doses (D<10 Gy) even in the presence of oxygen. At higher doses benzyl radicals decay via a bimolecular process. In all scintillating fibers studied up to now shortlived absorption centers have been detected, the observed effects are much stronger than in PMMA and PS [1,2].
The permanent induced absorption damage remaining after the end of the recovery process has been measured as a function of the absorbed dose. In all polystyrene based materials the induced absorption rises nonlinearly with dose. A comparison with independent investigations of PS [3,4] shows that the damage per absorbed dose is much higher at low doses (D<10 kGy) than at high doses (50-1000 kGy).
In an additional experiment it has been demonstrated that the permanent induced absorption can be reduced considerably by short light pulses [5]. This may be of interest for detectors working in a high radiation background.

References

[1] W. Busjan, K. Wick, T. Zoufal, Nucl. Instr. and Meth. B152, 89-104(1999)
[2] K. Wick, T. Zoufal, Nucl. Instr. and Meth. B185, 341-345(2001)
[3] A.D. Bross, A. Pla-Dalmau, ACS Symposium Series 475, 578-590(1991)
[4] J.S. Wallace, M.B. Sinclair, K.T. Gillen, R.L. Clough, Rad. Phys. Chem. 41, 85-100(1993)
[5] Ar. Ziegler, U. Holm, N. Latuske, K. Wick, T. Zoufal, In situ measurement of radiation damage in
scintillating fibers, will be published on Proc. of the 7th Int. Conf. on Advanced Technology and Particle
Physics, Como (Italy), 15-19 October 2001
Review score for abstract #100:
Comments:

#139
AFM AND SPECTROSCOPIC INVESTIGATIONS OF IONS AND FISSION FRAGMENTS TRACKS IN POLYMER FILMS

D.L.Zagorski1,A.I.Vilensky1, G.S.Zhdanov2,V.N.Popok3,I.I. Azarko3,N.N.Mel`nik4. 1Institute of Crystallography,Leninski pr.,59,117333,Moscow,Russia. Ingeneering, Obninsk, Russia 3Belarusian State University, F.Skorina Avenue 4, 220050 Minsk, Belarus 4Lebedev Physical Institute, Moscow, Russia

Thin polyethyleneterephthalate (PET) films were irradiated with Xe (1 MeV/nucl.) and Bi (3 MeV/nucl.) ions, (fluence 109 ions/cm2, cyclotron U-400 (JINR, Dubna)).
AFM images of the ion irradiated samples demonstrate the composite character of surface tracks. Small holes with diameter of 7 nm for Xe-irradiated samples and 100 nm in diameter hillocks with the craters (diameter 10-15 nm) on their tops in the case of Bi-irradiated ones were detected. These surface defects are the projectiles entries at the film surface: their surface density corresponds to the ion irradiation fluence. The thermal treatment of these samples (up to the temperatures 180 0C) was also carried out. The most interesting is thermal behavior of the crater (Bi-irradiated sample); these craters are detected up to the temperatures 70 0C and then they are disappearing. This fact is in good correlation with the peculiarities of etching of irradiated polymers: the etching speed is maximal up to the temperatures 70-100 0C. It may be connected with destruction and fast removing of radiolysis products. The changing of local adhesion in the area of track core was also detected by AFM. Other results are presented and discussed.
The Raman spectroscopy was also used in order to investigate the composition of the track area. The luminescence background increase for irradiated samples may be connected with the formation of carbon nano-particles in the track area; these particles are known to exhibit intensive luminescence. Spectra of electron paramagnetic resonance shown formation of centres with g=2.0036 associated to the graphite-like structures with broken bonds. As the results of the etching, making through pores, Raman spectra of the formed membrane shift converted to the initial film spectra and the paramagnetic centres had a tendency to essential weakening. It confirms that all changes in Raman and EPR spectra came from the track areas.
In the second part of this work irradiation by U235 fission fragments was carried out at nuclear reactor BR-10 (Institute of Physics and Power Ingeneering, Obninsk). The set of 15 ultra thin (2.5 mm) close-packed PET sheets was used. Investigation of different sheets from irradiated "set" gave us possibility to study defect structure along the track. The sheets from the 1st ("upper" in the set) to the 5th were tested with AFM and a monotonic decrease of the defect size was found. AFM study of these films also demonstrated two types of radiation defects probably corresponding to two types of unequal fragments of fission. The detailed results will be reported.
We would like to express our thanks to Dr.P.Yu.Apel and Dr.V.A.Skuratov (JINR, Dubna) for irradiation of the samples.
Review score for abstract #139:
Comments:

Topic #7 - Oxidation processes, aging
#063
THE INFLUENCE OF THE DOSE RATE ON THE DEGRADATION OF POLYMERIC CABLE MATERIALS

V. Pla_ek, B. Bartoní_ek, V. Hnát, B. Otáhal. Nuclear research institute _e_ plc, 25068 _e_, Czech Republic

Cable ageing under nuclear power plant (NPP) condition must be effectively managed to ensure that the required plant safety and reliability are maintained throughout plant service life. One of the main stressors causing age-related degradation of polymer-based cable materials in air is ionizing radiation. For an absorbed dose, radiation induced damage to polymer in air environment may depend on the dose rate of the exposure. The lower dose rate is applied the more severe decomposition in air of numerous materials occurs. These effects may be caused largely by the diffusion-limited oxidation even when chemical processes as e.g. breakdown of hydroperoxides or the long lived radicals reaction can also proceed
In this work, the influence of degradation rate on the dose rate has been studied. Three types of NPP cables have been irradiated at room temperature using 60Co gamma ray source at different dose rates in the interval of 3.5 – 100 Gy/h with the dose up to 600 kGy. The dose rate of 3.5 Gy/h is only several times higher than the dose rates at the real position in NPP. The dose rate of 100 Gy/h is usually used in NRI _e_ Testing laboratory for the simulation of radiation ageing of NPP cables. Following sheath/insulation material combinations have been tested: PVC/PE, PVC/PVC and PE/PE. These are the typical representatives of cable materials used in older NPP’s. The irradiated samples have been tested for their mechanical properties (mainly elongation at break), thermo oxidative-stability by differential scanning calorimetry (DSC) and density.
Despite of relative high scatter of the measured results, which is typical for commercial cable materials, some conclusions could be done. For PVC samples, the values of elongation at break, thermo-oxidative stability and density have shown apparent dose rate effects.
The PE insulations have generally shown no remarkable influence of the applied dose rates on the change of the tested material properties, while the values of elongation at break and the thermo-oxidative stability have decreased with the advanced degradation, density tends to increase with the absorbed dose. This can be partially explained by the increase of the crystallinity, which was also studied by the DSC determination of the crystalline phase amount.
Review score for abstract #063:
Comments:

#081
Glass transition changes upon irradiation in an amine crosslinked epoxy network

T. Devanne(1), A. Bry(1), L. Audouin(2), J. Verdu(2) (1)CEA Le Ripault, BP16, 37260 Monts, France (2)ENSAM-LTVP, 151 Boulevard de l’Hôpital, 75013 Paris, France

This paper deals with the radiochemical ageing (gamma rays) of an epoxy resin. This resin is a mixture of a tris-(hydroxyl phenyl)-methane-based epoxy and resorcinol diglycidyl ether crosslinked by diaminodiphenylsulphone (DDS). Samples were exposed at 30°C or 120°C in air with two different dose rates, 2 kGy/h and 20 kGy/h. After irradiation, they were characterized by dynamic mechanical analysis (DMA) using a dynamic torsiometer. The glass transition temperature, initially 528K, decreases with irradiation (Figure 1).

Figure 1: Changes of Tg versus dose at different temperatures of exposure and dose rates

It can be seen that the number of chain scissions for a given dose is dose rate independent. This fact carries many important consequences among which: i)chain scission results essentially from radiolytic decomposition of the network. Oxidation is confined into a very thin superficial layer owing to diffusion control of kinetics and can not play a significant role in properties changes of bulk specimens. ii) Chain scission occurs only in initiation or termination events of the radical chain degradation process. As a matter of fact, in the case where it would occur during propagation, its rate would be proportional to the square root of dose rate e.g. the points relative to 2 and 20 kGy/h in Figure 1 would lie on distinct curves. A theory based on configurational entropy proposed by Di Marzio [ ] was used to analyse the correspondent changes of crosslinked density and, thus, the number of chain scissions versus conditions of irradiation. A kinetic scheme based on the hypothesis of a radical chain reaction is proposed and ways for its validation are examined.
Review score for abstract #081:
Comments:

#083
INFLUENCE OF THE MOLECULAR MODIFICATIONS ON THE PROPERTIES OF VULCANISED EPDM ELASTOMERS UNDER IRRADIATION

J. Davenas(1), I. Stevenson(1), N. Celette(1), G. Vigier(2), L. David(2). 1Laboratoire des Matériaux Polymères et Biomatériaux , Univ. Claude Bernard Lyon 1, 43 Bd du 11 Novembre, 69100 VILLEURBANNE, France. 2GEMPPM, INSA Lyon, 21 Av. A. Einstein, 69100 VILLEURBANNE, France

The behaviour of elastomers used in the nuclear field is a subject of main importance needing an improved understanding of their long term evolutions. Effects of irradiation on the viscoelastic properties of different formulations of EPDM (Ethylene-Propylene-Diene Monomer): pure gum, vulcanised elastomer, vulcanised and protected by an antioxidant, have been investigated by Dynamic Mechanical Analysis (DMA). We have shown in a previous study [1] that EPDM property modifications were controlled by cross-linking for high dose rate irradiation performed under inert atmosphere (2 MeV electrons). Cross-linking is in particular evidenced by the rapid increase of the gel fraction, deduced from swelling experiments, with the irradiation dose. Such experiments have however indicated that low dose rate irradiation performed under oxygen (60 Co g radiation) leads to a rapid decrease of the gel content for irradiation doses larger than 100 kGy resulting from chain scissions. The combination of InfraRed spectroscopy and derivatisation methods [2] allowed the distinction between two types of radiochemical products according to these irradiation conditions: formation of unsaturated bonds and cross-linking under inert atmosphere, production of a large variety of oxidised fragments in the presence of oxygen. In this report our purpose is to correlate the molecular modifications to the resulting mechanical behaviour of EPDM irradiated under oxidising conditions. DMA shows the reduction of the molecular mobility through the shift of the a relaxation towards higher temperatures, whereas a decrease of the storage modulus with the irradiation dose is observed above the melting temperature of the crystallites (Tm ~ 40 °C). This evolution is interpreted by the competition between cross-linking and chain scissions, being hindered by the crystallites at room temperature, whereas the intrinsic irradiation effects can only be isolated after crystallite melting. Stress / strain measurements performed at 80 °C show a strong increase of the young modulus and reduction of the elongation at break of the pure gum becoming more brittle upon cross-linking. Softening of vulcanised EPDM resulting from irradiation is indicated by the tensile tests, in accordance with the reduction of the Young modulus observed by DMA after crystallites melting. The effect of reinforcement by the crystallites is evidenced by the one order of magnitude larger storage modulus at room temperature than at 80 °C. The reduction of the molecular mobility upon irradiation can be explained by a chemi-crystallisation process assisted by chain scissions, leading to a more rigid phase. The consequences on the prediction models of the non linear temperature effect resulting from semi-crystallinity will be discussed.

References
[1] N. Celette, I. Stevenson, J. Davenas, L. David, G. Vigier,
IRAP 2000, Nucl. Instr. and Meth. B, 185 305-310 (2001)
[2] J. Davenas, I. Stevenson, N. Celette, S. Cambon, J.L. Gardette, A. Rivaton, L. Vignoud,
REI 2001, Nucl. Instr. and Meth. B, in press
Review score for abstract #083:
Comments:

#095
THERMAL REGRESSION OF TRACKS OF HEAVY IONS IN POLYMER

A.I.Vilensky, N.V.Pervov, D.L.Zagorski. Institute of Crystallography, ,Leninski pr., 59, 117333,Moscow, Russia

Thermal stability of tracks in poly(ethylene terephthalate) (PET) , irradiated by Xe and Bi ions with energy 1-3 MeV/nucleon and fluence 108 – 109 ions/cm2 (cyclotron U-400, JINR, Dubna ) was investigated. Polymer samples were annealed in air at differnt temperatures (in interval 50- 180 0C) during 1 h. Alkali etching speed was measured by different methods for evaluation of polymer stability. Etched pores diameters were measured by AFM technique and by using hydrodynamic method (filtration of distilled water through the pores under applied trans-membrane pressure and calculation according to Haagen-Poiuiseiul equation). The concentration of etching products via etching time was measured by optical density of the etched solution (UV-spectrometry technique).
Temperature treatment did not affect on initial , non-irradiated polymer -the etching speed did not changed after annealing up to 160 0 C. The temperature dependence of irradiated polymer stability was found to have non-linear character: two temperature interval were detected. Annealing at low temperatures (below 100 0 C) leads to acceleration of polymer etching (thermo-sensitization), while annealing at the temperatures 100-180 0 C results in reduction of the etching speed (thermal regression). Thermo-sensitization process (at the temperatures lower than glass-transition) may be connected with thermo-oxidation and destruction of radiolysis products, which rapidly passe into the etchant [1]. On the other hand, high-temperature treatment results in complex process of the destructed areas change. This process leads to additional cross-linking which increase chemical stability of the track areas ( comparing with a non-annealed sample).
The reduction of etching speed gave possibility to investigate the last process in details: different features at the curve became detectable and steps were found at the curve. These steps are supposed to correspond to the areas of higher chemical stability of tracks in the annealed polymer. These areas probably connected with the zonal structure of tracks in irradiated polymer, investigated in earlier works [2,3].
The authors thank Dr.P.Yu.Apel and Dr.A.Yu.Didyk (JINR,Dubna) for sample irradiation.

References
1.T.E.Laricheva , A.A. Machula, V.K.Milinchuk and D.L. Zagorski, Colloid Journal 62 (2000) 575.
2.P.Apel, A.Shulz, R.Sphor, G.Trautmann and V.Vutsadakis, Nucl.Instr. Meth. Ph.R.., B131 (1997) 55.
3.A.I Vilensky, O.G Larionov., R.V.Gainutdinov., A.L.Tolstikhina., V.Ya. Kabanov, D.L. Zagorski, E.V.Khataibe, A.N.Netchaev and B.V.Mchedlishvili. Rad. Meas., 34 (2001), Issue 1-6, 75
Review score for abstract #095:
Comments:

#101
THERMAL AND ELECTRON BEAM AGEING OF EPOXY POLYMER

N. Longieras(1+2), P. Palmas(1), J.-L. Gardette(2), A. Rivaton(2). 1Commissariat à l’Energie Atomique Le Ripault, BP 16, 37260 Monts, France. 2Laboratoire de Photochimie Moléculaire et macromoléculaire, URA CNRS 433, Université Blaise Pascal (Clermont-Ferrand), F-63177 Aubière Cedex, France.

Epoxy polymers are multi purposes materials and are particularly used in nuclear area. Safety, reliability and lifetime prediction of nuclear power station are crucial. They depend on the polymers behaviour in thermal and nuclear ambiance. Therefore the understanding of the polymer degradation reaction mechanisms is essential for selecting correct polymer formulations. The goal of this work is the study of the chemical mechanisms which occur during thermal and electron beam ageing of two model epoxy materials. The first is a linear thermoplastic phenoxy resin with DGEBA sequences (Fig. 1). This polymer offers the advantage of being soluble in common organic solvents. In this way it can be studied with conventional analysis methods like liquid NMR, infrared spectroscopy, sterical exclusion chromatography (etc). Chemical derivations with compounds such as ammonia, nitrogen monoxide, dinitrophenylhydrazine (DNPH) are combined with infrared techniques in order to determine degradation products. The second material is a thermoset three-dimensional epoxy/aliphatic amine network : DGEBA/TETA (Fig. 2). This network is insoluble and infusible. Its ageing process is studied using both infrared spectroscopy and solid state NMR techniques. More than structural information, solid state NMR provides an insight into molecular and macromolecular motion of polymer chains. Molecular mobility is strongly connected to the network integrity which depends on chemical events occurring in the polymer like chain scission and crosslinking. A number of parameters (relaxation time, …) strongly dependent on molecular mobility can be measured. One parameter of interest is the T2 transversal relaxation time derived from Hahn spin-echo experiment. This gives a global molecular mobility approach. Another chemical shift specific information on local mobility is given by two-dimensional spectroscopy.

Review score for abstract #101:
Comments:

#122
RESULTS OF AGEING OF ELECTRICAL INSULATORS AFTER EXPOSURE FOR 11 YEARS IN THE LARGE ELECTRON-POSITRON COLLIDER AT CERN

M. Tavlet. CERN, TIS Division, 1211 Geneva 23, Switzerland

Keywords: radiation, degradation, epoxy, cable insulators, polyolefins, accelerators

During the design of the Large Electron-Positron Collider (LEP), all polymer-based materials to be used as electrical insulators have been qualified for their radiation behaviour. The selection was based mechanical tests, according to the recommendations of the IEC 60544 Standard. The lifetime of these insulators was assessed also taking into account the expected "dose-rate effect", following the recommendations of the IEC 61244 Technical Report. Today, after the decommissioning of LEP, samples have been taken out after their life exposure. Their were tested according to the same mechanical tests, and the results are compared with the expectations. The results show that lifetime estimation is quite hazardous over such long periods of time.
Review score for abstract #122:
Comments:

Topic #8 - Industrial, biological and medical applications, radiosterilization
#021
THE EFFECT OF RADIATION STERILIZATION ON CYTOTOXICITY ON POLYURETHANE FILM

N. Sheikh. Gamma Irradiation centre, Atomic Energy Org. of Iran, P. O. Box 11365-3486, Tehran, Iran

A biomaterial is expected to be selected from untoxical and biocompatible materials [1]. Also, in the most cases it must be capable of withstanding radiosterilization [2]. Nowadays a sequence of tests for evaluation of sterilized biomaterial includes an initial set of tests in vitro, both biological (cell culture) and nonbiological (mechanical tests). In this paper the cytotoxicity of a sterilized polyurethane film in order to use as biomaterial has been investigated. For this purpose NCO-terminated urethane prepolymer in medical quality was synthesized without ingredients beside monomers (polyethylene glycol / castor oil and toluene diisocyanate). Then a purification process was carried out on the final product [3]. The cured prepolymer films were prepared under ambient conditions due to the reaction of free NCO-groups of prepolymer with air moisture. The polyurethane films were sterilized by gamma-ray (25 kGy). The surface structure of sterilized polyurethane film was observed by SEM and compared to that of the unsterilized film. Also, the in vitro interaction of fibroblast cells and polyurethane film in culture medium containing serum was evaluated in comparison with control samples. Results showed no signs of cell toxicity.

References
[1] M. Donkerwolcke, F.Burny, D. Muster, Tissue and bone adhesives, Biomaterials, 19,1461-1466
(1998).
[2] P. Klemchuk, Protecting polymers against damage from gamma radiation,Radiat. Phys. Chem.,
41, 1-2, 165 (1993).
[3] N. Sheikh, A. A. Katbab, H. Mirzadeh, Isocyanate-terminated urethane prepolymer as
bioadhesive base material,International Journal of Adhesion & Adhesives, 20, 299-304 (2000).
Review score for abstract #021:
Comments:

#022
HEAT-RESISTANT COMPOSITION MATERIALS BASED ON RADIATION-PRODUCED PREPREGS

*Laricheva V.P., *Pleshanov V.P., **Nikulina I.P., **Vymorkov N.V. *Obninsk Branch of the Karpov Institute of Physical Chemistry 249033 Obninsk, Kaluga Region, Russia. **State Research Center of the Russian Federation "Scientific and Production Association "Technology"

Scientific criteria have been developed for obtaining high-strength heat- resistant polymeric compositions through
1) an alternative effect of ionizing radiation and temperature (a stage of long-lived prepregs) and
2) incorporation of heat- and radiation-resistant fragments into initial oligomer structure.

A radiation-chemical method can be used to obtain long-lived prepregs based on specially developed complex binders comprising the components with different sensitivity to ionizing radiation and different curing mechanisms. The method enables to obtain the materials with increased strength characteristics due to alternative interpenetration of the networks.
Based on a special computer program, the calculations were made to determine a shelf-life of prepregs, as well as temperatures and time intervals for processing the prepregs into composition materials. Heat-resistant fragments can be incorporated into polymeric structure during radiation copolymerisation of the compounds comprising these fragments and unsaturated bonds of maleinate and allyl types.
The subject of conducted research also included the regularities of radiation-and heat-induced radical copolymerisation of initial systems and the effect of substance initiators on the radical copolymerisation rate of investigated systems under simultaneous action of ionizing radiation. It was shown that substance initiators enabled to decrease the activation energy of thermally hardened prepregs from 30.6 to 21.3 kcal/mole. The activation energy of additional thermal hardening of prepregs was found dependent on the dose absorbed at the stage of prepreg production.

The developed prepregs enabled to obtain composition materials with high heatresistance (glass transition temperature 260° C).
Review score for abstract #022:
Comments:

#047
IMPROVEMENT OF RADIATION TECHNOLOGY FOR PRODUCTION OF NEW ANTITUBERCULOSIS PREPARATION «ISODEX»

V. A. Shkurupiy1, V. L. Auslender2, M. V. Korobeinikov2, E. P. Gulyaeva3, A. V. Troitskiy3,
O. V. Grishin3, L. A. Bogdanova3, T. V. Machneva3. 1RC for Clinical and Experimental Medicine, SB of RAMS, 2, Academician Timakov av., Novosibirsk 630117, Russia. 2BINP, SB RAS, 11, Academician Lavrentyev av., Novosibirsk 630090, Russia. 3ICG, SB RAS, 10, Academician Lavrentyev av., Novosibirsk 630090, Russia.

In our previous work [1] we have reported about the successful immobilization of antituberculosis preparation izoniasidum (chemical name is hydrazide of the isonicotinic acid) on the dextrane activated by electron beam treatment.
The present work describes improvement of dextrane’s electron beam activation due to additions sensibilizing the process of radiation oxidation. The results of studies have shown that the addition of small amount of hydrogen peroxide into the irradiated solution of dextrane increases the effective carbonyl capacity of activated dextrane.
We have elaborated a new complex antituberculosis preparation "Isodex" possessing prolonged action and the technology of its production. The balanced mixture of isoniazidum immobilized on dextrane and free isoniasidum is the basis of "Isodex". Free isoniasidum acts on the extracellular population of Mycobacterium tuberculosis, but it is quickly removed from the body. Immobilized isoniasidum enters into the phagocytes and stored inside them thus acting on Mycobacterium tuberculosis persisting in phagosytes. The pharmacological properties of new antituberculosis preparation "Isodex" will be reported.
Our studies allowed us to elaborate the laboratory technology of the "Isodex" production, to understand its pharmacological properties on in vivo models of mouse tuberculosis in comparison with the free isoniasidum. The results of the studies will be reported.

References

[1] V. A. Shkurupiy, V. A. Krasnov, E. P. Gulyayeva, A. V. Troitskiy, O. V. Grishin, L. A. Bogdanova, T. V. Machneva, V. L. Auslender, M. V. Korobeinikov, Production of new antituberculosis drug and other medical preparations by electron beam treatment. Radiat. Phys. and Chem. Vol. 63, Iss 3-6, 691-695 (2002).
Review score for abstract #047:
Comments:

#053
HEAVY ION TRACK - STRUCTURE CALCULATIONS OF MICRODOSIMETRIC DOSE IN ARBITRARY MATERIALS

A.1Taymaz, M.H. 2Khalil and H. 3Fuchs. 1Physics Division, Science Faculty, Istanbul University, Vezneciler Campus, 34459 Istanbul, Turkey. 2Physics Department, Science Faculty, Ain Shams University, Cairo, Egypt 3 Bereich Schwerionenphysik, Hahn Meither Institut Berlin, 390128, D- 14091 Berlin, Germany.
ABSTRACT.

An analytical model used to evaluate energy dissipation fluctuation in microscopic volumes by heavy ions through direct event and in direct delta ray electrons. The model can account for the increase in flux at low lineal energy when the incident ions are of very high energy. Ionising radiation produces biological damage in a target by atomic and nuclear collisions resulting in ionisations and in excitations of the atoms. As for the target size, the emphasis of microdosimetry is increasingly shifting toward to nanometric dimension as in the case of sub- cellular such as DNA molecules.
Since energy deposition fluctuations are simply related to fundamental quantities average yD and average zD in microdosimetry, the analytical model provides such calculations. Dose calculations for soft tissue, water and melinex are discussed. Reasonably good agreement is obtained between the calculated results and available data for laboratory ion beams.
Review score for abstract #053:
Comments:

#054
ELECTRON BEAM PROCESSING OF POLYMERS STILL VALID IN INDUSTRIAL MANUFACTURING?

G. Gielenz. HUBER+ SUHNER AG, Tumbelenstrasse, CH-8330 Pfäffikon, Switzerland

Electron Beam (EB) processing of polymers is a well established and mature technology for more than 35 years in numerous application for the polymer processing industry. In this lecture some of its key characteristics as related to material and process fundamentals are discussed and compared with competing crosslinking technologies. The future attractiveness of irradiation processing technologies, which today offer numerous advantages in comparison to conventional CV curing and silane crosslinking technologies, can only be maintained by improving their economic advantage, which is: high processing speed, high material throughput at low production costs, high process flexibility and versatility and comparatively low capital investment for the hardware involved. Some comments on the (dis)advantages and the future economic improvements which EB processing technologies could provide to the polymer processing industry are presented with respect to materials and irradiation equipment.
Review score for abstract #054:
Comments:

#070
DEVELOPMENTS IN LOW ENERGY ELECTRON BEAM MACHINERY AND PROCESSES

J. Chrusciel, (1) D.A. Cleghorn, (2) I. Rangwalla, (1) and S.V. Nablo (2) (1) Energy Sciences Inc., 42 Industrial Way, Wilmington, MA. 01887 (2) Electron Processing Systems Inc., 6 Executive Park Drive, N. Billerica, MA. 01862

The engineering and development of a new generation of low energy, high power electron beam equipment is presented. Operating voltages range from 80 to 125 kV at widths to 1.6 meters [1]. At 110 kV these systems deliver 1,000 Mrad m.min-1 at 110 kV. Equipment operating power levels and their impact on reducing equipment size and cost are reviewed. The advantages [2] of electron curing at these reduced operating voltages are described.
The principles of the electron beam fluidized bed process for the treatment of powders and particulates in high-speed pneumatic transport are discussed. Typical system performances for polymer dissociation and crosslinking, or for agroproduct disinfestation and disinfection are presented.[3]
A process for the sterilization of polymer food containers employing the injection of low energy electrons through the open mouth has been developed. Some of its capabilities for bottles up to 2 liters capacity are described.[4]

[1] Lauppi, U.V. and Rangwalla, I. J., "Advantages of Low Energy Electron Beam Processing (80-110 kV)", RadTech Europe Conference Proceedings, Berlin, Germany, (1999).
[2] Rangwalla, I.J. and Sanders, R., "The New Electron Beam for the New Millenium", Ink World, USA, (2000).
[3] Cleghorn, D.A., Nablo, S.V., and Ferro, D.N., "Performance of the Electron Beam Fluidized Bed Process for Disinfection and Disinfestation of Stored Products," Application of Accelerators in Research and Industry, 16th International Conference, AIP Conference Proceedings 576 pp. 779-782, 2000.
[4] Weiss, D.E., Cleghorn, D.A. and Nablo, S.V., "Electron Beam Process Validation for Sterilization of Complex Geometries," in press Rad. Phys. Chem. 63, (2002).
Review score for abstract #070:
Comments:

#079
ORIENTED IMMOBILIZATION OF PROTEINS ON GRAFTED POROUS POLYMERS

M. L. Carbajal(1), E. E. Smolko(2) and M. Grasselli(1) . 1Universidad Nacional de Quilmes. Roque Sáenz Peña 180. (B1876BXD) Bernal. Argentina. 2Comisión Nacional de Energía Atómica. Ezeiza. Argentina

The modification of polymers by radiation grafting has been already reported for several decades. Nevertheless, it remains as an area of real present industrial interest. This corresponds to the capability of obtaining a variety of polymer materials with the desirable properties of the bulk but, with superficial layers of macromolecules stuck onto it [1]. The facility to tailoring surfaces of a porous materials retaining its mechanical properties is a valuable tool to obtain ultra- and micro-filtration membranes, affinity membranes, chromatographic supports and materials for biocatalyst and also for biotechnology [2-4].
Porous material have the advantage of having a high surface area exposed to solvent in a small volume. In this work, we described the grafting of glycidyl methacrylate (GMA) onto a macroporous polysulfone material. Very reproducible amount of grafting, from 10 to 100% was obtained by choosing an initially favorable monomer concentration and gamma radiation doses of the order of 10 kGy.
Afterwards, iminodiacetic acid (IDA) and amino phenyl arsine oxide (APAO) were covalently attached to the grafted polyGMA in a homogeneous way, in direct correspondence with the grafting degree.
Later on, a recombinant thioredoxin protein (rTrx) was immobilised onto this surface by two different pathways, involving different specific protein orientations. The first one involves a complex IDA-Ni(2+) and three rTrx's histidines. The other one involves a co-ordination site between APAO and two proximal rTrx´s cysteines, which also corresponds to the active site of the enzyme. The presence of the rTrx on the polymer was detected by the attachment of polyclonal antibodies and the specificity was determined by measuring rTrx activity.
In this way, we were able to obtain by careful radiation grafting procedure and adequate ligand concentration, an oriented immobilisation of proteins onto a macroporous polysulfone material.

References

[1] R.L. Clough, Nucl. Instr. and Meth. B 185, 1-3 (2001).
[2] E.A. Hegazy, H.A. AbdEl-Rehim, H. Kamal and K.A. Kandeel, Nucl. Instr. And Meth. B 185, 235-240, (2001).
[3] S. Miura, N. Kubota, H. Kawakita, K. Saito, K. Sugita, K. Watanabe and T. Sugo, Radiat. Phys. Chem., 63, 143-149 (2002).
[4] M. Grasselli, A. A Navarro del Cañizo., S. A. Camperi, E. E. Smolko and O. Cascone, Radiat. Phys. Chem., 55, 203-20 (1999).
Review score for abstract #079:
Comments:

#084
RESENT SITUATION OF IRRADIATION APPLICATION INDUSTRY AND IRRADIATION FACILITIES IN JAPAN

K. Mizusawa. Nissin-High Voltage, 47 Umezutakase-cho, Ukyo-ku, Kyoto, Japan

Irradiation application industry and irradiation facilities in Japan have been making steady progress for these 2-3 years. Beside conventional applications new ones such as carbon fiber and membrane filter have come into the market. There are a lot of new applications about to emerge. PE tubing that already is in the European market is being evaluated at the end users. Treatment of VOC and dioxin was successfully tested at a pilot plant. Cross-linking of PTFE and polyamide is waiting customers’ evaluation as engineering plastic. Surface cross-linking of artificial polycarbonate teeth has made a remarkable experimental results. Cross-linking of poly-caprolactone will be useful for medical and biodegradable products.
Being aware of future growth of irradiation industry, contract service facilities were newly opened or increased its capability. Beside in-house facilities there are now, three Cobalt60 facilities and seven EB facilities available for contract irradiation.
As briefly described above this paper will report the present situation of irradiation application industry and irradiation facilities in Japan.
Review score for abstract #084:
Comments:

#085
Interaction between reinforce carbon black and polymeric matrix for industrial applications

S. Baccaro (1), A. Cecilia (1), F. Cataldo(2), A. Cemmi(1), F. Padella(3), A. Santini(3) (1)ENEA-FIS/ION, RC Casaccia, Via Anguillarese 301, 00060 S.Maria di Galeria (Rome, Italy) (2)Trellerborg Wheel System spa/Pirelli spa, Via Casilina 1626/A, 00133 Rome, (Italy). (3)ENEA-MAT/COM, RC Casaccia, Via Anguillarese 301, 00060 S.Maria di Galeria (Rome, Italy)

The aim of this work is the comprehension of the interaction mechanism between a polymeric matrix and the reinforcement carbon black to improve the life-time of mixtures used for industrial applications.
When carbon black is used as filler, the binding of rubber occurs both by physical and chemical processes. In the first case the polymer chains are adsorbed on the filler surface giving rise to the so called bound rubber phenomenon. As far as the chemical mechanism is concerned, carbon black sites could act as free radical acceptors, causing the chemical grafting of polymer macroradicals formed by mechanochemical degradation of rubber chains during mixing.
In order to verify the correspondence between the active centre increase in the filler and the polymer reinforcement, we have induced an active centre concentration enhancement through High Energy Ball Milling (HEBM) technique or g irradiation.
To induce a partial amorphisation, the graphite powder was treated by HEBM technique and the effect was monitored by X-ray diffraction. The radical production and the signal fading, were measured by EPR both in air and argon atmosphere at different milling times.
Carbon black powder were submitted to g irradiation at the 60Co radioisotope source Calliope plant at the Research Centre ENEA-Casaccia (Rome) at absorbed doses of 198, 585 and 1000 kGy with 2 kGy/h dose rate: free radicals induced by g irradiation were evaluated by ESR analysis too.
After the irradiation and the HEBM treatments, the graphite and carbon black powders were poured in mixtures at the Trellerborg laboratories to verify the theoretical expectation.
Review score for abstract #085:
Comments:

#110
COMMERCIAL APPLICATIONS FOR RADIATION PROCESSING OF MATERIALS

M. R. Cleland, L. A. Parks and S. Chen. IBA, 7695 Formula Place, San Diego, CA 92121

Practical applications for radiation processing of materials have been evolving since the introduction of this technology nearly fifty years ago. Crosslinking of plastic materials and sterilization of medical products were the earliest developments. Processes for curing or polymerizing monomeric coatings and inks were developed somewhat later. The use of these processes has grown and they are widely practiced today. The emphasis on polymers, both synthetic and natural, is influenced by a basic principle of radiation chemistry, namely that the energy per unit mass or absorbed dose needed to obtain beneficial effects is lower in materials with higher molecular weights. Exceptions to this rule are the treatment of dilute solutions, such as contaminated water and exhaust gases.
Electron beam crosslinking is used to produce heat-shrinkable plastic films for packaging foods and other consumer products, heat-shrinkable plastic tubing and encapsulations for industrial products, and hydrogels for medical applications. The insulation on electrical wires and the jackets on multi-conductor cables are crosslinked to increase heat tolerance and to improve the resistance to abrasion and solvents. Crosslinked plastic pipe is used for hot water distribution systems. Sheet rubber components for automobile tires are partially crosslinked before the tire is made to stabilize the thickness of these materials during the final thermal cure. Polymerized, solvent-free coatings and inks are used for magazines, newspapers and a variety of packaging materials. Other applications include reducing the molecular weight by scissioning of polymer chains, e.g. polytetrafluoroethylene, polypropylene and cellulose, grafting of monomers onto polymers to modify their surface properties, and curing or polymerizing fiber-reinforced composite materials.
Industrial irradiation processes using high-power electron accelerators are attractive because the throughput rates are very high and the treatment costs per unit of product are competitive with more conventional chemical processes. The utilization of energy in radiation processing is more efficient than typical thermal processes. Often, toxic reagents are not needed as part of the process as with chemical processes. Furthermore, these capabilities are unique in that beneficial changes can be induced in solid manufactured materials as well as powder and pelletized polymers.
Review score for abstract #110:
Comments:

#111
MEDIUM AND HIGH ENERGY ELECTRON BEAM RADIATION PROCESSING EQUIPMENT FOR COMMERCIAL APPLICATIONS

L. A. Parks, M. Cleland. IBA, 7695 Formula Place, San Diego, CA 92121

Electron beam processing systems are comprised of the accelerator, material handling subsystem, control subsystem, and radiological shielding. The two most important aspects of the accelerator are it’s beam energy and average beam power. Electron beam energy dictates the ability of the beam to penetrate materials. Medium and high energies are usually characterized by beam energies of 500 keV to 5 MeV, and 5 MeV and above, respectively. Higher power enables faster throughput and, for the processing of most materials to alter their properties, particularly polymers, very high beam powers are important. Common medium energy accelerators have power levels up to 300 to 350 kW and include insulated-core transformer (ICT) type, Cockcroft Walton type, and Dynamitrons“, which are similar to the Cockcroft-Walton type. Historically, linear accelerators (linacs) have been used for high energies. Typical beam powers are up to 20 kW, although some commercial machines operate at 50 to 60 kW. It is possible to build higher power linacs. Within the past 15 years, the Rhodotron“ has been developed which today can operate at power levels up to 200 kW at high energies. An evolving technology is the ability to use high energy x-rays created by high power, high energy electron beam accelerators.
Material handling subsystems depend upon the type of product to be processed. Common handling equipment includes belt conveyor systems on which the product (eg, cartons and continuous flow) is placed, floor- or overhead-mounted cart systems, web systems for continuous flow sheets, and reel to reel systems for wire, cable, and tubing. There are some unique, patented handling systems for specific applications. There may be other important aspects to the handling equipment besides assuring proper dose delivery. Usually, temperature changes from the absorption of the beam power by the product will affect the properties of the material being treated, and may be an integral part of the overall process. Temperature control may require cooling equipment, multiple passes of the material through the electron beam, and adequate cooling time between passes. Some materials may be sensitive to oxidation during irradiation and require treatment under inert or other atmospheres. The handling equipment must be constructed to be able to withstand increased temperature from absorption of the beam power and equipment in the irradiation cell must be radiation tolerant.
Environmental considerations include control of gases and other by-products from the irradiation process. Ozone is created in the process and depends upon the beam power and length of the beam path through air. Induced radioactivity for beam energies up to 10 MeV is usually not an issue, particularly for treated materials. If the materials to be treated are flammable, caution must be taken because of high power absorption rates that may occur from the process.
Radiological shields can be very massive, particularly at higher energies and powers. Shields are commonly made of concrete and soil, although removable and more portable shields have been made of steel and other materials.
Review score for abstract #111:
Comments:

#114
FACTORS INFLUENCING EQUIPMENT SELECTION IN ELECTRON BEAM PROCESSING

J.W. Barnard(1) 1Acsion Industries Incorporated, Whiteshell Laboratories, Pinawa MB, Canada R0E 1L0

During the eighties and nineties accelerator manufacturers dramatically increased the beam energy available for high power equipment. This effort was directed primarily at meeting the demands of the sterilization industry. During this era, the perception that bigger (higher power, higher energy) was always better prevailed since the operating and capital costs of accelerators did not increase with power and energy as fast as the throughput. High power was needed to maintain per unit treatment costs low. This philosophy runs counter to certain present-day realities of the sterilization business as well as conditions influencing accelerator selection in other electron beam applications. Recent experience in machine selection is described and factors affecting choice are presented.
Review score for abstract #114:
Comments:

#129
EFFECTS OF GAMMA IRRADIATION ON THE PHYSICAL AND CHEMICAL PROPERTIES OF ULTRA-HIGH MOLECULAR WEIGHT POLYETHYLENE

N. Naheed, M.S. Jahan, M. Ridley. Department of Physics, The University of Memphis, Memphis, TN 38152, USA

Gamma irradiation is the most convenient, clean method for sterilization of ultra-high molecular weight polyethylene (UHMWPE) components of total hip or knee joints. However, this method of sterilization is known to have adverse effects on the performance of the joints.1 The primary cause for this adverse effect is the formation of PE free radicals (P.) by breaking molecular chains (chain scission) or by knocking out hydrogen from the chain by ionizing radiation. As a result, short-chain molecules are formed, and the molecular weight of UHMWPE is reduced. Additionally, the free radical species P. can initiate oxidative degradation of UHMWPE by reacting with oxygen and, thus, forming oxygen-induced radicals (OIR), (PO.2 or PO.), or, in absence of oxygen, P.‘s can react with each other and form cross-link UHMWPE (P-P). The wear of UHMWPE joint components is degraded by the former reaction, but is improved by the latter. In this study, we performed quantitative analyses of the primary radicals in presence as well as in absence of oxygen. The OIRs are found to be very stable and can remain active in the polymer matrix for years. They are also detected in retrieved hip or knee joints.
While cross link process can be accelerated by increasing temperature, the primary radicals cannot be completely consumed or annihilated by heating a conventional UHMWPE rod (10mm long x3 mm in diameter, in this study) at or below 75°C. Between 1 to 5% of the initial (~1017 per gm) primary radicals remain trapped in the polymer matrix following annealing at 75°C for one year in nitrogen, argon or vacuum.2 Furthermore, we observed that when these residual radicals came in contact with oxygen, oxidation reaction started and OIRs were produced. There is no clinical evidence to suggest whether less than 5% radicals would have any adverse effects on the performance of the joint components; nonetheless, the results of this study contradict the claim that free radicals can be stabilized if UHMWPE is sterilized by gamma irradiation in nitrogen environment and subsequently heated to 50°C for 144 hours in the same environment.3
Materials and Methods: Three resin types of UHMWPE were selected for this study, GUR 4120, GUR 4150 and Himont 1900. Samples for free radical measurements were machined, cleaned in an ultrasonic bath, and each sample was then sealed in an evacuated (~10-6 Torr) quartz tube (Wilmad Glass Co.) or in a back-filled (Argon or Nitrogen) tube. Following sterilization (2.3-3.2 MRad, Co60), one group of sealed samples was placed in an oven at 75°C, and the open samples were stored at 23°C. After one year, annealed/stabilized samples were opened to air and maintained at 23°C for subsequent measurements. Free radical measurements were conducted using an electron spin resonance (ESR) spectrometer (Varian E-4 or Bruker EMX 300).
REFERENCES:
1. M.S.Jahan, C.Wang, G.Schwartz, J.A.Davidson, J. Biomed. Mater. Res.,25, 1991.
2. Jahan et al., Proc. Fifth. World Biomate.Cong., p. 298, 1996.
3. D. S. Sun and C. Stark, U. S. Patent No. 414,049, May 1995.

ACKNOWLEDGMENTS:
Work supported in part by the NSF/Industry/University Cooperative Research Center for Biosurfaces (IUCB) at the University of Memphis, and by Wright Medical Technology, Inc. and Smith & Nephew.
Review score for abstract #129:
Comments:

Topic #9 - Advanced materials, biomaterials
#001
Radiation-cured polymeric nanocomposites of enhanced surface-mechanical properties

F. Bauer, H.-J. Gläsel, E. Hartmann, R. Mehnert, A. Tauber. Institut für Oberflächenmodifizierung (IOM), Permoserstr. 15, D-04318 Leipzig, Germany

Abstract

Though polymerisation-active metallo-organic nanoparticles have proven exceedingly efficient in modifying the viscoelastic properties of UV and EB crosslinked polymeric nanocomposites, they are obviously unsuitable for practical applications. Rather, it seems more appropriate to impart polymerisation-activity on inorganic nanoparticles, e.g. silica and alumina, by grafting of functionalized trialkoxysilanes. The acid catalysed grafting reaction between surface hydroxyl groups and the silanol groups of the hydrolysed trialkoxysilanes results in covalent-bonded, hydrolysis-stable surface compounds. Their siloxane structure was elucidated by infrared, multinuclear MAS NMR and MALDI-TOF mass spectroscopy and a core-shell nanocapsule model was proposed. The hydrophobic polysiloxane shell formed around the inorganic nanoparticle is of major importance to the rheological behaviour of the nanodispersion with implication to the coating technology. The high content of inorganics and the crosslinks to the polymer after curing yield nanocomposite materials with improved properties, e.g. an increased modulus and heat resistance as well as reduced gas permeability. In particular, an improved scratch and abrasion resistance makes nanocomposite formulation very promising as coatings for technical applications.
Review score for abstract #001:
Comments:

#091
PVDF MULTIFILAMENT YARNS GRAFTED WITH POLYSTYRENE INDUCED BY g-IRRADITION : INFLUENCE OF THE GRAFTING PARAMETERS ON THE MECHANICAL PROPERTIES

P. Marmey , M.C. Porté, C . Baquey. INSERM U. 443, "Biomatériaux et Répartion Tissulaire", Université Victor Segalen Bordeaux 2, 146, rue Léo-Saignat, 33076 Bordeaux cedex, France.

There is great interest in developing an alternative prosthesis material because the successful substitution of small diameter arteries (Ø < 5 mm) by Polyester (PET) and Expanded Teflon (PTFEe) vascular grafts has not been achieved in humans. To this end, we have chosen to work with new biomaterial, multifilament yarns, from polyvinylidene fluoride (PVDF) which present suitable mechanical properties, i. e., lower tensile modulus than PET and PTFEe. We propose to modify its surface with "heparin-like" treatment and then modify its level of thrombogenicity [1]. A four steps method is necessary to make this "heparin-like" surface transformation [2]. The first step consist in grafting polystyrene (PS) on the PVDF surface after g irradiation. The purpose of this study was to evaluate the influence of the grafting parameters on the mechanical properties, (i) g-rays irradiation time and (ii) grafting time of styrene, witch polymerise in polystyrene from the PVDF surface.
This work has been carried out on commercial PVDF multifilament yarns provided from a spannish company : Polisilk SA (Manresa – Barcelona). We have investigated the size evolution with microscopies (optical, SEM and TEM). The young modulus and the fracture toughness variations with this treatment were studied with tensile test. The same samples were characterised by Differential Scanning Calorimetry (DSC), FTIR and XPS as well.
As expected, these analyses showed a weak influence on the Young modulus [3] for irradiation dose up to 100 kGy, but, a strong influence on the fracture toughness which increases up to 30 kGy dose due to cross-linking effect and fall down drastically for upper doses due to chain scissions.
These results allow us to investigate the yarns surface morphology, the chemical compositon of the polymers and to define the "ideal" grafting parameters (doses, time) in order to preserve biomaterial mechanical properties.
Future prospects are (i) preparation of tubular knitted yarns, (ii) mechanical behavior on dynamic flow tests and (iii) biomechanical in vivo tests.

References :

[1] C. Fougnot, J. Jozefonvicz, M. Samama, L. Bara, Ann. Biomed. Eng. 7, 429-439 (1979).
[2] M. C. Porte-Durrieu, C. Aymes-Chodur, N. Betz, C. Baquey, J Biomed Mater Res. 52, 117-119 (2000).
[3] J. Scheirs, Modern Fluoropolymers : High Performance Polymers for Diverse Applications, Scheirs, J. Ed. New York : Wiley (1997).
Review score for abstract #091:
Comments:

#098
RADIATION DEPOLYMERIZATION OF CHITOSAN TO PREPARE OLIGOMERS

Le HAI(1), Nguyen Quoc Hien(1) ,Tran Bang DIEP(2), NAOTSUGU Nagasawa(3), FUMIO Yoshii(4) and TAMIKAZU Kume(4) Nuclear Research Institute, VAEC, Vietnam. Institute for Nuclear Science and Technique, VAEC, Vietnam. Department of Biological and chemical engineering, faculty of engineering, Gunma University, 1-5-1 Tenjin-cho, Kiryu, Gunma 376- 8518, Japan. Takasaki Radiation Chemistry Research Establishment, JAERI, 1233 Watanuki, Takasaki, Gunma, 370-1292, Japan

Abstract

Radiation depolymerization of chitosan was carried out by gamma irradiation in solid state. The radiation yield of depolymerization, determined by GPC, are Gd= 0.94 in poor air and crosslinking yield is negligible. The absorbance at 255 and 290nm increased with irradiation dose. Irradiated chitosans were separated into various fractions with different low molecular weights by using methanol-water and acetone as the solvents. Due to differences in solubility revealed upon dialysis, extracts became subdivided into precipitates and soluble fractions. The separation yield of the second fraction decreased and that of the third fraction increased with the irradiation dose. The oligomer was obtained in the third fraction appeared two peaks 63.31oC (176.03j/g) and 137oC(29.60j/g), determined by DSC. The biological effect of oligomers in each fraction was evaluated, the preliminarily results showed the oligomer in the second fraction (Mw 2.104) inhibited the growth of fungi at 80ppm and that in the third fraction (Mw 800) only enhanced the growth of the same typical fungi even at 300ppm. Several results on utilization of radiation depolymerization of chitosan in agriculture and medicine were also summarized.
Review score for abstract #098:
Comments:

#130
DIFFERENTIAL CELL BEHAVIOR ON POLYMER SURFACES MODIFIED BY COLD PLASMAS AND ION BEAM IRRADIATION

C. Satriano (1), S. Carnazza (2), S. Guglielmino (2) and G. Marletta (1). (1) Dipartimento di Scienze Chimiche, Università di Catania, Viale Andrea Doria, 6, 95125 Catania, Italy. (2) Dipartimento di Scienze Microbiologiche, Genetiche e Molecolari, Università di Messina, Salita Sperone, 31, Vill. S.Agata, 98166 Messina, Italy.

The paper reports evidence of the very unusual differential cell sensitivity towards compositionally similar surfaces obtained by using two different irradiation-based treatments, i.e., cold plasmas and low energy ion beams. In particular, we studied the adhesion, proliferation and spreading of fibroblast cells onto poly(hydroxymethylsiloxane) (PHMS) and poly(ethyleneterephthalate) (PET) surfaces treated either by O2-plasma (and subsequently aged in air or water), or by low-energy Ar+-irradiation. The cell response, evaluated by means of Optical Microscopy and Epifluorescence Microscopy, is discussed with respect to the radiation-induced changes of surface chemical structure and physical properties, investigated by means of X-Ray Photoelectron Spectroscopy, Surface Free Energy measurements and Atomic Force Microscopy. It turns out that the biological response cannot be directly and univocally related to the commonly invoked biocompatibility factors as hydrophilic character, composition, polarity, morphology of the modified surfaces. The differential cell-substrate interaction is rather interpreted in terms of the complex interplay between wettability and electronic structure of the different types of altered layers, those characteristic of the ion-induced collision cascades leading respectively to the formation of a very peculiar ion mixed SiCyOx(Hz) phase for PHMS and of hydrogenated amorphous carbon phases for PET, and those due to the plasma treatment, producing an almost pure amorphous SiO2-like phase for PHMS and different oxidized carbon-containing species for PET. The diversity among the cell response to the different Si- and C-based surfaces will be discussed in terms of the biological parameters.
Review score for abstract #130:
Comments:

#131
ESR STUDY OF CHARGE TRAPPING IN IRRADIATED FROZEN SOLUTIONS OF POLY(PHENYLENE VINYLENES)

A.A. Zezin1, V.I. Feldman1,2, J.M. Warman3, J. Wildeman4 and G. Hadziioannou4 1Institute of Synthetic Polymeric Materials of RAS, 70 Profsoyuznaya Str. Moscow 117393 Russia. 2Karpov Institute of Physical Chemistry, 10 Vorontsovo Pole Str., Moscow 103064 Russia. 3IRI, Delft University of Technology, Mekelweg 15, 2629 JB Delft, The Netherlands. 4Department of Polymer Chemistry and Materials Science Centre, University of Groningen,
Nijenborgh 4, 9747 AG Groningen, The Netherlands

Substituted poly(phenylene vinylenes) (PPV), a new group of "conducting" conjugated polymers, has attracted considerable interest for various potential applications. The main advantage of these polymers results from their solubility in organic solvents, which strongly facilitates their processing. The key basic question is concerned with the nature and mobility of principal charge carriers in such polymers and the role of intrachain and interchain transport. Recent TRMC studies revealed high mobility of both electrons and holes along the isolated PPV chains in dilute benzene solution [1]. EPR spectroscopy is a valuable tool to probe the very nature of the distribution of excess electron or hole on a conjugated chain. Previous ESR experiments provided evidence for extensive delocalisation of electrons in negatively charged species in PPV solutions and cast films [2, 3]. Meanwhile, little is known about positive hole delocalisation and trapping on the PPV molecules.
In this work we have examined the structure of trapped hole in dilute glassy solutions of oligomers and polymers of alkoxy PPV derivatives irradiated at 77 K in the presence of electron scavengers. It was found that the linewidth of a singlet ESR signal resulting from trapped holes (radical cations) decreased with increasing the chain length in oligomers containing 2 to 6 vinylene phenylene units. This result implies extensive positive charge and spin delocalisation over isolated conjugated chain. Extrapolated length of positive hole delocalization on the MEH-PPV macromolecules was estimated to be of the order of 10 nm. This extensive delocalization indicates electron coupling between units is quite strong, which is consistent qualitatively with high hole mobility on isolated chains found in the TRMC studies.

References
[1] R. Hoofman, M. de Haas, L. Siebbeles and J.M.Warman, Nature 392 (1998) 54.
[2] R. Schenk, M Ehremfreund, W. Huber and K Mulen, J. Chem. Soc., Chem. Commun. (1990) 1673.
[3] S. Kuroda, K. Marimoto, H. Ito, N. Greenham, R. Friend, Y. Shimoi and S.Abe,
Chem. Phys. Lett. 325 (2000) 183.
The work was supported by the Russian Foundation for Basic Research
(grant _ 00-03-33115a)
Review score for abstract #131:
Comments:

#132
ESR STUDY OF CHARGE TRAPPING IN IRRADIATED FROZEN SOLUTIONS OF POLY(PHENYLENE VINYLENES)

A.A. Zezin1, V.I. Feldman1,2, J.M. Warman3, J. Wildeman4 and G. Hadziioannou4 1Institute of Synthetic Polymeric Materials of RAS, 70 Profsoyuznaya Str. Moscow 117393 Russia. 2Karpov Institute of Physical Chemistry, 10 Vorontsovo Pole Str., Moscow 103064 Russia. 3IRI, Delft University of Technology, Mekelweg 15, 2629 JB Delft, The Netherlands. 4Department of Polymer Chemistry and Materials Science Centre, University of Groningen,
Nijenborgh 4, 9747 AG Groningen, The Netherlands

Substituted poly(phenylene vinylenes) (PPV), a new group of "conducting" conjugated polymers, has attracted considerable interest for various potential applications. The main advantage of these polymers results from their solubility in organic solvents, which strongly facilitates their processing. The key basic question is concerned with the nature and mobility of principal charge carriers in such polymers and the role of intrachain and interchain transport. Recent TRMC studies revealed high mobility of both electrons and holes along the isolated PPV chains in dilute benzene solution [1]. EPR spectroscopy is a valuable tool to probe the very nature of the distribution of excess electron or hole on a conjugated chain. Previous ESR experiments provided evidence for extensive delocalisation of electrons in negatively charged species in PPV solutions and cast films [2, 3]. Meanwhile, little is known about positive hole delocalisation and trapping on the PPV molecules.
In this work we have examined the structure of trapped hole in dilute glassy solutions of oligomers and polymers of alkoxy PPV derivatives irradiated at 77 K in the presence of electron scavengers. It was found that the linewidth of a singlet ESR signal resulting from trapped holes (radical cations) decreased with increasing the chain length in oligomers containing 2 to 6 vinylene phenylene units. This result implies extensive positive charge and spin delocalisation over isolated conjugated chain. Extrapolated length of positive hole delocalization on the MEH-PPV macromolecules was estimated to be of the order of 10 nm. This extensive delocalization indicates electron coupling between units is quite strong, which is consistent qualitatively with high hole mobility on isolated chains found in the TRMC studies.

References
[1] R. Hoofman, M. de Haas, L. Siebbeles and J.M.Warman, Nature 392 (1998) 54.
[2] R. Schenk, M Ehremfreund, W. Huber and K Mulen, J. Chem. Soc., Chem. Commun. (1990) 1673.
[3] S. Kuroda, K. Marimoto, H. Ito, N. Greenham, R. Friend, Y. Shimoi and S.Abe,
Chem. Phys. Lett. 325 (2000) 183.
The work was supported by the Russian Foundation for Basic Research
(grant _ 00-03-33115a)
Review score for abstract #132:
Comments:

Topic #10 - Radiation curing
#019
NEW ELECTRON BEAM FACILITY FOR R&D AND PRODUCTION AT ACSION INDUSTRIES

V.J. Lopata, J.W. Barnard, T. M. Stepanik and C.B. Saunders, Acsion Industries Inc., Pinawa, Canada

 ABSTRACT

Since its incorporation in 1998, Acsion Industries Inc. has been working with clients to develop the industrial use of electron beam (EB) technology for improving products or industrial processes. Acsion has promoted this technology for treating wood pulp in the viscose/rayon process, for reducing pathogens in food, agricultural products and mail, and for curing advanced composites for the aerospace industry. As a result of significant developments in its composite repair programs, Acsion has recently made major modifications to its facilities to increase its production and R&D capabilities. This paper describes these modifications.

KEY WORDS: EB Facility, EB Processing, Curing, Radiation

Review score for abstract #019:
Comments:

#031
Direct Initiation of the Photopolymerization of Acrylates by Short-Wavelength Excimer UV Radiation

T. Scherzer, W. Knolle, S. Naumov, R. Mehnert. Institut für Oberflächenmodifizierung e.V., Permoserstr. 15, D-04318 Leipzig, Germany

Generally, the photopolymerization of functionalized monomers and oligomers requires the addi-tion of one or several photoinitiators to the formulation which serve for the initiation of the po-ly-me-ri-za-tion reaction. The absorption of the incident pho-tons by the photoinitiator leads to an elec-tro-nic excitation of the molecule, followed by the generation of initiating spe-cies from the ex-cited states with a high yield.
The introduction of excimer lamps as monochromatic UV sources with intense short-wave-length emis-sion opens up new possibilities for the init-iation of the photopolymerization of acrylates. Like most other organic compounds, acrylates strongly ab-sorb ra-diation with a wavelength shor-ter than about 220 to 240 nm. Therefore, acrylate molecules can be directly excited when they are exposed to -excimer UV radiation, e.g. from a KrCl* lamp with an emission at 222 nm, and initiation of the pho--to-poly-meri-za-tion of ac-rylates without the need of a photo-init-iator becomes possible.
Real-time FTIR-ATR spectroscopy was used to study the reactivity of various ac-rylates. In par-ti-cular, the influence of the molecular structure of the acrylates and their extinction co-ef-ficient at the wave-length of irradiation was investigated. The depth of cure profile was determined from the pe-ne-tration of the UV radiation into the acrylate layers. In some highly absorbing aromatic ac-ryl-ates, the depth of cure only reaches some hundred nanometres whereas aliphatic acrylates can be cured up to a thickness of several microns. Since the radical yield is low, pho-to-poly-me-ri-zation with--out pho-toinitiator has to be performed in an inert atmosphere.
In order to propose a possible me-cha-nism of initiation, laser photolysis experiments were performed. Additionally, quantum chemical calculations were carried out to assist the interpretation of the photolysis data. For all acrylates studied, direct excitation of acrylates at 222 nm first leads to the formation of a triplet state which is highly localized at the vinyl double bond (not at the carbonyl group as one would expect). Further possible reaction channels of the triplet state like inter- and intramolecular hydrogen trans-fer and biradical formation as well as the addition step have been in-ve-sti-gated. Results will be discussed in the presentation.
Review score for abstract #031:
Comments:

#145
REAL TIME IN-SITU SPECTROSCOPIC CHARACTERIZATION OF RADIATION INDUCED CATIONIC POLYMERIZATION OF GLYCIDYL ETHERS

Matteo Mascioni(1), James M. Sands(2) ,Giuseppe R. Palmese*(1). (1) Department of Chemical Engineering, Drexel University, Philadelphia, PA 19104, (2) U.S. Army Research Laboratory, Aberdeen Proving Ground, MD 21005

Radiation curable polymeric materials for composites offer a wide range of advantages over traditional thermally cured systems, including, low energy consumption and reduced manufacturing costs. However, such materials suffer from relatively poor mechanical properties. Moreover, the curing behavior of such systems (i.e. the exact relationship between chemical kinetics and key processing variables) is not fully understood. In order to design improved epoxy based electron beam (EB) curable systems, and in order to develop appropriate process models, a detailed knowledge of the kinetics of epoxy cationic polymerization induced by UV or EB irradiation is required. In this work, we present our development of a technique based on near infrared (NIR) spectroscopy for performing real-time in-situ kinetic analysis of radiation induced cationic polymerization of epoxy systems including phenyl glycidyl ether (PGE) and diglycidyl ether of bisphenol A (DGEBA). To our knowledge this is the first time such data have been collected for EB induced polymerization. A model was developed to describe the intrinsic chemical kinetics and the diffusion limitations for crosslinkable systems and to relate the cure behavior to processing variables. The model is based on intrinsic rate expressions and free volume theory. The modeling results show very good agreement with experimental data. Thus the model provides predictive capability for the dependence of chemical conversion on time, temperature, composition and radiation intensity.

KEYWORDS: e-beam, cationic polymerization, diffusion, chemical kinetics, epoxy, UV
* corresponding author
Review score for abstract #145:
Comments:

Topic #11 - Polymers in space environment
#024
Wasteless electron - beam technology for manufacturing prepregs .

V.P. Laricheva, A. F. Korotkiy, V.V. Krayushkin, V.P. Pleshanov Obninsk Branch, State Research Center "Karpov Institute of Physical Chemistry’, 249033 Obninsk, Kaluga Region, Russia

A principally new scheme of ecological soundness technology of radiation–chemical prepreg has been developed in the Branch of State Research Center of Karpov Institute of Physical Chemistry. In this case the electron accelerators (400-700 kV) are used. By contrast to a traditional thermochemical method of prepreg manufacturing by evaporation of 95 % solvents manufacturing from filler surface impregnated with the solutions of solid binders the radiation –chemical techniques is proposed in which prepregs are produced by partial radiation polymerization of complex binders specially workout for this purpose on the base of oligomers .

In order to produce the prepregs by this technique one can use liquid oligomers and eliminate solvents. The developed complex binders are cured via 2 stages. The first stage being initiated by electron beam, and the second stage being initiated by heat.

For the industrial manufacturing of the prepregs the technological line differs in drying block ( an electron accelerator is used ). The rest equipment is traditional .

The productivity of the line may be achieved 30 m/ min and limited by an impregnating rate.
The electron accelerators used by us (in individual radiation shielding) are expedient for personnel in working with fibrous fillers (twists and filament, in particular ) .It should be noted that radiation chemical technique is especially applicable in manufacturing unidirectional band prepregs as the strong bonds between discrete twists and filaments are formed in this case. This is impossible in thermochemical techniques.

The distinguished feature of the radiation –prepregs is high viability (from 2 till 24
months). The radiation –prepregs are reprocessed by known standard methods: winding, autoclave molding , pressing at 120 – 220 º C ( depending on the binder composition ) .
The composites on the base of the radiation –prepregs are more superior than the composites on the base of thermochemical prepregs in physico-mechanical properties and thermostability (softening temperature 260º C ) ..

Table 1 gives comparison between physico-mechanical properties of the composites based on radiation- and thermochemical prepregs. The filler and epoxy oligomers were the same in both cases. The epoxy oligomer used in the second process was modified.

Table 1. Physic-mechanical properties of carbonaceous plastics

Properties Composite based on radiation prepare
Composite based on thermochemical prepreg
Density, g/cm3 1.52 1.5
Tensile strength, MPa 984 700
Modulus of elasticity in tension, GPa 221 140
Strength in interlayer shear, MPa 70 55
Compressive strength, MPa 1050 700

As follows from the Table, physico-chemical characteristics of the composites based on radiation prepregs are higher than those of thermochemically produced materials.

To accomplish the second process, the authors recommend special binders (MiALL) , which transform in to copolymers under irradiation. The binders were used to obtain a carbonaceous plastic with a glass transition temperature 259º C by the method of winding during radiation curing (Table 2).

Table 2 Physico-mechanical characteristics of carbonaceous plastic YKH-P/500+MiALL

Properties
Values
Density, g/cm3 1.5
Glass transition temperature, &Mac176;C 259
Tensile strength, MPa 1470
Strength in interlayer shear, MPa 57

The newly developed composites have a higher radiation resistance.
Review score for abstract #024:
Comments:

#076
MEASUREMENT OF CHARGE STORAGE AND LEAKAGE IN POLYIMIDES

A. R. Frederickson1, C. E. Benson1, J. F. Bockman2. 1California Institute of Technology, Jet Propulsion Laboratory, 5800 Oak Grove Drive, Pasadena, CA 91109. 2NASA Langley Research Center, Langley, VA

Resistivity and electric charge storage properties of LaRC-SI and Kapton polyimide samples were studied in a dark evacuated environment, both before and after 5-megarad cobalt-60 gamma irradiation. The data is intended for application to spacecraft insulators that may experience charging induced by space radiations. A "new" measurement method is developed. Effects with both copper and aluminum electrodes were examined. In different tests, slow electrons, and 4-keV electrons were used to charge surfaces of 50-micron polyimide to about 500 volts while the opposite surfaces were metalized and grounded. The subsequent decay of surface voltage can be interpreted as a current through the resistivity of the dielectric. The same samples tested by classical ASTM and IEC methods [1,2] provided resistivities of order 1E16 ohm-cm, but when tested by our evacuated charge decay method the resistivity was 5E19 to 5E20 ohm cm or more. Charging with low energy electrons produced resistivity data reasonably similar to that produced by charging with 4-keV electron beams. The gamma irradiation, followed by one month of rest under no bias, reduced the resistivity by a factor of _ in both materials. Raising temperature from the normal 20C to 50C reduced the resistivity in Kapton, but the reduction was not observable in the LaRC-SI material. Even after twenty days of "constant-bias" the rate of fractional charge loss continued to decline indicating that polarization current rather than ideal resistivity was the cause of most voltage decay, and that the true resistivity is higher than the values determined here, and much higher by several orders of magnitude than the values [3,4] determined in classical ASTM and IEC test procedures. The effects of electron beams at 20 keV were also briefly studied. Under electron beams the LaRC-SI material was considerably less leaky than was Kapton, and the LaRC-SI produced fewer discharge pulses than did the Kapton.

[1] ASTM D 257-99, Standard Test Methods for DC Resistance or Conductance of Insulating Materials, (1999)
[2] IEC 93, International Electrotechnical Commission Publication 93, Methods of Test for Volume Resistivity and Surface Resistivity of Solid Electrical Insulating Materials, Second Edition, 1980.
[3] W. Tillar Shugg, Handbook of Electrical and Electronic Insulating Materials, 2nd Ed.
[4] The Guide to Plastics by the Editors of Modern Plastics Encyclopedia, McGraw Hill, Inc., N.Y., 1970.

Most of this work was performed at the California Institute of Technology, Jet Propulsion Laboratory as part of a program managed at NASA Langley Research Center, and under contract with NASA.
Review score for abstract #076:
Comments:

#137
RADIATION INDUCED DEGRADATION IN PET

M. Chipara, C. Foster, L. Constantinescu(2), K. Murray, C. Secu (2), M. D. Chipara, B. Constantinescu (3) Indiana University Cyclotron Facility, Bloomington, Indiana, IN 47403, USA. 1 Faculty of Physics, University of Bucharest, Romania. 2 National Institute For Materials Physics, Magurele, Bucharest, Romania. 3 Institute of Physics and Nuclear Engineering, Magurele, Bucharest, Romania.

Polyethyleneterephtalate (PET or Melinex) is frequently used for space applications, due to its physical and chemical properties such as high glass and melting transition temperatures, very low absorption coefficient in UV-Vis, good mechanical properties, and high stability towards oxidative and/or thermo-oxidative processes. It is well established [1] that the effect of space environment on polymers is dominated by radiation-induced modifications due to high-energy protons. Protons are the main component of galactic cosmic rays (90%, energies above 10 MeV), solar wind (95% with energies of about 1 keV), solar flares (95% with energies up to 30 MeV), and radiation belts (about 90%, energies up to 50 MeV). We report on a detailed study of physical and chemical modifications induced in PET by various ionizing radiations (gamma rays, electrons, neutrons, protons, and accelerated ions), performed by using Differential Scanning Calorimetry (DSC), Electron Spin Resonance (ESR) and dc electrical measurements (DCEC) and x-ray diffraction (XRD). The contribution aims at a better understanding of fundamental mechanisms responsible for the degradation of PET in outer space. A particular attention is paid to the effect of proton beams on PET and to the universal features of PET degradation. A stack of thin PET foils (thickness of about 100 mm), spaced by Lucite spacers, was irradiated in air, at room temperature, with protons accelerated up to about 202.6 MeV, up to a fluence of 1014 protons/cm2. The dependence of the concentration of free radicals on the energy deposited within each layer was investigated by using an ESR spectrometer, operating in X band (ª9 GHz). The changes in the numerical average molecular mass, induced by irradiation, affect the glass and melting temperature. The glass and melting transition temperatures of PET (estimated by DSC) are depressed by irradiation, indicating dominant scission reactions. In the initial stage of irradiation, a short increase in the glass transition temperature was observed (gamma irradiation) and ascribed to unreacted catalysts residues. At large deposited energies within the target, cross-linking contributions were observed in both proton and gamma irradiated PET. This effect is assigned to a local heating of the irradiated polymer above its glass transition temperature. The effect of irradiation with gamma rays and accelerated protons on PET conductivity is reported.

References

[1] Nuclear and Space Radiation Effects on Materials, NASA SP 8053 (1970).
Review score for abstract #137:
Comments:

Topic #12 - Other
#056
HYDROGELS OF POLYSACCHARIDE DERIVATIVES CROSSLINKED WITH IRRADIATION AT PASTE-LIKE CONDITION

F. Yoshii(1), R. A. Wach(2), N. Nagasawa(1), H. Mitomo(2) and T. Kume(1) 1Takasaki Radiation Chemistry Research Establishment, JAERI, 1233 Watanuki-machi, Takasaki, Gunma 370-1292, Japan 2Faculty of Engineering, Gunma University, 1-5-1 Tenjin-chou, Kiryu, Gunma 376-8515, Japan

It is well known that polysaccharides such as cellulose, starch and their derivatives in solid state and aqueous solution undergo degradation under action of ionizing radiation. Polysaccharide derivatives such as carboxymethylcellulose (CMC), methylcellulose, carboxymethylstarch (CMS) and carboxymethylchitin/chitosan were irradiated at very concentrated aqueous solution (more than 10%, paste-like state) resulted in formation of crosslinking structure. It was proved that the crosslinking was remarkably affected by degree of substitution (DS) of these derivatives and their concentration. It was apparent that high DS, 2.2 for CMC and high concentration of 50 to 60% for CMC and CMS are favorable for higher yield of gels. It is assumed that radiation formation of hydrogels of polysaccharide derivatives are due to the mobility of side chains. Side-chains radicals are formed mostly via indirect effects, by the abstraction of H atoms by the intermediate products of water radiolysis.
Degradability of the polysaccharide hydrogels were evaluated by weight reduction in the enzymatic test and measurement of carbon dioxide produced during biodegradation in the natural environment. It was found that biodegradation of crosslinked carboxymethylstarch was faster than derivatives of cellulose. However, all crosslinked derivatives of starch and cellulose still underwent biodegradation.
Review score for abstract #056:
Comments:

#060
Modification of Biodegradable Polymers by Radiation Crosslinking Technique with PFM

F. Yoshii1), M. Suhartini2), N. Nagasawa1), H. Mitomo2) and T. Kume1) Takasaki Radiation Chemistry Research Establishment, JAERI. 1233 Watanuki-machi, Takasaki-shi, Gunma-ken, 370-1292 Japan (1), Faculty of Engineering, Gunma University, Kiryuu, 376-Japan (2)

Aliphatic polyester such as poly(É&Mac195;-caploractone), (PCL), poly(butylenes succinate), (PBS) and poly(lactic acid), (PLA) converts to water and carbon dioxide by degradation under action of microorganism in soil. These polymers are so-called environmentally friendly polymers. However, their mechanical properties as deformation and melting resistance are diminished by contact with hot water (more than 70Åé), hence improvement of their heat stability is desired. We have attempted to radiation crosslinking of aliphatic polyester in the presence of polyfunctional monomers (PFM), of low concentration (less than 1%).
It was found that triallylisocyanurate (TAIC) and trimethallylisosyanulate (TMAIC) are effective for crosslinking of these polymers, even at concentration less than 1% and allow achieving gel fraction of 80% with dose of 50 kGy. Other PFM such as acrylate and methacrylate are not so effective, it was found that to obtain 80% of gel fraction of polymers under investigation about 5% of such PFM is necessary.
Crosslinked PCL with 1% of TMAIC exhibits much higher resistance to heat treatment (e.g. it does not undergo deformation even at 80Åé), and PBS crosslinked with TAIC is durable at autoclave sterilization temperature over 30 min. Crosslinked PLA does not deform at temperature higher than 50 to 60Åé over its glass temperature. This behavior was obtained by radiation crosslinking of PLA at present of 1% of TAIC.
It was pointed out that biodegradability evaluated by enzymatic and soil burial test of crosslinked polymers is slightly retarded, however they are effective destructed with a little smaller rate.
Review score for abstract #060:
Comments:

#036
PROPERTIES OF ION TRANSPORT THROUGH ASYMMETRIC NANOPORES PREPARED BY THE TRACK-ETCHING TECHNIQUE

Z. Siwy(1)(2), P. Apel(3), D. Dobrev(1), R. Neumann(1), R. Spohr(1), C. Trautmann(1), K. Voss(1). (1) Gesellschaft fuer Schwerionenforschung (GSI), Planckstr. 1, D-64291 Darmstadt, Germany. (2) Silesian University of Technology, Strzody 9, 44-100 Gliwice, Poland. (3) Flerov Laboratory of Nuclear Reactions, JINR, 141980 Dubna, Russia.

Ion-track etching is a widely used technique to prepare membranes with pores of diameters between tens of nanometers and several micrometers, offering high homogeneity of the pore diameter. Recently, a new etching technique has been developed, which enables the production of asymmetrically shaped nanopores in polymeric membranes irradiated with heavy ions [1, 2]. Asymmetric pores offer higher fluxes of transported media than cylindrical pores because their flow and electrical resistance is dominated by the narrow tip aperture. The crucial step in the preparation of conical pores is to apply the etchant only on one side of the membrane while the other side is in contact with a stopping solution [1]. The etching process is performed in a conductivity cell, where the electrical current is monitored.
We have irradiated polyethylene terephthalate (PET) (Hoechst, RN12) and polyimide (Kapton H, DuPont) foils with single heavy ions of several hundred MeV energy at the linear accelerator of GSI. Subsequently, PET membranes were etched in sodium hydroxide, and Kapton membranes in sodium hypochlorite. To obtain asymmetric pores with several nanometer opening diameter the etching process has to be stopped directly after the breakthrough occurs. With NaOCl as etchant, we used a solution of potassium iodide as stopping medium [2]. When the etching of the pore is completed, the iodide ions reduce OCl- to Cl- ions. The diameter of the small opening of the pore was tailored down to several nanometers. The transport properties of the pores obtained in this way were examined by current-voltage characteristics and ion-current time series. We show that the pores in both materials are effective ion-current rectifiers with the preferential direction of ion current flow from the narrow entrance towards the wide opening of the pore. The nanopore in PET produces voltage-dependent ion current fluctuations, with the kinetics of openings and closings similar to voltage-gated ion channels in biological membranes [3]. In contrast to this behaviour, the ion current through a polyimide nanopore is stable in the entire examined range of voltages. The origin of the rectification as well as the fluctuations of the ion current in time will be discussed in relation to the chemical structure of the membranes, effects of heavy-ion irradiation on the polymeric materials as well as chemical etching. We will also show that the studies can shed new light on the phenomenon of voltage-gating in biological systems.
References
[1] P. Apel, Y.E. Korchev, Z. Siwy, R. Spohr, M. Yoshida, Nucl. Instrum Meth. B 184, 337 (2001).
[2] Z. Siwy, D. Dobrev, R. Neumann, C. Trautmann, K. Voss, German and US patent, registration on 26.02.2002, nr 102 08 023.2, Verfahren zur Herstellung von Nanostrukturen in Membranen und Asymmetrische Membran.
[3] Z. Siwy, Y.Gu, H.A. Spohr, D. Baur, A. Wolf-Reber, R. Spohr, P. Apel, Y.E. Korchev, Rectification and Voltage Gating of Ion Currents in a Nanofabricated Pore, submitted to Angewandte Chemie, Int. Ed.
Review score for abstract #036:
Comments:

#037
RADIATION CROSSLINKING OF POLY(VINYL CHLORIDE) USED FOR WIRE AND CABLE INSULATIONS

F. Naimian. Gamma Irradiation Center, Atomic Energy Organization of Iran P. O. Box 11365-8486, Tehran, I. R. Iran

An investigation has been carried out into the effect of irradiation dose and the amount of the crosslinking-agent (sensitizer) on the radiation crosslinking of a dioctyi phthalate (DOP) plasticized PVC compound. In radiation-crosslinking process many properties of wire and cable insulations such as mechnical properties, heat resistance, deformation resistance, solvent resistance etc. are improved [1,2]. The advantage of the irradiation process over the chemical process is that it permits mass production of a wide range of wires with a lower operating cost, smaller space and energy requirement [3]. Our samples were irradiated by 60Co gamma ray at five different radiation doses. Gel content and tensile properties have been studied as a function of dose, before and after irradiation. Within the dose range studied, gel yield increased with increased irradiation dose and sensitizer content but tensile strength decreased at higher irradiation levels, suggesting the formation of a looser network.

References
[1] K. Ueno, I. Uda and S. Tada, J. Radiat. Phys. Chem., 37,N. 1, 89 (1991).

[2] V. K. Sharma, J. Mahajan and P. K. Bhattacharyya, J. Radiat. Phys. Chem., vol.45, No.5, pp 695-701 (1995).

[3] E. Saito, J. Radiat. Phys. Chem., 9, 675 (1977).
Review score for abstract #037:
Comments:

#041
Radiochemical Sterilization

Shalaby W. Shalaby, Ph.D. Poly-Med, Inc. 6309 Highway 187 Anderson, South Carolina 29625 USA

Radiochemical sterilization (RC-S) represents a novel approach to medical device sterilization. It is a hybrid process encompassing the attributes of chemical and high-energy radiation sterilization without the drawbacks associated with the use of the parent processes. It entails the use of a 5 to 7.5 kGy of gamma radiation and a polyformaldehyde insert capable of a radiolytic-controlled release of formaldehyde gas in a hermetically sealed package. The RC-S process has been applied successfully to radiation-sensitive sutures, namely polypropylene monofilaments and absorbable polyglycolide braids.
Review score for abstract #041:
Comments:

#042
EXPERIENCE OF ELECTRON BEAM TREATMENT IN PRODUCTION OF POLYETHYLENE OXIDE GELS PURPOSED FOR MEDICAL APPLICATIONS

Z. AJJI(1), M.Akou(1), V. Auslender(2), A. Gonchar(3), V. Gorbunov(2), V. Serbin(2). (1)Department Atomic Energy Commission of Syria, PTDRT,6091 Damaskus, Syria.. (2)BINP SB RAS, Lavrentev St.11, 630090 Novosibirsk, Russia.. (3)Institute of Cytology and Genetics SB RAS, Koptuga. St. 2, 630090 Novosibirsk, Russia..

Polyethylene oxide (PEO) gels produced by electron beam cross-linking (grafting) are finding the growing application in biotechnology and medicine as matrices (carriers) for enzymes and other biologically active substances and these new preparations are used for treatment of purulent-necrotic processes having various ethyology and localization, even for cleaning carious cavities [1, 2] and for hydrogel wound dressings. The PEO gels are used for production of gel pastes purposed for endoscopy examinations and usage as contact media for ultrasonic diagnostics, electrocardio- and encelography. The viscosity of the gel ought to be chosen according to requirements for the final product made of this gel. The research has shown that under influence of electron beam treatment or braking radiation on aqueous solution of PEO the carbonyl groups are formed due to radiation-chemical oxidation [3, 4]. We have studied the thermorheological properties of PEO gels produced by electron beam crosslinking of PEO solutions. The required viscosity of gels ranges greatly, so we use PEO solutions having the concentrations from 5% up to 60% and molecular weight of PEO from 1500 up to 20000. The electron beam with energy up to 2.5 Mev and power up to 20 kW generated by electron accelerator of ILU-6 type [5] was used as radiation source.

References

[1]Gonchar A. M., Auslender V. L. Radiation Phys. Chem.. 48, 795-797 (1996).
[2] Gonchar A. M., Auslender V. L. Radiation Phys. Chem.. 52, 213-216 (1998).
[3] Pikaev A. K. (1987) Modern radiating chemistry. A firm body and polymers. Applied aspects.
Science, Moscow.
[4] Pikaev A. K. Modern radiating chemistry. Radiolysis of gases and liquids. Science, Moscow. (1986)
[5] Auslender V.L. ILU-type electron accelerators for industrial technologies. Nuclear Instr. and Meth. in Phys. Research, B 89 46-48 (1994).
Review score for abstract #042:
Comments:

#102
LOW-TEMPERATURE EPR INVESTIGATION OF ORGANIC RADICAL CATIONS

W. Knolle, I. Janovsk_, S. Naumov and R. Mehnert. Institut für Oberflächenmodifizierung, Permoserstrasse 15, D-04303 Leipzig, Germany

Radical cations formed during electron beam or g-irradiation of neat monomer solutions were found to play an important role in the initiation of the polymerization process [1]. However, the relatively structureless spectra recorded during pulseradiolysis studies with optical detection did not allow further characterization of the reactive species.
EPR spectroscopy provides a direct inside into the electronic structure of radical cations. A wide variety of methods is now available [2], each with its particular advantages and disadvantages, for generating radical cations in liquid or solid matrix. For compounds with high ionisation energies or when the radical cations are short-lived in liquid solution, gamma- or electron beam irradiation of frozen freon matrices containing the solute is still a matter of choice. Typically a 10-3 M solution of the substrate in the Freon (CF3CCl3, CFCl2CF2Cl, CFCl3) is irradiated with the g-rays of a 60Co source up to a dose of 10 kGy (£ 1 hour). Usually the spectra can be assigned unambiguously to a particular radical or radical cation, but incorrect interpretations are known from the literature due to the fact that intramolecular rearrangements (especially H-shift, ring opening) may proceed even at 77 K (or lower) during the relatively long irradiation time.
The combination of short-time irradiation with a 10 MeV Linac (a dose of 10 kGy in less than 1 minute) with the subsequent EPR measurement at 77K offers the possibility to study some of those previously hidden rearrangement reactions directly. The capability of this combination will be illustrated with a few typical examples choosen from literature (methyl and ethyl formates and acetates, allylamine radical cations), where the proposed transformations are observed directly for the first time.
Similar rearrangment reactions, proceeding at 77K on a time scale of less than an hour, were found during the investigation of radical cations of typical monomers like acrylates [3], methacrylate, methacrylic acid and dihydrofuran. The results will be discussed in detail (e.g. influence of particular freon, solute concentration, transition state geometry) and the essential help of quantum chemical calculations for the identifiying a radical (cation) species will be highlighted.

References

[1] R. Mehnert, S. Naumov, W. Knolle and I. Janovsk_, Macromol. Chem. Phys. 201, 2447-2454 (2000)
[2] A.G. Davies, J. Chem. Res. (S) 253-261 (2001)
[3] W. Knolle, V.I. Feldman, I. Janovsk_, S. Naumov, R. Mehnert, H. Langguth, F.F. Sukhov and A.Yu. Orlov, J. Chem. Soc. Perkin Trans. 2, 687-699 (2002)
Review score for abstract #102:
Comments:

#118
RADIOCHEMICAL AND THERMAL AGEING OF POLYETHYLENE IN CONTACT WITH BITUMEN

L. Audouin(1), L. Secourgeon(2). 1 LTVP ENSAM-Centre de paris, 151 Bdl de l’Hôpital, 75013 Paris, France. 2 CEA/DRT/DTEN, 17 rue des Martyrs, 38074 Grenoble Cedex 9

Bitumization is an interesting way for radioactive waste confinement. Bitumen is highly impermeable to water and this reduces lixiviation. It is non reactive with most of chemicals and its low density is also an advantage compared to cements. It is envisaged to use polyethylene (PE) containers for the packaging of bitumen embedded radioactive wastes. Thus, it appears necessary to study the radiochemical ageing of polyethylene taking into account the bitumen-polyethylene interactions. The aim of this work was to study these interactions. Global kinetics of bitumen diffusion into polyethylene sheets of 5 mm thickness in total immersion have been followed by gravimetry at 115, 105, 95 and 85°C and at ambient temperature. Diffusion displays a pseudo-Fickian character and apparent diffusion coefficients and their apparent activation energy have been determined. Changes of cristallinity (by DSC), mechanical properties (by tensile testing) and residual thermal stability (by TIO) were recorded during more than 7000 hours exposure in bitumen. Relatively small changes of morphology and mechanical properties have been observed. After a weak initial decrease of cristallinity and yield stress due to bitumen absorption (dilution effect), both values stay constant, as well as the strain at break(non modified by bitumen absorption) during the whole exposure time. On the other hand, an important improvement of oxidation and radiochemical stability has been put in evidence. The induction time increased by a factor more than two for the samples containing absorbed bitumen and neither gel point nor lethal dose were achieved even after 200 kGy dose during irradiation at 100 Gy/h dose rate. Mechanisms and practical consequences of the observed phenomena are discussed in this paper.
Review score for abstract #118:
Comments:

#120
Effect of irradiation on the heat resistant properties of ethylene-propylene pure rubber vulcanized

Masayuki Ito. Japan Atomic Energy Research Institute, 2-48-29, Honkomagome, Bunkyo-ku, Tokyo
113-0021 JAPAN

The irradiation under oxidative condition changes the heat resistant properties of elastomers. The article studied the rate constant of scission reaction, the counts of chemiluminescence (CL), and the weight change along with heat aging to obtain the quantitative relationship between the dose and the changes of heat resistant properties.
Ethylene-propylene rubber (EPR) used was commercial grad EP07P obtained from JSR (Japan). The polymer was mixed with 3.0phr of dicumyl peroxide by using mixing roll. Heat press cured the samples. The sheets of EPR cured were irradiated with Co-60 g ray in air at room temperature. The dose rate was 1.0kGy/h.
The rate constant of scission reaction
Chemical stress relaxation of EPR irradiated various dose was measured in air oven kept at the constant temperatures ranged from 80&Mac176;C to 140&Mac176;C. The rate constant of scission reaction of irradiated more than 50kGy was found to be independent on dose and ten times higher than that of non-irradiated.
Chemiluminescence
CL of EPR irradiated at various dose was measured during heat aging under the constant temperatures ranged from 60&Mac176;C to 160&Mac176;C. Irradiation of 2.7kGy increases remarkably the amount of luminescence during heat aging. The counts of CL dose not increase linearly with increasing dose and were found to level off at about 50kGy.
Weight change
EPR irradiated at various dose was aged in air at various temperatures ranged from 90&Mac176;C to 130&Mac176;C. The weight of samples was measured periodically at room temperatures. The weight increases after a certain period of induction time at the early stage of aging. The irradiation of 40kGy decreases the induction time, but there is no significant change, nevertheless dose was increased more than 40kGy.
Conclusion
The results suggest that irradiation consume the antioxidant reagent added during polymer production process by the energy transfer from EPR to the antioxidant reagent. Heat resistant properties decrease remarkably by the consumption of the reagent.
Review score for abstract #120:
Comments:

#121
DETERMINATION OF NON-VOLATILE RADIOLYTIC COMPOUNDS IN ETHYLENE CO-VINYL ALCOHOL

Aparna Kothapalli (1), George Sadler (2). National center for food safety and Technology, IIT 6502 S Archer Rd, Summit -Argo, IL-60501, USA

The use of ionizing radiation on the food contact polymers is increasing due to the critical role of the package in holding or containing the irradiated foods [1]. Irradiation benefits the food if properly applied and the food is pre-packaged prior to irradiation so that it is protected from the subsequent recontamination. The United States Food and Drug Administration has approved the usage of ionizing radiation within the dosage range of 0-60kGy on limited films since the 1960’s [2]. The bottleneck toward approval of new polymers is that FDA fears that these polymers may undergo radiolytic changes during irradiation producing fragments that may migrate into the food causing a serious threat to the ultimate safety of it and in turn the consumer. Ethylene co-vinyl alcohol (EVOH), which is quite often used for the food applications, is not yet approved by the FDA for irradiated foods. The present work examines the non-volatile radiolytic compounds, which may be formed due to the exposure to the gamma irradiation at the dosage levels of 3 & 10 kGy versus non-radiated control. Irradiated EVOH is subjected to extraction with 95% ethanol as the food stimulating solvent for a period of 10 days at 40oC, which models the amount of radiolytic compound a food would extract in 1 year [3]. The food stimulating solvent is then analyzed for the presence of non-volatile compounds using the advanced liquid chromatographic techniques. The chromatograms obtained from different dosages show that radiolytic compounds are not formed in EVOH and it would therefore be in compliance with safety demands of USFDA [4]& [5].

References
[1] G. Sadler, W. Chappas and D. Pierce. Food Additives and Contaminants, 18(6), 475-501 (2001)

[2] USFDA 21CFR 179.45.

[3] USFDA Chemistry requirement for Food contact notification.

[4] http://www.cfsan.fda.gov/~dms/opa-guid.html#ref

[5] http://www.access.gpo.gov/nara/cfr/cfr-table-search.html#page1
Review score for abstract #121:
Comments: