Radiation Physics and Chemistry (1977)最新文献

Rubber insulated wires are still useful for internal wiring in motor vehicles and electrical equipment because of flexibility and toughness. Irradiated cross-linked rubber materials have been successfully introduced for use with fusible link wire and helically coiled cord.

Radiation-induced oxidative degradation of PVC films using ⁶⁰CO-γ radiation has been investigated at room temperature. Quantitative analyses of evolved gases and oxidative product during irradiation under vacuum conditions and in the presence of oxygen were determined. The G-values of evolved from PVC films irradiated under vacuum were: G(HCl) = 2.3, G(H₂) = 0.18, G(CH₄) = 0.001, G(CO₂) = 0.007, and G(CO) = 0.01 while in the presence of oxygen at an initial pressure of 500 Torr, and the G-values were: G(HCl) = 3.0, G(H₂) = 0.2, G(CH₄) = 0.006, G(CO₂) = 0.09, G(CO) = 0.1, and G(O₂) = 1.5. The evolved gases and oxygen consumption were found to depend on oxygen pressure during irradiation of the PVC films. The intrinsic viscosity of rigid PVC was found to decrease at low doses and then gradually increase at higher ones. This may be due to the oxidative degradation occuring at low doses. On the other hand, crosslinking may be the predominant effect at higher doses. Mechanical properties of irradiated PVC films show that there is no significant change in the tensile strength until 0.6 MGy. Meanwhile, elongation percent increases with dose to reach a maximum at 0.1 MGy, and thereafter it sharply decreases at higher irradiation doses.

ESR spectra of poly(ethyl methacrylate) γ-irradiated in vacuum at different temperatures were studied in different conditions. The change in the relative intensities of the four-and five-line components of the conventional nine-line spectrum is investigated in detail with respect to changes in the absorbed dose, irradiation, and decay temperatures. It is assumed that the propagating radical is the single radical type responsible for thecharacteristic nine-line spectrum. It is also found that a stable minor radical, quite probably of allyl or polyenyl type, giving a weak broad line, also overlaps the four-line component of the nine-line spectrum.

Radiation sterilization of ultrahigh molecular weight polyethylene (UHMW-PE) was recently found to cause changes in crystallinity, contradicting earlier observations on linear polyethylene of lower molecular weight. In this study, UHMW-PE (Hercules 1900) was gamma-irradiated up to 21 Mrad. Changes in melting and crystallization temperatures, enthalpies of melting and of crystallization, determined by differential scanning calorimetry, are reported. In particular, the temperature at the onset of crystallization provided a clearer view of the radiation damage to the polymer chains. A mechanism based on chain scission is proposed to explain the observed increase in crystallinity in agreement with recent findings. The crystallization temperature may be useful as an indicator of radiation and/or other damage to the UHMW-PE.

The theoretical model of the electron localized in frozen ionic solutions has been applied to investigate the influence of the trap distortion on the electron energy levels in the trap. It has been found that asymmetric traps are slightly more shallow than the symmetrical trap. The differences between electron absorption spectra obtained by pulse radiolysis and those by γ-radiolysis are then explained in terms of the relaxation of distorted ionic traps.

The absorption spectra of several perfluorosubstituted aromatic radical anions are compared with the corresponding perhydro compounds in which the various transitions involved have been assigned to those predicted theoretically. The electronic absorption spectra were obtained for pentafluorostyrene, pentafluorobenzaldehyde, pentafluorobenzoic acid, pentafluorobenzonitride, tetrafluorophthalic acid and pentafluoroaniline, by gamma radiolysis in 2-methyltetrahydrofuran at 77 K. A general similarity in the absorption spectra between the perfluorinated and the corresponding perhydro radical anion is observed except for a shift in the absorption band.

UV and EB curing represent complementary technologies with respective advantages and disadvantages. This paper deals with the design and evaluation of UV curable coatings to optimize cure rate and film properties. Topics included are state-of-the-art photoinitiator systems, light intensity effects, retardation of air-inhibition, adhesion, and amplification of photons for enhanced speed of cure.

Secondary emission sources “Laminar Process” allow the extension of the section of the beam in two directions and to control the density of the dose in any place of the beam.

Consequently the dose rate can be modulated and no beam is applied to the support of the window which allows much higher flux and less cooling problems.

This development has pushed us to develop a new type of inerting chamber with low leakage and automatic adaptation to the thickness of the product to be treated.

Recent developments in soft X-ray technology open new possibilities in areas such as surface processing and microscopic examinations of both biological tissues and thin films. These developments, along with the development of a compact, bright laboratory soft X-ray source, make it possible to use soft X-ray technology in individual laboratories and processing facilities. The most promising sources for laboratory applications are baseed on magnetic compression of a gas discharge. Magnetic compression creates a hot dense plasma which is an intense source of soft X-rays in the 100 to 3000 eV range. Applications demonstrated at Maxwell and elsewhere include X-ray lithography, X-ray microscopy, surface annealing, X-ray diffraction and EXAFS.