Changes in The Optical and Thermal Properties of a CR-39 Polymeric Detector Induced by Very High Doses of γ-Radiation

Effects of γ-radiation on the optical and thermal properties of a poly allyl diglycol carbonate (PADC), a form of CR-39 polymer, have been investigated. CR-39 detectors were exposed to γ-rays at very high doses ranging from 5.0×105 to 3.0×106 Gy. The induced changes were analyzed using ultraviolet-visible spectroscopy (UV-VIS) in absorbance mode, and thermogravimetric analysis (TGA). The UV-visible spectra of the virgin and γ-irradiated CR-39 polymer detectors displayed a significant decreasing trend in their optical energy band gaps for indirect transitions, whereas the direct transition ones showed a little change. This drop in the energy band gap with increasing dose is discussed on the basis of the gamma irradiation induced modifications in the CR-39 polymeric detector. The TGA thermo grams show that the weight loss rate increased with the increase in the dose, which may be due to the disordered system via scission followed by crosslinking in the irradiated polymer detector. The TGA thermo grams also indicated that the CR-39 detector decomposed in three/four stages for the virgin and irradiated samples. The activation energy for thermal decomposition was determined using a type of Arrhenius equation based on the TGA experimental results. The obtained results can be used in radiation dosimetry.