ULTRASONIC CHARACTERIZATION, HARDNESS AND DIELECTRIC-PROPERTIES OF GAMMA-IRRADIATED POLYVINYL-CHLORIDE

The ultrasonic compressional wave velocity (V(L)) and its attenuation (alpha) in unirradiated and gamma-irradiated polyvinyl chloride were m easured using the pulse-echo technique. V(L) and the calculated elasti c modulus were sensitive to the irradiation dose up to 100 Mrad, beyon d which the dose had no effect on such properties, whereas alpha and t he internal friction, Q-1, varied with the irradiation dose up to 300 Mrad. The compression behavior and hardness of polyvinyl chloride samp les subjected to gamma-radiation doses up to 300 Mrad were also examin ed. The compressive yield strength and hardness decreased with the irr adiation dose. Deforming the irradiated samples to some 45% reduction in height, resulted in a slight decrease in hardness. A linear relatio nship between the hardness and the compressive yield strength of polyv inyl chloride was observed. Dielectric measurements of unirradiated an d gamma-irradiated PVC were performed in air at room temperature and 0 .8 V in the frequency range 0.1 - 100 kHz. The analysis of the obtaine d results revealed a semiconductor behavior, primarily based on an ion ic mechanism. The ac and dc conductivities showed maxima and minima at 10 and 100 Mrad, respectively. These behaviors were thoroughly highli ghted and quantitatively interpreted in terms of the structural change s taking place during the irradiation process.