Heterogeneous oxidative degradation in irradiated polymers

TLDR: In this article, the authors describe the use of several recently developed techniques which are of general use for studying heterogeneous degradation in commercial polymeric materials, including optical evaluation of cross-sectioned, polished samples, cross-sectional profiling of changes in relative hardness, and profiling of density changes.

Abstract: : When polymeric materials are irradiated in the presence of air, oxygen-diffusion effects can, depending upon dose rate, lead to oxidative degradation which occurs only near the edges. This report describes the use of several recently developed techniques which are of general use for studying heterogeneous degradation in commercial polymeric materials. The techniques discussed are: optical evaluation of cross-sectioned, polished samples; cross-sectional profiling of changes in relative hardness; and profiling of density changes. Oxidation penetration depths are given for a number of major polymer types as a function of dose rate. A detailed example is given graphically illustrating the effects of differing oxidative penetration depths on the radiation-degradation behavior of a Viton(R) O-ring material; this particular material becomes hard and brittle when irradiated at high dose rate. but soft and stretchable when irradiated at low dose rates. jg p4