Heterogeneous oxidative degradation in irradiated polymers
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 commerical 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 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. The data presented show examples for several materials where the accelerated age is strongly influenced by environment application (e.g., dose-rate effects), or where the use of an overstress approach (i.e., effectively a large margin in total dose) cannot compensate for the effect of dose-rate. The techniques discussed in this report can aid in the determination of such effects and their magnitude and in the selection of appropriate accelerated aging methods. With such knowledge about material degradation, and with aging methods selected on these data-based approaches, there can be increased assurance that equipment qualification procedures are adequate.
- Research Organization:
- Sandia National Labs., Albuquerque, NM (USA)
- DOE Contract Number:
- AC04-76DP00789
- OSTI ID:
- 6636394
- Report Number(s):
- NUREG/CR-3643; SAND-83-2493; ON: TI84015593
- Country of Publication:
- United States
- Language:
- English
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