Physical techniques for profiling heterogeneous polymer degradation
This report describes the application of three complementary techniques for the study of oxidative inhomogeneities in degraded polymeric materials. Samples are mounted in epoxy, cut in cross-section, and polished. Areas of degradation are seen as bands of varying reflectivity when examined microscopically. Further information on gradient shapes may be obtained by profiling relative material hardness. Additional useful information on gradients in oxygen uptake may be obtained using density gradient columns. These techniques, together with solvent extraction, give consistent results. Heterogeneous effects can exert a major influence on polymer degradation. A striking example occurs with Viton. In the absence of oxygen, the material becomes progressively more cross-linked and harder. In the presence of oxygen, the material undergoes scission, and becomes progressively softer. Result is that samples irradiated at high dose rate, where oxidation occurs only near the surface, becomes brittle. Samples irradiated at comparatively lower dose rates, where extensive oxygen permeation occurs, degrade in the opposite way, becoming soft and stretchable. The occurrence of strongly heterogeneous oxidation in samples irradiated at high dose rates is an important consideration in the design of accelerated aging experiments. Even in the absence of oxygen diffusion effects, other herterogeneous mechanisms may significantly impact polymer degradation. An example was given in which the density profiling results showed a material incompatibility problem in which copper poisoning of an EPR cable insulation led to greatly enhanced oxidation adjacent to the copper conductor.
- Research Organization:
- Sandia National Labs., Albuquerque, NM (USA)
- DOE Contract Number:
- AC04-76DP00789
- OSTI ID:
- 6831438
- Report Number(s):
- SAND-83-2171C; ON: DE84013807
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360405* -- Materials-- Polymers & Plastics-- Degradation & Erosion-- (-1987)
360406 -- Materials-- Polymers & Plastics-- Radiation Effects-- (-1987)
CABLES
CHEMICAL REACTIONS
CONDUCTOR DEVICES
DENSITY
DISTRIBUTION
DOSE RATES
ELASTOMERS
ELECTRIC CABLES
ELECTRICAL EQUIPMENT
ELECTRICAL INSULATION
ELEMENTS
EQUIPMENT
HARDNESS
MECHANICAL PROPERTIES
NONMETALS
ORGANIC COMPOUNDS
ORGANIC POLYMERS
OXIDATION
OXYGEN
PHYSICAL PROPERTIES
PHYSICAL RADIATION EFFECTS
POLISHING
POLYMERS
RADIATION EFFECTS
RUBBERS
SPATIAL DISTRIBUTION
SURFACE FINISHING
VITON