Physical techniques for profiling heterogeneous polymer degradation

Technical Report · Sun Jan 01 00:00:00 EST 1984

OSTI ID:6831438

Clough, R L; Gillen, K T

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

Related Subjects

36 MATERIALS SCIENCE
ELECTRIC CABLES
ELECTRICAL INSULATION
POLYMERS
OXIDATION
VITON
PHYSICAL RADIATION EFFECTS
DENSITY
DOSE RATES
HARDNESS
OXYGEN
POLISHING
SPATIAL DISTRIBUTION
CABLES
CHEMICAL REACTIONS
CONDUCTOR DEVICES
DISTRIBUTION
ELASTOMERS
ELECTRICAL EQUIPMENT
ELEMENTS
EQUIPMENT
MECHANICAL PROPERTIES
NONMETALS
ORGANIC COMPOUNDS
ORGANIC POLYMERS
PHYSICAL PROPERTIES
RADIATION EFFECTS
RUBBERS
SURFACE FINISHING
360405* - Materials- Polymers & Plastics- Degradation & Erosion- (-1987)
360406 - Materials- Polymers & Plastics- Radiation Effects- (-1987)