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Processes in Polymer Degradation

المؤلف:  A. Ravve

المصدر:  Principles of Polymer Chemistry

الجزء والصفحة:  643

2026-03-01

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Processes in Polymer Degradation

There are many causes of degradation of polymers. The chief ones among them are heat, oxidation, light, ionic radiation, hydrolysis, and mechanical shear. The effect can be discoloration, loss of molecular weight, cross-linking, or cyclization. The loss of molecular weight can be so severe that the polymer is degraded to a mixture of monomers and oligomers. The other effects can be blackening or charring and loss of useful properties. On the other hand, mechanical shearing is often applied to some polymers like rubbers to deliberately reduce molecular weight for commercial processing. In the environment, synthetic polymers generally degrade due to man-made environmental pollutants in the atmosphere, like carbon monoxide, sulfur dioxide, nitrogen oxide, and oxidizing smog rich in ozone. Molecular weight loss occurs through the breaking of primary valence bonds. Such chain scissions may occur at random points along the polymer backbone or they may take place at the terminal ends of the polymer where monomer units are released successively. This last effect can be compared to unzipping. The response of any particular polymeric material to specific causes of degradation depends upon the chemical structure. This chapter presents the degradation processes in some typical commercial polymers. The materials selected were those that received major attention in the literature.