Polymer degradation is the loss of the useful properties of a polymer through a chemical or physical change in its structure, usually involving chain scission or crosslinking. The process is initiated by heat, light, oxygen, mechanical stress, or microorganisms, and the contributions are difficult to separate because they act together in service [1]. Photo-oxidation begins with the absorption of ultraviolet light by a chromophore, either in the backbone or in a residual catalyst, and proceeds through a radical chain reaction [2]. The earliest sign is usually a loss of elongation rather than of strength, so a tensile test on an aged specimen is more sensitive than a spectroscopic measurement [3]. Stabilisers act either by absorbing the ultraviolet light or by trapping the radicals, and the two mechanisms are combined in a commercial package [4]. Predicting a service life requires an accelerated test, and the extrapolation is valid only when the degradation mechanism is unchanged, which is rarely verified [5].
- chain scission
- photo-oxidation
- radical reaction
- stabilizer
- accelerated ageing
- service life
- crosslinking
Polymer Science and Applications·Mechanical Engineering·Engineering·Physical Sciences
References
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