A degradation mechanism is the sequence of chemical steps by which a polymer loses its useful properties under a given environment. Hydrolytic degradation proceeds by the attack of water on a hydrolysable bond, and the rate depends on the accessibility of that bond rather than on its intrinsic reactivity [1]. Oxidative degradation starts with a radical, and the propagation step consumes oxygen while the termination step crosslinks or scissions the chain [2]. Thermal degradation at low temperature is usually oxidative, while pyrolysis above the ceiling temperature proceeds by unzipping to the monomer [3]. Because several routes can act at the same time, distinguishing them requires the kinetics to be measured at more than one condition [4]. The mechanism determines whether the product is a harmless fragment or a persistent microplastic, and that distinction governs the end-of-life assessment [5].
- hydrolytic scission
- oxidative degradation
- radical propagation
- pyrolysis
- chain unzipping
- kinetics
- microplastic
Polymer Science and Applications·Mechanical Engineering·Engineering·Physical Sciences
References
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