Mechanisms of chemical ageing hydrolytic processes

Hydrolytic processes are especially important in two main polymer matrix families containing ester or amide groups in the chain. In these cases, each hydrolysis event is a chain scission  

Taking [-CO-X-] = E, [-COOH] = [HX-] = b, and S = number of chain scissions (mole per mass unit), one can write  

Equilibrium occurs at high conversions (SJEq 1). Since embrittlement occurs at low conversions, far from equilibrium, one can neglect the reverse reaction. Then, the rate of chain scissions is well approximated by  

Polymers containing ester gronps (linear or cross-linked polyesters, anhydride-cnred epoxies, urethane cross-linked polyesters, polycarbonate, etc.) belong to this category. 

22 (a) Molar mass-temperature map (b) lifetime versus temperature. 

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