Changes in crosslinking structure of thermo-oxidative aging chloroprene rubber and its effect on strain-induced crystallization

Chloroprene rubber (CR) is frequently quoted as an example of strain-induced crystallizing elastomer. Many researchers have focused on studying the aging mechanism and mechanical properties of aged CR, little has been done on the effect of crosslinking structure on strain-induced crystallization (SIC). The present paper related systematic investigations combining the changes of crosslinking structure and its influence on SIC. It was firstly investigated based on FTIR, crosslinking density test and GPC. The results showed that the molecular chains were oxidized in the early stage of aging, but the crosslinking reaction still dominated. At the same time, sol content and polydispersity decreased. In the later stage of aging, CR was oxidized, resulted in severe molecular chains fracture and an increase in the free sol content and polydispersity. The impact of aging on SIC under tensile condition was further investigated by the tensile tests. An obvious stress-hardening was found for unaged CR, but not in aged CR. The crystallinity and microcrystalline region orientation tests showed that oxidation, crosslinking by double bonds and dechlorination during aging were not conducive to the orientation of molecular chains during stretching. It is the aging process that has an adverse effect on the SIC of CR.