The novelty role of polyamide elastomer in the determination of crosslink density and the formation of crosslink network of EPDM vulcanizates

Abstract The effect of polyamide elastomer (PAE) on the crosslink network of ethylene propylene diene monomer (EPDM) was systematically investigated by using equilibrium swelling method and rheological experiment. The swelling systems of the EPDM‐PAE vulcanizates were discussed by classification way. The results showed that PAE was involved in the construction of the crosslink network and decreases the chemical crosslink density and the total crosslink degree of EPDM vulcanizate. By linearly fitting the relationship between chemical crosslink density and total crosslink degree, the physical crosslink degrees of EPDM, EPDM‐PAE and PAE were estimated as 9.135, 2.934, and 0.820 dNm, respectively. The physical crosslink degree of EPDM vulcanizates was mainly contributed by the entanglement of rubber macromolecular chains. By contrast, the interaction of the inter‐macromolecular chains of EPDM‐PAE and the physical crosslink of PAE itself contributed less to the physical crosslink degree of EPDM vulcanizates. With the increase of aging time under 150°C, the roles of PAE in continuously promoting the crosslink reaction and leading to the degradation of crosslink network resulted in various changes in crosslink density and mechanical properties. It could be expected from this study that the construction of the crosslink network of EPDM‐PAE composite was unique, which provided a novel perspective on the microscopic crosslink structures and macroscopic properties of EPDM‐PAE based products.