EPDM/polyamide TPV compatibilized by chlorinated polyethylene

Abstract

A thermoplastic vulcanizate (TPV) of ethylene-propylene-diene (EPDM) and polyamide (PA) with excellent mechanical properties was prepared by dynamic vulcanization. The effects of the vulcanizing agents, compatibilizer, PA content, aging and reprocessing on mechanical properties of EPDM/PA thermoplastic vulcanizate were investigated. Experimental results indicate that chlorinated polyethylene has a better effect in compatibilizing the EPDM/copolyamide blends compared with the other compatibilizers, including maleic anhydride grafted ethylene propylene rubber (MAH-G-EPR), maleic anhydride grafted EPDM (MAH-G-EPDM) and epoxidised ethylene-propylene-diene rubber. Tensile strength and elongation at break go through a maximum value at a compatibilizer resin content (on total rubber content) of 20%. EPDM/PA TPV using sulfur as a vulcanizing agent has higher tensile strength and elongation than that of TPVs using a brominated tert-butyl phenolic resin or peroxide as vulcanizing agent. Tensile strength and elongation at break increase with PA content. DMA results indicated a phase separation in the blend system of EPDM/CPE/PA. The glass transition temperature (Tg) of PA moves towards a high temperature with increasing CPE content, but the Tg of EPDM changes very slightly toward a lower temperature. The loss factor, tanδ, of PA also increases with increasing CPE content. In the blend EPDM/CPE/PA, small PA contents do not cause an immediate increase of storage modulus (E′). Scanning electron microscopy was used to examine the phase morphology of the blends; the results show that the particles of the dispersed EPDM phase have an average size of 2 μm in the dynamically vulcanized EPDM/CPE/PA TPV.