Observation of morphology in EPDM/nylon copolymer thermoplastic vulcanizates by atomic force microscopy

Abstract

AbstractA thermoplastic vulcanizate (TPV) of an ethylene propylene diene terpolymer (EPDM) and nylon copolymer (PA) was prepared. Maleic anhydride‐grafted EPDM (EPDM‐g‐MAH) and MAH‐grafted EPR (EPR‐g‐MAH) were used as compatibilizers and sulfur was used as a curative. The phase morphology of EPDM/PA TPVs was investigated by atomic force microscopy (AFM). AFM images showed that, although there was a compatibilization reaction between EPDM‐g‐MAH and PA, phase inversion always existed for EPDM/EPDM‐g‐MAH/PA TPVs and the rubber phase could be finely dispersed in the PA matrix with an increasing compatibilizer content. For TPVs using EPR‐g‐MAH as a compatibilizer, three phases existed because of noncrosslinkability of EPR by sulfur. Crosslinked EPDM particles dispersed in a comatrix of PA and EPR‐g‐MAH could be observed by increasing the content of EPR‐g‐MAH to 26 wt %. For an EPR‐g‐MAH content of 26 wt %, the uncrosslinked EPR‐g‐MAH existing in the interface between crosslinked EPDM and PA tended to coalesce and thus resulted in a morphology of large rubber regions composed of small crosslinked particles. When the dosage of EPR‐g‐MAH was 52 wt %, the phase morphology of the blends changed to being one of PA and crosslinked EPDM particles dispersed in the MAH‐g‐EPR matrix. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1242–1248, 2003