A 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-gMAH 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. (C) 2003 Wiley Periodicals, Inc.