Styrenic thermoplastic vulcanizates (STPVs) were developed for long-term high-temperature applications. These STPVs consist of polypropylene as the continuous phase and a crosslinked modified hydrogenated styrenic block copolymer (mHSBC) as the dispersed phase. The present study compared STPVs with conventional TPVs (CTPVs) containing EPDM/PP. The STPVs showed a 20% improvement in solvent resistance after 500 h of immersion in IRM 903 oil at 125 degrees C, and the swelling of oil did not increase with time. The elastic recovery was 50% better than with CTPVs. Tensile property retention was approximately 10% higher after aging for 1440 h at 125 degrees C when compared to CTPVs. These observed property improvements for STPVs relative to conventional TPVs can possibly be explained by the unique morphology of the resulting STPV compounds. These performance characteristics make STPVs more suitable for high-temperature air and chemical environmental applications. This new TPV technology is expected to bridge the gap between polypropylene/EPDM TPVs and more costly engineering TPVs. (C) 2007 Wiley Periodicals, Inc.