Morphology evaluation and mechanical properties of oil-resistant thermoplastic vulcanizates comprising carboxylated nitrile butadiene rubber and thermoplastic polyurethane and their comparison with commercial grades

Abstract

The morphology, the mechanical properties, and the oil-resistance of thermoplastic vulcanizates (TPVs) of carboxylated nitrile butadiene rubber (XNBR) and thermoplastic polyurethane (TPU) were studied & compared with the commercial ethylene-propylene-diene monomer (EPDM)/polypropylene (PP) TPVs from two suppliers. The rubber phase in these new generations of TPVs was cured with an addition-type curative, and no oil & compatibilizer were required to make these TPVs processable. Three XNBR/TPU TPVs were made with different rubber/plastic ratios (15/85, 30/70, and 45/55). The AFM analysis showed that the morphology shifted from a continuous plastic phase to a co-continuous phase with increased rubber content. The rubber domains in these TPVs were not as discrete as reported in the literature for the EPDM/PP TPVs. Still, because of using an addition-type curative, unlike peroxide and resole phenolic resin curatives for the latter, the former TPVs had a significantly better balance of rubber and plastic properties. The oil resistance of these TPVs was 3.5–5 times better than the commercial EPDM/PP TPVs. These promising results show advancement in the TPV world and make these TPVs appealing for hydraulic oil applications.