Development and preparation of high-performance thermoplastic vulcanizates based on blends of natural rubber and thermoplastic polyurethanes

Natural rubber (NR)/thermoplastic polyurethane (TPU) blends were prepared with a dynamic vulcanization technique. The main objective was to prepare high-performance thermoplastic vulcanizates (TPVs) based on natural rubber [thermoplastic natural rubber (TPNR)] with low hardness values and improved thermal and mechanical properties. In this study, the preparation of dynamically cured NR/TPU blends was carried out systematically, and the final properties were compared to those of typical commercial TPVs. The influence of sulfur-cured systems, accelerator types, process parameters, and rubber types were investigated. The developed NR/TPU-based TPNRs showed better tensile strengths and thermal properties than commercial TPVs with similar hardnesses. Moreover, the epoxidized natural rubber (ENR)/TPU-based TPNRs exhibited a low compression set. The incorporation of NR into the TPU reduced the Shore A hardness to about 60 in comparison to a value of about 85 for the neat TPU; the blends also showed improved oil resistance (oil swelling = 12%) in comparison to commercial TPVs with similar hardnesses. The experimental results indicate that high-performance TPNRs with low hardness values could be prepared with the proper conditions developed in this study. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013