S. S. Banerjee, A. K. Bhowmick This paper reviews different types of high-temperature thermoplastic elastomers (TPE). The preparation, structure, and functional properties of these materials are discussed briefly. Strategies to further improve the high-temperature performance of these materials are presented herein. A synopsis of the applications of these high-performance materials in the automotive industry is reported, pointing out the gaps to motivate potential research in this field. High-temperature TPEs based on heat resistant rubbers In the following sections, several high-temperature TPEs (based on heat resistance rubbers) will be discussed, highlighting their preparation, several functional properties, and morphology. Polypropylene/nitrile rubber TPEs Coran et al. have developed oil resistance thermoplastic elastomers by dynamic vulcanization from PP/NBR composition (Geolast). They have used phenolic resin curative to technologically compatibilize the blend components . It was revealed that there is formation of in situ graft copolymer. Significant improvement of mechanical properties was obtained in technologically compatibilized blend as compared to unvulcanized blend. The hot oil resistance of compatibilized PP/NBR blends is excellent. However, low temperature performance of these blends is poor. It is important to note that oil resistance of PP/NBR blends is superior as compared to PP/EPDM-based TPVs. On the other hand, mechanical properties of both TPVs are comparable. Polyolefin/acrylate TPEs Polypropylene/acrylic elastomer blends having good strength and heat resistance were developed by DuPont de Nemours in 1987. These blends were prepared by reactive processing using a combination of PP, ethylene-butyl acrylate-glycidyle methacrylate and an ionomer (ethylene-butyl acrylate-acrylic acid Zn salt methacrylate. Acrylate rubber-based TPVs are commercially available from Kraiburg TPE. PP/acrylate rubber TPVs could be used under the hood because of their high thermal stability up to 140 °C. Other probable applications are seals, cable bushings, and water tank cover. Soares et al. have prepared a thermoplastic elastomer based on PP and ACM by melt blending process and given special attention to the compatibilization and dynamic vulcanization. The compatibilized blends (with maleic anhydride-functionalized PP/ TETA system) exhibited excellent improvement in mechanical properties, oil resistance (5.8 – 8.1 % in ASTM oil #3 at 100 °C for 22 h), elasticity and decrease of damping characteristic. The dynamically vulcanized blends showed superior mechanical performance. It should be noted here that finer morphology of PP/ACM blends (fig. 17) was achieved for compatibilized blends which could be due to the decrease of the interfacial tension, better interfacial adhesion and the crosslinking of the rubber particles, imparted by TETA in combination with PP-g-MA. Specially designed acrylate elastomer (Sunigum) was also used for developing a soft PP-based thermoplastic elastomer. Ethylene methylacrylate-glycidyl methacrylate (EMA–GMA)/ ethylene-octene elastomer was used as a compatibilizer. Polyolefin/silicone rubber TPEs Polyolefins (high-density polyethylene/ polypropylene)/silicone rubber TPEs were prepared using a compatibilizer (a polymer comprising both olefin- and silicone- containing moieties). Polyolefins/silicone rubber TPEs provide superior resistance to organic oils (naturally occurring oils, such as vegetable oils and animal fats, and other hydrocarbon oils), particularly at high temperatures especially at over 140 °C, compared to those based on comparable PP/EPDM composition. High temperature performance of polypropylene in polypropylene/silicone rubber TPEs could be due to the presence of silicone rubber, a layer of which can bloom out on the surface. In addition, the polyolefins/ silicone rubber TPEs have significant advantages such as flexibility, lubricity, resistance to hydrocarbon chemicals, dielectric properties, water repellence, and relative inertness to ozone, corona, and other extreme weather environments, as compared to TPEs in general, due to the presence of silicone rubber. TPEs based on silicone rubber greatly expand the applicability due to the relative ease of processing and product design flexibility possessed by such compositions. Summary and future directions In this review, different types of high-temperature TPEs, their preparation, morphology, various functional properties, and applications are discussed briefly. Strategies to improve the high-temperature performance of TPEs are presented. Considering recent progress, as discussed in this review, there is lot of scope for further development of high-temperature TPEs. On one side, novel new materials and applications would be explored, which are still challenging today. On the other side, there is a need to improve particular properties of existing materials, which influence applications of these systems. These would be the driving force for future developments of high-temperature TPE materials and their applications. Source: TPE magazine