High temperatures have immediate and delayed effects. Modulus and strengths immediately decrease by softening but in addition the fall speeds up with time. Chemical structure is more or less rapidly damaged leading to a chemical decomposition and a brittle structure.
High temperature requirements must be clearly defined for the actual targeted application and a strategy must be chosen between two philosophies: suitable thermoset rubbers or thermoplastic elastomers (super TPE). Crosslinked rubbers have advantages and disadvantages of 3D networks: low thermoplasticity, better elasticity, better dimensional stability, long experience but specific processing, higher end cost and difficult recycling after curing.
Super-TPEs have the basic advantages of TPEs allowing the manufacture on conventional thermoplastics equipment with high outputs. In addition, they combine the advantages of high-performance vulcanized elastomers (for instance ethylvinyl acetate, acrylate rubber, silicone, fluorinated rubber) and high-performance plastics, for instance copolyester, polyamide, silicone, fluorinated polymers and other engineering plastics. Among others, let us quote, for example Hipex by Kraiburg, FluoroXprene by Freudenberg-NOK, ETPV by DuPont, Zeotherm TPV by Zeon, TPSiV by Dow (Multibase), Geniomer by Wacker. Perfluororubbers, fluororubbers, silicones and fluorosilicones offer a unique range of thermal and collateral properties allowing to satisfy the most requiring applications when super TPEs are generally somewhat less thermal resistant but with the huge advantage of easier processing methods, lower processing costs and ease of processing integration in thermoplastic processing chains avoiding post processing steps, which eases a steady flow of the manufacturing chain.
Each chemical family is proposed in numerous versions and the first step of the choice is to determine the suitable grades among ready-to-use compounds or raw polymers needing a specific formulation. This one can be more or less complete and, in the most sophisticated evolutions is quite comparable to that of conventional elastomers incorporating stabilizers, antioxidants, processing aids, plasticizers, curing agents, fillers, fire retardant systems etc.