Chapter 8 - Thermoplastic Elastomers

Abstract

This chapter discusses the three high performance types of Thermoplastic elastomers (TPEs) namely: thermoplastic polyurethane elastomers (TPUs), thermoplastic copolyester elastomers (TPE-Es or COPEs), and thermoplastic polyether block amide (PEBA) elastomers. TPEs have two big advantages over the conventional thermoset (vulcanized) elastomers, namely ease and speed of processing. Other advantages of TPEs are recyclability of scrap, lower energy costs for processing, and the availability of standard uniform grades. TPEs are molded or extruded on standard plastics processing equipment in considerably shorter cycle times than those required for compression or transfer molding of conventional rubbers. They are made by copolymerizing two or more monomers, using either block or graft polymerization techniques. One of the monomers provides the hard, or crystalline, polymer segment that functions as a thermally stable component; the other monomer develops the soft or amorphous segment, which contributes the elastomeric or rubbery characteristic. Varying the ratio of monomers and the length of the hard and soft segments can control physical and chemical properties. Block techniques create long-chain molecules that have various or alternating hard and soft segments. Graft polymerization methods involve attaching one polymer chain to another as a branch.