Polyurethanes for elastomers

Abstract

Polyurethanes consisting of hard and soft segments—chemically linked together with covalent bonds along a linear or crosslinked polymeric backbone—display mechanical properties ranging from soft elastomers to tough rubbers (depending on their chemical compositions), along with chain topologies and bulk morphologies. The availability of a wide selection of starting materials—with a large variety of physical and chemical properties—allows the tailoring of the design and synthesis of a very large number of linear, highly branched, and crosslinked polyurethane elastomers. In this chapter, preparation of polyurethane elastomers is discussed. This chapter also discusses the effects of various critical parameters, such as chemical composition, segment type, segment molecular weight, solubility parameters, and the nature and extent of hydrogen bonding on the morphology and properties of these materials. Although the focus will be on linear, segmented thermoplastic polyurethane/urea elastomers, this chapter also provides a discussion on the preparation and properties of hyperbranched and crosslinked polyurethane/urea elastomers.