General Purpose Elastomers: Structure, Chemistry, Physics and Performance

Elastomers are unique to polymers and exhibit extraordinary reversible extension with low hysteresis and minimal permanent set. They are the ideal polymers relieved of molecular interactions, crystallinity and chain rigidity constraints. The common elastomers have characteristic low modulus, though with poor abrasion and chemical resistance. Theoretical concepts have been established for their thermodynamics and kinetics and this knowledge has been applied to extending their properties by design of chemical and molecular structures, or by modification by control of crosslinking, blending or additions of fillers. This chapter reviews elastomer theory and the demanding range of properties expected. Natural rubber is the starting material for introduction of chemistries that introduce damping, abrasion resistance and higher modulus through copolymerization and interacting functional groups. Heteroatoms such as fluorine, silicon, oxygen and nitrogen are shown to extend properties and give chemical resistance. Thermoplastic elastomers move beyond typical cured systems due to formation of two-phase block copolymers. Finally modification by filler and blended systems is considered, followed by introduction to shape memory materials and a brief comment on the future trends. The unique and diverse properties and performance of elastomers continues to be a fascinating field for science and application.