1 - Introduction to Plastics and Elastomers

Abstract

This chapter provides an introduction to plastics and elastomers. The basic component of plastic and elastomer materials is polymers. Polymers are large molecules comprising many repeating units, called monomers that are chemically bonded into long chains through polymerization. It is the process of chemically bonding monomer building blocks to form large molecules. It can proceed by several methods. The two most common methods are addition and condensation polymerization. In addition polymerization, a chain reaction adds new monomer units to the growing polymer molecule through double or triple bonds in the monomer. Each new monomer unit creates an active site for the next attachment. The other common method is condensation polymerization in which the reaction between monomer units and the growing polymer chain-end group releases a small molecule, often water. Polyesters and polyamides are among the plastics made by this process. Elastomers are a class of polymeric materials that can be repeatedly stretched over twice the original length with little or no permanent deformation. Elastomers can be made of either thermoplastic or thermoset materials, and generally are tested and categorized differently than rigid materials. They are commonly selected according to their hardness and energy absorption characteristic. Elastomers are found in numerous applications such as automotive bumpers and industrial hoses.