Chapter 7 - Polyolefins and Acrylics

Abstract

This chapter discusses polyethylene (PE) and polypropylene (PP) plastics, which are formed when the two simplest alkenes ethylene and propylene are polymerized. Acrylic polymers are also polymerized through the carbon–carbon double bond. Methyl methacrylate is the monomer used to make poly (methyl methacrylate). PE can be made in a number of ways. The way it is produced can affect its physical properties. It can also have very small amounts of comonomers, which will alter its structure and properties. A modification of high-density polyethylene (HDPE) is called crosslinked polyethylene (PEX). The HDPE has undergone a chemical or physical reaction that causes the molecular structure of the PE chains to link together. This reaction creates a three-dimensional structure that has superior resistance to high temperature and pressure. PEX is primarily used in tubing. There are three main types of PP generally available: homopolymers, random copolymers (homophasic copolymers), and impact copolymers (heterophasic copolymers). Polymethylpentene, ultra high molecular weight polyethylene, rigid polyvinyl chloride, and cyclic olefin copolymer (CDC) are also discussed in the chapter. While a large number of acrylic polymers are manufactured, polymethyl methacrylate (PMMA) is by far the most common. There are a large number of acrylic/olefin copolymers manufactured. One of the best known is the copolymer of ethylene and methacrylic acid forming a polymer known as ethylene-methacrylic acid (EMAA).