The word polymer is derived from Greek words, poly which means many and meros means ‘parts or units of high molecular mass’. Each molecule consists of a very large number of single structural units joined together in a regular manner by covalent bonds. Polymers are the giant molecules of high molecular weight called macromolecules which are formed by linking together a large number of small molecules, called monomers. The process by which monomers combine to form polymer is known as polymerization. The polymerization is defined as a chemical reaction in which two or more substances combine together with or without evolution of water, heat or any other solvents to form a molecule of high molecular weight. The product obtained is called polymer and the starting material from which the polymers are made is called monomer.