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59.1 INTRODUCTION

Polymers are the chief products of modem chemical industry which form the backbone of present society. Daily life without the discovery and varied applications of polymers would not have been easier and colourful. The materials made of polymers find multifarious uses and applications in all walks of our life. They have influenced our day-to-day life to such an extent that it is impossible to get through the day without using a material based on polymers. Common examples of these include.

Plastic dishes, cups, non-stick pans; automobile tyres and seat covers, plastic bags, rain coats, plastic pipes and fitting; radio, ‘TV and computer cabinets; wide range of synthetic fibres for clothing, synthetic glues, flooring materials and materials for biomedical and surgical operations.

The word polymers means “many parts” (Greek: poly means many and meros means parts). A polymer is a compound of high molecular mass formed by the combination of large number of small molecules. The small molecules which constitute the repeating units in a polymer are called monomer units. The process by’ which the monomers are transformed into polymer is called polymerisation. For example, polyethylene is a polymer which is obtained by the polymerisation of ethylene. The ethylene molecules are referred to as monomer units.

Specific Objectives

After studying this unit the students will be able to:

    • describe synthetic polymers
    • describe addition and condensation polymerization
    • describe how the properties of polymers depend on their structural features
    • describe ways of modifying the properties of polymers
    • describe plastics and resins
    • explain the chemical tests for plastics

state the uses of polymers
As polymers are single, giant molecules, i.e., big size molecules, they are also called macromolecules.

HOMOPOLYMERS AND COPOLYMERS

Polymers are divided into two broad categories depending upon the nature of the repeating structural units. These are homopolymers and co-polymers.

The polymer formed from one kind of monomers is called homopolymer while polymer formed from more than one kind of monomer units is called copolymer or mixed polymer. For example, polyethylene is an example of homopolymer whereas Buna-S rubber which is formed from 1,3-butadiene (CH2 = CH-CH = CH2) and styrene (C6H5CH = CH2) is an example of copolymer.