12.2 Plastics
The word "plastic" is derived from the Greek word "plastikos" which means "malleable" or "moldable" and "plastos" meaning "mouldable." Plastics are synthetic materials made from organic polymers, such as PVC (polyvinyl chloride), polyethylene (polyethylene), nylon, etc. These materials can be melted down and then transformed into solid or slightly flexible shapes. They are also referred to as "long carbon chain polymers". The ability of a material to be moulded or malleable during the manufacturing process means that it can be cast, pressed, or extruded into a variety of forms, including film, fiber, sheet, tube, bottle, and box.
12.2.1 Properties of Plastics
The properties of plastics are directly derived from the characteristics of the polymers they are made from. Some of these are:
1. Molecular Structure
Polymer chains tend to be longer and more durable which can be linear or branched. Branched polymers are softer and more flexible. On the other hand, linear polymers are stronger and more rigid. Cross- linking is also possible, with high cross- linking resulting in tough and heat- resistant plastics, such as vulcanized rubber.