Plastics and Rubber, In Brief

Plastics are defined as shaped and hardened synthetic materials composed of long chain organic molecnles called polymers, plus various additives. Hence, plastics are not pure, in what they contain, and they must also be shaped to their final form of nse. 

The physical and chemical properties of a plastic material are mainly determined by the size (molecular weight) and structure, respectively, of the polymer molecules of which it is composed. 

Polymers are large molecules composed of two to several thousand simple molecules as repeating units, called monomers. Monomers are converted into the polymer through special reactions known as polymerisation. Hence the polymer is the pure material. Almost all synthetic polymers are synthesised from petroleum, although there are natural polymers as well, for example, cellulose, wool and so on. 

Rubbers are highly elastic materials composed of polymers (because of their high elasticities, rubbers are considered to be a special class of plastics). 

There are two main types of plastics, in terms of their response to heat  

---