How the plastic is produced?
Plastics are derived from natural, organic materials such as cellulose, coal, natural gas, salt and of crude oil. Crude oil is a complex mixture of thousands of compounds. The production of plastics begins with the distillation of crude oil in an oil refinery. This separates the heavy crude oil into groups of lighter components, called fractions. Each fraction is a mixture of hydrocarbon chains, which differ in terms of the size and structure of their molecules.
Two main processes are used to produce plastics - polymerisation and polycondensation. In a polymerisation reaction, monomers such as ethylene and propylene are linked together to form long polymer chains. In a polycondensation reaction, different monomer units are linked together to form long polymer chains. Each polymer has its own properties, structure and size depending on the nature of monomer different quality plastics are produced.
There are many different types of plastics, and they can be grouped into two main polymer families:
- Thermoplastics (which soften on heating and then harden again on cooling).
Thermosets (which never soften once they have been moulded).