What is plastic?

Tuesday, August 10, 2010

An introduction to plastics
What is plastic?

Plastic is a common name for Polymers: materials made of long strings of carbon and other elements. Each unit in a string is called a monomer, and is a chemical usually derived from oil.

The monomer is made into polymer by chain-linking reactions. This is like making a daisy chain. Instead of flowers, carbon atoms are joined together. The appearance of the daisy chain will be different if you use different coloured flowers, and so will polymers.

There are many different types of plastic, depending on the starting monomer selected, the length of polymer chains, and the type of modifying compounds added. Each plastic has been developed for a special purpose.
There are two main groups of plastics:

1. THERMOPLASTICS soften with heat and harden with cooling.

* Some typical thermoplastics are: Acrylic (Perspex)
* Acrylo-nitrile (Nylon)
* Polyethylene (Polythene)
* Polypropylene
* Poly Vinyl Acetate (PVA)
* Poly Vinyl Chloride (PVC)
* Polystyrene and ABS
* PTFE (Teflon)

2. THERMOSETS are cured or hardened by heat.

Some typical thermosets are:


* Bakelite
* Epoxy
* Melamine
* Polyester
* Polyurethane

Properties

Plastics are used because they are:

* Attractive
* Hard and slippery
* Soft and rubbery
* Tough and slippery
* Flexible
* Good insulators of heat or electricity
* Light weight
* Hygienic
* Non-rusting
* Easy to shape and colour
* Cheap

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