designtechnology
Plastics
----------------------------------------------------------------------------------------------------Why are plastics so popular?
Plastics are used in a wide variety of products not just in packaging. They compete fiercely
with the more traditional materials such as: wood, metal, glass, paper and board. Their
popularity has increased because they are cheaper than these traditional materials, selfcoloured, self-finished, lightweight and are very good electrical and thermal insulators.
What are plastics made from?
The vast majority of plastics in use today are made from non-renewable resources such
as: gas, oil and coal. These plastics are referred to as synthetic polymers. There have been
increasing developments in semi and non-synthetic plastics. These are made from
vegetable and plant fibres, which are deemed to be more environmentally friendly.
Types of plastic
Plastics can be categorised under three main groups: thermoplastics and thermosetting
plastics.
Thermosetting Plastics
Thermosetting plastics, also know as thermosets, are moulded into shapes using heat and
pressure. When a thermoset is heated and moulded there is a chemical change in the
structure of the plastic, called ‘cross-linking’. When ‘cross-linking occurs, bonds are formed
which link one polymer chain to another. A thermoset plastic cannot be re-melted and reshaped after it has cured (cross-linking has occurs), therefore, they cannot be recycled.
Thermosets have few uses in packaging; however, they are generally stronger than
thermoplastics and are suited to high temperature applications, such as kitchen work
surfaces.
Thermoplastics
Like thermosetting plastics, thermoplastics can be shaped using heat and pressure.
However, when they are formed, no ‘cross-linking’ occurs, allowing them to be reheated
and remould into new shapes. This means many thermoplastics can be recycled offering a
better alternative to the environment
VISIT: www.canon-slade.bolton.sch.uk/tech.htm
> Year 11 > GCSE Graphic Products > Plastics