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Thermoplastics and thermosetting plastic
There are two broad families of plastics,
thermoplastics and thermosetting plastics. They are both produced by the petrochemical
industries and although there are naturally occurring plastics such as rubber, in the main
oil, water, air and salt are processed to produce various types of plastic. These
processes result in the production of granules, powders and resins which are reshaped to
make the familiar things that were see about us.
Thermoplastic
By far the most common in the school
workshop. These plastics do not resist heat very well and so can be easily formed into
other shapes. On heating this type of plastic does not undergo a chemical change (as is
the case with thermosetting plastic) and waste can be re-ground into granules and re-used.
A heated sheet of thermoplastic which has been moulded into a shape can be reheated and it
will go back to its original shape. This returning to shape is referred to as plastic
memory.
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