3.1 Types of Plastics Materials

There are three main types of plastics materials:

• Thermoplastic

• Elastomer

• Thermosetting

3.2 Definition of Plastics

It is not easy to give a precise, clear-cut definition of plastics and perhaps the best definition is the one that a plastics chemist may give, that plastics materials belong to a larger family of materials known as synthetic organic polymers.

By synthetic is meant man-made; the term organic to a chemist signifies that they are carbon-containing compounds; and the term polymer comes from the Greek word meaning having many parts .

To summarise there are three terms commonly used in plastics technology:

• Synthetic (man-made)

• Organic (carbon based)

• Polymer ( many-units )

Understanding what a polymer is requires a modest knowledge of elementary chemistry, and this is given in the following discussion.

3.3 The Nature of Plastics Materials

Elements, Atoms and Molecules

All matter in the universe is made up of small particles called atoms. There are over 100 different types of atoms constituting the chemical elements. The atomic number of an element is the number of protons in the nucleus of an atom. This is also known as the proton number.

The mass number or nucleus number is the number of nucleons in its nucleus: in other words it is the total number of protons + neutrons.

The elements most commonly found in plastics are:

Under normal circumstances the...