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2.But what is a plastics and why are the chemists so enthusiastic over them? Synthetic plastics are man-made substances which not only change their shape when moulded under great heat and pressure, but change their chemical state as well.
3.They are light, hard and amber-like, being produced by mixing together a number of gases and liquids. A synthetic-or man-made- product must necessarily be both better and cheaper in order to justify its manufacture at all. This is essentially true of the various plastics when compared to the material they are to replace.
4.As for plastics themselves, there are two kinds- those which are affected by heat and those which are not, or cast plastics and moulded plastics. Cast plastics are manufactured as liquid resins and are then cast in the desired forms. Cast resins can be coloured before being poured. The resulting plastics can be produced in all sorts of colours, more than three hundred different shades and colours, being now available in the cast plastics.