Naturally occurring organic plastics have been in use for over 2,000 years. Plastics based on chemically modified organic polymers date back only about 100 years, and those based on synthetic polymers about 50 years._x000D_
The development of ,these two latter groups up to the present day is outlined, and the basic techniques currently available for polymer-building and modi- fication (blending, copolymerisation, quantitative and qualitative struc- tural control, and'si de-group reactions)-are reviewed.