The relatively low density of most plastic materials means the end products are lightweight. They also have excellent thermal and electrical insulation properties. However, some can even be made as conductors of electricity when required. They are corrosion resistant to many substances which attack other materials, and some are transparent, making optical devices possible. They are also easy to mould into complex shapes and forms, allowing integration of different materials and functions. And in the event that the physical properties of a given plastic do not quite meet the specified requirements, the property balance can be modified with the addition of reinforcing fillers, colours, foaming agents, flame retardants, plasticisers etc., to meet the demands of the specific application.
For these reasons and more, plastics are increasingly used in:
Basically these plastics are man-made. In principle any combination of properties can be developed to accommodate almost any application you can think of.