Plastic

Hi guys,
Plastics fall into two main classes according to the way they react to heat. Thermoplastics, such as polythene and Perspex, can be repeatedly softened and hardened by heating and cooling. Thermosetting plastics, such as epoxy resins and polyurethane, are initially soft but set hard after heating, and cannot be softened again by further heating. Some plastics are given added strength by reinforcing them with fibers; these are known as composites. Thank you.