(2) Thermoset, or thermosetting plastics are synthetic materials that strengthen during the process of heating. However, these cannot be successfully remolded or reheated after their initial heat-forming. This is in contrast to thermoplastics,which soften when heated and harden and strengthen after cooling. Thermoplastics can be heated, shaped and cooled as often as necessary without causing a chemical change, while thermosetting plastics will burn when heated after the initial molding.