Thermosetting Materials

Initially, thermosetting materials (also called Thermosets) will soften when heated. But will remain soft for only a short time and will set (and harden) if the heat continues to be applied.

The process of thermosets becoming hard when heated is called curing, which can also be achieved by chemical (exothermic) reactions.

During the curing process, the long-chain molecules of the material cross-link (link together between chains). Once the cross-links are formed, the plastic becomes hard and cannot be re-softened by heating.

Thus, thermosets are chosen where a plastic component will be exposed to relatively high temperatures, as some of them can tolerate temperatures in excess of 250ºC before beginning to char.

Note: Thermosetting materials are generally stronger, have a lower ductility and lower impact properties than the thermoplastics.