What are thermosetting plastics?
Answers
Answer:
thermosetting polymer, resin, or plastic, often called a thermoset, is a polymer that is irreversibly hardened by curing from a soft solid or viscous liquid prepolymer or resin.[1] Curing is induced by heat or suitable radiation and may be promoted by high pressure, or mixing with a catalyst. Heat is not necessarily to be applied externally. It is often generated by the reaction of the resin with a curing agent (catalyst, hardener). Curing results in chemical reactions that create extensive cross-linking between polymer chains to produce an infusible and insoluble polymer network.
Left: individual linear polymer chains
Right: Polymer chains which have been cross linked to give a rigid 3D thermoset polymer
The starting material for making thermosets is usually malleable or liquid prior to curing, and is often designed to be molded into the final shape. It may also be used as an adhesive. Once hardened, a thermoset cannot be melted for reshaping, in contrast to thermoplastic polymers which are commonly produced and distributed in form of pellets, and shaped into the final product form by melting, pressing, or injection molding.
Explanation:
Thermosetting plastics, once processed into the finished article, cannot be re-melted and used again. In other words once it is set that’s it, it’s cured, there is no going back now.
Even if you heat up a finished thermoset plastic item a lot, it will not melt, it will just char.
The very first man made plastics, like Bakelite were thermosetting.
Now I’m not an expert on thermosetting but whenever I hear the term I think of cross linking. What makes a thermoset polymer distinctive is the Polymer chains are cross linked. Generally cross linking is achieved chemically sometimes with heat, or pressure etc. tonpromote the cross linking.