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A5.2 Thermosetting Polymers

Key information

A thermosetting polymer is formed from a prepolymer which can be in a soft solid or viscous state but it is changed irreversibly into a polymer network by curing.
These polymers have a network of cross-linked chains, joined by strong covalent bonds, which cannot be loosened and separated by heating. So once they have formed, the shape is fixed permanently.
Objects made from these polymers have to be created in moulds in their final shape. They are very difficult to recycle.
Curing can take place as the result of a chemical reaction, heating or exposure to electromagnetic radiation.
Examples include Bakelite, polyurethane, melamine, vulcanised rubber, polyester resin.