Thermoplastic

A polymer that cures irreversibly through crosslinking, forming a rigid three-dimensional network that cannot be re-melted or reshaped by heating. Epoxy, polyester, vinyl ester, phenolic and polyurethane resins are common thermosets used as composite matrices, adhesives and coatings.

The temperature region over which an amorphous or partly amorphous polymer changes from a rigid, glassy state to a softer, rubbery one. It sets a practical upper service temperature for resins and adhesives and can be reduced by absorbed moisture or incomplete cure.

A composite whose matrix is a thermoplastic polymer, such as polypropylene, polyamide or PEEK, rather than a curing thermoset. Thermoplastic composites can be formed and reformed with heat, joined by welding rather than bonding, and are more readily recycled at end of life.

The formation of chemical bonds between polymer chains, tying them into a three-dimensional network. It is the reaction underlying thermoset cure and determines rigidity, chemical resistance and the inability of cured resins to be re-melted.