Thermoset

A polymer that softens when heated and hardens again on cooling without chemical change, so it can be reshaped, welded or recycled. Thermoplastics range from commodity materials such as polypropylene and PVC to high-performance matrices such as PEEK used in advanced composites.

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.

The chemical process by which a liquid resin or adhesive hardens into its final solid state through crosslinking, driven by a hardener, catalyst, heat, moisture or radiation depending on the chemistry. Full properties develop only when cure is complete, which can take considerably longer than the initial set.

A thermosetting resin based on molecules containing epoxide groups, cured by reaction with a hardener such as an amine or anhydride. Valued for strong adhesion, low cure shrinkage, chemical resistance and high mechanical performance, it is widely used in structural adhesives, laminating resins, coatings and composite matrices.

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.