Crosslinking

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 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 controlled period at elevated temperature applied after a resin has initially hardened, driving the crosslinking reaction closer to completion. Post-curing raises the glass transition temperature and improves mechanical and chemical properties, and is routine for epoxy laminates and structural bonded assemblies.