Glass transition temperatureTg

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.

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 at which a standard plastic bar deflects by a specified amount under a defined bending load while being heated at a set rate, measured to ISO 75 or ASTM D648. It is used to compare the short-term temperature resistance of resins and compounds, but it is not a safe continuous service temperature.

A thermal analysis technique that measures heat flow into or out of a small sample as it is heated, cooled or held at constant temperature. For thermosets it reveals the glass transition temperature, residual exotherm and degree of cure; for thermoplastics it shows melting and crystallisation behaviour.

A polymer whose molecular chains have no long-range order. Amorphous polymers soften gradually above their glass transition temperature rather than melting sharply, and many, such as polycarbonate and acrylic, are naturally transparent.