Gel time

The length of time a mixed, reactive resin or adhesive remains usable in the mixing vessel before it thickens beyond application. Pot life shortens as temperature and mixed quantity increase, because the curing reaction generates its own heat.

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.

The heat released by a thermosetting resin as it cures. In thick sections or large mixed volumes the temperature rise can be severe enough to cause discolouration, cracking or degradation, so laminate thickness per pass and mixing quantities are managed to control it.

A substance that initiates or speeds a resin's curing reaction without being consumed in stoichiometric amounts. In the GRP trade the organic peroxide added to polyester resin, usually MEKP, is called the catalyst, although strictly it acts as an initiator.

A chemical added in small amounts to a reactive resin to delay the onset of cure, extending shelf life and working time and protecting against premature gelation in storage or transport. Adjusting inhibitor level is one of the ways manufacturers tune the gel time of polyester and vinyl ester resins.