H

Hardener
Substance or mixture of substances added to a resin to promote or control the curing reaction by taking part in it.
Syn. Crosslinking agent, Curing agent

Heat stabilizer
Additive that increase the ability of the material to withstand the negative effects of heat exposure. They are used to increase the overall service temperature of the polymer.

Hot melt adhesive (extended definition)
100% solids adhesive requiring heat to raise the temperature of the adhesive to a workable viscosity.

Hot Tack
A characteristic of hot melts, in which they have holding power even while in the liquid hot state.

Humectant
Soluble compound that is used to preserve the moisture content.