Control of gel time and exotherm behaviour during cure of unsaturated polyester resins

The curing behaviour of an unsaturated polyester resin has been studied by gel time and pseudo-adiabatic exotherm measurements. The gel time correspon ded closely with the initial rise in exotherm temperature. Incorporation of tert-butyl catechol inhibitor increased the gel time in a linear fashion a nd the exotherm was similarly delayed. An increase in the concentrations of initiator (either methyl ethyl ketone peroxide or acetyl acetone peroxide) or cobalt octoate accelerator decreased the gel time in a reciprocal fashi on and increased the rate of polymerization. These results are fitted to a theoretical model for inhibition and initiation. (C) 2001 Society of Chemic al Industry.