Gel time and exotherm behaviour studies of an unsaturated polyester resin initiated and promoted with dual systems

In this study, the various combinations of low- and high-decomposition temperature initiators and dual promoters were used to cure an unsaturated polyester resin. Methyl ethyl ketone peroxide (MEKP) and acetyl acetone peroxide (AAP) solutions were used as low-temperature initiators. Benzoyl peroxide (BPO) and t-butyl perbenzoate (TBPB) were used as medium and high-temperature decomposition initiators, respectively. Gel time and pseudo-adiabatic exotherm measurements have been used to study the curing behaviour. It is demonstrated that the low-temperature initiator decomposition does not interfer with the high-temperature initiator decomposition. It is also found that the exotherm peak and cure rate have been affected by the decomposition rate of low-temperature initiator at different ways. It is shown in this study that for cobalt naphthenate and dimethyl aniline (DMA) dual promoters systems, with the increasing of DMA concentration, namely high reactive promoter, causes the exotherm parameters sharply change. It might be due to the more reactive nature of DMA in comparison with the cobalt naphthenate reactivity. Now we can say, a judicious choice of a dual initiator or a dual promoter can avoid short time exothermic reactions, so a dual system can be much more effective than a single one.