Thermal and Cure Kinetics of Epoxy Molding Compounds Cured with Thermal Latency Accelerators

The cure kinetics and mechanisms of a biphenyl type epoxy molding compounds (EMCs) with thermal latency organophosphine accelerators were studied using differential scanning calorimetry (DSC). Although the use of triphenylphosphine-1,4-benzoquinone (TPP-BQ) and triphenylphosphine (TPP) catalysts in biphenyl type EMCs exhibited autocatalytic mechanisms, thermal latency was higher in the TPP-BQ catalyst in EMCs than in the TPP catalyst in EMCs. Analyses of thermal characteristics indicated that TPP-BQ is inactive at low temperatures. At high temperatures, however, TPP-BQ increases the curing rate of EMC in dynamic and isothermal curing experiments. The reaction of EMCs with the TPP-BQ latent catalyst also had a higher temperature sensitivity compared to the reaction of EMCs with TPP catalyst. In resin transfer molding, EMCs containing the TPP-BQ thermal latency accelerator are least active at a low temperature. Consequently, EMCs have a low melt viscosity before gelation, and the resins and filler are evenly mixed in the kneading process. Additionally, flowability is increased before the EMCs form a network structure in the molding process. The proposed kinetic model adequately describes curing behavior in EMCs cured with two different organophosphine catalysts up to the rubber state in the progress of curing