Cure kinetics of neat versus reinforced epoxies

An investigation was carried out into the cure kinetics of neat vs reinforced epoxy systems. The formulations were composed of tetraglycidyl 4,4′‐diaminodiphenyl methane (TGDDM) epoxy resin and diaminodiphenyl sulfone (DDS). Glass was used as reinforcement. A series of isothermal differential scanning calorimetry (DSC) thermograms were run and analyzed by the proposed autocatalytic kinetic model. An increase in reaction rate was observed at higher temperature and higher DDS concentration in both neat and reinforced formulations. The presence of reinforcement had an effect on the cure kinetics. The observed effect, however, was not very pronounced. Slightly lower values of the reaction rate constant and longer times needed to reach the maximum reaction rate were recorded in reinforced systems. After reaching the peak value, the rate of reaction dropped off faster in reinforced formulations, resulting in lower average value of H_ult, the ultimate heat of reaction. It was suggested that the reinforcement imposes restrictions on the molecular mobility of reactive species.