Isothermal Cure Kinetics of an Epoxy Resin Prepreg

The isothermal cure kinetics of a glass fiber-epoxy resin prepreg was investigated over the temperature range 80 to 135°C using high performance liquid chromatography (HPLC) and differential scanning calorimetry (DSC). Gel content was monitored gravimetrically. The prepreg resin (ca. 32% by weight) consisted of three different types of epoxy resins, an accelerator (Monuron) and the curing agent dicyandiamide. Cure kinetics parameters determined by DSC correlated with compositional parameters determined by HPLC. The curing chemistry of the prepreg resin was found to be highly dependent upon the cure temperature. Both the extent of reaction at the onset of gelation and crosslink density of the reaction products compared at the same % gelation increased with increasing temperature. The magnitude of the temperature effect suggests that curing temperature could have a profound effect on the network structure of the cured resin matrix and, therefore, on the properties of composites manufactured from this prepreg.