Curing of DGEBA epoxy using a phenol-terminated hyperbranched curing agent: Cure kinetics, gelation, and the TTT cure diagram

The cure of diglycidyl ether of bisphenol A (DGEBA) epoxy with a novel phenol-terminated hyperbranched curing agent in stoichiometric ratio was studied comprehensively. The cure behavior was investigated using differential scanning calorimetry (DSC) in both isothermal and dynamic modes. The gelation times were determined by thermal mechanical analysis (TMA). Ramp cure data were analyzed by means of the Vyazovkinʹs model free method. The isothermal cure data were analyzed using the Kamal model and the time–temperature-superposition (TTS) kinetic method. In spite of a high ultimate conversion, onset of diffusion control sets in well before vitrification. The effects of diffusion were incorporated into the overall kinetics expression using a diffusion factor. The gel conversion is found to be independent of cure temperature, and an effort has been made to compare the measured gel conversion with the theoretical prediction. In addition, the isothermal time–temperature-transformation (TTT) cure diagram was reported.