Tetrafunctional epoxy resins: Modeling the curing kinetics based on FTIR spectroscopy data

The curing kinetics of two thermosetting systems based on a tetrafunctional epoxy resin was investigated by Fourier transform infrared spectroscopy. T wo formulations were studied, in which the hardener was an aromatic diamine and a carboxylic dianhydride, respectively. The quantitative evaluation of the epoxy conversion was based on spectra collected in the near-infrared r ange (8000-4000 cm(-1)) as well as in the medium infrared range (4000-400 c m(-1)). The kinetic parameters evaluated in the above frequency intervals w ere significantly different. The reasons for such a discrepancy are discuss ed critically. Several kinetic models, based on the widely employed Kamal a pproach, were applied to verify their predictive capability. Satisfactory r esults were obtained for the amine-cured system, particularly with a modifi ed equation taking into account the autocatalytic nature of the process as well as a limiting diffusional effect. Less accurate results were achieved for the anhydride-cured system. (C) 1999 John Wiley & Sons, Inc.