Cationic cure of epoxy resin by an optimum concentration of N-benzylpyrazinium hexafluoroantimonate

Cure behavior of an epoxy resin was investigated at different cure temperatures (110, 120, 130, 140, and 150 degreesC) and cure times in the presence of 2 wt% of an N-benzylpyrazinium hexafluoroantimonate (BPH) cationic catalyst by means of differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The glass transition temperature (T-g) and chemical conversion (x) at the different temperatures were determined from DSC thermograms. The T-g and x vs. In time data were superposed up to T-g = 100degreesC and x = 0.70 by shifting horizontally at a reference temperature of T-g = 130degreesC. It is interesting that the T-g and x of the superposed data increase rather slowly in the early stage of cure and rapidly thereafter. Therefore, the increase of the T-g and x can be divided into two regions; R-I = -18.4(= T-go) similar to 5degreesC and R = 5 similar to 100degreesC in T-g, and R-I = 0 similar to 0.24 and R-II = 0.24 similar to 0.70 in x. The R, is closely related to the initiation reactions between BPH and epoxy and between hydroxy group and epoxy in this epoxy/catalyst system. From the kinetic analysis of the T-g-shift. activation energy was 12.5 kcal/mol. The relationship between T-g and x was also considered. The gelation and vitrification times for different cure temperatures were obtained from DMA curves.