COMPETITIVE PRIMARY AMINE EPOXY AND SECONDARY AMINE EPOXY REACTIONS - EFFECT ON THE ISOTHERMAL TIME-TO-VITRIFY

The effect of temperature on the ratio of the kinetic rate constants, k2/k1, has been investigated using FTIR spectroscopy for the competing reactions of epoxy with secondary amine (k2) and primary amine groups (k1) in a trimethylene glycol di-p-aminobenzoate/diglycidyl ether of the bisphenol A system. The ratio of the rate constants increases from 0.16 to 0.33 in the temperature range 100-160-degrees-C. The corresponding difference in the activation energies for the competing reactions is about 3.7 kcal/mol. The effect of the ratio on the time-to-vitrify contour of the isothermal time-temperature-transformation (TTT) cure diagram is discussed: The effect is more significant at higher curing temperatures.