Networks by fast epoxy polymerization

A fast curing epoxy system, suitable for reactive processing, was investigated. The reaction of epoxy resin (Epon 815, Shell), comprising 85% diglycidyl ether of bisphenol-A and 15% butyl glycidyl ether with boron trifluoride etherate was extremely fast and uncontrollable at room temperature. The reaction rate could be controlled by complexing boron trifluoride with a polyether triol (Voranol 2070, Dow). The new system was ideal for reactive processing. It exhibited an induction time at an initial temperature of 40°C before undergoing very rapid curing. The induction time decreased from 55 to 2 seconds with increasing ratio of boron trifluoride to epoxy and with reactant temperature. The triol was fully incorporated in the network, affecting the final properties of the polymer network. Thus, it was possible to manipulate the gel times and material properties by varying the reactant ratios. A model system comprising phenyl glycidyl ether and octanol was used to investigate the mechanism. The incorporation of triol and the presence of cyclic oligomer indicates that both activated monomer and active chain end mechanisms were operating during the curing of these systems. The low molecular weights of the polymers made from the model system indicated the presence of chain transfer and termination reactions.