Epoxy prepolymers cured with boron trifluoride-amine complexes, 1. Influence of the amine on the curing window

Different pure complexes were synthesized by an interchange reaction of BF₃-etherate with amines in dichloromethane. All of the resulting complexes are solid, but they can be dissolved in a low-molecular-weight poly(ethylene oxide) to favour their use as initiators. DSC analysis demonstrated strong interactions between the BF₃-complex and the polyether. This is probably caused by the formation of hydrogen bonding between the hydrogens of the amine and the ether groups. The reactivity of amine complexes was characterized by reaction with the epoxy prepolymer. The reactivity increases with decreasing basicity of the amine, showing a relationship between the initiation and propagation of the expoxy homopolymerization and the stability of the complex. A slight influence on the reaction temperatures by the amount of polyether is observed, but the glass transition temperature of the epoxy network decreases when a large excess is used.