Crosslinking of mixtures of DGEBA with 1,6-dioxaspiro[4,4]nonan-2,7-dione initiated by tertiary amines. Part IV. Effect of hydroxyl groups on initiation and curing kinetics

The anionic homopolymerization of DGEBA epoxy resin and its anionic copolymerization with a bislactone was studied using two alternative tertiary amines, 1-methylimidazole (1MI) and dimethylaminopyridine (DMAP) as initiators. 1MI caused slower cure than DMAP in neat DGEBA and DGEBA-bislactone formulations. Studies of the influence of the hydroxyl concentration in the DGEBA oligomer on its homopolymerization explain descrepancies in the literature regarding the ability of these initiators to produce full cure of the epoxy groups. In contrast, in the copolymerization of DGEBA-bislactone formulations, full cure could be readily achieved with either 1MI or DMAP as initiators, irrespective of the hydroxyl content. FTIR and DSC experiments show that this behaviour is associated with the formation of the carboxylate anion which plays an important part on the curing kinetics and the completion of cure.