Reduction of the shrinkage of thermosets by the cationic curing of mixtures of diglycidyl ether of bisphenol A and 6,6-dimethyl-(4,8-dioxaspiro[2.5]octane-5,7-dione)

Ytterbium and lanthanum triflates were used as initiators to cure mixtures of diglycidyl ether of bisphenol A and 6,6-dimethyl-(4,8-dioxaspiro[2.5]octane-5,7-dione) in several proportions. The evolution of the epoxy and 6,6-dimethyl(4,8-dioxaspiro[2.5]octane-5,7-dione) bands during curing and the linear ester groups in the final materials were evaluated with Fourier transform infrared in the attenuated-total-reflection mode. The use of a conventional cationic initiator, boron trifluoride monoethylamine, was also studied to test the advantages of lanthanide triflates. The shrinkage after curing and the thermal degradability of the materials with variations in the comonomer ratio and the initiator were evaluated and related to the chemical structure of the final network. (c) 2006 Wiley Periodicals, Inc.