New thermosets obtained from DGEBA and Meldrum acid with lanthanum and ytterbium triflates as cationic initiators

Ytterbium and lanthanum triflates were used as cationic initiators to cure mixtures of diglycidylether of bisphenol A (DGEBA) and Meldrum acid (MA) in several proportions of comonomers and initiators. The evolution of epoxy and lactone groups during curing, and of linear ester formed in the final materials were evaluated by Fourier transform infrared in the attenuated-total-reflection mode (FTIR/ATR). The global evolution of the curing process was investigated by calorimetric analysis and the activation energy was calculated by isoconversional procedures. Shrinkage on curing and thermal degradability of the final materials on varying the initiator and the proportion of Me]drum acid in the mixtures were evaluated. The expandable character of MA was confirmed. The materials obtained were more degradable than conventional epoxy resins due to the tertiary ester groups incorporated into the network by copolymerization, especially those obtained with ytterbium triflate. On increasing the proportion of initiator the degradability was also increased. (C) 2008 Elsevier Ltd. All rights reserved.