Characterization of new reworkable thermosetting coatings obtained by cationic and anionic curing of DGEBA and some Meldrum acid derivatives

Rare earth metal triflates, BF3 center dot MEA and N,N-dimethylaminopyridine (DMAP) were used as cationic and anionic initiators to cure mixtures of diglycidylether of bisphenol A (DGEBA) and Meldrum acid (2,2-dimethyl-4,6-dioxo-1,3-dioxane) derivatives in several proportions. The copolymerization process led to poly(ether-ester) three-dimensional networks. The linear ester groups in the final materials were evaluated by Fourier transform infrared in the attenuated-total-reflection mode (FTIR/ATR). The shrinkage after curing and the thermal degradability of the materials on varying the lactone structure, comonomer ratio and the initiator used were evaluated and related to the chemical structure of the final network. The addition of lactones to the reactive mixture reduced the shrinkage on curing, which improve the reliability of coatings. The materials obtained were more degradable than conventional epoxy resins due to the tertiary alkyl ester groups incorporated into the network, which facilitates to remove the coatings when the service life is over. The flexibilizing effect of the linear ester introduced into the network by copolymerization with DGEBA was studied by DMTA. Microhardness and adhesion characteristics of these materials, which are interesting characteristics in coating industries, were also evaluated. (C) 2008 Elsevier B.V. All rights reserved.