Epoxy formulation including an acrylic triblock copolymer adapted for use in filament winding

Abstract

Commercial triblock copolymers with a poly(butyl acrylate) (PBuA) central block joined to two poly(methyl methacrylate) (PMMA) end blocks (denoted as MAM) or to two random copolymers end blocks based on MMA and N,N′-dimethylacrylamide (DMA) (denoted as MAM-N), can be employed as toughening agents for thermoset composites. However, their use in epoxy formulations for filament winding, requiring low viscosities during the fiber-impregnation step associated with an adequate glass transition temperature of the cured product is not trivial. In this study, we show that a blend of diglycidylether of bisphenol A (DGEBA), 4,4′-diamino-3,3′-dimethyldicyclohexylmethane (3DCM) and benzylamine (BA), with 20% of amine hydrogens provided by BA, and containing 5 wt% MAM, can be used for these purposes. The addition of MAM increased the critical stress intensity factor from 0.63 MPa.m1/2 to 1.0 MPa.m1/2, the glass transition temperature from 138°C to 145°C, and the glassy modulus at 25°C from 2.95 GPa to 3.15 GPa. MAM was a better choice for the envisaged applications than MAM-N because it led to solutions of lower viscosity. The higher viscosity produced by MAM-N was explained by specific interactions between the epoxy-amine solvent and DMA units present in its terminal blocks.