TOUGHENING OF EPOXY-RESINS BY MODIFICATION WITH REACTIVE ELASTOMERS COMPOSED OF BUTYL ACRYLATE, GLYCIDYL METHACRYLATE AND ACRYLONITRILE OR STYRENE

Acrylic elastomers with pendant epoxy groups were used to improve the toughness of bisphenol-A diglycidyl ether epoxy resin cured with p,p'-diaminodiphenyl sulphone. The elastomers were prepared by terpolymerization of butyl acrylate (BA), glycidyl methacrylate (GMA) and acrylonitrile (AN) or styrene (St). BA-GMA-AN terpolymers were more effective as modifiers for toughening of the epoxy resin system than those containing St. The use of the latter terpolymers tended to separate macroscopically because of poor compatibility with the epoxy matrix. The addition of 20 wt% of the terpolymer (66 mol% BA. 20 mol% GMA and 14 mol% AN units, M(n)BAR 8700) led to a 40% increase in the fracture toughness (K(IC)) of the cured resin at slight expense of its mechanical properties. The modified resins had two-phase morphologies in which the volume fraction and average diameter of the dispersed particles were dependent on the structure and concentration of the terpolymers. The glass transition temperatures of cured resins were equal to or less than that of the parent epoxy resin. The toughening mechanism is discussed in terms of the morphological and dynamic viscoelastic behaviours of the modified epoxy resin system.