Reactive blending of functionalized acrylic rubbers and epoxy resins

A high molecular weight acrylonitrile/butadiene/methacrylic acid (Nipol 147 2) rubber is chosen to control processability and mechanical properties of a TGDDM (tetra glycidyl diphenyl methane) based epoxy resin formulation for aerospace composite applications. The physical blend of rubber and epoxy r esin, achieved by dissolution of all the components, in a common solvent, f orms a heterogeneous system after solvent removal and presents coarse phase separation during cure that impairs any practical relevance of this materi al. A marked improvement of rubber-epoxy miscibility is achieved by reactiv e blending ('pre-reaction') the epoxy oligomer with the functional groups p resent in the rubber. The epoxy rubber 'adduct' so obtained appears as a ho mogeneous system at room temperature and also after compounding with the cu ring agent. Depending on the nature and extent of interactions developed be tween the rubber and the epoxy resin during 'pre-reaction,' materials with different resin flow characteristics, distinctive morphologies and mechanic al properties after curing were obtained. The effect of 'pre-reaction' on t he resin cure reaction kinetics has been also investigated.