Studies on the adhesive properties of solid elastomer-modified novolac epoxy resin

Adhesive properties like lap shear strength and T-peel strength of novolac epoxy resin modified with carboxyl terminated butadiene acrylonitrile (CTBN) solid resin and cured with two different curing agents namely, dicyandiamide (DICY) and 3,3′-diaminodiphenyl sulphone (DDS) were evaluated using aluminium adherends. Substantial improvement in adhesive properties was obtained by the inclusion of moderate concentrations of CTBN in the formulations. Adhesive properties of the formulations were evaluated when used as paste, nylon-carrier supported and unsupported film adhesives. Optimum concentrations of 20 parts by weight (pbw) and 25 pbw of solid CTBN in epoxy were obtained for the DICY and DDS cured systems, respectively. Inclusions of larger amounts of CTBN led to flexibilisation of the systems thereby reducing the adhesive properties. CTBN also reduced the glass transition temperatures and high-temperature strength retention of both the systems. The development of two-phase morphology for the CTBN-modified systems was evident from scanning electron micrographs (SEM).