Effect of aluminum silicate on the impact and adhesive properties of toughened epoxy resins

Carboxyl randomized poly(2-ethyl hexyl acrylate) (CRPEHA) and epoxy randomized poly(2-ethylhexyl acrylate) (ERPEHA) have been used to toughen aluminum silicate filled epoxy resin cured with 4,4'-diaminodiphenyl methane. CRPEHA (A-1) and ERPEHA (B-1) were synthesized by solution polymerization technique in the form of liquid rubbers. The toughened epoxy networks were evaluated for their impact and adhesive properties. The epoxy/liquid rubber compositions were varied to study the effect of toughener concentration on the adhesive and impact properties for both filled and unfilled systems. Improved properties were obtained for epoxy resins toughened with (1 : 1) mixture of CRPEHA and ERPEHA. Lap shear strength of filled epoxy resins was higher than that of unfilled ones but the reverse was the case for impact strength. Analysis of adhesive failure surfaces by scanning electron microscopy (SEM) indicated the presence of a two-phase microstructure.