Effect of carboxyl‐terminated butadiene acrylonitrile copolymer concentration on mechanical and morphological features of binary blends of nonglycidyl‐type epoxy resins

Blend samples were prepared by physical blending of nonglycidyl‐type epoxy resin with varying weight ratios of carboxyl‐terminated butadiene acrylonitrile (CTBN) copolymer ranging between 0 and 25 wt%. The blend samples were cured with stoichiometric quantity of diamine. A comparative study of prepared blend samples by Fourier transform infrared (FTIR) spectroscopy showed the modification as a result of chemical reactions between cycloaliphatic epoxy, CTBN, and 4,4′‐diamino diphenyl sulfone. The impact strength of the blend systems increased up to 15 wt% addition of CTBN in the blend and decreased thereafter. The toughness and elongation at break increased, whereas tensile strength decreased up to 20 wt% loading of CTBN in the blends. Two‐phase morphology appeared with the incorporation of CTBN in the cycloaliphatic epoxy resin matrix.