Mechanical characterization of epoxy composites modified with reactive polyol diluent and randomly-oriented amino-functionalized MWCNTs

Increased fracture toughness of diglycidyl ether of bisphenol A (DGEBA) type epoxy resin was obtained without compromising other desired mechanical properties, such as strength and stiffness, by combining the benefits of adding polyether polyol and amino-functionalized multi-walled carbon nanotubes (NH2-MWCNTs) simultaneously. The effect of concentration on the morphology of three-phase nanotube/polyol/epoxy composites was investigated using scanning electron microscopy (SEM). Mechanical properties were evaluated by three point flexure and single edge notch bend (SENB) fracture toughness tests. Addition of a polyether polyol to the epoxy resin increased mode-I fracture toughness and flexural strain energy, while adversely affecting flexural strength and stiffness. A synergistic effect was observed with the addition of amino-functionalized multi-walled carbon nanotubes (NH2-MWCNTs) into polyol toughened epoxy, with significant improvements in fracture toughness and strain energy as well as in flexural strength and stiffness. Matrix plastic deformation and lower crosslink density due to polyether polyol in the epoxy system increased toughness while reducing flexural strength and stiffness. However, incorporation of uniformly dispersed 0.3 wt.% loading of NH2-MWCNTs into the polyol-toughened epoxy composites improved the mechanical properties as well as fracture toughness, compared with pristine epoxy and polyol-toughened epoxy.