Effect of processing parameters and clay volume fraction on the mechanical properties of epoxy-clay nanocomposites

The influence of processing parameters and particle volume fraction was experimentally studied for epoxy clay nanocomposites. Nanocomposites were prepared using onium ion surface modified montmorillonite (MMT) layered clay and epoxy resin (DEGBF). Two different techniques were used for dispersing the clay particles in the epoxy matrix, viz. high-speed shear dispersion and ultrasonic disruption. The volume fraction of clay particles was systematically varied from 0.5 to 6%, and mechanical properties, viz. flexural modulus and fracture toughness, were studied as a function of clay volume fraction and the processing technique. The flexural modulus was observed to increase monotonously with increase in volume fraction of clay particles, while, the fracture toughness showed an initial increase on addition of clay particles, but a subsequent decrease at higher clay volume fractions. In general, nanocomposites processed by shear mixing exhibited better mechanical properties as compared to those processed by ultrasonication. Investigation by X-ray diffraction (XRD) revealed exfoliated clay structure in most of the nanocomposites that were fabricated. Morphologies of the fracture surfaces of nanocomposites were studied using a scanning electron microscopy (SEM). Presence of river markings at low clay volume fractions provided evidence of extrinsic toughening taking place in an otherwise brittle epoxy.