Thermomechanical and fracture properties of exfoliated nanoclay nanocomposites

Abstract

This article investigates the dispersion of nanoclay and its effect on the properties of nanoclay/epoxy nanocomposites developed using a high-shear mixing technique. Epon 828, Nanomer 1.30 E, and a compatible amine-curing agent (Epikure W) were the materials used. The dispersion of nanoclay was studied using XRD and TEM at different levels of magnification. Even though nanoclays were found to have exfoliated based on XRD’s d-spacing data (>8 nm), they remained as tactoids based on TEM data. The effect of curing on the dispersion of nanoclay was also studied using XRD analysis, which showed polymerization of resin in-between the nanoclay layers during curing. This polymerization was only helpful for the exfoliation of nanoclay, it could not completely delaminate and disperse the individual nanoclay layers. The nanocomposites were characterized using dynamic mechanical analysis and ASTM standard fracture tests. Measured elastic modulus was compared with the predicted modulus using modified Halpin—Tsai model. The experimental value was less than the predicted value and the difference was attributed to the poor dispersion of nanoclays. However, addition of 5.3 wt% nanoclay increased the storage modulus and the fracture toughness of epoxy resin by 21 % and 16%, respectively. The fracture morphologies indicated that the major toughening mechanism was due to crack deflection around nanoclay tactoids.