Modeling properties of nylon 6/clay nanocomposites using composite theories

The reinforcement of nylon 6 by layered aluminosilicates (LAS) and glass fibers was examined using the composite theories of Halpin-Tsai and Mori-Tanaka. Theoretical comparisons show that exfoliated LAS offer superior reinforcement to glass fibers owing to the filler's high modulus, high aspect ratio, and its ability to reinforce in two directions. The effect of incomplete exfoliation of simple stacks of LAS on nanocomposite modulus was also examined. Increasing the number of platelets per stack and the gallery spacing between platelets results in a dramatic decrease in reinforcing efficiency. The predictions were benchmarked against experimental data for nylon 6 nanocomposites based on organically modified montmorillonite and glass fibers. The quantitative determination of the morphology of the nanocomposites is non-trivial due to the large distribution of filler shapes and sizes present. Thus, a detailed experimental procedure for determining the aspect ratio of the nanocomposites is reported. The composite theories satisfactorily capture the stiffness behavior of both types of composites. Furthermore, experimental heat distortion temperatures and those predicted from modeling the dynamic mechanical properties of nanocomposites are in reasonable agreement. (C) 2003 Elsevier Science Ltd. All rights reserved.