The Effect of Different Clay Dispersion Methods on the Properties of Polyurethane/Clay Nanocomposites

Polyurethane/clay (PU/clay) nanocomposites were synthesised using polymerisation and dispersion blending methods. The intercalation and exfoliation properties of the PU/clay nanocomposites were investigated by X-ray diffraction and transmission electron microscope. Clay intercalation of polymerised PU/nanocomposites was achieved and the interlayer spacing of clay was greatly enlarged from 17 angstrom to similar to 30 angstrom. Expansion in d-spacing was also observed for PU/clay nanocomposites prepared using dispersion methods. PU/clay nanocomposites prepared from dispersion of clay particles in the prepolymer matrix, followed by chain extension reaction, showed much high molecular weight and significant improvement in mechanical properties as compared with PU/clay nanocomposites produced using polymerisation or a simple high speed blending method in which clay was blended into the PU matrix. For PU/clay nanocomposites prepared using the blending method, high speed dispersion of 2% clay in PU resulted in approximately a two-fold increase in the Young's modulus. Further increase in the clay loading from 2 to 6% made the corresponding nanocomposite polymer films more rigid and stiffer. This study shows that PU/clay nanocomposite properties are highly dependent on the preparation methods and provides useful guidelines for the future design and preparation of PU/clay nanocomposites.