Morphology and properties of thermoplastic polyurethane composites incorporating hydrophobic layered silicates

Polyurethane (PU) composites incorporating Cloisite 15A (15A) were prepared via melt compounding and solvent casting. The melt-compounded composites had better dispersion and a smaller silicate stack size as a result of the higher shear forces associated with twin-screw extrusion. The PU microphase separation and hard domain order were greater in the melt-processed materials. At the concentrations of 15A employed in this study (<= 7 wt %), the filler did not have an observable effect on the microphase texture of either the solvent- or melt-processed PU. The tensile properties of the melt-compounded materials were lower than those of their solvent-cast counterparts because of thermal degradation. The solvent-cast composite containing a 3 wt % loading of 15A displayed improved tensile strength and elongation, primarily because of plasticization by the silicate organic treatment. The addition of layered silicates with high aspect ratios increased the hysteresis and permanent set of this PU elastomer. (c) 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 300-309, 2005.