Polyurethane/clay nanocomposites with improved helium gas barrier and mechanical properties: Direct versus master-batch melt mixing route

Thermoplastic polyurethane (TPU)/clay nanocomposite films were produced by incorporation of organo-modified montmorillonite clay (Cloisite 30B) in TPU matrix by two different melt-mixing routes (direct and master-batch-based mixing), followed by compression molding. In master-batch mixing where the master-batch was prepared by mixing of clay and TPU in a solvent, better dispersion of clay-layers was observed in comparison to the nanocomposites produced by direct mixing. As a consequence, superior mechanical and gas barrier properties were obtained by master-batch mixing route. The master-batch processing resulted in 284 and 236% increase in tearing strength and tearing energy, respectively, with 5 wt % clay-loading. Interestingly, in case of master-batch mixing, the tensile strength, stiffness as well as breaking extension increased simultaneously up to 3 wt % clay-loading. The helium gas permeability reduced by about 39 and 31% for the TPU/clay nanocomposites produced by mater-batch and direct mixing routes, respectively, at 3 wt % loading of clay. Finally, the gas permeability results have been compared using three different gas permeability models and a good correlation was observed at lower volume fraction of clay. (c) 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46422.