High performance polyurethane composites with isocyanate-functionalized carbon nanotubes: Improvements in tear strength and scratch hardness

A microwave-assisted functionalization of carbon nanotubes (CNTs) with isocyanate groups allowed a reduction of functionalization time from 24 h to 30 min with no change in the degree of functionalization or in the nanotube characteristics. Polymer nanocomposites with enhanced mechanical properties were obtained because of the tailored interface by the covalent linkage between the surface-modified multiwalled-carbon nanotubes (MWCNTs) and an elastomeric polyurethane (PUE) matrix. The mechanical data revealed that the composite containing 0.25 wt % of MWCNT-NCO showed an increase of 31% in tear strength and 28% in static toughness. A good adhesion between the matrix and individually dispersed nanotubes was observed in the scanning electron microscopy and transmission electron microscopy images. Nanoindentation and nanoscratch experiments were conducted to investigate the properties on the sub-surface. An increase by a factor of 3 in the scratch hardness was observed for the composite with 0.50 wt % of MWCNT-NCO with respect to the neat PUE. (C) 2016 Wiley Periodicals, Inc.