Thermoplastic polyurethane/multiwalled carbon nanotubes nanocomposites: Effect of nanoparticle content, shear, and thermal processing

In this study, nanocomposites of thermoplastic polyurethane and multiwalled carbon nanotubes (MWCNTs) with varying nanofiller content (ranging from 0 wt% to 1 wt%) were prepared via the melt compounding method. Moreover, the influence of shear field and thermal processing on electrical conductivity has been evaluated. The evaluation of the phase separation degree revealed that with the increase in the nanofiller content from 0% to 0.4%, the phase separation degree increased by 25%. However, a further increase in the nanoparticle content slightly decreased the phase separation degree. Moreover, by increasing the nanofiller content up to 0.4%, the melting temperature and the melting enthalpy of the soft phase as well as the melting temperature of the hard phase increased. With the increase in the nanofiller content to 0.4%, a 3D network of MWCNTs was developed, corroborating the formation of an electrically conductive nanocomposite. The conductivity increased 3750-fold in the quenched and 5000-fold in the annealed samples with the increase in the nanofiller content from 0.2% to 1%. In general, the annealed nanocomposites featured lower conductivity than the quenched ones. The effect of the shear on conductivity was nanofiller content-dependent. Exposure to shear below and above the percolation threshold decreased and increased the electrical conductivity, respectively.