Processing of polyurethane/carbon nanotubes composites using novel minimixer

Thermoplastic polyurethane (TPU)/multiwalled carbon nanotube (MWNT) composites were prepared through mixing and extrusion process in a minimixer equipped with a single screw plus twin shaft paddles. In order to improve the dispersion of MWNT and the compatibility between MWNT and polyurethane, the MWNT were functionalised with polytetramethylene ether glycol (PTMEG) through a grafting process to get the MWNT-g-PTMEG. The relationship between the structure and properties of the TPU/MWNT composites was examined. The results showed that MWNT-g-PTMEG can be uniformly dispersed in the TPU matrix, and the tensile strength and elongation at break were both improved. For 1 wt-% MWNT-g-PTMEG/TPU composites, the tensile strength and elongation a break were enhanced to similar to 41 MPa and 568% respectively, while for pristine TPU, they were similar to 34 MPa and 508% respectively. Dynamic mechanical analysis showed that the storage modulus at room temperature increased, and the maximum tan delta decreased with increasing MWNT-g-PTMEG contents. The simultaneous small and wide angle X-ray scattering measurements showed that with the incorporation of MWNT-g-PTMEG, the degree of crystallinity, interdomain distance, hard domain thickness as well as the degree of microphase separation increased. It appears that the functionalised MWNT-g-PTMEG promotes the formation of the ordered lamellar structure of polyurethane hard segments.