The effect of different hard segments in polyurethane on the electrical conductivity of polyurethane grafted multi-walled carbon nanotube/polyurethane nanocomposites

► Polyurethane (PU) was grafted on the surface of multi-walled carbon nanotubes. ► PU/PU-g-MWNTs film was obtained using a simple blending method. ► HDI-based PU film demonstrated homogeneously dispersed MWNTs in the matrix. ► The critical exponent of HDI film calculated based on fitted data was 2.43. ► HDI film led to enhanced electro-conductivity compared to the MDI film. Polyurethane (PU) grafted multi-walled carbon nanotubes (MWNTs) (PU-g-MWNTs) containing different hard segments (hexamethylene diisocyanate, HDI, and methylenediphnyl 4,4′-diisocyanate, MDI) were synthesized to fabricate an electro-conducting nanocomposite. The PU conducting nanocomposites were obtained using a simple blending method. PU-g-MWNTs can improve the interfacial compatibility between the MWNTs and PU matrix. The HDI-based PU nanocomposite showed enhanced dispersibility of the functionalized MWNTs than the MDI-based nanocomposite. The difference in dispersity was related to its electrical conductivity. The critical concentration of the MDI-based nanocomposite was lower than the HDI-based nanocomposite because less dispersed and more aggregated MWNTs partially formed a conducting path at a lower concentration. The critical exponent of the HDI-based nanocomposite revealed that the better dispersed MWNTs exhibited enhanced electrical conductivity, compared to the MDI-based nanocomposite, as the filler concentration was increased.