Piezoresistive thermoplastic polyurethane nanocomposites with carbon nanostructures

Abstract

Piezoresistive strain sensors for structural health monitoring (SHM) and human body motion detection applications commonly use polymer nanocomposites based on carbon fillers such as carbon black (CB), carbon nanotubes (CNTs) or graphene nanoplatelets (GNPs). Here, we report on new nanocomposites from thermoplastic polyurethane (TPU) with branched carbon nanotubes (known as carbon nanostructures (CNS)) as well as hybrid fillers (CNS + CNT or CNS + GNP) with superior electrical conductivity. These composites manufactured by melt mixing show also exceptional piezoresistive sensitivity. As an example, at only 2 wt% filler concentration, the TPU/CNS and TPU/CNS/GNP nanocomposites have a gauge factor (GF) up to 28 and 144, respectively, under 50% strain (very low for elastomers), which is currently the highest reported values for TPU composites with carbon nanofillers. This study sheds light on the effects of filler morphological structure on electrical conductivity and piezoresistive sensitivity of polymer nanocomposites, introducing a new strategy to prepare multifunctional polymer nanocomposites with very high piezoresistive sensitivity for SHM and body motion detection applications.