Strain-sensing behavior of flexible polypropylene/poly(ethylene-co-octene)/multiwalled carbon nanotube nanocomposites under cyclic tensile deformation

In this study, the associations between the structural evolution and physical properties of polypropylene/poly(ethylene-co-octene)/multiwalled carbon nanotube (PP/POE/MWCNTs) composites were established. The MWCNTs particles preferentially migrating from PP matrix to disperse in POE phase, which contributed to a richer network structure, thus resulting in a significant improvement for electrical conductivity, as well thermal stability, and toughness property with the elongation at break from 300% to 800%. Furthermore, the online strain-resistance analysis showed that introducing POE phase had a big advantage in improving the recovering resilience and stability of the conductive network structure of PP/POE/MWCNTs composites under a multi-time circular tensile test with a strain of 5%. It was highlighted that the maximum and minimum electrical conductivity levels of PP/POE composites remained almost constant and even the ratio of the real-time resistance to the initial one was negative just at the beginning of each circulation regarding the strain stretching and recovery. This was attributed to the oriented conductive network structure of PP/POE nanocomposites induced by the applied strain, thereby increasing the electrical conductivity. Overall, this research provides a basic guidance for preparing composites with ultrahigh flexibility and stability under a circular deformation, which is an essential element taken into consideration for smart sensors with high sensitivity.