Largely Enhanced Stretching Sensitivity of Polyurethane/Carbon Nanotube Nanocomposites via Incorporation of Cellulose Nanofiber

Stretchable sensors have drawn a great deal of attention due to their importance and necessity in high-technology areas. However, it is difficult to obtain sensors with high sensitivity accompanied by high tenacity. Taking advantage of the very large aspect ratio and amphiphilicity of nanofibrillated cellulose (NFC), in this study, we fabricated polyurethane (TPU)/multiwall carbon nanotube (CNT) nanocomposites with excellent dispersion using NFC as stabilizer. Then the mechanical and electrical properties, particularly the stretching sensitivity of the prepared TPU/NFC@CNTs nanocomposites, were investigated. It was found that the prepared TPU/NFC@CNTs has much better mechanical properties and electrical conductivity compared with those of TPU/CNTs composites. More importantly, a linear change of electrical conductivity as a function of stretching is observed for at least strains up to 300% and a very high sensitivity whose gauge factor close to SO could be achieved. The excellent stretching sensitivity could be attributed to the unique role of NFC: (1) assisting the dispersion of CNTs, (2) enhancing the interaction between NFC and TPU matrix as due to its amphiphilicity, and (3) increasing the overall aspect ratio of CNTs via connecting many tiny CNTs bundled together along the long axis.