Improved strain sensing property of functionalised multiwalled carbon nanotube/polyaniline composites in TPU matrix

Polyaniline (PANI)/functionalised multiwalled carbon nanotube (FMWCNT) based conductive thermoplastic polyurethane (TPU) films were prepared to study their strain sensing property. The composites were prepared by solution casting method using FMWCNT coated with polyaniline. The coating was done by in-situ and ex-situ polymerization of aniline. The composites thus prepared were designated as FMWCNT-PANI/TPU (I) and FMWCNT-PANI/TPU (E), respectively. The electrical resistivity and resistivity - strain behaviour of these composites were measured. The percolation threshold and the strain sensitivity of these films depended on the dispersion of conductive fillers in the polymer matrix. The well-dispersed filler in FMWCNT-PANI/TPU (I) composites resulted in low percolation threshold and improved strain sensitivity. These composites with 2 weight% filler content, showed a gauge factor of 1075 at 100% strain and exhibited high reversibility in resistivity upon elongating to 20%. A coating of PANI on FMWCNT reduced its entanglement and enhanced the interfacial interaction between the nano fillers and TPU, leading to improved strain sensitivity. The experimental data for strain sensing was in good agreement with the theoretical equations derived from a model based on the tunneling theory by Simmons.