Facile preparation of TPU/PCL/carbon nanotubes double-percolation conductive nanocomposite and evaluation of the application as flexible sensors for rapid and selective response in volatile organic compounds

Severe environmental pollution resulting from improper emissions of volatile organic gases (VOCs) has posed significant menaces to human health, ecosystem security, and the pursuit of socially sustainable development. Herein, we present a convenient approach to crafting conductive gas-sensitive nanocomposites with double-percolation microstructure by employing a blend of thermoplastic polyurethane (TPU) and polycaprolactone (PCL) as the compositing matrix, combined with multi-walled carbon nanotubes (MWCNTs) as the functional nanofiller. The analysis of the interface energy between the components inside the nanocomposites revealed that MWCNTs were preferentially dispersed within the TPU phase. By adjusting the TPU-to-PCL ratio and the adding sequence of components during compositing, a two-phase continuous matrix structure and a double-percolation conductive microstructure were attained, which was benefited to the enhancement of electrical conductivity. When the mass ratio of TPU-to-PCL was fixed at 50:50, the lowest resistivity of the TPU/PCL/MWCNTs nanocomposite, measuring 2.57 × 10⁵Ω·m was achieved when MWCNTs were initially blended with TPU followed by PCL. Gas-sensitive assessments of the TPU/PCL/MWCNTs nanocomposite revealed its exceptional selectivity, responsiveness, and recovery to formaldehyde, surpassing other targeted VOCs such as benzene, xylene, ammonia, and ethanol. Notably, gas responsiveness to formaldehyde at 25 °C and 500 ppm registers at 74% for the TPU/PCL/MWCNTs nanocomposites. Furthermore, responsiveness exhibits a robust linear correlation with increasing formaldehyde concentration.