Multiwalled carbon nanotube-coated poly-methyl methacralate dispered thermoplastic polyurethane composites for pressure sensitive application

Abstract

Thermoplastic polyurethane (TPU) is a widely used polymer for a variety of pressure

sensing applications because of its softness and shape memory. This work reports the synthesis

of novel TPU-based three-dimensional structured (3D) pressure-sensitive composites via the melt

mixing method. Poly-methyl methacrylate (PMMA) microbeads of different sizes (5, 10, and 20 µm)

were first coated with multi-walled carbon nanotubes (MWCNT) and then incorporated into the

TPU matrix for achieving an early electro conductive percolation threshold compared to without

PMMA beads. The addition of MWCNT coated PMMA beads reduced the TPU insulated areas

by creating a 3D conductive network that finally reflected the early percolation threshold during

external pressure. Raman microscopy and XRD results confirmed the MWCNT coated nicely on the

surface of PMMA beads. The pressure sensitivity results also confirmed the decrease in resistance of

the composites with the increase in the applied external pressure. Composites with 10 µm PMMA

bead size showed the most linear responses to the decrease in resistance with increasing pressure

and showed a higher strain gauge factor value (3.15) as compared to other composites, which had

values of 2.78 and 2.42 for 20 and 5 µm, respectively. Microstructure analysis of the composites by

SEM, capacitance, permeability, and thermal conductivity measurements was also investigated to

support the above evidence. The results support the suitability of this novel composite as a potential

candidate for pressure sensing applications.