Effect of MWCNTs Loading on the Piezoelectric and Sensing Performance of P(VDF-HFP) Nanocomposites

This study explores the development of flexible and efficient piezoelectric materials by incorporating multiwalled carbon nanotubes (MWCNTs) into poly(vinylidene fluoride-hexafluoropropylene) [P(VDF-HFP)] polymer films. The MWCNTs, acting as nucleating agents, significantly improve the electroactive β phase content in the polymer, enhancing its piezoelectric performance. Composite films were prepared using a solution casting technique with varying MWCNTs concentrations (0.25%, 0.5%, 0.75%, and 1.0%). Morphological analysis through SEM and AFM confirmed increased surface roughness and pore size with higher MWCNTs content, resulting in better hydrophobic, mechanical and electrical properties. It is evident that the WCA values of all samples ranged from 96.73° ± 4.82° to 117.07° ± 2.10°, confirming the inherent hydrophobicity of the films and demonstrating good water repellence. FTIR and XRD analyses showed a phase transformation from the non-polar α phase to the polar β phase, enhancing the piezoelectric effect. With increasing MWCNTs content, the crystallinity of the composite improves, rising from 50.04% in the pure P(VDF-HFP) sample to 54.83% in the 1.00% MWCNTs composite, leading to more ordered structures. This boosts the mechanical properties, notably raising the tensile strength from 14.56 MPa to 45.13 MPa. TGA analysis further shows that the composites have higher thermal stability compared to pure P(VDF-HFP), due to increased crystallinity and stronger intermolecular forces. Dielectric measurements showed enhanced dielectric constant and reduced energy loss with increasing MWCNTs concentrations. This finding is pivotal in understanding the piezoelectricity mechanisms within these composites. Finally, piezoelectric sensitivity tests demonstrated an optimal concentration of 0.75% MWCNTs, achieving a voltage output of 16.58 V under applied mechanical stress, making these composites promising candidates for advanced sensing technologies.