Characterization and Electromechanical Behavior of Developed PVDF Yarn and Fabric as Pressure Sensor

Poly­(vinylidene fluoride) (PVDF) yarns and fabrics are developed as pressure sensors, and their manufacturing and characterization are described. PVDF multifilament yarns are produced using the melt spinning method, and an additional post-treatment process is applied with draw ratios ranging from 0 to 6. To investigate the influence of the poling process on the piezo response, a poling setup is used to polarize yarns under different conditions, including a temperature of 80 °C, a high voltage of 18.5 kV, and varying draw ratios from 2 to 6. Plain fabrics of poled and unpoled PVDF yarns are prepared with different weft densities. The presence of the crystalline phases in each sample was confirmed by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and X-ray diffraction (XRD). A simple mathematical model is also presented to consider the influence of weft density on the piezoelectric response. The results showed good conformity with the response of the piezo compression tester device. Two different electromechanical tests were performed: compression (for yarn and fabric samples) and compression-bending (for one fabric sample). The electromechanical results indicate that the drawing and poling processes highly contribute to the output electrical responses. In particular, the highest electrical voltage (1.5 mV) corresponds to the yarn sample poled at a draw ratio of 6. However, the results of this work suggest that increasing the poled PVDF fabric deformation through a piezo compression-bending tester enhances the output electrical response from 1.09 to 60 mV.