Enhancing energy harvesting capabilities using lead-free, flexible piezoelectric poly (vinylidene fluoride) tapes

Abstract

Poly(vinylidene fluoride) (PVDF) has been widely investigated as an energy harvesting material not only for its piezoelectric properties but also for being flexible, lead-free piezoelectric properties, and processing versatility. To enhance its piezoelectric performance, in this study, an additive was blended with PVDF to facilitate the crystalline transformation from α-phase to β-phase. This study explores the influence of two manufacturing processes, extrusion (EX) and compression moulding (CM), and the influence of different stretching and polarisation conditions on the piezoelectric performance of PVDF tapes for their integration into a cantilever beam for energy harvesting applications. The heat stretching process for EX and CM tapes was conducted at distinct temperatures (80° and 120 °C) and stretching speeds (300 and 10 mm/min), leading to different stretch ratios (3.0 and 4.50) that effectively raised the β-phase. Structural changes in the crystalline phases were identified using X-ray diffraction and Fourier transform infrared spectroscopy. Following this, the dipoles were oriented in the direction of an applied electric field (400–500 kV/cm). The piezoelectric performance was characterized by d₃₃ values, and peak-to-peak voltage, under sinusoidal tensile stress, was obtained using a universal tensile testing machine. A d₃₃ value of 25–30 pC/N and a peak-to-peak voltage of 27–35 V were obtained. Additionally, the piezoelectric behaviour was observed by arranging the tapes in a cantilever made of fibreglass composite and subjecting it to vibrational excitation at the resonance frequency. Maximum values of output voltage of 12 V for each tape were obtained under cantilever fixture.