Enhanced mechanical energy-harvesting performance of eggshell-derived hydroxyapatite/polyurethane piezocomposites through mixture design approach: a promising route for advanced dielectric materials

Abstract

Piezocomposites provide lightweight, flexible and scalable technologies for efficiently converting mechanical energy into electrical energy. For sustainable energy production, we examined a low-cost, biobased alternative to convert mechanical energy into piezoelectric energy. Hydroxyapatite (HA) having a particle size of 53.26 nm made from chicken eggshell waste was combined with polyurethane (PU) to produce piezoelectric composites. In situ polymerization was performed using aliphatic isocyanates, isophorone diisocyanate, poly(propylene glycol) and 1,4-butanediol. The piezoelectric properties of six different composite films with varying HA concentrations (0–25%) were optimized using a statistical mixture design approach. Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray diffraction analysis, dynamic mechanical analysis and scanning electron microscopy were utilized for physicochemical characterization. As the HA concentration was increased, the mechanical properties were enhanced, as a uniform dispersion of HA was observed within the PU matrix. An oscilloscope displayed an output voltage of 17.46 V at 16 Hz, with 3 N force applied to a 25% HA composite film. The dielectric constant, dielectric loss and resistivity are frequency functions, and impedance analysis showed low-frequency values with high dielectric properties. The present study has indicated that PU/HA biocomposites are cost-effective and lightweight and can be used in piezoelectric devices in biomedical and wearable electronics. © 2025 Society of Chemical Industry.