Castor‐oil derived polyurethane/barium titanate piezoelectric smart composite coatings for energy harvesting applications: Prediction and experimental characterization of electro‐elastic properties

Abstract Sustainable and environment‐friendly polymer composite smart paints/coatings with polyurethane (PU) derived from castor‐oil (CO) as the matrix and barium titanate (BTO) microparticles as piezo‐active inclusions (2, 4, 6, 8, and 10 vol.%) have been prepared employing ultrasonication and solvent casting, followed by contact DC poling method. Relative dielectric constants varied from 5.26 ± 0.37 for pristine COPU to 8.9 ± 0.36 for COPU/10 vol.% BTO composite, at a frequency of 1 kHz. Piezoelectric strain constant d ₃₃ of the poled films varied from 0.0 pC/N for pristine castor‐oil based polyurethane (COPU) to 1.2 pC/N for COPU/10 vol.% BTO (CPBT‐5) composite. Tensile tests showed that the elastic modulus varied from 1.98 ± 0.003 MPa for pristine COPU to 5.13 ± 0.02 MPa for COPU/10 vol.% BTO composite. Dynamic mechanical analysis confirmed the viscoelastic nature of the smart paints. Measurement of current–voltage response under different compressive loads indicates that COPU/10 vol.% BTO composite can generate a current of ~28 nA and voltage of ~8 V under a dynamic compressive load of 40 N, applied at a frequency of 1 Hz. These experiments were complemented by Fourier transform infra‐red spectroscopy and scanning electron microscopy. In addition, finite element analyses based on periodic boundary conditions have been performed to predict the effective electro‐elastic properties of these piezoelectric smart composite coatings. Highlights Castor‐oil‐based PU piezoelectric composites with BTO inclusions were developed. Increase in BTO content up to 10 vol.% increases dielectric constant by ~1.7 times. COPU/BTO composites exhibit significantly increased piezoelectric response. Elastic and viscoelastic properties are also enhanced with increasing BTO content. Finite element models show a good match with experimental results.