Valorization of eggshell waste in designing flexible polyurethane-based piezoelectric composite materials for ultrasonic transducers

Abstract

In this study, we have prepared a new formulation from flexible polyurethane/calcined waste eggshell (FPU/CWES) composites as a novel piezoelectric foam material for transducer applications. The CWES was loaded into the FPU matrix with different ratios (1–5%) by weight. The FPU/CWES composites were characterized using FESEM, EDX, and FTIR techniques. Furthermore, gel fraction and apparent density tests were estimated for the obtained composites. The results disclosed that FPU/CWES 3% composite achieved maximum values of 88.5% and 36.62 kg/m3 for gel fraction and density, respectively, compared to control FPU foam. TGA analysis displayed that adding (1–3 wt%) CWES increased thermal stability compared to control FPU foam. The FPU/CWES composites’ mechanical characteristics showed that the compressive and tensile strengths of the FPU/CWES 3% were increased to 17.85% and 15.78%, respectively, compared to the control FPU foam. At the same time, the elongation at break decreased with an increase in the CWES content. The piezoelectric coefficient (d33) for FPU/CWES 3% composites showed superior enhancement compared to other traditional piezoelectric materials and thus can be considered a promising piezoelectric element for medical ultrasonic transducer fabrication and ultrasonic non-destructive testing to detect defects in different solid materials. Furthermore, FPU/CWES composites displayed advantages over other piezoelectric materials, such as ceramics or polymers, including increased sensitivity, enhanced performance at low frequencies, and greater adaptability to irregular and curved surfaces. Additionally, their lightweight nature and low cost make them an attractive option for developing innovative and valuable piezoelectric devices. Therefore, utilizing FPU/CWES composites as a piezoelectric material holds tremendous potential for advancements in various fields, including wearable electronics and biomedical applications.