Development of sunflower seed husk-reinforced unsaturated polyester thick composites: Optical, dielectric, and mechanical performance

synthesized and studied the composite films of unsaturated polyester (UP) reinforced with different weight percentages of sunflower seed husk powder (SSP) were manufactured and characterized. The results optical properties of UP/ SSP composites showed an increase in absorption and a gradual widening of the optical band gap from 2.6 to 2.9 eV with increasing SSP (x = 0%, 1%, 3%, 5%,7%) content. This led to a decrease in defect states and an improvement in structural order. The refractive index changes reflected variations in the interaction of light with the material of the composite system. Atomic force microscopy (AFM) scanning analysis confirmed the nanoscale characteristics of SSP particles, which have a mean diameter of around 68.9 nm, promoting their successful dispersion throughout the polymer matrix. The dielectric properties showed frequency-dependent features where the dielectric constant value reduced with frequency. Higher SSP content resulted in improved dielectric properties, reaching a maximum value of 7.42 at 1 MHz Furthermore, the mechanical properties showed a gradual improvement, with stiffness increasing from 81.5 to 83.6 and tensile strength rising from 28.12 MPa to 28.83 MPa as the SSP content increased. These improvements have enhanced the surface interaction and stress transfer efficiency within the composite material. Overall, incorporating SSP results in balanced improvement in optical, electrical, and mechanical properties, highlighting its potential as a sustainable reinforcement material for multifunctional polymer composites.