Development and Characterization of Waste Polystyrene/Calcite Composites Prepared by Solution Casting

This work reports the development of sustainable composites based on waste polystyrene (WPS) reinforced with natural calcium carbonate (CaCO3), aiming at both plastic waste valorization and performance enhancement. The composites were fabricated via a solvent casting approach using recycled polystyrene cutlery and varying CaCO3 loadings. Structural analyses performed by X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), and photoluminescence (PL) spectroscopy confirmed the effective incorporation of calcite within the polymer matrix, as evidenced by characteristic peak shifts and intensity variations indicative of interfacial interactions. PL spectra exhibited two emission bands centered around 365 and 400 nm for all samples, with enhanced emission intensity at low filler contents (2 and 6 wt%), followed by pronounced quenching at 10 wt%, highlighting a concentration-dependent interaction and uniform filler dispersion at lower loadings. Thermal analyses (DSC, TGA, and DTA) demonstrated a systematic improvement in thermal stability upon CaCO3 addition, with decomposition temperatures increasing up to 432 °C compared to 429 °C for neat WPS, attributed to the barrier effect of the inorganic filler and restricted polymer chain mobility. Overall, these results demonstrate that natural calcite is an efficient, low-cost, and locally available reinforcing agent for recycled polystyrene, providing a viable and scalable strategy for the upcycling of plastic waste into value-added, thermally stable composite materials.