Preliminary Characterization of Calcined Eggshell and Silica as Fillers for Thermally Stable Bioplastic Production

Abstract

The limited thermal stability of starch-based bioplastics restricts their application in high-temperature environments necessitates the need to reinforce them with thermally robust fillers. This study explores calcined eggshell (CES) and silica as potential bio-based and inorganic fillers to enhance the thermal and structural performance of starch-derived bioplastics. Both materials were characterized using the Brunauer–Emmett–Teller method (BET), Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis, and a Scanning Electron Microscope equipped with Energy Dispersive X-ray Spectroscopy (SEM-EDX). BET analysis revealed mesoporous structures in CES and silica, with pore diameters of 2.8 nm and 2.7 nm, and pore volumes of 0.125 cm³/g and 0.132 cm³/g, which favors filler–matrix interactions. FTIR confirmed the presence of hydroxyl and carbonate groups in CES and silanol groups in silica, which promotes compatibility with hydrophilic polymers. Thermal analysis showed both materials to be stable above 600°C, with CES decomposing into thermally inert CaO and silica, exhibiting minimal mass loss post-dehydration. SEM–EDX analysis confirmed high surface area morphologies and dominant Ca and Si elemental compositions for CES and silica, respectively. The findings support the suitability of CES and silica as effective fillers for thermally stable bioplastics, offering environmentally friendly and cost-effective alternatives to conventional additives.