Calcination-controlled structural evolution of clay fillers for enhancing thermal stability and mechanical performance of polyester composites

The growing demand for cost-effective, lightweight polymer composites in industrial uses necessitates the development of scalable, high-performance filler materials. Calcined clay has emerged as a viable inorganic filler for improving mechanical and thermal properties in polyester-based composites. This work hypothesizes that calcination-induced structural evolution of clay increases interfacial bonding, resulting in better thermo-mechanical performance of polyester composites. The results reveal that calcined clay greatly improves composite characteristics compared to neat polyester, with greater calcination temperatures producing better results. Composites with appropriately calcined clay showed 28-35% improvement in tensile strength (65 ± 2.6 MPa), flexural strength (82.57 ± 2.1 MPa), and impact resistance (19.17 ± 1.14 kJ/m 2 ) compared to the unfilled matrix. Thermal stability also enhanced, with deterioration beginning shifting by about 45 o C, indicating better interfacial adhesion and stress transfer. This study provides a direct structure-property-processing relationship in calcined clay-polyester systems, which provides a novel and practical framework for building high-performance, inexpensive composite materials. These findings show a straightforward and scalable method for converting abundant clay into value-added fillers, which could provide economic benefits for mass-produced composite manufacture and help sustainable material development. • Calcination temperature significantly alters the structure of natural clay fillers. • Structural evolution of clay improves compatibility with polyester matrices. • Calcined clay reduces water absorption and increases composite density stability. • Mechanical properties (tensile, flexural, and impact strength) are enhanced. • Improved thermal stability demonstrates potential for lightweight composite applications.