Synergistic Effects of ATH, APP, Zinc Borate, and Antimony Oxide on the Mechanical and Flame-Retardant Properties of Glass Fiber-Reinforced Polyester Composites

Composite materials are widely utilized across various industries due to their exceptional mechanical properties and versatility. However, their inherent flammability poses a critical challenge, especially in applications requiring stringent fire safety standards. This study investigates the synergistic effects of aluminum trihydroxide (ATH) combined with ammonium polyphosphate (APP), zinc borate, and antimony oxide on the mechanical and flame-retardant properties of glass fiber-reinforced polyester composites. Composites were fabricated using a hand lay-up process with single and dual filler formulations. Viscosity, tensile strength, flexural strength, and flame retardancy were assessed. Results revealed that combining ATH with secondary fillers, particularly APP and antimony oxide, significantly improved flame retardancy without entirely compromising mechanical performance. Notably, composites with 40 wt% APP or antimony oxide exhibited self-extinguishing behavior in ASTM D635 testing, while dual filler combinations showed synergistic effects that enhanced flame retardant performance. This work provides valuable insights into optimizing filler formulations for applications requiring a balance between mechanical integrity and flame resistance.