<p>This study investigates the impact of zeolite and aluminium trihydrate (ATH) on the mechanical and flame-retardant properties of natural rubber (NR) composites. Unlike conventional flame retardants, these additives offer a halogen-free alternative with potential benefits in both fire resistance and mechanical performance. Incorporating zeolite and ATH increases Mooney viscosity, density, and hardness, with zeolite exerting a more pronounced effect due to its lower density and higher particle count. However, the addition of flame retardants reduces crosslink density, tensile strength, elongation at break, and tear strength. tc90 values measured by moving die rheometer (MDR) indicate the curing times are influenced by the type and concentration of flame retardants, with zeolite-filled NR composites showing more variability in optimum cure time (t_c90), suggesting slower curing at lower loadings and faster curing at higher loadings. Despite these trade-offs, significant enhancements in flame retardancy are observed, with both zeolite and ATH achieving a UL 94V-0 classification at optimised concentrations. Comparative thermogravimetric analysis (TGA) confirms distinct thermal degradation profiles, with zeolite exhibiting a two-stage water release mechanism that differs from ATH. The findings suggest that zeolite can serve as a viable flame-retardant alternative, offering comparable performance to ATH while potentially reducing material costs. These results directly affect fire-sensitive automotive, electrical, and construction applications, underscoring the potential for optimising NR formulations to balance mechanical integrity with flame resistance.</p> Graphical abstract <p></p>