Toward Advanced Biocomposites Based on Thermoplastic Biopolyester and Halogen‐Free Flame‐Retardant Additives for Industrial Solutions

This work investigates halogen-free flame-retardant biocomposites based on poly(butylene succinate) (PBS) containing magnesium dihydroxide (MDH) and aluminum trihydroxide (ATH). Hybrid MDH/ATH systems (1:1, 1:2, 1:3) show synergistic flame-retardant and smoke-suppressive effects due to their different thermal activation ranges, outperforming single fillers while maintaining acceptable processability. PBS composites with ∼60 wt.% metal hydroxides were prepared by melt mixing. ATH dispersed better than MDH, which showed irregular morphology and impurities. All fillers reduced peak heat release rate, improved ignition resistance, and suppressed smoke. MDH/ATH hybrids exhibited strong synergies via stable char formation, achieving significant heat reduction and near-complete smoke suppression. Despite reduced ductility at high filler loading, all composites showed shear-thinning behavior and acceptable processing performance. Overall, this study shows that MDH and ATH act as effective halogen-free flame-retardant additives, transforming highly flammable PBS into flame-retardant bio composites suitable for several industrial applications supporting the development of environmentally friendly materials.