Together We Can: Synergistic Flame Retardancy by Melamine Polyphosphate and Phosphorylated Microalgae in Polylactide Biocomposites

ABSTRACT A strategy for enhancing the sustainable flame retardancy of polylactide (PLA) composites by partially replacing melamine polyphosphate (MPP), a commercial flame retardant proposed for PLA, with wastewater polyphosphate‐enriched microalgae (P‐Algae) has been explored. The incorporation of P‐Algae at a 1:1 ratio with MPP leads to a notable synergistic effect, surpassing the expected additive behavior of the individual components. Comprehensive characterization encompassing thermogravimetric analysis coupled with FTIR, pyrolysis combustion flow calorimeter (PCFC), cone calorimeter, oxygen index (LOI), UL‐94 tests, and rheological measurements—demonstrates that the presence of this biomaterial can significantly enhance flame retardant performance. Replacing 50% of MPP with P‐Algae in PLA resulted in a 17% reduction in peak heat release rate (pHRR) and maintained a V‐0 rating in UL‐94 testing. The use of P‐Algae does not compromise the flame retardancy of PLA but rather contributes positively, offering a promising path toward more sustainable flame‐retardant systems. By leveraging naturally derived biomass, this approach aligns with the growing demand for novel eco‐friendly technologies in polymer engineering. Insights into an innovative renewable additive as a functional and effective component in flame‐retardant biocomposites have been achieved.