Towards sustainable flame retardancy of poly(limonene carbonate): Melem phytate with bio-based charring agents or aluminum trihydroxide

Poly(limonene carbonate) (PLimC) is an emerging bio-based polymer produced from renewable limonene and carbon dioxide. To enable its use in technical applications, its fire performance must be improved through effective and environmentally compatible flame-retardant (FR) strategies. Bio-based FRs—melem phytate, phosphorylated lignin (P-lignin), and biochar—were valorized through investigation of thermal and mechanical properties, flammability, and fire behavior, with aluminum trihydroxide (ATH) included as an environmentally benign mineral FR. Individual effects were assessed using formulations containing 5 wt% melem phytate or 20 wt% of P-lignin, biochar, or ATH. Potential synergistic interactions were subsequently examined by combining melem phytate with each adjuvant at a total loading of 25 wt%. Each additive alone reduced key fire properties, including fire load and peak heat release rate. When melem phytate was combined with an adjuvant, these reductions became even more pronounced—as seen in the Petrella diagram—demonstrating that the mixed formulations provide enhanced FR performance. These enhancements highlight the complementary roles of phosphorus-rich and charring agents in promoting condensed-phase protection. Overall, the results demonstrate a viable pathway toward sustainable, flame-resistant PLimC materials and confirm the effectiveness of bio-based FR systems for meeting fire safety requirements. • Melem phytate + adjuvants delivered enhanced reductions in key fire metrics • Biochar system achieved the lowest peak heat release and the highest char residue • Work establishes sustainable flame-retardant strategies for poly(limonene carbonate)