CoFe-PBA decorated P-N flame retardant for catalytic carbonization, smoke suppression, toxicity reduction and antimicrobial properties of TPU

Thermoplastic polyurethane (TPU), as a typical thermoplastic elastomer, is highly flammable, posing significant safety challenges. Phosphorus-nitrogen flame retardants (P-N FRs) are commonly employed to reduce the fire hazard of TPU but limited by low flame retardant efficiency and production of toxic gases during combustion. In this study, a novel multifunctional flame retardant (P-N@CoFe-PBA) was synthesized by decorating cobalt-iron Prussian blue analogue (CoFe-PBA) onto the surface of a P-N FR. The results showed that P-N@CoFe-PBA significantly improves the flame retardancy, smoke suppression, toxicity reduction, and antimicrobial properties of TPU composites. For TPU-6 %P-N@CoFe-PBA, the peak heat release rate (pHRR) and total smoke production (TSP) values were reduced by 59.2 % and 51.9 % compared with pure TPU, respectively. Meanwhile, the total CO production (TCOP) and total CO₂ production (TCO₂P) values were reduced by 43.9 % and 51.7 %, respectively. The improvement in flame retardant performance of TPU-6 %P-N@CoFe-PBA is due to the catalytic carbonization ability of P-N@CoFe-PBA, which promotes TPU composites to form an excellent char residue layer structure, providing effective thermal insulation and preventing mass transfer. Furthermore, P-N@CoFe-PBA suppresses the generation of toxic gases and flammable volatiles during combustion and imparts antimicrobial properties to TPU. This work is significant for the preparation of multifunctional flame retardant TPU composites and expanding the application fields of TPU.