High-efficiency synergetic clustered triazinylphosphinate composite flame retardant system enhance fire resistance, smoke suppression, and resilience of flexible polyurethane foams

Flexible polyurethane foams (FPUF) with superior flame retardancy, smoke suppression, and high resilience remain a significant challenge, particularly in achieving a limiting oxygen index (LOI) above 26%. To address this, a novel clustered aluminum triazinylphosphinate (CATP) was synthesized, and a ternary flame-retardant system (CED), comprising CATP, expandable graphite (EG), and dimethyl methylphosphonate (DMMP), was developed. The effects of CED on the flame retardancy, smoke suppression, and mechanical properties of FPUFs were systematically investigated. In flame retardancy, 20%CED/FPUF achieved an LOI of 29.1% and attained a UL-94 HF-1 rating in horizontal combustion tests, a notable milestone for flame-retardant FPUFs. Compared to neat FPUF, the peak heat release rate, total heat release, and total smoke release of 20%CED/FPUF were reduced by 67.2%, 60.0%, and 50.5%, respectively, with a remarkable char yield of 60.1%. These results significantly outperformed those of FPUF with 20% formulation based on commercial aluminum diethylphosphinate (ADP) (20%AED/FPUF). This highlights the ability of the CATP/EG/DMMP system to impart exceptional flame suppression and efficient charring effects to FPUFs. Moreover, CATP enhanced the cross-linking density of the FPUF matrix, increasing the tear strength of CED/FPUF from 560 N/m to 810 N/m while maintaining excellent foam resilience. In summary, this study offers a promising strategy for developing FPUFs with high LOI values, outstanding flame retardancy and smoke suppression, and robust mechanical properties.