A low loading synergistic flame retardant rigid polyurethane foam with high mechanical retention after combustion

Abstract

Flame retardant property is crucial in practical application of rigid polyurethane foam. Other studies have indicated that incorporating flame retardants at high concentrations (15-25 wt%) is required to achieve the desired flame-retardant effect, with a pronounced strength reduction observed after burning. Modified expanded graphite (KEG) (1-3 wt%) compounded with dimethyl methylphosphonate (DMMP) as a synergistic flame retardant to foam system. The synthesized foams were subjected to cone calorimetry, vertical combustion tests, and physical properties such as compression properties and density and thermal conductivity of the foams. The results showed that the KEG/DMMP composite system was able to significantly enhance the flame retardancy of polyurethane foams at a lower addition amount, This enhancement was manifested in a marked increase in the oxygen index (LOI) and a substantial reduction in the heat release rate (HRR). Meanwhile, the introduction of KEG enhances the mechanical properties of polyurethane foam with minimal impact on pore structure, and still maintain high mechanical retention after combustion, demonstrating its stability and feasibility in foam systems. This study provides a new insight for developing highly efficient, low-additive flame-retardant polyurethane foams.