Enhancing flame retardancy of waterborne polyurethane via ethylenediamine-intercalated black phosphorusOA

Ethylenediamine-intercalated black phosphorus nanosheets(eda-BP NSs)were synthesized via a solvothermal process on a 50-g scale.In contrast to the bare black phosphorus nanosheets(BP NSs)which typically involves high-cost gasphase synthesis and subsequent complex exfoliation process,eda-BP NSs exhibit superior environmental stability and offer greater potential for industrial application in flame retardancy.A series of eda-BP NSs/waterborne polyurethane(WPU)composites with various loadings were prepared,and their flameretardant properties were evaluated using thermogravimetric analysis,cone calorimetry,and limiting oxygen index(LOI)measurements.With the incorporation of only 0.2 wt.%eda-BP NSs,the composite showed 40.79%reduction in peak of heat release rate,55.44%decrease in peak of smoke production rate,and 22.5%reduction in total smoke production,along with 2.5%increase in LOI and 2.17 wt.%rise in residual char compared to pure WPU.At the same filler loading,the flame-retardant performance of eda-BP NSs/WPU composites was comprehensively superior to that of BP NSs/WPU.The enhanced flame retardancy is attributed to the unique quasimonolayer intercalation structure of eda-BP NSs and a phosphorus-nitrogen synergistic mechanism facilitated by the amine groups.The outstanding flame-retardant behavior observed in WPU underscores the promise of this organic-inorganic intercalated phosphorus material for broadening application prospects.Furthermore,such a flame-retardant mechanism arising from this distinctive intercalation structure may provide valuable insights for the development of next-generation flame retardants.