Synergistic effects of molybdenum disulfide on a novel intumescent flame retardant polyformaldehyde system

A novel intumescent flame retardant (IFR) composed of ammonium polyphosphate (APP), benzoxazine containing trialkoxysilane (BA-a-Si) and melamine (ME), is compounded with different specifications of MoS2 as synergist to flame retard polyformaldehyde (POM). The flame retardancy and mechanism of the composites are analyzed by limiting oxygen index (LOI), vertical combustion (UL-94) and cone calorimeter. At the same time, the mechanical properties and lubricating properties are tested by electromechanical testing machine and wear testing machine. The experimental results show that MoS2 has a good synergistic effect with IFR, and the smaller the average particle size of MoS2 is, it seems to be more beneficial to improve the flame retardancy of POM composites. Only a small amount of MoS2 (0.8 wt%) is needed to synergize with IFR, the flame retardant POM composite (FR-POM) can achieve UL-94 (3.2 mm) V-0 rating, LOI of 62.5%, and heat release rate reduction of 25.3%, total smoke release decreased by 29.5%. In addition, from the mechanical properties analysis, it is found that the microscale MoS2(M2) can better improve the bending and tensile properties of the FR-POM composites, while the nanoscale MoS2(N80) is more helpful to improve the lubricating properties.