Combination effect of MoS2 with aluminum hypophosphite in flame retardant ethylene-vinyl acetate composites

Abstract

A series of flame retardant ethylene-vinyl acetate (EVA) composites, with different aluminum hypophosphite (AHP), melamine cyanurate (MCA) and MoS₂ content, has been prepared. The synergistic flame retardant effects of MoS₂ with AHP and MCA in EVA/AHP/MCA blends have been studied by limiting oxygen index (LOI), UL-94 tests, cone calorimetry tests, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The LOI and UL-94 results show that when 2 wt% AHP/MCA is substituted with MoS₂ (total content of the flame retardant system is 30 wt%), the LOI value can be raised to the maximum value of 38.5 among all of the samples. The data obtained from the cone test show that the heat release rate (HRR) and total smoke production (TSP) values of the EVA/AHP/MCA/MoS₂ sample are decreased compared with EVA/AHP/MCA composites. From the TGA measurement, with the incorporation of AHP, MCA and MoS₂, the thermal stability of the composites and char residue yield is increased obviously. Residue analysis shows that the presence of MoS₂ in EVA/AHP/MCA composites promotes the formation of a compact protective char layer resulting in the improvement of thermal stability and flame retardant properties combined with the physical barrier effect of MoS₂ nanosheets. The incorporation of MoS₂ also enhances the mechanical properties of the flame retardant EVA composites.