A novel strategy for preparing ethylene-vinyl acetate composites with high effective flame retardant and smoke suppression performance by incorporating piperazine pyrophosphate and Ce-MOF

Abstract

Cerium-containing metal organic framework defined as Ce-MOF was prepared and then combined with piperazine pyrophosphate (PAPP) for preparing flame retardant ethylene vinyl acetate (EVA) copolymer composites. The samples of EVA/PAPP/Ce-MOF achieved UL-94 V-0 rating with the limiting oxygen index (LOI) value of 31.3% when 17 wt% PAPP/Ce-MOF with the mass fraction of 97:3 was introduced. Under the same loading amount of PAPP, the EVA/PAPP only obtained UL-94 V-1 rating with the LOI value of 26.9%. Cone calorimeter test confirmed that the total heat release and total smoke production of EVA/PAPP/Ce-MOF significantly reduced from 132.8 MJ m⁻² and 11.5 m² for EVA/PAPP to 98.8 MJ m⁻² and 7.3 m², with a reduction of 25.6% and 36.5%, respectively. Besides, the maximum smoke density decreased from 488.8 and 375.9 for EVA and EVA/PAPP to 177.5 for EVA/PAPP/Ce-MOF. It indicated that the addition of Ce-MOF and PAPP effectively exerted synergistic flame retardant and smoke inhibition effect for EVA. Moreover, the addition of Ce-MOF enhanced the compatibility of PAPP with EVA matrix, and water resistance of EVA/PAPP/Ce-MOF was higher than that of EVA/PAPP. The x-ray photoelectron spectroscopy texts of residual char of EVA composites indicated that the cerium ion complexed with phosphoric acid and polyphosphate generated by the thermal decomposition of PAPP and then more phosphorus elements remained in condensed phase. As a result, the sufficient, crosslinking and dense char layer with excellent intensity was formed, and the heat, combustible gas and smoke were efficiently inhibited. Consequently, the EVA materials were endowed excellent fire safety as well as low heat and smoke release.