Synergistic effect of expandable graphite and aluminum hypophosphite in flame‐retardant ethylene vinyl acetate composites

Abstract

AbstractIn this work, flame‐retardant ethylene vinyl acetate (EVA) composites were prepared by compounding expandable graphite (EG) and aluminum hypophosphite (AHP). The combustion behavior and mechanical properties of EG and AHP in flame‐retardant EVA composites were tested, and flame retardant mechanism was also investigated. According to the thermogravimetric analysis (TGA) results, AHP and EG can promote the carbonization of EVA to form the char layer at high temperature. The limiting oxygen index (LOI) test and vertical burning test (UL‐94) test results show that when the mass ratio of EG to AHP is 2:1, the sample (EVA/10EG/5AHP) passes the UL‐94 V‐0 rating, and its LOI value reaches 30.5%. The cone calorimetry test (CCT) results show that the EVA/10EG/5AHP sample has a significantly reduction on heat release and smoke release. Mechanical tests show that as the content of EG decreases and the content of AHP increases, both the strength and the elongation at break of EVA composites increase and the rigidity decreases. Whatever, we used SEM, Raman, and TG‐IR to understand the flame‐retardant mechanism of the EVA composites and the synergistic effect of EG and AHP It was found that the combination of condensed‐phase and gaseous‐phase is realized in the burning process.