Thermal Degradation and Flammability Behaviour of Hdpe/Eva/Eg Composites

In this work, high density polyethylene (HDPE), ethylene-vinyl acetate (EVA) copolymer and expandable graphite (EG) flame retardant composites were prepared by using a twin screw extruder technique. The thermal stability and flame retardant properties of the composites were investigated by the thermogravimetric analysis (TGA) and cone calorimeter, respectively. The char morphology after combustion was also further characterized. The experimental results indicated that intumescent EG greatly enhanced the thermal stability and fire resistance of polymer matrix materials. The presence of EG improved the degradation temperature of HDPE/EVA blend and increased its char residue at high temperature. The results from cone calorimeter demonstrated that the addition of EG led to the decrease of the heat release rate (HRR), total heat release (THR) and smoke production rate (SPR) of materials and could retard the emission of the toxic and flammability gases by promoting the formation of a compact char layer. This char layer will prevent the polymer matrix further degradation and protect it effectively from heat penetrating inside, resulting in lower weight loss rate and better flame retarded property.