An Investigation on the Flammability of Halogen-Free Fire Retardant PP–APP–EG Systems

Both natural graphite (NG) and home-made expandable graphite (EG) were blended with polypropylene (PP) and intumescent flame retardant (IFR) by a melt process. The resulting composites contain filler of 1–5 phr (parts per hundred parts of PP–IFR). The limiting oxygen index (LOI) and thermal gravimetric analysis (TGA) were employed for the study of fire retardance. It shows that the incorporation of EG into systems of PP–IFR would impart flame retardance and thermal stability to the virgin formulation PP–IFR with optimal synergy at a loading of 2 phr, rather than the NG. The mechanical properties of the three systems and fracture surface morphology by SEM were also described.