Abstract: Microcapsule red phosphorus (MRP), zinc borate (ZnBO3), Al(OH)3(ATH) and Mg(OH)2(MH)were applied to soft poly(vinyl chloride)(PVC) to impart flame retardance, and limiting oxygen index,cone calorimeter test and thermal analysis were used to study the flame retardance and smoke suppression. It was shown that PVC/MRP/ZnBO3/ATH/MH composite with a mass ratio of 100/3/1/20/20 have the largest limiting oxygen index value of 33.9 %;PVC/MRP/ZnBO3/ATH/MH exhibits better flame retardancy and smoke suppression than PVC/ATH/MH and pure PVC. Moreover, data from CONE and TG show that in contrast with PVC/ATH/MH, the release of heat, smoke gas of PVC/MRP/ZnBO3/ATH/MH was much decreased, the charring ability was enhanced appreciably, and CO and CO2 gas release was lower;it was more difficult to ignite, and the fire performance index (FPI) was improved, FGI fire spread index was decreased to reduce fire risk. In the summery,MRP/ZnBO3/PVC composite exhibits optimal comprehensive fire retardancy.

Key words: microcapsulated red phosphorus, zinc borate, soft poly(vinyl chloride), flame retardant