Study On Flame Retardant Properties And Combustion Behaviors Of Polypropylene With Inorganic Synergistic Flame Retardants

Due to the disadvantages of polypropylene,which is easy to burn and melt drips generated during the combustion process,it is easy to cause the fire to spread,which has seriously affected the widespread application of polypropylene.With the growing demand for polypropylene,in order to improve the safety performance of polypropylene and prevent fire hazards caused by the flammable properties of polypropylene in fires,the necessary task is to improve the flame retardancy of polypropylene.By adding flame retardants,the flame retardant properties of polypropylene can be improved.At the same time,with the increase of environmental protection awareness,more and more flame retardants are developing in the direction of high efficiency and halogen-free.In this paper,expandable graphite(EG),polycarbosilane(PCS),graphene flakes(GNP)and magnesium hydroxide(MH)are used as flame retardants to prepare inorganic flame retardant polypropylene composites MH / EG by melt blending / PP,MH / PCS / PP,MH / GNP / PP and MH / GNP / PCS / PP composites.The thermal degradation process of composites was studied using thermogravimetric analysis(TG).The oxygen index(OI)and vertical combustion(UL 94)evaluated the flame retardant properties of the composites,and studied the combustion behavior of the composites using cone calorimetry(CONE).The results show that there is a significant synergistic flame retardant effect between MH and EG.When the flame retardant content is 60 wt.%,The oxygen index of MH / PCS and MH / EG(mass ratio of 5/1)flame retardant polypropylene composites can reach 29.7%,which is 11.2% higher than that of MH / PP composites;EG and MH have a good effect of reducing heat release.Compared with MH / PP,the heat release of MH / EG / PP composites Peak-HRR decreased by 31.2% respectively;compared with PPM(MH60/PP40),the time it took PPMC(MH50/PCS10/PP40)to reach the peak of heat release was prolonged by 160 s,indicating that there is a significant synergistic flame retardant effect between PCS and MH;The synergistic effect greatly reduces the thermal weight loss rate of PPMG(MH50/EG10/PP40);combined with the morphological results of the residual carbon,it is revealed that the key to the synergistic flame retardant mechanism of EG and MH lies in enhancing the barrier and heat insulation of the carbon layer.It was further revealed that the synergistic flame retardant effect of PCS and MH is to improve the denseness of the carbon layer and to effectively block the transmission of heat insulation.