Synergistic Effect Of Silica-magnesia Mixed Oxides On Intumescent Flame Retardant Polypropylene

The synergistic effect of silica-magnesia mixed oxides on intumescent flame retardant polypropylene was investigated and the synergistic effectivity was analyzed in this paper. The silica-magnesia mixed oxides was introduced into intumescent flame retardant, which can solve the defects of the low flame retardant efficiency and low thermal stability. At the same time, it also broadens the application fields of magnesium resources. What is more, it has a certain guiding significance to the development and utilization of magnesium resources.The intumescent flame retardant polypropylene composites were prepared by a method of melt blending using silica-magnesia mixed oxides as a synergistic agent and the polypropylene as a substrate. The thermal stabilization, flame properties and char formation of polypropylene/intumescent flame retardant/silica-magnesia mixed oxides composites were studied by the instrument of limiting oxygen index (LOI), cone calorimeter (CONE) and scanning electron microscope (SEM). The mechanical properties of polypropylene/intumescent flame retardant/silica-magnesia mixed oxides composites were researched by the tensile testing and impact testing. The synergistic efficiency was analyzed by the parameter of synergistic effectivity (SE), onset degradation temperature (Tswt%), integral procedure decomposition temperature (IPDT) and so on. The main research contents and results are as follows:(1) Magnesium silicate was introduced into the polypropylene composites. The results show that the flame properties, thermal stabilization and the Smoke suppression properties were highly enhanced and the fire hazardous of the composites was significantly decreased with the addition of magnesium silicate. With the addition of 1 wt% magnesium silicate, The LOI increased by 10.2%, and the IPDT increased by 16.7%. Otherwise, the amount of smoke production rate (SPR) and total smoke release (TSR) decreased by 16% and 9.8%, respectively. The fire growth index (FGI) also increased by 39.6%. What is more, the tensile strength at first increases with increasing the amount of magnesium silicate until a maximum is reached, but with the further increase in magnesium silicate content, the tensile strength starts to decrease. However, magnesium silicate has little influence on the impact strength of composites.(2) Sepiolite was introduced into the polypropylene composites. The results of LOI and TGA show that the LOI increased by 4.2% with the addition of 1 wt% sepiolite. The T5wt%, T50wt% and IPDT increased by 9.8%,4.8% and 14.1%, respectively. The char layer becomed more intensity than before. Otherwise, the tensile strength was enhanced by the addition of sepiolite, but the impact strength had a little change.(3) Attapulgite was introduced into the polypropylene composites. The results of LOI and TGA show that the LOI increased by 10.0% with the addition of 1 wt% attapulgite. The T5wt%, T50wt%, IPDT and the carbon layer intensity were highly enhanced. The tensile testing and impact testing results show that the tensile strength increases with increasing the amount of attapulgite until a maximum is reached, but with the further increase in attapulgite content, the tensile strength starts to decrease. The highest tensile strength was 27.45 MPa when the addition of attapulgite was 1.5 wt%, and increased by 6.1%. However, attapulgite had a little influence on the impact strength of composites.(4) The synergistic efficiency was analyzed by the parameter of SE, T5wt%, IPDT and so on. The results show that the intumescent flame retardant and silica-magnesia mixed oxides have a good synergistic effect. The synergistic effectivity at first increases with increasing the amount of silica-magnesia mixed oxides until a maximum in synergistic effectivity is reached, but with the further increase in silica-magnesia mixed oxides content, the SE starts to decrease. Magnesium silicate is the best synergistic agent in improving the flame retardant of composites and the thermal stability of char residue. Sepiolite is the best synergistic agent in improving the stability of composites. Comparing with all the SE, magnesium silicate has the highest value, which is 1.254 with the addition of 1 wt%. Thus, magnesium silicate is a high effective synergistic agent.