Studies Of The Flame Retardancy And Thermal Stability Of The Hydrogen-containing Polysiloxane Flame Retardants In Polycarbonate

Safety in fire has been becoming more and more important in modern life. While polycarbonate (PC) as a kind of engineer materials has been widely used in every aspects owing its exceptional properties. Although PC itself possess a given flame retardancy, for satisfy the requirement of safety and environment, it still need to be flame retarded. The silicone-containing flame retardants have attracted attention duo to their high-efficiency, no-toxic and environmental-benign properties.In this work, we firstly investigate the effect of hydrogen-containing polysiloxane (HP) on the flame retardancy, thermal decomposition and mechanical properties of PC with the presence of 4A molecular sieve. Results show that the HP combining with 4A molecular sieve has a positive influence on the LOI, thermal stability. When the content of HP is 3 wt%, the concentration of 4A molecular sieve is 0.5 wt%, the PC materials get the best flame retardancy (LOI:30.8, UL-94:V0). However, because of low molecular weight of HP, the addition of it lower the mechanic properties of PC.Secondly, the Si-H bonds in hydrogen silicone was used to react with hydroxy groups on the nano-sized SiO2 surface to obtain polysiloxane modified SiO2 materials (STNS). Then we incorporate STNS to polycarbonate (PC) by melt blending method to studying its effects on the flame retardancy and other performances of PC. The thermal stability, mechanical properties and flame retardancy of PC were characterized by thermogravimetric analysis(TGA), limiting oxygen index(LOI), vertical burning tests(UL-94) and universal testing machine. The results of shows that the hydrogen-containing silicone oil could reacted with nano SiO2 through dehydrogenation condensation reaction under appropriate conditions. The obtained STNS have good thermal stability, carbonization ability and flame retardancy. When the content of STNS is 3wt%, the LOI value of PC composites is 31.8% and the UL-94 rating reaches V-O.When the content of STNS increase to 7wt%, the UL-94 rating is V-0 and the LOI value of the composites further enhance to 31.8%. In mechanical properties, notched impact strength and breaking elongation increases 89.9% and 108.7% respectively, at the same time, bending strengh and tensile strength decreased slightly. In addition, we propose a possible flame retardant mechanism for the STNS in PC.