Study On The Synthesis Of Halogen-Free Flame Retardants And Their Application On Polycarbonate

As one of the five major engineer thermoplastics, Polycarbonate (PC) has beenwidely applied in many areas due to its outstanding properties, such as high strength,thermal stability, transparency and dimensional stability. Because of relatively lowheat of combustion and high tendency to foaming and charring, PC by itself shows aV-2rating in the UL-94test, and the LOI of pure PC can reach22-29%. However, it isstill essential to develop highly flame retardant PC with the increasing concern forsafety and recycling, particularly for electric and electronic applications.Halogen-containing flame retardants have outstanding flame-retarded efficiency, buttheir application has been restricted because they may generate toxic substances suchas dioxin derivatives during combustion. It is essential to develop halogen-free flameretardant to meet the constantly changing demand of new regulations, standards andtest methods. In the area of PC, the development of halogen-free flame retardantswhich have good thermal stability and high efficiency receives more and moreattention.In this paper, two kinds of halogen-free flame retardants were synthesized andused as the flame retardants of PC. One is DOPO-HQ containing phosphorus and theother is SiPP containing phosphorus and silicon. The thermal properties of DOPO-HQand SiPP were investigated by thermogravimetric analysis (TGA) in air. The TGA results show that both DOPO-HQ and SiPP have good thermal stability, which canmeet most plastic processing temperature needs.We prepared PC/DOPO-HQ composites and PC/SiPP composites through meltblending and studied the flame-retardancy and thermal properties of composites. Itwas found that the flame retardancy was significantly improved for thePC/DOPO-HQ composite when10phr DOPO-HQ was added. The LOI value ofPC/DOPO-HQ composite with10phr DOPO-HQ reached as highly as34%, the Timeto Ignition (TTI) increased to89s from54s, the Peak of Heat Release Rate (PHRR)decreased to526.00kW/m~2from578.94kW/m~2, the Average Heat Release Rate(AHRR) within the front200s from heat radiation decreased to144.9kW/m~2from226.0kW/m~2. Compared to the pure PC, the flame retardancy of PC/SiPP compositeswas improved with the adding of SiPP. LOI, PHRR, AHRR, Heat Release Rate (HRR),Total Heat Release (THR) of PC/SiPP composites all had improvement than those ofpure PC.The TGA results showed the adding of DOPO-HQ or SiPP decreased the initialdecomposition temperature of composites slightly, which had little influence on thethermal stability of composited material.