Synthesis Of Halogen-free Flame Retardant And Research Of Its Flame Retardancy Effect On Polycarbonate

Polycarbonate (PC) is commonly used as a high-performance amorphous engineering thermoplastic dues to its outstanding properties, including high impact strength, transparency, heat resistance, dimensional stability, and excellent electrical properties. For the flame retardant properties of PC, it shows a V-2 rating in the UL-94 test and it's oxygen index is between 21% to 24%. But strict flame retardant performance is often required for electronic and electric applications, the flame retardant technologies of polycarbonate have been developed.As people are paying more attention to the environment and the requirement of forbidding using halogen grows, development of novel non-halogen FR becomes a focus nowadays, and phosphorus is attracting a lot of attention. Certain numbers of new non-halogen FR have been developed based on phosphorus.In this paper, phenyl phosphonothioic dichloride (DCPPS) was synthesized from phosphorus trichloride and benzene through the Friedel-Crafts reaction, toluene was then used to react with DCPPS to get the desired product—bis(4-methylphenyl)phenyl phosphine sulfide(BMPPS). The effects of feed composition, catalyst concentration and reflux reaction time on DCPPS and BMPPS yield were investigated. The effect of BMPPS on the mechanical properties, thermal properties and flame retardancy of PC was also investigated. The results show that: with the addition of 4% BMPPS, PC/BMPPS is up to UL94 V-0 (3.2mm), the OI of PC is up to 30.6%. Thermal decomposition datum show that BMPPS can't improve the char yield of PC, but it can accelerate crosslinking and char forming of PC.Silicone starts attracting people's attention as an effect part of FR. It's reported that there are some synergetic function between silicon and phosphorus. In this paper, two novel flame retardants containing phosphorus, nitrogen and silicon were synthesized. The chemical structure of the intermediates and flame retardants were investigated by infrared spectroscopy (IR) and nuclear magnetic resonance (NMR).The thermal stability of the flame retardants were investigated by TGA under air and nitrogen, and char yield more than 30% can be got at 700℃Last, the effect of PNSi on the flame retardancy and thermal properties of PC were investigated.The PNSi enhance the flame retardancy of PC successfully through the results of LOI test .TGA result reveals the addition of PNSi improves the high thermal stability of PC. IR analysis confirmed that the P and Si played a great role in process of char forming. PNSi changed the degradation molding of PC by a series reaction of phosphate ester and siloxane and formed the char abundant in Si.The char acted as a good barrier to the transfer of heat and combustible gas between the flame zone and the substrate, and thus protected the underlying materials from further burning.