Synthesis Of Nitrogen-sulfur Flame Retardants And Their Application In Polycarbonate

Polycarbonate（PC）has a certain flame-retardant,the serious droplet phenomenon and the generation of a large amount of toxic and harmful fumes in the combustion can not meet the requirements of some applications.Therefore,it is necessary to modify PC with flame retardancy in some fields such as electrical and electronics,construction and automobile,where fire safety accidents are high.Four intermediates of flame retardants（D₃,D₄,D₅and D₆）were synthesized by nucleophilic substitution reaction of cyanuric chloride with N-methylallylamine and diallylamine respectively.Two kinds of flame retardants（D₃S₃and D₆S₃）were synthesized by click-reaction of D₃and D₆with 3-mercapto-1-propysulfonate respectively.The flame retardant D₃S₃S was synthesized by oxidizing sulfoxide in D₃S₃with hydrogen peroxide as oxidant.All molecular structures were characterized by high resolution mass spectrum（ESI-MS）,nuclear magnetic resonance spectrum（NMR）and Fourier infrared transform spectrum（FTIR）Thermogravimetric Analysis（TGA）showed that the initial decomposition temperatures of D₃S₃,D₆S₃and D₃S₃S in nitrogen atmosphere are 282℃,282℃and 317℃,respectively,above 280℃,meeting the processing requirements of PC.Flame retardant performance tests showed that D₃S₃,D₆S₃and D₃S₃S all significantly improved Flame retardant performance in PC.When D₃S₃was added at 0.1 wt.%,the LOI value of PC/D₃S₃composite was 36.4%,reaching UL-94 V-0 level;when D₆S₃was added at 0.5 wt.%,the LOI value of PC/D₆S₃composite was 34.6%,reaching UL-94 V-0 level;When D₃S₃S was added at 0.1 wt.%,the LOI value of PC/D₃S₃S composite was 36.6%,which reached UL-94 V-0 level.Gas phase decomposition products and residual carbon structure of PC/0.1%D₃S₃,PC/0.1%D₆S₃,PC/0.5%D₆S₃and PC/0.1%D₃S₃S composites were analyzed by TG-IR,SEM,Raman and XPS.The results showed that the gas phase decomposition products of PC and PC/0.1%D₃S₃composites were essentially the same,but the pyrolysis of PC/D₆S₃and PC/D₃S₃S produced fewer small molecule hydrocarbon compounds.The carbon layer formed by PC/0.1%D₃S₃and PC/0.1%D₆S₃composites was more compact and continuous during combustion with cavernous micropore structure and higher graphitization than the carbon layer formed by PC/0.1%D₆S₃composites.The tensile strength and bending strength of the composites did not change significantly compared to pure PC at 0.01%to 0.5%,but the impact strength decreased significantly with the addition of three flame retardants.