Preparation Of Controlled Molecular Weight Brominated Polystyrene Based On Reverse Atom Transfer Radical Polymerization

As a new type of high molecular bromine flame retardant,brominated polystyrene?BPS?is a good substitute for decabromodiphenyl ether and can avoid dioxin problems and meet the restrictions on the use of certain restrictions in electrical and electronic equipment.The Environmental Directive?RoHS?is an environmentally friendly standard for the flame retardant treatment of engineering plastics such as nylon?PA66?and polybutylene terephthalate?PBT?.However,at present,domestic BPS products have large molecular weight and wide molecular weight distribution,resulting in poor product compatibility and insufficient thermal stability,and Lewis acid is usually used as a catalyst,which is sensitive to water.Therefore,the optimization of low molecular weight and bromination conditions is of great significance for the synthesis of BPS products with great thermal stability and compatibility.In this paper,polystyrene?PS?with low molecular weight and narrow molecular weight distribution was synthesized based on reverse atom transfer radical polymerization?RATRP?and passed through infrared spectroscopy?FTIR?,nuclear magnetic?NMR?,gel chromatography?GPC?,the effects of initiator,catalyst,ligand,monomer dosage,reaction time and reaction temperature on the molecular weight and molecular weight distribution of PS were studied.Secondly,based on this,bromination of PS,using dichloroethane?EDC?as solvent,bromine chloride?BrCl?as brominating agent,and antimony trioxide?Sb₂O₃?instead of traditional Lewis acid as catalyst synthesis BPS,whitch was tested by sodium biphenyl sodium potentiometric titration,FTIR,NMR and thermogravimetric analysis.The factors such as antimony trioxide?Sb₂O₃?,bromine?BrCl?,reaction time and temperature were studied.Finally,a simple application experiment was carried out on the prepared BPS.The effect of the amount of flame retardant on the flame retardant effect and mechanical properties of PBT and PA66 was investigated by combination with Sb₂O₃.The results are as follows:?1?The specific ratio of the initiating system in the PS polymerization is determined to be azobisisobutyronitrile?AIBN?:copper bromide?CuBr₂?:bipyridyl?Bipy?:styrene?St?=1:1:2:150.The reaction time is 6h,the reaction temperature is 110?,the obtained PS molecular weight is is between 10,000 and 20,000,and the molecular weight distribution is narrow?PDI<1.3?.?2?During the bromination process,the amount of catalyst Sb₂O₃ is determined to be3wt%?based on PS?,n?BrCl?:n?PS?=3.05:1,the dropping temperature is 5¹0?,the holding reaction temperature is 20²5?,the dropping time is 4h,and the heat preservation reaction time was 8h.The obtained BPS bromine content was up to 67%,the 1%weight loss temperature was 331?,and the 5%weight loss temperature was 359?.?3?In the application experiment,when the BPS mass fraction reaches 18%²0%,the LOI of PBT is 28,the flame retardant grade reaches V-0 grade,and the mechanical properties except the elongation at break decrease greatly.The change of other mechanical properties has been a slightly decline.The LOI of the modified PA66 is 33%,and the vertical burning grade reaches V-0,and it has a good flame retardant effect.With the addition of the flame retardant,the tensile,bending and impact strength of the PA66 slightly decreases.