Synthesis And Flame Retardancy Of Theic Polyester Derivatives

Intumescent flame retardant(IFR)is a kind of green flame retardant with development potential,and charring agent is the key component affecting its flame retardant efficiency.THEIC is a kind of small molecule charring agent with triazine structure,which is water-solubility,so the flame retardant material made of THEIC is not water-resistant and easy to migrate and precipitate.In order to overcome the shortcomings of THEIC,some scholars used THEIC as raw material,through polycondensation with polybasic acids,synthesized some new macromolecular triazine charring agents,which not only overcome the shortcomings of THEIC,but also had a small emission of three wastes in the synthesis process,but the char forming ability was not ideal.Therefore,it is of great theoretical and practical significance to further optimize the structure of THEIC derivatives and improve their char forming ability.In this paper,four kinds of THEIC polyester derivatives(THEIC-succinic acid polyester,THEIC-maleic acid polyester,THEIC-phthalic acid polyester and THEIC-terephthalic acid polyester)are synthesized by polycondensation from THEIC and dibasic acid like succinic anhydride.Among them,the optimum synthesis conditions for charring agent-1 are as follows:the molar ratio of moles is:n(THEIC):n(succinic anhydride)=0.8:1.0,the reaction temperature is 180?,the reaction time is 4 hours,and the amount of catalyst i.e.concentrated sulfuric acid is 5%of the total amount of reactants.Under these conditions,the yield of charring agents were 95.1%,88.4%,90.8%,and 89.3%.The water solubility were 0.18 g/100m L,0.22 g/100m L,0.08g/100m L and 0.11g/100m L.Except for the color of charring agent-3 was yellow,the others were white.The results of thermogravimetric analysis show that the thermal stability of charring agent-1 and 2 are better than that of 3 and 4,both better than that of THEIC.The results of vertical burning test and limit oxygen index(LOI)measurement show that IFR-1,IFR-2,IFR-3,IFR-4 and IFR-SAI,which are compounded with APP respectively,have certain flame retardant effect on polypropylene(PP).When the flame retardant PP reaches grade V-0,the minimum addition amounts are 28%,32%,40%,40%and 22%.IFR-1 and IFR-2 have better flame retardant effects than those of IFR-3and IFR-4,but they are all worse than those of IFR-SAI.However,the water resistance test results show that the water resistance of IFR-SAI flame retardant is very poor,and the sample has no flame retardant effect after soaking for 24 hours,while the water resistance of other IFRs flame retardants is better,and the vertical combustion performance of the material can still reach V-0 level after soaking for 48 hours.Although IFR-1 and IFR-2have no significant differences in flame retardancy and water resistance,the color of PP prepared by IFR-1 is whiter than that by IFR-2,while the color of PP produced by IFR-2is tan.Cone calorimetry results show that the heat release rate(HRR),total heat release rate(THR),effective heat of combustion(EHC)and CO release(COP)of PP with IFR were significantly lower than those without IFR,and the fire performance index(FPI)of PP with IFR was significantly higher than that without IFR,indicating that IFR can reduce fire intensity,inhibit flame combustion and propagation,reduce smoke emission and reduce heat transfer.Among all IFRs,IFR-1 had the most outstanding effect on reducing smoke and CO.The results of thermogravimetric analysis,composition and structure analysis of CCT residue of flame retardant PP show that the flame retardant mechanism of IFR.The IFR is composed of THEIC or polyester charring agent and first,APP decomposes into polymetaphosphoric acid because of heating,then polymetaphosphoric acid dehydrated the charring agent to form incombustible or refractory amorphous carbon,graphitized carbon,carbons compounds and compounds containing nitrogen.Carbon with its compounds and nitrogen compounds not only improve the stability of polymetaphosphoric acid,but also melt with polymetaphosphoric acid.Under the influence of inert gases such as NH₃,N₂,CO₂and H₂O released from APP and charring agent,PP foams can form a continuous and dense intumescent layer covering on the surface of PP.The intumescent layer performs flame retardant effect by insulating heat,oxygen to prevent PP decomposition products from the combustion zone and inhibit further decomposition.The residues of IFR-1/PP and IFR-2/PP form a dense intumescent layer,which has good flame retardancy;the residues of IFR-3/PP have dense structure,but the expansion is not ideal;the residues of IFR-4/PP have rich intumescent layers,but the density is poor,so the flame retardancy of IFR-3 and IFR-4 is poor.In addition,the content of graphitized carbon has not a definite correlation with the flame retardancy.