The Study On Flame Retardant Properties Of Polyphosphate Ester Flame Retardant Modified Vinyl Ester Resin

As a thermosetting resin,vinyl ester resin(VER)combines the excelent characteristics of epoxy resin and unsaturated polyester resin,which is widely used in various fields.Its application in many fields is restricted because VER is extremely flammable.Therefore,it is of great significance to flame retardant modified VER.In this research,uses two kinds of polyphosphate flame retardants of polyphenoxy diphenyl phosphate(PBPP)and poly(2-10-hydrogen-9-oxa-phosphaphenanthrene hydroquinone phenyl phosphate)(POPP).Then respectively compound with iammonium polyphosphate(APP)and add it to VER to prepare flame-retardant modified VER.In order to improve the flame-retardant properties of composite materials and the degree of graphitization of residual carbon,POPP compound with carbon nanotubes(MWCNTs)were used to further modify VER.The main research contents and results are as follows:PBPP compounded with APP to form the different composite flame retardant system were added into VER.The test results of vertical combustion(UL-94)and limiting oxygen index(LOI)showed that flame retardancy of VER was significantly enhanced after added PBPP and PBPP/APP of flame retardants.Among them,PBPP/APP has better flame retardant performance,the UL-94 test with 15% PBPP/APP composite material reaches V-0 level,and the LOI value reaches 25.1%.Thermogravimetric analysis(TGA)results show that both flame retardants can increase the char-forming ability of VER and improve its thermal stability.Among them,PBPP/APP has stronger char-forming ability for VER.Cone calorimetry(CONE)test results show that PBPP can effectively reduce the Pk-HRR and THR values of the VER matrix,indicating that PBPP can improve the fire safety of composite materials.Characterization of char morphology by scanning electron microscopy(SEM),Raman spectroscopy(Raman)and X-ray photoelectron spectroscopy(XPS)showed that the introduction of PBPP were conducive to the formation of char layer and P content in char layer.Such a char layer structure was conducive to the condensed phase flame retardant effect of the composite material.POPP and its compound with APP form different flame retardant systems were added to the VER,respectively.The test results of LOI,UL-94 and TGA showed that flame retardancy of VER was better flame retardant effect added POPP/APP of flame retardants.When POPP/APP adding volume was10%,the VER composites UL-94 test reaches V-0rating,and POPP needs to add 15% to reach V-0 level.Furthermore,the thermal stability and char-forming ability of POPP/APP/VER were significantly stronger than that of POPP/VER.The tensile strength and impact strength results show that the POPP/APP/VER system modified composite material has better mechanical properties.Further research on the POPP/VER system found that POPP could effectively reduce the Pk-HRR,THR,SPR and TSR values of the matrix resin.It showed that the introduction of POPP could reduce the release of heat and smoke during a fire,and effectively improve the fire safety of composite materials.Thermogravimetric analysis-Fourier transform infrared spectroscopy(TG-FTIR)results showed that after adding POPP the presence of phosphorus-containing substances in the pyrolysis gaseous phase products of the composite material was detecte.The presence of these phosphorus-containing substances was conducive to give play to the gas-phase flame retardant effects of composite materials.Characterization of char morphology by SEM,Raman and XPS showed that the introduction of POPP were conducive to the formation of char layer,the degree of graphitization of the char layer and P content in char layer.Dense char layer structure was conducive to the condensed phase flame retardant effect of the composite material.By comparing the thermal properties of POPP and compounded with three kinds of MWCNTs,the results showed that the addition of three flame retardants improves the thermal stability of VER and promotes the formation of char layer.Among them,POPP/MWCNT-OH can even improve the VER thermal stability.The results of LOI,UL-94 and CONE showed that all three compound flame retardants can effectively improve the flame retardant performance of VER.POPP/MWCNT-COOH has a better flame retardant effect on the VER matrix,when loading was 10%,the VER composites reached V-0 rating.The addition of the three kinds of compound flame retardants all effectively reduces the Pk-HRR,THR,SPR and TSR values of the materials,and increases the FPI value of the materials,and effectively improves the fire safety of the composite material.The analysis results of the char layer by SEM,Raman and XPS showed that after adding POPP/MWCNTs,the char layer structure of the three kinds of composite materials is smoother,continuous and dense.Among them,the addition of MWCNT-OH and MWCNT-COOH significantly increases the degree of graphitization of the char layer of the materials,and the P content in the char layer increases significantly.It is more conducive to play the role of the cohesive phase flame retardant of the composite material,and reduces the flammability parameters of the material and the risk of fire.These phosphorus-containing substances may play a good character in flame retardant effect during the combustion process,indicating that the addition of MWCNT was beneficial to the gas phase flame retardant effect of the composite materials.All three kinds of flame-retardants can improve the mechanical properties of composite materials to varying degrees,but the mechanical properties of POPP/MWCNT-OH were better.