Synthesis And Properties Of Novel Salen-based Metal Complex Type Polyphosphazene Flame Retardant

Since the 1980 s,halogenated flame retardants have developed rapidly in the flame retardant industry because of their excellent characteristics.However,with the development of society and technology,people pay more and more attention to environmental protection.The development and application of halogen-free flame retardants have become the focus of research by experts in the field of flame retardants all over the world because of the great threat to the environment caused by the poisonous gas produced during the combustion of halogen-free flame retardants.The main research of this paper is as follows:(1)An intermediate monomer Salen containing Schiff base structure was synthesized firstly using o-phenylenediamine and 2,4-dihydroxybenzaldehyde as raw materials,and a kind of Salen was prepared by polycondensation with hexachlorocyclotriphosphazene.A new type of Salen-metal complex polyphosphazene Salen-PZN-M(M = Ni,Zn,Cu).The morphology and structure of Salen-PZN-M were characterized by electron microscope(SEM),infrared spectroscopy(FTIR)and X-ray photoelectron spectroscopy(XPS);Thermogravimetric analyzer(TGA),limiting oxygen index test(LOI),cone calorimeter(CCT)were used to characterize the thermal stability and flame retardancy of composite materials;The flame retardant mechanism of Salen-PZn-M /EP was investigated by thermogravimetric infrared analysis(TG-FTIR),SEM,Raman and FTIR.TGA results show that when the mass fraction of 5% Salen-PZN-M is added,different coordination metals have different effects on the composite material.The results of the cone calorimetry test show that compared with EP,the total heat release(PHRR),total smoke release(TSP)and the release of toxic CO gas of 5% Salen-PZN-M flame-retardant epoxy resin composites respectively the maximum reduction of 20.41%,16.93% and 37%.At the same time,the flame-retardant mechanism of Salen-PZN-M in the condensed phase and the gas phase was discussed.(2)Salen-PZN-Ni and 3-aminopropyl triethoxy silane(APTES)were used as raw materials to modify the surface of polyphosponitrile containing metal.A new type of cross-linked polyphosponitrile microspheres containing phosphorus,nitrogen and silicon were prepared by coating APTES on the surface of Salen-PZN-Ni.Then,Salen-PZN-Ni-A/EP composite was prepared by adding it to EP,and its thermal stability and flame retardant properties were tested.The flame retardant mechanism was further analyzed from the gas phase and the condensed phase.The structure and morphology of the flame retardant were analyzed by FTIR,SEM,XPS and EDS.The thermal properties of EP and its composites were investigated by TGA.The flame retardant properties of EP and its composites were studied by limiting oxygen index test and cone measurement.TGA results showed that the addition of Salen-PZN-Ni-A to EP could catalyze carbon formation,increase the carbon residue rate and reduce the peak DTG.The results of cone volume test showed that compared with pure EP,the PHRR and PSPR of 5% Salen-PZN-Ni-A decreased by 28.83%and 25.71%,respectively.The residual carbon was analyzed after conical measurement,and the results showed that Salen-PZN-Ni-A exhibited flame retardant mechanism in both gas phase and condensed phase.(3)A novel and efficient borosilicate containing functional flame retardant Salen-PZN-Ni@BA@A was prepared by ultrasonic stirring of Salen-PZN-Ni,boric acid and APTES in ethanol aqueous solution.Salen-PZN-Ni@BA@A/EP composite was prepared by adding Salen-PZN-Ni@BA@A into EP.The structure and morphology of the flame retardants were characterized by FTIR,XPS,SEM and EDS.The thermal stability of Salen-PZN-Ni@BA@A/EP composite was studied by TGA.The flame retardant properties of Salen-PZN-Ni@BA@A/EP composites were investigated by limiting oxygen index and conical combustion tests.The flame retardant mechanism of Salen-PZN-Ni@BA@A/EP was investigated by SEM,Raman and FTIR test results.The experimental results show that the thermal stability and carbon residue of epoxy resin can be significantly improved by adding Salen-PZN-Ni@BA@A into the epoxy resin.In addition,compared with pure EP,the heat release rate and amount of heat release of 5% Salen-PZN-Ni@BA@A/EP composites are reduced by 41.96% and 38.3%,respectively.At the same time,the smoke emission is reduced by 46.85%,and the flame retardant property of 5%Salen-PZN-Ni@BA@A microspheres is better than that of 5% Salen-PZN-Ni microspheres.With the addition of Salen-PZN-Ni@BA@A content,the heat release,smoke release and CO release decreased significantly.The flame retardant mechanism of Salen-PZN-Ni@BA@A in epoxy resin was also investigated.