The Synergistic Effect Of Ball-milled Graphene Composite And Hexaphenoxy Cyclotriphosphazene In Flame Retardant Application In EP

Epoxy resin(EP)has been widely used in various fields of life and production because of the outstanding thermal stability,mechanical properties and insulation properties.However,it is vital to handle the flame retardant of EP since the flame retardancy of pure EP is poor,and a lot of smoke will be produced in the combustion process,which greatly improves the potential fire risk of the material.Graphene,as an efficient and environmentally friendly flame retardant additive,has been widely used in polymer materials because it can play a good physical barrier effect in composite materials and enhance the flame retardant effect of condensed phase of matrix.At present,the preparation of graphene can be roughly divided into two categories:one is physical preparation method,which mainly includes micro mechanical stripping method,ball milling method,ultrasonic separation method and supercritical fluid stripping method;the other is chemical preparation method,which has high cost and serious pollution.In this paper,Graphene doped Sn(Gn PSn)and graphene doped ionic liquid(Gn P@ILs)were prepared from expandable graphite(EG)by ball milling and were added into EP.The effects of two kinds of flame retardants and hexaphenoxy cyclotriphosphazene(HPCTP)on the flame retardancy and mechanical properties of EP composites were analyzed.The details are as follows:Part one:Preparation of Gn PSn by ball milling and its flame retardant application in EP.In this chapter,Gn PSn was successfully prepared by wet ball milling with EG and Sn as raw materials.The chemical structure,crystal structure,surface morphology and lamellar thickness of Gn Psn were characterized by X-ray photoelectron spectroscopy(XPS),X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM)and atomic force microscopy(AFM).The results indicated that Sn is successfully loaded on graphene,and the thickness of Gn PSn is 3.9 nm,which is composed of several layers of graphene.Then the EP composites were prepared by adding Gn PSn alone or Gn PSn and HPCTP together to EP(EP/Gn PSn or EP/HPCTP/Gn PSn),respectively.The flame retardancy of EP composites were investigated by limit oxygen index(LOI),vertical combustion(UL-94)and cone calorimeter test(CCT).The result indicated that Gn PSn can improve the fire resistance of EP and inhibit the generation of smoke.The EP/6.3wt%HPCTP/2.7wt%Gn PSn composites have the best flame retardancy with the LOI value of 33.6%and UL-94level of V 0 rating,and the peak heat release rate(PHRR)and the total heat release(THR)decreased by 44.80%and 23.93%,respectively.Moreover,it decreased the total smoke release(TSP)by 7.97%.Moreover,the results of SEM,fourier transform infrared spectroscopy(FTIR)and Raman spectra of char residue after CCT showed that EP/6.3wt%/2.7wt%Gn PSn can produce compact char layer after combustion,which can effectively play the role of physical barrier.Part two:Preparation of Gn P@ILs by ball milling and its flame retardant application in EP.In this chapter,Gn P@ILs was successfully prepared by green and simple ball milling method using EG and 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid([BMIM]PF₆)as raw materials in deionized water.The structure was characterized by TEM,XRD,FTIR,AFM and XPS.The results indicated that the addition of[BMIM]PF₆ can improve the milling efficiency.Then the Gn P@ILs was added alone or mixed with HPCTP to EP to study its effect on the comprehensive properties of EP composites.The results of LOI,UL-94 and CCT showed that the fire resistance of EP composites can be improved by Gn P@ILs,and the EP composites(EP/7.2wt%HPCTP/1.8wt%Gn P@ILs)containing both Gn PSn and HPCTP has the best flame retardancy.The LOI reached 33.8%,and it has passed UL-94 V 0.The PHRR and THR of EP/7.2wt%HPCTP/1.8wt%Gn P@ILs decreased by 55.54%and 44.28%,respectively.At the same time,the addition of[BMIM]PF₆ enhanced the interfacial compatibility between flame retardants and EP,and the tensile and impact strength of EP composites were significantly improved.