Preparation Of Functionalized Graphene Oxide-aluminum Hypophosphite Nanohybrid And Its Effect On The Flame Retardancy Of Polystyrene

Polystyrene（PS）is one of the five general plastics.Due to its good electrical insulation performance,corrosion resistance and processability,together with the advantages of good dimensional stability,easy coloring,and low cost,PS has been widely applied in various industries such as electronics and architecture currently.However,PS molecular structure is composed of flammable hydrocarbon segments and benzene ring side groups.The PS molecular chain is easily decomposed by heat,and releases a large amount of heat and toxic smoke during combustion,which can cause serious fires.The application of polystyrene materials,therefore,is limited in plenty of industrial fields.Thanks to the extremely high specific surface area of graphene oxide（GO）nanomaterials,when they uniformly disperse in polymer matrix,their own high conductivity,heat conductivity and thermal stability properties can effectively reduce fires caused by friction static electricity,reduce fire hazards caused by local heating of composite materials,and delay thermal degradation behavior of matrix.Chemical modification of graphene oxide can effectively solve the problem that graphene oxide is easy to aggregate in polymer collectives,and improve the comprehensive properties of the matrix.Meanwhile,the catalytic synergy between the functional graphene components can effectively promote the formation of carbon layer and improve the flame retardant efficiency.The new flame retardant aluminum hypophosphite can play a flame retardant role by capturing cracking free radicals in the gas phase and interrupting chain-breaking degradation reactions.However,the single addition of AHP has the several disadvantages such as large addition amount and uneven dispersion.Based on the above situation,in order to solve the problem of dispersion of graphene oxide and aluminum hypophosphite and improve the synergistic flame retardant effect of each flame retardant,in this paper phosphorus-containing functional groups were grafted onto GO surface by"grafting from"method to prepare functionalized graphene oxide（FGO）.Next,functionalized graphene oxide-aluminum hypophosphite nano hybrid materials（FGO-AHP）were prepared by chemical deposition method.And to study the pyrolysis and flame retardant mechanism of PS/FGO-AHP combined materials,polystyrene/functionalized graphene oxide-aluminum hypophosphite（PS/FGO-AHP）combined materials with flame retardation were prepared through the method of introducing functionalized graphene oxide-hybrid nano-compounds into PS matrix by melt-mixing and other methods.The details are as follows:1.Graphene oxide（GO）was prepared by improved Hummers method.The GO was combined with DOPO-OH by the intermediate,high active phosphorus oxychloride（POCl₃）,which can easily react with the oxygen-containing functional groups on the GO surface.The effects of reaction conditions on the functional structure were studied,and FTIR,XRD and SEM were employed to characterize the structure and morphology of GO,and TGA was used to analyze the thermal stability of FGO.2.Functionalized graphene oxide-aluminum hypophosphite（FGO-AHP）nano-hybrid material were prepared by one-step hydrothermal synthesis of aluminum hypophosphite loaded on FGO surface.The structure and morphology were characterized by XRD,SEM and FTIR,and the thermal stability was analyzed by TGA analysis.3.The master batch of PS combined materials was prepared by ultrasonic dissolution.PS/GO,PS/FGO and PS/FGO-AHP combined materials were prepared by melt-mixing.The combustibility and thermal stability of PS/GO,PS/FGO and PS/FGO-AHP combined materials were studied by MCC and TGA respectively.The result shows that the HRC value of heat release capacity decreases from 1051 J/g·k（PS）to 627 J/g·k（PS/FGO-AHP5.0）,which decreases by 40.3%.Under nitrogen conditions,the carbon residue of PS/FGO-AHP5.0is 4.66 wt%at 700℃,which is significantly higher than that of pure PS that is 0.38 wt%.4.TG-IR analysis and NBS test show that during PS combustion FGO-AHP can significantly reduce the release of organic volatiles such as aromatic derivatives and inhibit the formation of toxic smoke,which can be attributed to the catalytic carbon formation of FGO-AHP and the physical barrier effect of nano-sheets.The result shows that the introduction of FGO-AHP into PS can significantly improve the flame retardant and smoke suppression properties of PS.