Preparation Of High Quality Graphene Oxide And Study On Its Modification By Phosphorus And Silicon For Flame Retardant

Graphene is a two-dimensional honeycomb lattice which is connected by C-C formed by sp2 hybridization.It gets a lot of attention at home and abroad because of its high conductivity,high thermal conductivity,high specific surface area and so on.Graphene oxide which is widely regarded as the precursor of reduction graphene oxide gets a lot of attention too.In this work,graphene oxide was prepared by oxidation method firstly.And then,we characterized and discussed three points of the preparation process,including the selection of oxidation method,ultrasonic time and drying method.At last,a high quality graphene oxide with high oxidation degree,less layer,large layer area and no stacked was prepared.Then,this graphe oxide was connected with DOPO by covalent bond.A graphene oxide functionalied by phosphorus element DGO was prepared.What’s more,this DGO was then connected with KH560 by convalent bond.A graphene oxide functionalized by phosphorus and silicon element KDGO was prepared.Finally,GO,DGO and KDGO were added into the epoxy resin as flame retardant.And the thermal stability,flame retardant properties and mechanical properties were tested.The main achievements of our work are shown as follows:(1)Oxidaton method,ultrasonic time and drying metod was discussed respectively.And a high quality of graphene oxide with high oxidation degree,single layer,large layer area and no stacked was prepared.The oxidation degree was proved by FTIR,XRD,EDS and Ranman spectrum.AFM and TEM showed that the optimum ultasonic time is 17-20 h.Raman and AFM showed that graphene oxide would stack when dried by the vacuum drying.But graphene did not stack when dried by freeze drying(2)In this work,graphene oxide was connected with DOPO by covalent bond.A graphene oxide functionalied by phosphorus element DGO was prepared.What’s more,this DGO was then connected with KH560 by convalent bond.A graphene oxide functionalized by phosphorus and silicon element KDGO was prepared.And the success of synthesis was proved by FTIR,XRD,EDS,Raman spectrum,AFM and TEM,(3)GO,DGO and KDGO were added into the epoxy resin as flame retardant.The thermal stability,flame retardant properties and mechanical properties were tested by TGA,DTG,DMA,LOI and UL-94.TGA and DTG curve show that Td of GO/EP decrease,but the rate of residual carbon increase from 17.35%to 24.66%.Td of DGO/EP decrease and the rate of residual carbon increase from 24.66%to 26.27%.It prove that the thermal stability decrease and the flame retardant properties increase.But the Td of KDGO/EP increase and the rate of residual carbon increase from 26.27%to 27%.It prove that the silicon element not only increase the flame retardant properties of EP but also increase the thermal stability.DMA show that Tg of KDGO/EP increase significantly.It is because lots of C-O-C existed in KDGO increase the compatibility with epoxy resin.So the crosslinking density increase which could be proved by(E’190 ℃)and tanδ.According to the LOI and UL-94 analysis,the flame retardant properties of GO is small.This is because a large number of oxygen groups exist on the surface of graphene oxide which decrease the flame retardant performance.But DGO and KDGO show good flame retardant properties.On the one hand,DOPO and KH560 cost many oxygen groups of GO,which reduce the effect of flame retardant.On the other hand,the flame retardant element phosphorus and silicon increase the flame retardant of the material.The significance of this work is that the flame retardation and physical mechanical properties increase with small amount of P and Si modified graphene oxide(1%).Compared with the current general flame retardant additives which usually lead to weakening of mechanical properties of materials,it shows a certain practical value.