Research On Preparation And Performance Of Graphene,BN/Epoxy Composites By Electric Field-assisted Mechanical Force

Graphene is a new kind of two-dimensional material with single atomic layer thickness as well as its unique physical and chemical properties which make it broad application prospects.A lot of systematical works have been done on the preparation,structure,properties and applications of graphene and its composites in recent years.Although great progress has been made in the preparation of graphene and its polymer composites,some key bottlenecks still need to be solved to realize large-scale preparations.On the one hand,interaction between the resin matrix and the graphite is weak,and the slips are easy to occur at the interfaces,resulting in the difficulty of effectively converting the mechanical force into the interlayer shear force of the graphite.Thereby,a severe lamellar fragmentation and low exfoliation efficiency are caused by this phenomenon.On the other hand,the intrinsic graphene with low surface chemical activity has inevitable interfacial separation with the matrix,which greatly limits the exfoliation efficiency and the performance improvement of the composites.Therefore,it is vital to find high quality,high efficiency and low-cost methods to prepare graphene and its polymer compositesIn consideration that mechanical force can be effectively converted into interlayer shear force,electric field-induced polarization is expected to enhance the interactions between epoxy(Ep)and graphene(G)or boron nitride(BN)nanosheets interfaces.The graphite or BN/Ep system was treated under the coupling effect of force field and electric field by the three-roller machine which is designed independently and trial-produced by our research group.The G/Ep composite material is prepared in one step by in-situ compounding with Ep while graphite(BN)is exfoliated efficiently to prepare G(BN).In this paper,the effects of roller spacing,electric field intensity and content of electropolymerizable monomer were studied systematically on the exfoliation efficiency of G and the interface's improvement of composites.The main research contents and results are as follows:1?The graphite/Ep system was treated by the three-roller machine that can be applied with electric field and designed independently and trial-produced by our research group.The G/Ep composite was prepared in one step by in-situ compounding Ep.Some key factors like roller speed,solid content,roller spacing,and voltage between rollers were systematically discussed on the exfoliation efficiency and dispersion of G.Under non-electric condition,the peak intensity of the(002)crystal plane in the G/Ep system is 76.6%lower than that of the raw graphite after treated 10 times.Compared to the experimental results under non-electric field conditions,the peak intensity of the(002)crystal plane in G/Ep system is 85.2%lower than the raw graphite after treated 10 times under 10 V.It shows that the electric field has a significant effect on the exfoliation efficiency of G.In the same way,under the condition of 5 or less processing times,BN/Ep system can realize fast and efficient exfoliation of BN.The mechanical properties show that when the graphite content is 0.5 wt%,tensile strength of the G/Ep system increases to 74.9±5.8 MPa after treated under electric field,which is 24.8%higher than that of pure Ep.Results show that the electric field plays a vital role in promoting the performance of G/Ep composites.2?In order to better reflect the polarization effect induced by the electric field,PPy-G/Ep three-phase composite materials bridged with polypyrrole(PPy)was prepared in one step by introducing pyrrole(Py)monomer based on the above work.The effects like the amount of Py monomer and the applied intensity of electric field were systematically studied on the exfoliation efficiency and the properties of the composites.By means of the infrared spectroscopy(FT-IR),laser Raman spectroscopy(Raman),dynamic thermomechanical performance analysis(DMA),transmission electron microscope(TEM),X-ray diffraction(XRD),etc,the structure and morphology of the composites are evaluated synthetically.The results show that the peak intensity of the(002)crystal plane in 0.2 PPy-G/Ep composites material is greatly reduced by 52%after treated with 10 V.By testing the mechanical properties of PPy-G/Ep composites with different mass fractions,the results show that when Py is added with mass ratio of 1 wt%,the tensile and bending properties of PPy-G/Ep composites are the best.Compared to the G/Ep composites,the tensile strength of PPy-G/Ep composites increase to 81 MPa which is 8.1%higher than G/Ep composites at the same conditions.At a tensile rate of 2 mm/min,the breakage elongation of PPy-G/Ep increases to 4.8%.In addition,the PPy compounded by in-situ way that improves the thermal stability of the composites compared to the G/Ep composites,and the glass transition temperature is increased by 6.7?compared to the pure Ep.Above series researches show that introduction of conductive polymer PPy in in-situ way in G/Ep system can not only improves the exfoliation efficiency of G,but also promotes the mechanical properties and thermal stability to a certain extent.