Preparation Of Few-layer Graphene And Characterization Of Its Epoxy Resin Composites

Graphene i s a cell ular structur e formed by sp~2hybridizati on of a singl e layer of carbon atoms.It has excellent mechanical,electrical and thermal properties.Epoxy resin has been widely used in the fields of national economic construction and aerospace due to it s excell ent mechanical properties,chemical resi stance and strong weather resi stance,but its performance in preventing crack propagation,heat resist ance and wear resist ance still need to be improved.In order to make up for the defects of epoxy resin and give full play to the excellent properties of graphene,adding it into t he epoxy resin matrix as a reinforcing material can greatly improve the mechanical properties of epoxy resin,and at the same time can give the material good thermal and electri cal properties.Based on natural graphite as raw material,a monolayer of,grap hene oxide(GO)was prepared by improved.Humm ers method with GO as the precur sor,reduced graphene oxide(RGO),functionalized graphene and graphene aerogel(GA)were prepared by chemical reduction and hydrot hermal reduction respectively,monolayer graphene nanosheet s(GNPs)wer e prepared by high pressure homogenizati on method and their characterization was tested.On this basis,the graphene/epoxy resin composit es were prepared by graphene prepared in different ways.The influence of various types of grap hene on the com posites was studied through the test characteri zation of the cross-secti on morphology,mechanics,thermal and electrical properties of the material s.The main research results are as follows:1.GO prepared by improved Hummers method has a hi gh degree of oxidation and fewer layers.Its surface contains a large number of oxygen-containi ng functional groups.RGO prepared wit h hydrazine hydrate as reducing agent can effectivel y remove a large number of oxygen-containi ng functional groups from the GO sheet layer and restore it s partial el ectrical conductivity,but agglomer ation is very easy t o occur.Using the surfactant(sodium dodecyl sulfat e SDS,hexadecyl trimethyl ammonium bromide CTAB)and polymer(polyvinylpyrrolidone PVP,polyet her amine D230)preparation of functionalized graphene,by scanning electron microscope(SEM),Fourier infrared(FTIR),Raman spectroscopy(Raman)and X-ray diffraction(XRD)charact erization m ethods,prove that graphene is functi onal.Compared with the graphene reduced by hydrazine hydrate,the layer spacing of the functionalized graphene was increased,and the van der Waals force between the sheet s was reduced,which improved the dispersibilit y of the functionalized graphene.2.Graphene oxide(GO),reduced graphene oxi de(RGO)and functionalized graphene(DGO)as the filler added to the epoxy resin(EP)matrix by solution blending method,three different kinds of composite m aterial i s prepared,they are graphene oxide/epoxy resin composit es(EP-GO),reduced graphene ox ide/epoxy resin composit es(EP-RGO)and functionalized graphene/epoxy resin composit es(EP-DGO).Using universal testing machine,thermal conductivity m eter and four point probe instrument charact erization of composite material performance,the results show that when the GO or RGO mass fraction was 0.5%,the modulus and strength of the composite materi al system reached its peak,the EP-GO syst em tensil e strength and shear strength were 70.3 and 7.86 MPa,higher than the pure epoxy resin(45.2 MPa)about 33.5%and 48%,EP-RGO system tensile strength and shear strengt h were 60.2 and 7.5 MPa,about 25.7%and 41.2%higher than the pure epoxy resin.It indicates that the additi on of GO or RGO can improve the modulus and strengt h of composit e material s,and the E P-GO system is more significantly improved than the EP-RGO system,mainly because the GO sheet layer contai ns a large number of oxygen-cont aining functional groups that r eact with the epoxy resin to enhance the interface interacti on,that is the mechanical strength increases.With the addition of graphene nanom aterial s into pure epoxy resin,the thermal conductivity of different epoxy resin composite system s tended to increase.When0.5wt%GO or RGO were added,the thermal conductivity of the systems reached the maximum value,and the peaks of EP-GO and EP-RGO systems were 0.56w/m?K and0.42w/m?K,respectively.When the DGO mass fraction was 0.5%,the bending strength and tensile strengt h of the functional graphene/epoxy resin composit e material(EP-DGO)increased from 66.8MPa and 45.2MPa to 121.6MPa and 70.5MPa,increasi ng by 82%and 56%respectively,indicating that the addition of functionalized graphene enhanced the toughness and strength of the epoxy resin composit e material.3.High pressure homogenization method was used to prepare graphene nanosheet s(GNPs)with good quality and few layers.Adding them to the epoxy resin matrix can improve the m echani cal and t hermal properties of the composite.The results show that with the increase of the content of GNPs strength of epoxy resi n composit es showed a trend of increase,when the GNPs adding amount was 5%,graphene nanosheets/epoxy resin composi te material syst em(EP-GNPs)tensil e strength is 48.2 MPa,EP-GNPs system of thermal conductivity is 0.605 W/m?K,increased by 173%,the weight loss of 20%when the thermal decomposition temperature is 383℃,improved 14℃.In addition,under the effect of magnetic field assi sted,graphene nanosheet s(GNPs)have been magnetized deflect,directional arrange ment along the directi on of orientation,was prepar ed with anisotropi c EP-GNP s composites,the results show that the thermal conductivity of the composit e material increase to 0.704 W/m?K,compared with t he thermal conductivity of pure epoxy resin(0.22 W/m?K),increased by 220%,the sample cured in the direction parallel to the magnetic field of thermal conductivity higher than vertically samples.