Graphene Modification And Its Application In Polymer Composites

The graphene material has excellent electron transport capacity, largespecific surface area and the Holzer effect under normal temperature,which attract a lot of attention from researchers. As a kind of excellentfunctional materials, graphene and its derivatives are widely used in avariety of polymer composites.Graphene oxide (GO) was prepared by oxidation of graphite usingthe Hummers method. The dispersion of GO in aqueous solution is well.Then GO is modified by amine-terminated polyether D2000, PEG800andphenyl isocyanate. It is found that GO modified by PEG800and phenylisocyanate can disperse well in DMF solution. The dispersion of GOmodified by amine-terminated polyether D2000in DMF solution is verypoor.Actually, polyurea composites is prepared in DMF solution. So it isnecessary to get the information about dispersion of modified GO inDMF solution. It is clear that GO-PEG800and isocyanate-GO can beused as the filler into polyurea matrix by in-situ polymerization.Microstructure of polyurea/isocyanate-GO composites were characterizedby SEM and TEM. It indicated that isocyanate-GO sheets were welldispersed in polyurea composites. Isocyanate-GO sheets can improve the glass transition temperature and mechanical properties of composites at acertain content (<1wt%). At the content of1wt%, the tensile strength ofthe composite increased by37%, the elongation at break increased by14%. Polyurea/GO-PEG800composites were characterized by SEM andTEM. It is found that GO-PEG800dispersed in polyurea matrix with acurled shape. The glass transition temperature and mechanical propertiesof composites increased with the addition of GO-PEG800. At the contentof2wt%, the tensile strength of the composite increased by75%.GO-PEG800is more effective to enhance mechanical properties andthermal stability of polyurea than isocyanate-GO.Hydrazine hydrate is used to reduce GO. The results showed thatmost of oxygen element disappear, only about10%were still exist on thesurface of graphene. Then graphene dispersed in polyether polyol system.It was used to prepare PU/graphene composites. Microstructure ofcomposite materials was characterized by SEM. Scanning electronmicroscopy indicated that with the content of graphene increased(<1.3wt%), it can effectively reduce the cell size of polyurethane foam.Thermogravimetric Analysis and other Analysis methods indicated thatgraphene can appropriately reinforced thermal stability of polyurethanefoam. Resistance tests show that graphene sheets substantially improvedthe electrical conductivity of polyurethane composites.