Synthesis And Properties Of Modified Graphene Oxide/Polyimide Composite Films

Polyimides have attracted much attention due to their outstanding thermal resistance and excellent mechanical strength.However,because of the rapid development in the advanced technology,superior properties of polyimides are needed.In recent years,graphene and its derivatives attracted wide interests due to their excellent properties,improving the synthetic properties of polyimides by adding graphene or its derivatives has become a promising research direction.In the current study,classical Hummers method was used to prepare graphene oxide(GO)with oxygen-containing active groups,and the phenyl isocyanate-treated graphene oxide(mGO)was obtained by chemical modification with phenyl isocyanate.The GO before and after modification was characterized by SEM,FT-IR,Raman,XRD and XPS,the results showed that GO and mGO have been synthesized successfully.The dispersion of GO before and after modification has been studied by Uv-vis,and the dispersibility of mGO in DMF was higher than that of GO.A series of polyimide films with different GO and mGO contents were synthesized using 4,4-oxydianiline(ODA)and 4,4’-methylenedianiline(MDA)as the diamine monomer and 3,3’,4,4’-benzophenonetetracarboxylic dianhydride via in situ polymerization.The structure and properties of the composite films were characterized by FT-IR,XRD,SEM,TGA,DSC.And contact angle tests,water absorption tests and tensile tests were conducted.The results showed that GO and mGO have good compatibility with PI matrix,the addition of GO and mGO affected the absorption peak intensity,position and crystallinity of the composite films,and the addition of mGO made the crystal orientation structure of polyimides more orderly.The composite films had good thermal stability,the glass transition temperature Tg was higher than 355 ℃,and the thermal stability of the PI1-type composite films were higher than that of the PI0-type composite films.All The composite films had certain hydrophobicity,the contact angle was higher than that of the pure polyimide film,and the water absorption decreased with increasing the content of GO and mGO.The addition of GO and mGO increased the tensile strength and tensile modulus of the composite films,while the elongation at break decreased.