Preparation And Properties Of Graphene/Polyimide Composite Films

Polyimides have attracted much attention due to their excellent mechanical strength and outstanding thermal resistance.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,improved hummers method was used to prepare graphene oxide(GO)with oxygen-containing active groups,and the p-phenylene diamine-treated graphene oxide(PPD-GO)was obtained by chemical modification with p-phenylene diamine,and the hydrazine hydrate-reduced graphene oxide(rGO)was reduced by chemical modification with hydrazine hydrate.The GO before and after modification and reduction was characterized by SEM,FT-IR,Raman,XRD and XPS,The analysis of SEM and XRD showed that the microstructure of graphene and its derivatives were different,and the PPD-GO was more obvious than the GO slice structure.According to the Bragg equation,the PPD-GO layer spacing was 1.36nm,and the GO layer spacing was 0.82nm,which means that PPD-GO was easier to slice.FT-IR and XPS analysis showed that GO contained more oxygen functional groups and and the oxygen content was 26.78%.The p-phenylenediamine modified PPD-GO had an amino functional group,which contains 15.63%oxygen and 2.80%nitrogen.The oxygen functional groups of rGO after reduction were reduced,and the oxygen content was9.43%.In conclusion,the results showed that GO,PPD-GO and rGO have been synthesized successfully.A series of polyimide films with different GO,PPD-GO and rGO contents were synthesizedusing4,4-oxydianiline(ODA),4,4'-methylenedianiline(MDA)and1,5-Bis(4-amino-2-trifluoromethylphenoxy)naphthalene(BATN)as the diamine monomer and3,3',4,4'-benzophenonetetracarboxylic dianhydride(BTDA)via in situ polymerization.The structure and properties of the composite films were characterized by FT-IR,XRD,SEM,TGA,DSC.And tensile tests were conducted.FT-IR analysis showed that the thermal imidization of composite films was complete.XRD analysis showed that the addition of graphene and its derivatives affected the crystallinity of polyimide.The addition of GO resulted in the conversion of the crystalline of the film to amorphous,and the addition of PPD-GO changed the crystallization of the film into order.TGA analysis showed the composite films had good thermal stability.DSC analysis showed their glass transition temperature T_g was higher than 260 ~oC.The addition of GO,PPD-GO and rGO improved the tensile properties of the composite films,The tensile strength of the film was increased by16.8%with the addition of 2%rGO.