Study On Performance Of Graphene(Oxide)/Nano Cellulose Composite Film

The nano cellulose film was prepared by acid-alkali direct treatment- grinding-ultrasonic method and acid-alkali alternate treatment-grinding-ultrasonic method. Then use the graphite powder as raw materials, the graphene oxide made by one step oxidation method, pre oxidation-oxidation method and cycle oxidation-expansion method.Use nanocellulose as matrix, and graphene oxide as reinforcing phase, fabricate the graphene oxide/ nano cellulose composite film by vacuum filtration. Graphene oxide was reduced under a mild condition by using vitamin C as reducing agent. Finally the graphene/cellulose composite films were produced by ultrasonic mixing graphene suspension and cellulose suspension, then use vacuum filtration method. The chemical components and micro morphology were measured by infrared spectrometer(FTIR), Raman spectroscopy and scanning electron microscopy(SEM). tensile property, thermal stability and electrical properties were analysed by mechanical testing machine, thermogravimetric analyzer and Four-Point Probes tester, respectively.The results of this paper is as follows:(1) The acid-alkali alternate treatment-grinding-ultrasonic method can obtain nano cellulose film which interwoven into three-dimensional network structure and had clear structure, and the diam eter of fibre was 50 nm, the proportion of length and diameter was 1500~3000. Nano cellulose suspension was uniformly dispersed colloid could occur Tyndall effect. The tensile strength of cellulose film made by acid-alkali alternate treatment is up to 95.31 MPa, which is higher than the film made by acid-alkali direct treatment, and the light transmittance is 79.6%, which can be used in transparent packaging film materials.(2) Under scanning electron microscope, the graphene oxide made by cycle oxidation-expansion method was unfairness, like wavy up and down, the layer edge was as thin as gauze. The quality of graphene oxide made by cycle oxidation-expansion method was superior to the graphene oxide made by one step oxidation method and preoxidation-oxidation method. Under the determination of the Raman spectra, graphene oxide of cycle oxidation-expansion method contained more oxygen groups, had a high degree of oxidation. And the intensity ratio of G/ D peak was 0.92, the structure of sp2 carbon atoms convert to sp3, the materials become more disorder.(3) When the graphene oxide content was 0 ~ 4.40%, the tensile strength of graphene oxide/nano cellulose composite film kept rising, when the adding amount was 4.40 ~ 8.45%, tensile strength of composite film was decreasing. Along with the increasing content of graphene oxide, the elastic modulus of composite films has been rising. The fracture surface of GO/nano cellulose film with 4.40% GO displayed uniformity structure, rough but without any aggregations of GO, revealing that the GO was well dispersed in the cellulose matrix. Whereas, the film with 8.45 wt% GO exhibited severe aggregation of GO, showing poor interfacial adhesion between GO and cellulose.(4) Under the same frequency, with the increasing of GO, the storage modulus(E’)-temperature(T) curves showed a vertical upward trend. The storage modulus of the nano cellulose film is 4885 MPa, when the GO content were 4.4% and 8.45%, the storage modulus of the GO/cellulose composite films were 9357 MPa and 14760 MPa, respectively.(5) In the thermal stability test, the terminal degradation temperature of nano cellulose film and GO made by cycle oxidation-expansion method were 380℃ and 450℃, respectively. The char residues after decomposition(600℃) were 20%, 45.91% respectively. The sharp pyrolysis temperature of GO/nano cellulose films(with 0~8.45% GO) were all about 387℃. The residual carbon amount was increasing linearly with the increase of GO content. This observation showed the enhancement of the thermal stability of the composite films as the GO loading level increased.(6) After the reduction of GO with vitamin C, the oxygen functionalities of GO removed heavily, the agglomeration of graphene suspension occured, graphene after reduction had more sp2 domain, but there are still exist more sp3 domain. The graphene obtained by the reduction of GO can’t recover into graphite structure totally, moreover, the section uniformity of graphene/nano cellulose composite film was higher than that of graphene film, which demonstrate that the nano cellulose can be used as the substrate material of graphene composites materials.(7) Thermogravimetric analysis showed that during the reduction of GO, the oxygen functionalities removed, the weightlessness rate of graphene was higher than GO and graphene/ nano cellulose film. The maximum decomposition rate of graphene/nano cellulose film was 333℃. The terminal degradation temperature and the char residues after decomposition(600℃) were 415℃ and 32%, which were both higher than cellulose film’s. This proved that graphene can significantly improve the material’s thermal stability.(8) The electrical conductivity of graphene sheets can reach to 81.16 s/m. As the graphene is difficult to make film, while the graphene/ nano cellulose film can be a uniform and stable whole, and when graphene content was 20.18 wt %, the electrical conductivity of graphene/ nano cellulose film was 0.28 s/m. The composite film is expected to become conductive material, this aspect should be studied further.