Preparation, Characterization, and Application in Polymer Composites of Graphene
|School||Zhejiang University of Technology|
|Keywords||graphene graphene oxide polymer composites supercritical CO2 foaming properties|
Nanocomposite is one of hot topics of current material sience areas, which is relating to many branches of learning and possessing large theory and application value. Recently, as a new form of carbon, graphene sheets which pocess excellent physical and chemical properties have become an important direction in the composite research.Herein, graphene oxide （GO） was prepared by oxidation of graphite using the Hummers method, and its morphology, dispersion situation and the degree of oxidation were characterized. Solution blending and emulsion blending was applied to prepare polymer/GO and polymer/graphene composites with the purpose of improving the mechanical and thermal properties of bulk polymer, as well as the cell morphology of polymeric foam. The influence of GO and graphene concentration, surface modification, dispersion state on these properties were systematically investigated, and the mechanism was researched as well.GO sheets were fully oxidized and exfoliated from the nature graphite by the various characterization methods, such as X-ray diffraction （XRD）, X-ray photoelectron spectroscopy （XPS）, etc. Meanwhile, the morphology and the well-dispersed situation of GO in water could be obtained from visual study and the transmission electron microscopy （TEM） image. GO was modified by phenyl isocyanate, and its Fourier transform infrared spectrometer （FT-IR） spectra revealed the reaction of phenyl isocyanate on the functional groups of GO surface occurred and leaded to their chemical bonding.Using GO sheets modified by isocyanate, PS/GO composites were prepared by a solution blending method using DMF as solvent. The result of surface morphology characterization shows that GO was not well-dispersed in PS matrix, which resulted in slight increase on the mechanical and thermal properties. Meanwhile, the heterogeneous nucleation effect of GO sheets in supercritical carbon dioxide （CO2） foaming was not as obvious as expected, while slightly higher cell density and smaller cell size was really caused by GO sheets. Thus, GO could also act as heterogeneous nucleation agents.In order to improve the dispersion of GO sheets in polymer matrix, a simple approach to the preparation of polymer composites was described. That is, cationic emulsifier （MAETAC） was applied to modify PMMA, and then blended with the GO aqueous solution. Utilizing the interaction between the anti-charges of GO and PMMA surface, the PMMA composites with well-dispersed GO were prepared. Meanwhile, due to electrostatic attraction, GO sheets in emulsion could be in situ reduced into graphene sheets by a chemical method without the aggregation. As a result, graphene sheets were also well-dispersed in PMMA matrix.The influences of GO and graphene sheets on the properties of PMMA were investigated by differential scanning calorimeter （DSC） and dynamic mechanical analysis （DMA）. Moderate improvements caused by GO sheets, while much higher enhancements caused by graphene sheets were found in the glass transition temperature and storage modulus. Moreover, the electrical conductivity of the PMMA/graphene composites was drastically increased by several quantitative degrees. Thus, the composites possess good application prospect.