| Summary: | 碩士 === 國立臺北科技大學 === 化學工程研究所 === 100 === Polymeric foam possesses many advantages such as cost reduction, insulation, weight saving, high modulus/density ratio and improved fatigue resistance. It has been commonly used in livelihood tools, aerospace and the automotive industry. In addition, the graphene research increased dramatically in recent years. It has great electrical properties, mechanical properties, thermal properties, high specific surface area. Due to the availability and easiness of production, the price of graphene could be lower than that of carbon nanotubes and carbon nano fibers in the future. One of the characteristics of graphene is its ultrahigh specific surface area which would improve the nucleation rate during the foaming process. Thus, graphene was compounded with polystyrene and polymer-graphene nanocomposite foam was prepared using a batch foaming technique. Combining the advantages of polymer nanocomposite and foam may create a new class of lightweight, high strength materials which could have many new possibilities.
In the first part of this study, natural graphite was oxidized by Hummers method and followed by thermal reduction to obtain graphene nanoplatelets. The graphene and graphite oxide nanoparticles were characterized by XRD, EDS and FTIR .In the second part of this study, graphene was compounded with polystyrene by solvent blending. The dispersion of grapheme was characterized by TEM. Finally, the polymer-graphene nanocomposites were foamed using supercritical carbon dioxide as the blowing agent using a batch foam process. The graphene/polystyrene nanocomposites were foamed at 120 ° C and various foaming pressure. The foam structure was characterized by SEM.
The experiment results showed that adding nanoparticles can significantly enhance the nucleation rate and decrease the cell size. To compare the nucleation effect of different nanoparticles, thermally reduced graphene (TRG), carbon nanotubes, carbon nano fiber, commercially available nanographite platelets and talc were used as nucleating agents. Among the different nanoparticles, graphene showed the best nucleating efficiency. The cell size is 7.8 μm while the cell density is 3.54×109cell/cm3foamed at 120˚C and 2000 psi. In addition, it is worth noting that adding nanoparticles as a nucleating agent can make foams of similar cell size and cell density with a much lower foaming pressure.
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