熱還原石墨烯對超臨界流體二氧化碳發泡聚苯乙烯泡孔之影響

Effect of thermally reduced graphene oxide on the Properties of Supercritical CO2 Foamed Polystyrene/Graphite Nanocomposites

柯明青(Ming-Qing Ke)

指導教授 ： 葉樹開

國立臺北科技大學/工程學院/化學工程研究所/碩士(2012年)

摘要

高分子發泡材料有許多優點，包括節省成本、絕熱隔音、減輕重量、提高抗衝擊性及抗疲勞性等等，常用於民生工具和航太、汽車工業。另外近年來石墨烯的研究大幅提升，無論是電性、機械性質、導熱性質、比表面積，石墨烯都有驚人的表現，而未來石墨烯的價格可能會低於奈米碳管和奈米碳纖維，因此石墨烯很有發展的前途。因為石墨烯的高比表面積有利於發泡程序的成核速率，所以我們將石墨烯與聚苯乙烯製成高分子發泡材料，結合石墨烯與發泡材料的優點提升性能，創造新的可能。
本實驗第一階段先使用Hummers method把天然石墨氧化成氧化石墨，再將氧化石墨經由高溫熱還原成石墨烯。後續利用XRD、EDS、FTIR等儀器來分析氧化石墨和熱還原石墨製備的成效。第二階段我們使用溶劑混合法將石墨烯添加到聚苯乙烯中形成奈米複合材料，並以TEM確認石墨烯在複合材料中的分散性。最後使用超臨界二氧化碳作為發泡劑，對石墨烯/聚苯乙烯奈米複合材料做批次發泡程序，以120℃作為發泡溫度，改變發泡壓力和添加不同成核劑來做發泡結構之探討。
實驗結果表示，添加奈米顆粒可以明顯提升成核速率並且使泡孔縮小。分別以熱還原石墨烯、奈米碳管、奈米碳纖維、xGnP層狀石墨與滑石粉作為成核劑來比較發泡效果，而石墨烯的發泡效果最好，在發泡溫度為120℃，發泡壓力為2000 psi下，泡孔直徑只有7.8 μm；泡孔密度為3.54×109 cell/cm3。另外在低壓時添加奈米顆粒可以使泡孔直徑趨近於高壓下聚苯乙烯泡體的泡孔大小，如此一來在高分子加工過程中使用低壓就可得到性質優越的發泡材料。

關鍵字

石墨烯 ； 奈米碳管 ； 奈米碳纖維 ； 奈米層狀石墨 ； 聚苯乙烯 ； 超臨界二氧化碳 ； 發泡

並列摘要

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.

並列關鍵字

Graphene ； carbon nanotube ； carbon nanofiber ； nano-Graphite platelets ； polystyrene ； supercritical CO2 ； foam

參考文獻

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