Functionalized Graphene: Characterization and Mechanical Reinforcement
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Polymer nanocomposites with better performance and lower cost are in constant demand. One of the challenges inherent in this field is balancing these two factors. Graphene provides the possibility of producing high performance polymer nanocomposites but is too expensive for adoption in a wide variety of commercial applications. Currently, oxidation of graphite followed by reduction is the most cost effective method for providing graphene like material for use in polymer nanocomposites. This method often requires the use of organic solvents, which are expensive and harmful, or surfactants, which are not easily removed and affect the properties of the resulting material. The results shown in this study demonstrate that functionalized graphene, derived from humic acid, provides mechanical reinforcement in polymer nanocomposites. This provides a new, alternative source for graphene-like material and eliminates the need for an oxidative step currently used to exfoliate graphite. Functionalized graphene has properties similar to that of graphene including being atomically thin. It also has the compatibility necessary for inclusion in a water dispersible polyurethane matrix. Functionalized graphene was well dispersed in these systems and provided storage modulus mechanical reinforcement of 150% at 1.0% loading which is higher than the level of reinforcement reported in comparable materials. This level of storage modulus mechanical reinforcement would require a 4% loading level of montmorillonite nanoclay to get an equivalent amount of reinforcement and is 45% of the storage modulus reinforcement predicted with the Halpin-Tsai theoretical model.