Self-aligned Graphene Sheets-Polyurethane Nanocomposites
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Self-aligned Graphene Sheets-Polyurethane Nanocomposites
Mohsen Moazzami Gudarzi1,2, Seyed Hamed Aboutalebi1, Nariman Yousefi1, Qing Bin Zheng1, Farhad Sharif2, Jie Cao3, Yayun Liu3, Allison Xiao3 and Jang-Kyo Kim1* 1
Department of Mechanical Engineering, Hong Kong University of Science and Technology,
Clear Water Bay, Kowloon, Hong Kong 2 Department of Polymer Engineering, Amirkabir University of Technology, 424 Hafez Ave, Tehran, Iran Advanced Technologies, Henkel Corporation, 10 Finderne Ave. Bridgewater, NJ 08807, USA
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ABSTRACT Processing graphene and graphene polymer nanocomposites in an aqueous medium has always been a big challenge due to the hydrophobic nature of graphene (or reduced graphene oxide) nanosheets. In this work, a waterborne latex of polyurethane has been used both as the matrix material for embedding the graphene nanosheets and as a unique stabilizer to help produce an up to 5 wt% graphene/PU nanocomposites. The graphene oxide/polyurethane latex aqueous suspension is reduced in-situ using hydrazine, without any trace of aggregation/agglomeration upon completion of the reduction process, which would otherwise have occurred severely were PU not present. A highly aligned nanostructure is produced when graphene content is increased beyond 2 wt%, resulting in a remarkable improvement in electrical and mechanical properties of the nanocomposite. The exceptionally low electrical percolation threshold of 0.078%, as well as 21-fold and 14 fold increases in tensile modulus and strength, respectively, have been attained thanks to the alignment of graphene nanosheets in the polymeric matrix. INTRODUCTION Graphene, a single atomic layer of sp2 carbon atoms has gained much attention in recent years. This unique arrangement of carbon atoms bring about exclusive electrical, thermal, magnetic and mechanical properties [1-4]. Graphene is known to be the hardest and stiffest material on earth. What adds up to these fascinating properties of graphene is the mere fact that it can be produced from cheap and naturally occurring graphite flakes [5-7]. Being one of the thinnest and strongest materials with exceptionally high electron mobility and thermal conductivity suggests that one of the most efficient ways to benefit from the properties of graphene is to incorporate them in a polymeric material to form nanocomposites [8]. Therefore, graphene oxide (GO) and reduced graphene oxide (rGO) sheets have attracted significant attention as filler for polymer nanocomposites that are now finding diverse applications [9-11].
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This paper presents a simple method for the production of polymer-ultra-large graphene composites using water-borne polyurethane (PU) latex where the polymer serves both as stabilizer in the reduction step as well as the matrix material. Interparticle interactions between the ultra-large size GO sheets and PU particles are considered as the key underlying mechanism for the stabilization. The unique morphology of PU-graphene dispersion resulted in self-alignment of GO sheets with strong interfa
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