Optimization of Three-Roll Mill Parameters for In-Situ Exfoliation of Graphene
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Optimization of Three-Roll Mill Parameters for In-Situ Exfoliation of Graphene Yan Li 1,2, Han Zhang 1,2, Emiliano Bilotti 1,2, Ton Peijs 1,2,* School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, E1 4NS London, UK 2 Nanoforce Technology Ltd., Joseph Priestley Building, Queen Mary University of London, Mile End Road, E1 4NS London, UK
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ABSTRACT Three-roll milling (TRM) has proven to be an effective method to disperse 1D nanofillers like carbon nanotubes in polymer resins. However, until now only limited research has been performed on using this method to exfoliate and disperse 2D nanofillers, such as graphene and graphene nanoplatelets (GNP) with preserved lateral dimension. In the present work, a systematic study of TRM processing parameters on final nanocomposite properties is presented, resulting in improved GNP/epoxy nanocomposite properties after the optimization of TRM parameters such as mode, speed, cycles, gap distance, and resin temperature. Electrical conductivity of the final GNP/epoxy nanocomposites is increased by six orders of magnitude, while at the same time a high mechanical reinforcement is achieved as well. INTRODUCTION Interest in graphene and its potential applications has grown rapidly since 2004, when the material was first isolated by Geim and Novoselov [1]. Graphene-filled polymers are of particular interest because of the excellent multifunctional properties of graphene, which include high theoretical specific surface area (2360 m2/g), high thermal conductivity (5000 W/mk), high intrinsic mobility (200,000 cm2/sv), and an extremely high Young’s modulus (1.0 TPa), making these fillers of interest for a wide variety of applications, including conductive composites [2], sensors [3, 4], flexible electronics, etc. GNPs represent a new class of carbon nanoparticles with multifunctional properties, exhibiting a 2D “platelet-like” morphology, meaning that they can be very thin but with a high aspect ratio. It has the potential for replacing commercial nanofillers currently in use for the fabrication of nanocomposite [2, 5]. GNPs can improve mechanical properties of the host polymer, such as: stiffness, strength and surface hardness, offering an alternative to carbon nanotubes (CNTs) [6]. However, the availability of processable GNPs in large quantities is essential to the success in developing GNP based nanocomposites. Conventional methods to produce graphene or GNP filled resins typically involves three steps. The 1st step generally involves a solvent-based chemical treatment of graphite, often in conjunction with mechanical stirring, in order to produce individual graphene sheets or GNPs. In a subsequent step it is then necessary to remove the solvent (2nd step), before finally attempting to disperse the resultant material in a polymer (3rd step). Current production methods for graphene or few layer graphene require large quantities of organic solvent, resulting in difficulties in industrial scale application due to costs and environmental impact.
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