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Controlled Structure Evolution of Graphene Networks in Polymer Composites
journal contribution
posted on 2018-02-14, 00:00 authored by Stephen
C. Boothroyd, David W. Johnson, Michael P. Weir, Carl D. Reynolds, James M. Hart, Andrew J. Smith, Nigel Clarke, Richard L. Thompson, Karl S. ColemanExploiting
graphene’s exceptional physical properties in
polymer composites is a significant challenge because of the difficulty
in controlling the graphene conformation and dispersion. Reliable
processing of graphene polymer composites with uniform and consistent
properties can therefore be difficult to achieve. We demonstrate distinctive
regimes in morphology and nanocomposite properties, achievable through
systematic control of shear rate and shear history. Remarkable changes
in electrical impedance unique to composites of graphene nanoplatelets
(GNPs) are observed. Low shear rates ≤0.1 s–1 break up the typical GNP agglomerates found in graphene composites,
partially exfoliate the GNPs to few-layer graphene, and reduce orientation,
enhancing electrical conductivity in the composite materials, whereas
at higher shear rates GNP orientation increases and the conductivity
reduces by four orders of magnitude, as the graphene filler network
is broken down. The structure of the composite continues to evolve,
reflected in further changes in conductivity, after the shear force
has been removed and the process temperature maintained. This work
provides critical insights for understanding and controlling GNP orientation
and dispersion within composites and will have important consequences
in the industrial processing of graphene polymer composites via the
informed design and choice of processing conditions.
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Keywords
shear forcepolymer compositesgraphene conformationshear rategraphene nanoplateletsgraphene polymer compositesgraphene filler networkGNP orientationconductivityprocess temperatureControlled Structure EvolutionReliable processingnanocomposite propertiesshear rates GNP orientation increasesgraphene compositesprocessing conditionsRemarkable changesshear historyGraphene NetworksGNP agglomeratesfew-layer graphene
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