10.1021/acs.chemmater.7b04343.s001
Stephen
C. Boothroyd
Stephen
C.
Boothroyd
David W. Johnson
David W.
Johnson
Michael P. Weir
Michael P.
Weir
Carl D. Reynolds
Carl D.
Reynolds
James M. Hart
James M.
Hart
Andrew J. Smith
Andrew
J. Smith
Nigel Clarke
Nigel
Clarke
Richard L. Thompson
Richard L.
Thompson
Karl S. Coleman
Karl S.
Coleman
Controlled Structure Evolution of Graphene Networks
in Polymer Composites
American Chemical Society
2018
shear force
polymer composites
graphene conformation
shear rate
graphene nanoplatelets
graphene polymer composites
graphene filler network
GNP orientation
conductivity
process temperature
Controlled Structure Evolution
Reliable processing
nanocomposite properties
shear rates GNP orientation increases
graphene composites
processing conditions
Remarkable changes
shear history
Graphene Networks
GNP agglomerates
few-layer graphene
2018-02-14 00:00:00
Journal contribution
https://acs.figshare.com/articles/journal_contribution/Controlled_Structure_Evolution_of_Graphene_Networks_in_Polymer_Composites/5926264
Exploiting
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<sup>–1</sup> 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.