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The “Superlubricity State” of Carbonaceous Fillers on Polyethylene-Based Composites in a Molten State
journal contribution
posted on 2019-12-16, 05:29 authored by Eder.
H. C. Ferreira, Ricardo. J. E. Andrade, Guilhermino J. M. FechineIt is very well known that the incorporation of fillers
into polymers
increases their viscosity in a molten state; however, results contrary
to this have been reported when graphite (Gr), graphite oxide (GrO),
and graphene oxide (GO) among other carbonaceous fillers are used.
Many authors have justified the reduction in polymer viscosity due
to the slipping interlayers of the Gr, GrO, and GO fillers. The slipping
interlayer cannot explain the reduction in polymer viscosity since
the shear stresses produced or applied during rheological tests are
lower than the interlayer shear strength of these fillers. Here, rheological
experiments with two types of polyethylenes and Gr, GrO, and GO as
fillers were carried out to elucidate this phenomenon. Remarkably,
it was observed that the viscosity reduction occurs due to the presence
of agglomerates in the composites. The agglomerates contain many flake–flake
contacts out of registry (superlubricity state), which have very low
slipping resistance. The slipping of these contacts promotes the reduction
in polymer viscosity during rheological tests. The elucidation of
the superlubricity state phenomenon proposed here may contribute to
the understanding of the carbonaceous filler influence during the
deformation of polymer composites.