writer：J. Huang , Y. Zhu*, W. Jiang, R. Cardinaels, P. Moldenaers, D. Shi
keywords：clay/polymer composites, rheology
source：期刊
specific source：Intern. Polymer Processing
Issue time：2014年
In the current study, 70/30 (w/w) polypropylene (PP)/polyamide
6 (PA6)/organoclay ternary blends were prepared by
melt mixing in three different blending sequences, i. e., organoclay
premixed with PA6 and then mixed with PP (S1 blending
sequence), organoclay premixed with PP and then mixed
with PA6 (S2 blending sequence), and organoclay, PA6 and
PP mixed simultaneously (S3 blending sequence). The effects
of organoclay on the phase morphologies, rheological properties
and mechanical properties of the blends are examined to
reveal the role of organoclay in these immiscible blends. First
of all, the dispersion and distribution of organoclay is investigated
using XRD and TEM techniques. The organoclay is exfoliated
and distributed in the dispersed PA6 phase as well
as at the interface between PA6 and PP. Interestingly, more
organoclay sheets are observed at the interface when the S2
or S3 blending sequences are utilized. From the SEM images,
it is clear that the domain size of the PA6 phase decreases remarkably
after introducing organoclay into the PP/PA6
blends. Two different rheological protocols are applied to
probe the effect of organoclay on the morphology of the blend
by in-situ monitoring the morphological evolution. The rheological
results reveal that the phase morphology of the PP/
PA6 blends remains relatively stable during shear for a wide
range of shear rates when 1.0 wt% organoclay has been
added. For the blends with a relatively high clay loading
(5.0 wt%), a characteristic and pronounced \plateau" is observed
in the low frequency range of the G’-x curves, which
indicates the presence of a percolating network of clay nanosheets.
From the mechanical measurements, we find that
the tensile strength of the blends increases slightly first and
then declines dramatically with increasing organoclay content.
Moreover, the elongation at break drops sharply as the
organoclay content increases. In summary, it is clear that the
organoclay can effectively reduce the domain size of the dispersed
PA6 phase and stabilize the phase morphology in
shear flow. However, the mechanical properties of the blends
are not really improved by clay addition, even though a cocontinuous
morphology with a percolated clay network was
generated.