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Amir Saadat, Hossein Nazockdast, Fatemeh Sepehr, Milad Mehranpoor
Viscoelastic modeling of extrudate swell of Acrylonitrile-Butadiene-Styrene/Clay nanocomposite
Appl. Rheol. 23:1 (2013) 12131 (11 pages)
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The aim of the present work was to predict the extrudate swelling behavior of organoclay containing Acrylonitrile-
Butadiene-Styrene (ABS) nanocomposite. The modeling was performed on the basis of unconstrained recovery concept originally
introduced by Tanner but employing Wagner viscoelastic model with generalized Wagner damping function which is
believed to be capable of taking into account the effect of organoclay on viscoelastic properties of nanocomposite sample.
This approach enabled us to evaluate the effect of organoclay on extrudate swell in terms of disentanglement kinetics and
chain relaxation behavior.
In our modeling, the effect of die entrance region on the extent of extrudate swelling was also considered.
In order to evaluate the validity of our modeling, the extrudate swell was measured as a function of wall shear stress
for samples varying in organoclay content. The results predicted from the model were found to be in relatively good agreement
with the experimental results.
► Cite this publication as follows:
Saadat A, Nazockdast H, Sepehr F, Mehranpoor M: Viscoelastic modeling of extrudate swell of Acrylonitrile-Butadiene-Styrene/Clay nanocomposite, Appl. Rheol. 23 (2013) 12131.
Ehssan Nazockdast, Hossein Nazockdast
Rheological Modeling of Polymer/layered silicate Nanocomposites
Appl. Rheol. 21:2 (2011) 25434 (11 pages)
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This work takes a phenomenological approach to modeling the rheology of polymer/clay nanocomposites in (shear rate)
γ ≤ 1 / s
based on experimental observations [10]. The total stress was divided to three contributions: Matrix stress, σM,
inter-particle
(matrix/particle) stress, σP,
and hydrodynamic stress σH. Based on the superposition of complex viscosities, η*, plotted against
strain rate amplitude, γ0ω,
at different nonlinear strain amplitudes, a modified Bingham-type constitutive equation proposed
by Doiraswamy et. al [16] was used to model σM+σP
while σH was modeled by using constitutive equation proposed by
Lipscomb et. al [25] for ellipsoidal particles. The comparison between experimental and modeling results showed that steady
hydrodynamic stress in simple shear flows scales with complex viscosities in oscillatory experiments when compared at
γ = γ0ω.
On the basis of this observation, the network-like behavior of the polymer nanocomposite was attributed to retarded
chain dynamics as a result of polymer/clay interactions. In order to take into account the thixotropic behavior of network
structure, the constitutive equation proposed by Coussot [18] was employed for modeling σM+σP.
Both Coussot and Doraiswamy equations gave a reasonable
quantitative prediction of transient stress in simple shear flow up to shear rates as
high as γ = 0.1 / s.
► Cite this publication as follows:
Nazockdast E, Nazockdast H: Rheological Modeling of Polymer/layered silicate Nanocomposites, Appl. Rheol. 21 (2011) 25434.
Reza Foudazi, Hossein Nazockdast
Rheology of Polypropylene/Liquid Crystalline Polymer Blends: Effect of Compatibilizer and Silica
Appl. Rheol. 20:1 (2010) 12218 (9 pages)
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The effect of classical compatibilizers and silica fillers, which are a new potential type of compatibilizers, on the rheological
properties of PP/LCP blends was investigated.The frequency sweep, shear stress growth and stress relaxation upon cessation
of steady shear were performed to probe the effect of the interfacial modification and the role of silica, on the rheological
behaviour of the blend. It was found that SEBS-g-MA improves the interfacial interaction more than SEBS due to the possible
chemical bonding between maleic anhydride groups and LCP chains. The results showed while the hydrophilic silica fills
both matrix and the LCP dispersed phases, the hydrophobic silica has some compatibilizing effect on PP/LCP blend samples.
► Cite this publication as follows:
Foudazi R, Nazockdast H: Rheology of Polypropylene/Liquid Crystalline Polymer Blends: Effect of Compatibilizer and Silica, Appl. Rheol. 20 (2010) 12218.
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