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M. Greim, W. Kusterle
23. Conference and Workshop Rheology of Building Materials
Appl. Rheol. 24:3 (2014) 61-62
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► Cite this publication as follows:
Greim M, Kusterle W: 23. Conference and Workshop Rheology of Building Materials, Appl. Rheol. 24 (2014) 61.
A.H. Al-Muslimawi, H.R. Tamaddon-Jahromi, M.F. Webster
Numerical computation of extrusion and draw-extrusion cable-coating flows with polymer melts
Appl. Rheol. 24:3 (2014) 34188 (15 pages)
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This paper is concerned with the numerical solution of polymer melt flows of both extrudate-swell and tube-tooling dieextrusion
coatings, using a hybrid finite element/finite volume discretisation fe/fv. Extrudate-swell presents a single dynamic
free-surface, whilst the complex polymer melt coating flow exhibit two separate free-surface draw-down sections to
model, an inner and outer conduit surface of the melt. The interest lies in determining efficient windows for process control
over variation in material properties, stressing levels generated and pressure drop. In this respect, major rheological influences
are evaluated on the numerical predictions generated of the extensional viscosity and Trouton ratio, when comparing
solution response for an exponential Phan-Thien Tanner (EPTT, network-based) model to that for a single extended Pom-Pom
(SXPP, kinematic-based) model. The impact of shear-thinning is also considered. Attention is paid to the influence and variation
in Weissenberg number We, solvent-fraction β (polymeric concentration), and second normal stress difference N2 (ξ
parameter for both EPTT, and α anisotropy parameter for SXPP). The influence of model choice and parameters upon field
response is described in situ through, pressure, shear and strain-rates and stress. The numerical scheme solves the momentum-
continuity-surface equations by a semi-implicit time-stepping incremental Taylor-Galerkin/pressure-correction finite
element method, whilst invoking a cell-vertex fluctuation distribution/median-dual-cell finite volume approximation for the
first-order space-time hyperbolic-type stress evolution equation.
► Cite this publication as follows:
Al-Muslimawi A, Tamaddon-Jahromi H, Webster MF: Numerical computation of extrusion and draw-extrusion cable-coating flows with polymer melts, Appl. Rheol. 24 (2014) 34188.
Martin Boisly, Markus Kästner, Jörg Brummund, Volker Ulbricht
Large amplitude oscillatory shear of the Prandtl element analysed by Fourier Transform Rheology
Appl. Rheol. 24:3 (2014) 35478 (11 pages)
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This work contributes to the theory of strain controlled large amplitude oscillatory shear (LAOS) as well as modelling the key
properties of type III behavior of Hyun, the decreasing storage modulus and a loss modulus with considerable maximum. The
latter two can be modelled with the help of the Prandtl element. Since it is a yield stress fluid, the use of LAOS is necessary
to calculate the storage and loss modulus. Furthermore, a condition is presented which has to be met in order to avoid even
harmonics. The storage and loss modulus as well as the higher harmonics of the Prandtl element are determined analytically
in this work. They are given as mathematical functions which can be discussed conveniently. This allows the identification
of characteristic points which are related to material parameters of the Prandtl element and enable a physically motivated
material parameter identification. Beside this, it is observed that the yield strain do not coincide with the crossover
G'(γ) = G''(γ) but with the increasing of the loss modulus and the decreasing of the storage modulus. Thanks to the analytical calculations,
it is also obvious that the stress response of yield stress fluids does not necessarily include even harmonics. In this
work the steady state stress response of the Prandtl element is also presented as Lissajous plots and Pipkin diagrams to visualise
the rheological fingerprint.
► Cite this publication as follows:
Boisly M, Kastner M, Brummund J, Ulbricht V: Large amplitude oscillatory shear of the Prandtl element analysed by Fourier Transform Rheology, Appl. Rheol. 24 (2014) 35478.
Katarina Dimic-Misic, Kaarlo Nieminen, Patrick A.C. Gane, Thad Maloney, Herbert Sixta, Jouni Paltakari
Deriving a process viscosity for complex particulate nanofibrillar cellulose gel-containing suspensions
Appl. Rheol. 24:3 (2014) 35616 (9 pages)
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Phase-separable particulate-containing gel structures constitute complex fluids. In many cases they may incorporate component
concentration inhomogeneities within the ensemble matrix. When formulated into high consistency suspensions, these
can lead to unpredictable time-dependent variations in rheological response, particularly under shear in simple parallel plate
and cylindrical rotational geometries. Smoothing function algorithms are primarily designed to cope with random noise. In
the case studied here, namely nanocellulose-based high consistency aqueous suspensions, the system is not randomised but
based on a series of parallel and serial spatial and time related mechanisms. These include: phase separation, wall slip, stress
relaxation, breakdown of elastic structure and inhomogeneous time-dependent and induced structure re-build. When vacuum
dewatering is applied to such a suspension while under shear, all these effects are accompanied by the development of
an uneven solid content gradient within the sample, which further adds to transitional phenomena in the recorded rheological
data due to spatial and temporal differences in yield stress distribution. Although these phenomena are strictly speaking
not noise, it is nevertheless necessary to apply relevant data smoothing in order to extract apparent/process viscosity parameters
in respect to averaging across the structural ensemble. The control parameters in the measurement of the rheological
properties, to which smoothing is applied, are focused on parallel plate gap, surface geometry, shear rate, oscillation frequency
and strain variation, and relaxation time between successive applications of strain. The smoothing algorithm follows the
Tikhonov regularisation procedure.
► Cite this publication as follows:
Dimic-Misic K, Nieminen K, Gane PA, Maloney T, Sixta H, Paltakari J: Deriving a process viscosity for complex particulate nanofibrillar cellulose gel-containing suspensions, Appl. Rheol. 24 (2014) 35616.
N. Antonova, N. Koseva, A. Kowalczuk, P. Riha, I. Ivanov
Rheological and electrical properties of polymeric nanoparticle solutions and their influence on RBC suspensions
Appl. Rheol. 24:3 (2014) 35190 (7 pages)
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Rheological and electrical properties of polymeric nanoparticle solutions and their influence on the rheological and electrical
properties of red blood cell (RBC) suspensions have been studied. Poly(acrylic acid) macromolecules of different architecture
and molecular weight were used: (i) a new core.shell type star polymer whose interior forms hyperbranched polystyrene
bearing arms of poly(acrylic acid) with molecular weight Mn = 56 920 Da and (ii) linear polyacrylic chains with average molecular
weights Mn = 6000, 20000, and 225000 Da. The polymers dissolved in physiological solution with weight concentrations
1 mg/ml and 0.2 mg/ml were used for the experiments. Under physiological conditions the star-shaped macromolecules present
spherical nanoparticles while the linear poly(acrylic acid)s adopt an extended chain conformation close to rod-like particles.
The apparent viscosity of the nanoparticle solutions and RBC suspensions in the presence and absence (the control) of
nanoparticles were measured using a rotational viscometer Contraves Low Shear 30 (LS 30) at a steady flow at shear rates
from 0.0237 to 94.5 s-1 and temperature 37 C.
A method, based on the measurement of dielectric properties of dispersed systems
in Couette viscometric blood flow was applied. A concurrent measurement system and data acquisition system implied
into the Contraves LS 30 were used to quantify the electrical conductivity. The main advantage of this technique is that blood
is subjected to a uniform shearing field in a Couette rheometric cell as well as the information about the mechanical and
electrical properties of the fluid is obtained in parallel. The results show that rheological and electrical properties of the
nanoparticle solutions and RBC suspensions, namely their electrical conductivity and apparent viscosity, are dependent on
the shear rates, shape, concentration and molecular weight of the polymers.
Key
► Cite this publication as follows:
Antonova N, Koseva N, Kowalczuk A, Riha P, Ivanov I: Rheological and electrical properties of polymeric nanoparticle solutions and their influence on RBC suspensions, Appl. Rheol. 24 (2014) 35190.
Hsiao Wei Tan, Misni Misran
Effect of chitosan-modified fatty acid liposomes on the rheological properties of the polysaccharide-based gel
Appl. Rheol. 24:3 (2014) 34839 (9 pages)
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Incorporation of liposome into gel is the most common approach for the preparation of topical and transdermal liposomal
formulation, due to the ability of liposome to improve the drug deposition and permeation rate within the skin. In this study,
the liposomal gel consisted of iota-carrageenan, carboxymethyl cellulose, and chitosan-coated-oleic acid liposome were prepared.
The effect of liposomes on the rheological properties of the iota-carrageenan-carboxymethyl cellulose mix gel was
evaluated. The rheological result indicated that the presence of the chitosan-coated-oleic acid liposomes in the gel had modified
the viscoelastic and flow characteristics of the gel. The input energy from the oscillatory test could be stored more effectively
in the elastic component of the liposomal gels, as compared to the original gel itself. This result showed that the liposomal
gels exhibited greater elasticity and were more solid-like when compared with the original gel system. The complex
viscosity of the liposomal gels was slightly higher than the original gel. The complex viscosity of the liposomal gels was also
found to decrease with increasing frequency, indicating the shear thinning behavior of the liposomal gels. The lower Power
Law Index (PDI) of the liposomal gels indicated a greater shear thinning behavior and better spreadability.
► Cite this publication as follows:
Tan HW, Misran M: Effect of chitosan-modified fatty acid liposomes on the rheological properties of the polysaccharide-based gel, Appl. Rheol. 24 (2014) 34839.
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