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1.
Y. Auffret D. C. D. Roux N. El Kissi D. E. Dunstan I. Pignot-Paintrand 《Rheologica Acta》2009,48(4):423-432
We present the results of extensive strain- and stress-controlled rheometry performed on an AOT–water–iso-octane system, which
forms lamellar structures with a high density of topological defects. In spite of different time-scales, both measurement
methods, strain- and stress-controlled, are shown to be controlled by the level of strain experienced by the material. In
both cases, after a complex transition, an apparent steady state is reached. Whereas both apparent steady states are identical
for intermediate shear rate and shear stress following a power law, these are found to differ once the lower values of applied
shear rate and shear stress are considered. The origin of this difference is discussed in terms of supplied energy to the
sheared sample.
I. Pignot-Paintrand is affiliated with The Université Joseph Fourier and member of the Institut de Chimie Moléculaire de Grenoble 相似文献
2.
Einsatz von DMS- und Piezomeßtechnik zur direkten Schubspannungsermittlung in der Kapillarrheometrie
P. Braun 《Rheologica Acta》1990,29(3):243-251
Zusammenfassung Der Stand der Kapillarheometrie mit den Vor- und Nachteilen der einzelnen Systeme und Meßverfahren wird dargestellt. Ausgehend von diesem Stand werden zwei alternative Meßverfahren, nämlich Piezo-Einzelkraftund DMS-Meßverfahren, zur direkten Schubspannungsermittlung besprochen und eine nach diesem Prinzip konzipierte Versuchsdüse vorgestellt. Die mit dieser Düse erhaltenen Meßergebnisse zeigen im Vergleich zu konventionell, d. h. unter Anwendung des Bagley-Verfahrens, ermittelten Fließkurven im Falle der Einzelkraftmessung gute Übereinstimmung. Das Problem der Einlaufdruckkorrektur ist bei diesem Konzept von vornherein nicht vorhanden, und der ununterbrochene Fließkanal erlaubt, bei entsprechender Erweiterung auf zwei Kraftaufnehmer, einen unproblematischen Einsatz im On-line- oder sogar im In-line-Betrieb in der Polymerverarbeitung.Schlüsselwörter Rheometrie; Kapillarrheometrie; Schubspannungsermittlung; Piezokraftmessung; DMS-Anwendung; Kunststoffschmelzen; On-line-Rheometrie
The state-of-the-art of capillary rheometry, especially the advantages and disadvantages of different systems, is presented. Two measuring methods, a piezo single-force transducer, and a strain-gauge device combined in a testing die are compared. The strain gauges are fixed at the outside of a small capillary to detect the resulting wall shear stress between inner surface of the die and polymer flow by measuring the axial strain in the wall of the die. The single force method uses an elastic section of the die which uncouples the die from the supporting structure without changing the cross-section of the flow. The uncoupled part of the die is supported by a stiff, piezo-force transducer that detects the integral effect of wall shear stress. The resulting flow curves compare well with those using the Bagley method. With the novel die no entrance pressure-loss correction is needed. In principle, it also could be used as an on-line device for polymer processing.
Vortrag, gehalten auf der Jahrestagung der Deutschen Rheologischen Gesellschaft, TH Darmstadt, 19.–21. April 1989. 相似文献
3.
Nicolas Sbirrazzuoli Alice Mititelu-Mija Luc Vincent Camille Alzina 《Thermochimica Acta》2006,447(2):167-177
The curing reaction of stoichiometric and off-stoichiometric diglycidyl ether of bisphenol A (DGEBA) and 1,3-phenylene diamine (m-PDA) mixtures was studied by differential scanning calorimetry, thermogravimetric analysis and rheological measurements. In order to highlight the side reactions such as etherification and homopolymerization, the neat DGEBA and DGEBA/DMBA (N,N-dimethylbenzylamine) mixture were examined. The classical model-fitting and the advanced isoconversional methods were used to determine the activation energy of the different reactions. The advanced isoconversional method leads to a good agreement between isothermal, nonisothermal and rheological results. The effective activation energies of primary amine epoxy reaction, etherification and homopolymerization were estimated to about 55-60, 104 and 170 kJ mol−1, respectively. 相似文献
4.
The complex velocity field of an oscillating Couette flow is measured with a Laser-Doppler velocimeter. Different evaluation methods are used for the determination of material functions such as relaxation times and the dynamic complex viscosity. 相似文献
5.
This paper investigates the thermal gelation of a chitosan-β-glycerophosphate system using rheometry. The gelation, performed
for two polymer concentrations, was achieved in isothermal conditions to examine the effect of various temperatures (between
35 and 65 °C) on the sol-gel transition. The oscillatory shear data was used to verify the scaling behavior (G′ ~ G″ ~ ω
n
) at the gel point, and the power-law index n was found to be dependent to some extent on chitosan concentration and temperature. The solutions zero shear viscosity (η
0) and the gels low frequency modulus (G
e) were analyzed in terms of the relative distance to gelation time (ɛ). The two properties showed power–law relationships with ɛ, i.e., η
0 ~ ɛ
−s
and G
e ~ ɛ
z, and the indexes slightly increased with temperature. The dynamic scaling theory predicts a relationship between the indexes,
i.e., n
=
z/(z
+
s), and this was in reasonably good agreement with the experimental findings. 相似文献
6.
The effects of complex formation between sodium dodecylsulfate (SDS) and the positively charged (3-(2-methylpropionamide)propyl)trimethyl-ammonium
chloride-acrylamide (MAPTAC-AM) copolymer have been studied in dilute and semidilute aqueous solution in the presence of 10 mM
NaCl. Two different charge densities of the copolymer have been used in the study: 0.31 and 0.66, corresponding to the proportion
of MAPTAC units. Dynamic light scattering (DLS) and rheometry (static low-shear and capillary viscometry) have been performed
on the systems at different charge ratios, i.e., SDS/MAPTAC molar ratios, r. Regarding the phase behavior, the maximum binding ratio prior to precipitation differs between the copolymers. A 1.0% w/v
solution of SDS/31% MAPTAC-AM is soluble at r = 0.4 , while an SDS/66% MAPTAC-AM solution of 1.0% w/v shows phase separation at this ratio. With excess surfactant, the
complex in the former system is resolubilized at r=2.0, whereas the latter system is still phase-separated at r=5.0. DLS results show that, for both copolymers, the hydrodynamic radius, R
h, of the single-chain copolymer-surfactant complex decreases as a function of r, but then increases slightly prior to phase separation. The corresponding hydrodynamic virial coefficient, k
D, changes in the same manner as R
h. The light-scattering data also show that the formation of larger structures is promoted as the polymer concentration is
increased from 0.2 to 1.0% w/v. This is shown by the increase in the relative aggregate-to-single coil peak areas in the relaxation
time distributions. Both systems have this common trend. The results from rheological measurements support the results from
DLS. A reduction in intrinsic viscosity, [η], is observed on increasing r up to phase separation. The major part of the static low-shear measurements showed Newtonian behavior for both systems at
different copolymer concentrations (27.6–138 mM), and at different r. These systems, partially ionic polymer/oppositely charged surfactant, present very interesting rheological behavior at relatively
high polymer concentrations and at low r values. Their behavior is similar to those of hydrophobically modified polyelectrolytes.
Received: 17 June 1998 Accepted: 12 August 1998 相似文献
7.
G. H. Meeten 《Rheologica Acta》2008,47(8):883-894
The rheology and slip of a dry shaving foam are investigated using squeeze-flow and rotating-vane methods. Constant-force
squeeze flow between planar surfaces is used to study the effect of surface roughness on slip and to obtain the yield stress.
Non-slip vane measurements are used to obtain the linear shear viscosity and elasticity at small strains, and the yield stress
and strain at large strains. Data are compared with the small-strain Maxwell and Kelvin–Voigt linear-viscoelastic models.
An apparent dependence of the yield stress and elasticity on the rotational speed of the vane is shown to result from time-dependent
rheological parameters as the foam ages. The effect of viscosity in the pre-yield region may give an erroneous identification
of yield. 相似文献
8.
Rheometry for large-particulated fluids: analysis of the ball measuring system and comparison to debris flow rheometry 总被引:2,自引:0,他引:2
M. Schatzmann G. R. Bezzola H.-E. Minor E. J. Windhab P. Fischer 《Rheologica Acta》2009,48(7):715-733
For large-particulated fluids encountered in natural debris flow, building materials, and sewage treatment, only a few rheometers
exist that allow the determination of yield stress and viscosity. In the present investigation, we focus on the rheometrical
analysis of the ball measuring system as a suitable tool to measure the rheology of particulated fluids up to grain sizes
of 10 mm. The ball measuring system consists of a sphere that is dragged through a sample volume of approximately 0.5 l. Implemented
in a standard rheometer, torques exerted on the sphere and the corresponding rotational speeds are recorded within a wide
measuring range. In the second part of this investigation, six rheometric devices to determine flow curve and yield stress
of fluids containing large particles with maximum grain sizes of 1 to 25 mm are compared, considering both rheological data
and application in practical use. The large-scale rheometer of Coussot and Piau, the building material learning viscometer
of Wallevik and Gjorv, and the ball measuring system were used for the flow curve determination and a capillary rheometer,
the inclined plane test, and the slump test were used for the yield stress determination. For different coarse and concentrated
sediment–water mixtures, the flow curves and the yield stresses agree well, except for the capillary rheometer, which exhibits
much larger yield stress values. Differences are also noted in the measuring range of the different devices, as well as for
the required sample volume that is crucial for application. 相似文献
9.
Patrice Estell Christophe Lanos Arnaud Perrot 《ournal of non Newtonian Fluid Mechanics》2008,154(1):31-38
This paper presents an approach to computing the shear flow curve from torque–rotational velocity data in a Couette rheometer. The approximation techniques in shear rate calculation are generally dictated by the radius ratio between coaxial cylinders and the rheological behaviour of fluid tested. Here, the approach consists in analysing the sheared material as a Bingham fluid and computing an average shear rate when the fluid in the cylindrical gap is partially and fully sheared. We focus in particular on the applicability of the Bingham approximation in shear rate calculation. First, the approach is assessed by examining synthetic data generated with Newtonian, non-Newtonian and yield stress materials with known properties, varying the gap radius ratio. The results, which are compared with commonly used techniques in shear rate calculation, prove the relevance of the proposed approach. Finally, its efficiency is examined by applying it to process Couette data of yield stress fluids taken from published works. 相似文献
10.
This paper gives details of new data on neutralized Carbopol 940 dispersions. Appropriate techniques have been used to characterize the physical properties of the bulk gel and inter-phase slip at the wall. Previously published data are analysed and used wherever possible. Terminology and measurement difficulties are also addressed. 相似文献