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  • 1
    Electronic Resource
    Electronic Resource
    Behavior of low molecular weight model HEUR associative polymers in concentrated surfactant systems (1993)
    s.l. : American Chemical Society
    Langmuir 9 (1993), S. 708-715 
    Details
    ISSN: 1520-5827
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/la00027a017
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of elongational flow on polymer adsorption (1988)
    s.l. : American Chemical Society
    Macromolecules 21 (1988), S. 1070-1074 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00182a038
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  • 3
    Electronic Resource
    Electronic Resource
    Hydrodynamic chromatography as a probe of polymer dynamics during flow through porous media (1989)
    s.l. : American Chemical Society
    Macromolecules 22 (1989), S. 775-781 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00192a044
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  • 4
    Electronic Resource
    Electronic Resource
    Comparison of galactomannan crosslinking with organotitanates and borates (1988)
    Springer
    Colloid & polymer science 266 (1988), S. 145-155 
    Details
    ISSN: 1435-1536
    Keywords: Crosslinking ; gelation ; titanate ; galactomannan ; guar ; dynamiclight scattering ; nuclear magnetic resonance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Water-soluble polymers crosslinked with metal ions form stable gels that are used in oil and gas production processes. We present an investigation of the chemistry of the binding between guar galactomannans and both borates and titanates using NMR and dynamic light scattering. The two monosaccharides comprising guar — methyl-β-D-galactopyranoside and methyl-α-D-mannopyranoside — have been studied as model compounds. High resolution13C NMR detected complexation of the sugars with borate but displayed no sign of complexation with either of the two titanates even at high titanate concentrations. Dynamic light scattering studies demonstrated the existence of colloidal titanium dioxide particles for both titanate crosslinkers. The loss of free titanium to the colloidal particles reduces the concentration of titanium crosslinking sites to below the detectable limits of NMR. The role of colloidal titanium dioxide colloids in these crosslinking reactions has not been reported previously. Data are presented following the growth of these particles with time as a function of pH and salt concentration. The observed particle growth kinetics explains the observed sensitivity of the guar gelation process to these variables.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01452812
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  • 5
    Electronic Resource
    Electronic Resource
    Electric-field-induced rupture of polymer-stabilized oil films (1999)
    Springer
    Colloid & polymer science 277 (1999), S. 957-964 
    Details
    ISSN: 1435-1536
    Keywords: Key words Emulsions ; Thin films ; Coalescence ; Graft copolymer ; Electroporation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Water-in-oil emulsions stabilized by polymeric surfactants are robust, but the reasons for their stability are poorly understood. We studied oil films stabilized by a comb–graft copolymer having a poly(siloxane) backbone and poly(ethylene oxide)/poly (propylene oxide) and C16 grafts (Abil EM-90) with a total number-average molecular weight of 62,000. Electric fields imposed in the aqueous phases on either side of the oil films were used to induce rapid rupture, and the response of the film was monitored using optical interference and electrical conductance measurements. Film thickness values ranged between 30 and 50 nm and rupture at field strength values between 2 × 107 and 5 × 107 V/m. Unexpectedly, in some cases, stable pores were formed and the films became electrically conductive. Often the pores persisted for more than 20 min after the voltage had been removed. Since the current was independent of film area, very few pores are involved in conduction. This behavior is similar to that found in lipid films; however, the persistence time is greater for polymer-stabilized films. Because the films are thick, it is possible that pores are formed by multimolecular self-assembly as with pore-forming proteins. Polymer purification also influenced film stability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003960050475
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  • 6
    Electronic Resource
    Electronic Resource
    Rheology of concentrated microgel solutions (1988)
    Springer
    Rheologica acta 27 (1988), S. 531-539 
    Details
    ISSN: 1435-1528
    Keywords: Yield stress ; yield strain ; strain modulus ; dynamic modulus ; microgel solution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract Viscosity, modulus, and yield stress for 0–6 wt% aqueous solutions of Carbopol 941 were investigated using constant shear rate, constant shear stress, and dynamic oscillatory experiments. The microgel character of the polymer was evident from the solid-like behavior of the solutions above 1 wt%. Yield stress increased with concentration, but yield occurred at a critical shear strain of 40%, independent of concentration. The static stress-strain relationship became non-linear at ~ 25% strain, in fair agreement with the onset of non-linear response in the storage modulus at ~ 10% strain. Small strain moduli from static and low frequency measurements agreed rather well; modulus values obtained from the recoverable strain after yielding were 30–40% smaller. Solutions flowed at near-constant stress in the low shear rate regime; at higher rates the stress increases with shear rate more rapidly. The viscosity did not obey the Cox-Merz rule. Steady-state viscosity scaled with polymer concentration to the 3/4 power. Results were interpreted using a cellular, deformable sphere model for the polymer, in analogy to emulsions and foams.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01329353
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  • 7
    Electronic Resource
    Electronic Resource
    Comparison of the rheology of polymer melts in shear, and biaxial and uniaxial extensions (1987)
    Springer
    Rheologica acta 26 (1987), S. 144-151 
    Details
    ISSN: 1435-1528
    Keywords: Extensional deformation ; polymer melt
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract The experimental properties of different polymer melts, polystyrene, high density polyethylene and low density polyethylene are compared for the first time in three different deformations: step shear, step biaxial extension and steady uniaxial extension. Properties of three other melts are also studied in step biaxial and shear experiments. For our comparative purposes some data of Laun and Winter from the literature are used, as well as new data reported here. In all the step strain experiments, the stresses can be factored into a time dependent relaxation modulus and a strain dependent damping function. The data are interpreted using a differential constitutive equation of Larson which satisfies this time-strain separability and has a single parameter that describes the strain softening character of the material. Results show that differences in the properties of the melts are most pronounced in uniaxial extension and least in biaxial extension. All melts follow the Doi-Edwards prediction relatively closely in biaxial extension. In uniaxial extension, the branched material shows a strong strain hardening effect although its shear and biaxial properties are similar to the other melts. The constitutive model gives a reasonably good fit to the data in all three deformations for unbranched materials for the same value of the adjustable parameter; the model, however, fails for the branched low density polyethylene.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01331972
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  • 8
    Electronic Resource
    Electronic Resource
    Effect of drop size distribution on the flow behavior of oil-in-water emulsions (1994)
    Springer
    Rheologica acta 33 (1994), S. 303-306 
    Details
    ISSN: 1435-1528
    Keywords: Oil-in-water emulsions ; steady shear viscosity ; drop size distribution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract The effect of drop size distribution on the viscosity was experimentally examined for oil-in-water emulsions at volume fractions of Φ = 0.5, 0.63 and 0.8. At Φ = 0.5, the hydrodynamic forces during drop collisions govern the viscosity behavior. The viscosity versus shear rate curve is scaled on the root-mean-cube diameter which is related to the number of drops per unit volume. At Φ = 0.8, the resistance to flow arises from the deformation and rearrangement of thin liquid films between drops. The viscosity at a given shear rate is inversely proportional to the volume-surface mean diameter which is related to the total interfacial area per unit volume. However, since the drops come into contact and the liquid film separating adjacent drops is generated without drop deformation at Φ = 0.63, the viscosity curve is not scaled on the mean diameter. The flow behavior near the critical volume fraction strongly depends not only on the mean drop size, but also on the width of the distribution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00366956
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  • 9
    Electronic Resource
    Electronic Resource
    Instabilities in multi-hole converging flow of viscoelastic fluids (1991)
    Springer
    Rheologica acta 30 (1991), S. 511-522 
    Details
    ISSN: 1435-1528
    Keywords: Flow instabilities ; spinneret ; Boger fluid ; multi-hole contraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract Studies of the onset of instabilities were conducted on single hole and multi-hole contractions using laser speckle visualization. A well characterized elastic fluid was used with constant viscosity of 13.1 Pa · s and elasticity characterized by a longest relaxation time constant of 2.233 s. The onset of instabilities was characterized in terms of the Deborah number and the contraction ratio. Three types of instabilities were observed: pulsing vortices, azimuthally rotating vortices, and swirling vortices. For the single hole contractions the critical Deborah number for instability increased from 4.4 to 5.07 to 5.25 as the contraction ratio increased from 4: 1 to 8: 1 to 12: 1. The magnitude of the instabilities was much greater for the 4: 1 contraction than for the other two contraction ratios. For the multi-hole contraction a square array of nine holes was used and the ratio of the hole diameter to hole spacing was varied. The height of the vortices is very similar for the single hole and multi-hole contractions at low Deborah numbers. At high Deborah numbers the effect of adjacent holes is to reduce the height of the vortices by a factor of three. For the 4: 1 spacing no secondary vortex was observed below a Deborah number of De = 3.7. Secondary vortices occurred for the 8:1 and 10:1 spacing at all Deborah numbers. Unstable pulsing vortices appeared for all spacings at a critical Deborah number around 5.5. Adjacent holes decreased the strength of the unsteady vortex motions. The centerline velocities were measured for the multi-hole contraction at shear rates of 5, 30, and 300 s−1. The elongational strain rates are similar at a low shear rate of 5 s−1. As shear rate is increased the onset of stretching occurs closer to the plane of the contraction for the smaller contraction ratios.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00444369
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  • 10
    Electronic Resource
    Electronic Resource
    Response of an elastic Bingham fluid to oscillatory shear (1987)
    Springer
    Rheologica acta 26 (1987), S. 428-436 
    Details
    ISSN: 1435-1528
    Keywords: ElasticBingham fluid ; yieldstress ; oscillatoryshear ; oil-in-wateremulsion ; nonlinear rheological behavior
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract The response of an elastic Bingham fluid to oscillatory strain has been modeled and compared with experiments on an oil-in-water emulsion. The newly developed model includes elastic solid deformation below the yield stress (or strain), and Newtonian flow above the yield stress. In sinusoidal oscillatory deformations at low strain amplitudes the stress response is sinusoidal and in phase with the strain. At large strain amplitudes, above the yield stress, the stress response is non-linear and is out of phase with strain because of the storage and release of elastic recoverable strain. In oscillatory deformation between parallel disks the non-uniform strain in the radial direction causes the location of the yield surface to move in-and-out during each oscillation. The radial location of the yield surface is calculated and the resulting torque on the stationary disk is determined. Torque waveforms are calculated for various strains and frequencies and compared to experiments on a model oil-in-water emulsion. Model parameters are evaluated independently: the elastic modulus of the emulsion is determined from data at low strains, the yield strain is determined from the phase shift between torque and strain, and the Bingham viscosity is determined from the frequency dependence of the torque at high strains. Using these parameters the torque waveforms are predicted quantitatively for all strains and frequencies. In accord with the model predictions the phase shift is found to depend on strain but to be independent of frequency.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01333843
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