Shear Dependence of Viscosity and Molecular Weight Transitions. A Study of Entanglement Effects

1967 ◽  
Vol 40 (2) ◽  
pp. 522-531
Author(s):  
Suresh N. Chinai ◽  
William C. Schneider
Keyword(s):  
Molecular Weight ◽  
Shear Rate ◽  
Polymer Solutions ◽  
Shear Rates ◽  
Molecular Weights ◽  
Critical Molecular Weight

Abstract Flow of concentrated polymer solutions covering molecular weights up to 150,000 was examined at shear rates up to 200,000 sec−1. The viscosity, molecular weight, and shear rate results of previous workers recognizing only single critical molecular weight M*, above which ordinary Bueche entanglements dominated the flow, were compared with our findings in which two distinct critical molecular weights, upper M* and lower M** exist. These results are compared with the theory, and new interpretations are presented.

Nonnewtonian Flow of Poly(Dimethyl Siloxane)

1967 ◽  
Vol 40 (5) ◽  
pp. 1483-1491
Author(s):  
Yoshio Ito
Keyword(s):  
Shear Rate ◽  
Polymer Solutions ◽  
Flow Behavior ◽  
Degree Of Polymerization ◽  
High Shear ◽  
Newtonian Viscosity ◽  
Shear Rates ◽  
Molecular Weights ◽  
Dimethyl Siloxane ◽  
Wide Range

Abstract Nonnewtonian flow of poly(dimethyl siloxanes) of various molecular weights has been studied with a short capillary viscosimeter. The experiment covered a wide range of shear rate, from 10−1 to 3×106sec−1. Results were as follows: (1) Flow behavior of the sample changes with the degree of polymerization. For siloxanes with degrees of polymerization less than 1.55×102, flow of the fluid is newtonian throughout the whole range of shear rates; for siloxanes with degrees of polymerization from 3.22×102 to 2.63×103, flow is nonnewtonian at moderate shear rates; it again becomes newtonian at high shear rates. With degrees of polymerization more than 3.31×103, the spiral flow rises to a high shear rate. (2) Plow behavior of the samples is expressed by modifying Shishido's equation proposed for nonnewtonian polymer solutions. (3) When the observed flow curve contains its inflection point, the upper newtonian viscosity can be estimated by a new method proposed here. (4) The relations among the end correction of capillary, the pressure loss, and the shear stress proposed by Shishido for polymer solutions are applicable to poly(dimethy! siloxane) also.

Rheological Properties of Polybutadienes Prepared by n-Butyllithium Initiation

1965 ◽  
Vol 38 (4) ◽  
pp. 881-892
Author(s):  
J. T. Gruver ◽  
Gerard Kraus
Keyword(s):  
Molecular Weight ◽  
Shear Rate ◽  
Flow Behavior ◽  
Average Molecular Weight ◽  
Polymer System ◽  
Newtonian Flow ◽  
Newtonian Viscosity ◽  
Long Chain Branching ◽  
Shear Rates ◽  
Molecular Weights

Abstract The flow behavior of n-butyllithium-polymerized polybutadienes was investigated as a function of molecular weight, temperature, and shear rate. At low shear rates these polymers exhibit Newtonian flow up to molecular weights of several hundred thousand so that “zero shear” Newtonian viscosities can readily be determined without the risk of long extrapolation. Above 10,000 molecular weight the Newtonian viscosities obey the well-known 3.4 power dependence on weight-average molecular weight. The entanglement spacing molecular weight is estimated at 5600. The temperature dependence of viscosity is substantially independent of molecular weight and shear stress and can be represented analytically by functions proposed in the literature. The apparent activation energy for viscous flow is not constant, but decreases with rising temperature. The flow of the polymers becomes increasingly non-Newtonian with the product of shear rate, molecular weight and Newtonian viscosity. However, the departure from Newtonian behavior is apparently less than for any polymer system whose flow behavior has been described in the literature. The indications are, therefore, that sharp molecular weight distribution and freedom from long chain branching favor Newtonian flow and that the n-butyllithium initiated polybutadienes represent some of the most perfectly linear, narrow distribution polymers known.

Temperature dependence of tracer diffusion coefficients in polystyrene

1986 ◽  
Vol 1 (1) ◽  
pp. 202-204 ◽  
Author(s):  
Peter F. Green ◽  
Edward J. Kramer
Keyword(s):  
Molecular Weight ◽  
Diffusion Coefficient ◽  
Shear Rate ◽  
Temperature Dependence ◽  
Diffusion Coefficients ◽  
Tracer Diffusion ◽  
Tracer Diffusion Coefficient ◽  
Critical Molecular Weight ◽  
Tracer Diffusion Coefficients ◽  
Monomeric Friction Coefficient

The temperature dependence of the tracer diffusion coefficient D* of long deuterated polystyrene (d-PS) chains of molecular weight M>Mc, where Mc is the critical molecular weight for entanglement, diffusing into highly entangled PS matrices, each of molecular weight P = 2×107, is studied using forward recoil spectrometry. It is found that the temperature dependence of D*/T, reflected primarily in the monomeric friction coefficient, is accurately described by a Vogel equation. The constants that are used to fit these results are independent of M and are the same as those used to fit the temperature dependence of the zero shear rate viscosity of polystyrene.

Experimental Study on Flow-Front Fingering Instabilities in Injection Molding of Polymer Solutions and Melts

2004 ◽  
Author(s):  
Kalonji K. Kabanemi ◽  
Jean-Franc¸ois He´tu ◽  
Samira H. Sammoun
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Polymer Solutions ◽  
Low Molecular Weight ◽  
Flow Front ◽  
High Molecular Weight Polymer ◽  
Molecular Weight Polymer ◽  
Polymer Molecules ◽  
Molecular Weights ◽  
Solvent Molecules

An experimental investigation of the flow behavior of dilute, semi-dilute and concentrated polymer solutions has been carried out to gain a better understanding of the underlying mechanisms leading to the occurrence of instabilities at the advancing flow front during the filling of a mold cavity. Experiments were performed using various mass concentrations of low and high molecular weight polyacrylamide polymers in corn syrup and water. This paper reports a new type of elastic fingering instabilities at the advancing flow front that has been observed only in semi-dilute polymer solutions of high molecular weight polymers. These flow front elastic instabilities seem to arise as a result of a mixture of widely separated high molecular weight polymer molecules and low molecular weight solvent molecules, which gives rise to a largely non-uniform polydisperse solution, with respect to all the kinds of molecules in the resulting mixture (solvent molecules and polymer molecules). The occurrence of these instabilities appears to be independent of the injection flow rate and the cavity thickness. Moreover, these instabilities do not manifest themselves in dilute or concentrated regimes, where respectively, polymer molecules and solvent molecules are minor perturbation of the resulting solution. In those regimes, smooth flow fronts are confirmed from our experiments. Based on these findings, the experimental investigations have been extended to polymer melts. Different mixtures of polycarbonate melts of widely separated molecular weights (low and high molecular weights) were first prepared. The effect of the large polydispersity of the resulting mixtures on the flow front behavior was subsequently studied. The same instabilities at the flow front were observed only in the experiments where a very small amount of high molecular weight polycarbonate polymer has been mixed to a low molecular weight polycarbonate melt (oligomers).

scholarly journals High Performance Conditioning Shampoo with Hyaluronic Acid and Sustainable Surfactants

Cosmetics ◽  
2021 ◽  
Vol 8 (3) ◽  
pp. 71
Author(s):  
Kelly Yorke ◽  
Samiul Amin
Keyword(s):  
Molecular Weight ◽  
Surface Tension ◽  
Hyaluronic Acid ◽  
High Performance ◽  
Low Cost ◽  
Hair Follicles ◽  
Shear Rates ◽  
Molecular Weights ◽  
Surface Activity Properties ◽  
Alkyl Polyglucoside

Recently, consumers have become invested in more natural and sustainable ingredients contained in personal care products. Unfortunately, cationic surfactants are still heavily relied on as primary conditioning agents in products such as conditioning shampoos because of their ability to cling well to the negatively charged surface of hair follicles. Additionally, sulfates are utilized as cleansing agents because they are highly effective and low cost. The objective of this study is to find a more sustainable formulation for a conditioning shampoo without compromising the desired wet combing, rheological, and surface activity properties. The systems which were investigated contained hyaluronic acid (HA) at a variety of molecular weights and concentrations, in combination with a surfactant, either acidic sophorolipid (ASL) or alkyl polyglucoside (APG), and varying the presence of sodium chloride. A Dia-stron was utilized to test the wet combing force, a rheometer recorded the viscosity at various shear rates, and a tensiometer measured the surface tension of the samples before a visual foaming study was conducted. Molecular weight and concentration seemed to have a large impact on wet combing force, as well as rheology, with the largest molecular weight and concentration producing the lowest friction coefficient and desired rheological profile. The addition of a surfactant significantly aids in the reduction in surface tension and increased foamability. Therefore, the optimal system to achieve the largest reduction in wet combing force, large viscosity with shear-thinning behavior, and relatively low surface tension with decent foaming is composed of 1% HA at 800 kDa, 10% ASL and 1% NaCl. This system shows a viable sulfate-free and silicone-free option that can achieve both conditioning and cleansing.

Molecular Degradation of Lubricants in Sliding Elastohydrodynamic Contacts

1975 ◽  
Vol 97 (3) ◽  
pp. 390-395 ◽  
Author(s):  
D. L. Walker ◽  
D. M. Sanborn ◽  
W. O. Winer
Keyword(s):  
Molecular Weight ◽  
Weight Loss ◽  
Small Samples ◽  
Lubricant Degradation ◽  
Shear Rates ◽  
Molecular Weights ◽  
Average Shear ◽  
Bulk Polymers ◽  
Energy Dissipated ◽  
Viscosity Changes

The extent of lubricant degradation in a sliding elastohydrodynamic contact has been investigated. The lubricant was subjected to peak Hertz pressures of approximately 109 N/m2 and average shear rates of 106 to 107 s−1. Hydrocarbon lubricants, bulk polymers and polymer containing hydrocarbon solutions were examined. Small samples (10−8m3) of test lubricant were extracted from the entrance and exit regions of the EHD contact. These samples were then analyzed to determine alterations in the molecular weight distribution. In addition, a microcapillary viscometer was developed to determine viscosity changes. Degradation resulting in up to a 70 percent viscosity loss was found in fluids which had molecular weights of over 1000. High degrees of correlation were found between molecular weight loss, viscosity loss and the energy dissipated in the contact.

Rheological Properties of Multichain Polybutadienes

1965 ◽  
Vol 38 (4) ◽  
pp. 893-906 ◽  
Author(s):  
Gerard Kraus ◽  
J. T. Gruver
Keyword(s):  
Molecular Weight ◽  
Branched Polymers ◽  
Linear Polymers ◽  
Newtonian Viscosity ◽  
Zero Shear Viscosity ◽  
Shear Rates ◽  
Molecular Weights ◽  
High Shear Rates ◽  
Long Chain ◽  
Newtonian Behavior

Abstract The introduction of one or two long chain branches into a polybutadiene molecule to form trichain or tetrachain molecules, respectively, leads to profound changes in Theological behavior. At low molecular weights the Newtonian (zero shear) viscosity is decreased relative to a linear polymer of the same molecular weight. At molecular weights exceeding 60,000 (trichain) or 100,000 (tetrachain), the Newtonian viscosity rises rapidly above the corresponding value for a linear polybutadiene. However, non-Newtonian behavior of the branched polymers becomes more pronounced the higher the molecular weights, so that at moderate to high shear rates the viscosity of the branched polymers is uniformly lower than that of linear polymers of identical molecular weight.

New Absolute Molecular Weight Method—Linear High Polymers

1959 ◽  
Vol 32 (1) ◽  
pp. 97-98
Author(s):  
F. Bueche ◽  
S. W. Harding
Keyword(s):  
Molecular Weight ◽  
Shear Rate ◽  
Shear Viscosity ◽  
Rate Dependence ◽  
Zero Shear Viscosity ◽  
Molecular Weights ◽  
Weight Method ◽  
Shear Rate Dependence ◽  
High Polymers

Abstract It has been shown that the shear-rate dependence of the viscosity of concentrated polymer solutions can be explained in terms of known parameters of the solution. If the concentration, temperature, zero shear viscosity, and molecular weight of the polymer are known, the decrease in viscosity with increasing shear rate can be predicted. Conversely, if one measures the shear-rate dependence of the viscosity, the molecular weight may be computed. We believe this provides a convenient method for the absolute determination of molecular weights of linear, coiling, high polymers.

scholarly journals Rheopectic Behavior for Aqueous Solutions of Megamolecular Polysaccharide Sacran

Biomolecules ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 155 ◽  
Author(s):  
Fitri Adila Amat Yusof ◽  
Miho Yamaki ◽  
Mika Kawai ◽  
Maiko K. Okajima ◽  
Tatsuo Kaneko ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Shear Rate ◽  
Aqueous Solutions ◽  
Shear Viscosity ◽  
Shear Rates ◽  
Viscosity Increase ◽  
Thixotropic Behavior ◽  
Transition Concentration ◽  
Gelation Concentration ◽  
Low Shear

The rheopectic behavior of sacran aqueous solutions, a natural giant molecular polysaccharide with a molecular weight of 1.6 × 107 g/mol, was investigated. When a low shear was applied to 1.0 wt.% sacran solution, the shear viscosity increased from 7.2 to 34 Pa·s. The increment in the viscosity was enhanced as the shear rate decreased. The shear viscosity was independent of the time at a shear rate of 0.8 s−1; simultaneously, thixotropic behavior was observed at shear rates higher than 1.0 s−1. A crossover was observed at 0.15 wt.% for the concentration dependence of both the viscosity increase and zeta potential, which was the vicinity of the helix transition concentration or gelation concentration. It was clear that the molecular mechanism for the rheopexy was different at lower and higher regions of the crossover concentration.

Shear Viscosities of Ionic Polyacrylamide Solutions

1972 ◽  
Vol 12 (06) ◽  
pp. 469-473 ◽  
Author(s):  
Necmettin Mungan
Keyword(s):  
Porous Medium ◽  
Porous Media ◽  
Shear Rate ◽  
Polymer Solution ◽  
Polymer Solutions ◽  
Mobility Control ◽  
Permeability Reduction ◽  
Experimental Conditions ◽  
Molecular Weights ◽  
Stock Solutions

Abstract Solutions of ionic polyacrylamide polymers behave pseudoplastic in purely viscometric flow. Flow rate, polymer molecular weight and electrolytes affect solution viscosities to a large extent. Equations are given for the viscosity-shear rate relations in a form that can be used conveniently to account for the effect of viscosity on mobility. Introduction Polymers are being used increasingly in oil recovery operations, and therefore, an understanding of their flow behavior is gaining pragmatic importance. Past studies have shown that in the flow of polymeric fluids through porous media, the increase in solution viscosity, decrease in permeability, and viscoelastic deformations cause permeability, and viscoelastic deformations cause the fluid mobility to be greatly reduced. In general, viscoelasticity, i.e., extensional flow, is not so important because, for the largest part of a reservoir, polymer solution moves at very low and fairly steady polymer solution moves at very low and fairly steady velocities. Jennings et al. have concluded this for the specific polymers that they studied. Permeability reduction plays an important role in Permeability reduction plays an important role in the mobility control, particularly in porous media having low permeabilities initially. Reductions ranging from 25 to 70 times have been reported. However, the alterations that take place in a porous medium during polymer flow, the coupling between the geometry of the porous medium and the properties of the flowing fluid, and the influence of the flow regime on permeability have not been looked into in sufficient detail. A separate study, directed to the understanding of these important phenomena is required. In the present work, the purely viscous behavior of solutions of three partially hydrolized polyacrylamide polymers was obtained under experimental conditions far polymers was obtained under experimental conditions far more extensive than any reported in the literature. Some data have been available in the past for two of the polymers, but the third is a new polymer for which no data have been reported before. Using a Weissenberg rheogoniometer, Cannon-Fenske viscometers, and various capillary cubes, viscosities were measured over 8 decades of shear rate, ranging from 10 to to 10 (5) sec-1. These are the limits of measurable rates of shear and cover those that may apply to flow in reservoirs. Distilled water and various NaCl solutions were used as solvents to afford comparison of the rheological properties between fresh and saline solutions. Measurements were also made with solutions containing calcium' and magnesium to study the effect of divalent cations. EXPERIMENTAL The three polymers, Nos. 500, 700 and NC 1870, are partially hydrolized polyacrylamides manufactured by The Dow Chemical Co., and were from lots 8085, 52 and 87-8100E, respectively. Polymer NC 1870 is currently at a developmental stage and can be obtained in limited quantities; the other two have been available commercially for some time, have been used in the laboratory and in the field. All three are hydrolized to the same extent, containing approximately 25 percent polyacrylate, with the remainder being polyacrylamide. The molecular weights of Nos. 500 and 700 are 2 to 3 and 3 to 7 million, respectively. That of the NC 1870 is higher, but has not been measured due to the usual difficulties in measuring such high molecular weights. Polymer and salt concentrations are given on a weight-parts per million basis. Reagent grade chemicals and double-distilled deaerated water, having a pH of 6.5, were used in all solutions. Formaldehyde was added as a bactericide. To the extent possible, air was kept out of the solutions to avoid oxidation-type degradation of the polymers. Polymer solutions were mixed using magnetic Polymer solutions were mixed using magnetic stirrers and carefully avoiding any mechanical degradation. Solutions of desired concentrations were prepared from stock solutions by dilution. The latter had been passed through 1-micron millipore filters, were optically clear, containing no fish-eyes. The polymer concentration of stock solutions was determined by turbidimetry and nitrogen analysis, the two methods usually agreeing within a few percent. percent. SPEJ P. 469

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