scholarly journals Drag Reduction Performance of Mechanically Degraded Dilute Polyethylene Oxide Solutions

2020 ◽  
Vol 142 (9) ◽  
Author(s):  
Yasaman Farsiani ◽  
Zeeshan Saeed ◽  
Brian R. Elbing
Keyword(s):  
Molecular Weight ◽  
Drag Reduction ◽  
Polyethylene Oxide ◽  
Flow Behavior ◽  
Current Data ◽  
Turbulent Pipe Flow ◽  
Mechanical Degradation ◽  
Degraded Samples ◽  
The Mean ◽  
Mean Molecular Weight

Abstract Mechanical degradation of dilute solutions of polyethylene oxide (PEO) via chain scission was investigated within a turbulent pipe flow. Comparisons of the drag reduction performance with and without degradation were made by matching the onset of drag reduction conditions, which has been shown for PEO to be related to the mean molecular weight. The bulk flow behavior of both the degraded and nondegraded samples were generally consistent with trends observed in the literature, but a subset of conditions showed significant deviation in the slope increment (drag reduction performance) between the degraded and nondegraded samples. When they deviated, the degraded samples were consistently more efficient than the nondegraded samples even though they had the same mean molecular weight. The deviations were shown to scale with the normalized difference between the initial and final molecular weights. The current data and analysis as well as the literature suggest that the deviations in the polymer performance (slope increment) are related to changes in the molecular weight distribution. More specifically, the improved performance of the degraded samples relative to the nondegraded ones at the mean molecular weight of the degraded sample indicates an excess of longer polymer chains since the higher chain fractions in a degraded solution more effectively control the flow properties when within a certain degree of degradation and Reynolds number.

scholarly journals The Toms phenomenon: turbulent pipe flow of dilute polymer solutions

1967 ◽  
Vol 30 (2) ◽  
pp. 305-328 ◽  
Author(s):  
P. S. Virk ◽  
E. W. Merrill ◽  
H. S. Mickley ◽  
K. A. Smith ◽  
E. L. Mollo-Christensen
Keyword(s):  
Molecular Weight ◽  
Drag Reduction ◽  
Polymer Solution ◽  
Flow Structure ◽  
Pipe Flow ◽  
Turbulent Pipe Flow ◽  
Slip Model ◽  
Pipe Axis ◽  
Effective Slip ◽  
The Mean

Drag reduction caused by dilute, distilled water solutions of five polyethylene oxides, molecular weights from 80,000 to 6,000,000, in turbulent pipe flow was studied experimentally in 0·292 and 3·21 cm ID pipes. It was found that the onset of drag reduction occurs at a well-defined wall shear stress related to the random-coiling effective diameter of the polymer. Laminar to turbulent transition is not, in general, delayed. The extent of drag reduction induced by a homologous series of polymers in a given pipe is a universal function of concentration, flow rate, and molecular weight. The maximum drag reduction possible is limited by an asymptote that is independent of polymer and pipe diameter. Flow structure measurements in a single polymer solution, 1000 ppm of molecular weight 690,000, showed that the mean flow follows an ‘effective slip’ model. In this, the mean velocity profile consists of a ‘Newtonian plug’ convected along at an additional, ‘effective slip’ velocity. The turbulent flow structure follows the ‘effective slip’ model towards the pipe wall, but is significantly different from Newtonian towards the pipe axis; in particular, the inertial subrange observed in isotropic Newtonian turbulence was absent in an energy spectrum taken on the pipe axis in the polymer solution.

Turbulent flow drag reduction and degradation with dilute polymer solutions

1970 ◽  
Vol 43 (4) ◽  
pp. 689-710 ◽  
Author(s):  
R. W. Paterson ◽  
F. H. Abernathy
Keyword(s):  
Molecular Weight ◽  
Turbulent Flow ◽  
Drag Reduction ◽  
Average Molecular Weight ◽  
Experimental Studies ◽  
Polymer Degradation ◽  
High Viscosity ◽  
Turbulent Pipe Flow ◽  
Shear Stresses ◽  
Flow Drag

Experimental studies of drag reduction and polymer degradation in turbulent pipe flow with dilute water solutions of unfractionated polyethylene oxide are described. Drag reduction results indicate that the magnitude of the reduction cannot be correlated on the basis of weight average molecular weight, rather the phenomenon depends strongly on the concentration of the highest molecular weight species present in the molecular weight distribution. Polymer degradation in turbulent flow is found to be severe for high molecular weight polymers causing appreciable changes in drag reduction and molecular weight with the duration of flow. Data indicates that drag reduction exists in the limit of infinite dilution suggesting that the phenomenon is due to the interaction of individual polymer molecules with the surrounding solvent and that the extent of reduction is relatively independent of pipe diameter when a comparison is carried out at equal solvent wall shear stresses. Consideration of the high viscosity obtained with solutions in an irrotational laminar flow field suggests this is due to polymer molecule deformation and that this phenomenon is central to the mechanism of turbulent flow drag reduction.

Study of the Preparation and Degradable Characteristics of CaCO3-PE Film

2012 ◽  
Vol 499 ◽  
pp. 85-89
Author(s):  
Xue Yong Zhou ◽  
Xiang Yun Liu ◽  
Lei Lu ◽  
Lei Gu ◽  
Jing Jing Liu
Keyword(s):  
Molecular Weight ◽  
Tensile Strength ◽  
Ultraviolet Light ◽  
Light Irradiation ◽  
Breaking Elongation ◽  
Average Tensile Strength ◽  
Ultraviolet Light Irradiation ◽  
Filling Method ◽  
The Mean ◽  
Mean Molecular Weight

The CaCO3-polyethylene (PE) film was prepared by filling method, and the filling amount of calcium carbonate in film was 20%(w/w). The effects of natural weathering, ultraviolet light irradiation on the tensile strength, breaking elongation and molecular weight of the CaCO3-PE film was investigated comparing with the photosensitizer-PE film. After being located in the open air for 30 d, the average tensile strength, average breaking elongation and the mean molecular weight of CaCO3-PE film decreased 80.6%, 99.3% and 25.3%, respectively, as for the photosensitizer-PE film, the corresponding items decreased 18.8%, 45.0% and 11.7%, respectively. After ultraviolet light irradiation for 120 h, the average tensile strength of CaCO3-PE film decreased 29.9%, the average tensile strength of the photosensitizer-PE film, however, increased 20.5%. The average breaking elongation of CaCO3-PE film and photosensitizer-PE film decreased 97.3% and 84.1% respectively, the mean molecular weight of both films decreased 66.7% and 26.6% respectively. After covered by soil for 200 d, the weight loss of the CaCO3-PE film and photosensitizer-PE was 2.15% and 0.22%, respectively. The results showed that the degradability of CaCO3-PE film is superior to the photosensitizer-PE film.

Chlorinated Rubber and Nitrogenous Plasticizers. I. Viscosity of Mixtures of Chlorinated Rubber and Anhydroformaldehyde Urethan

1957 ◽  
Vol 30 (1) ◽  
pp. 274-282
Author(s):  
Michele Giua ◽  
Corrado Mancini
Keyword(s):  
Molecular Weight ◽  
Molecular Weights ◽  
Mixed Solutions ◽  
Quantitative Basis ◽  
The Mean ◽  
Mean Molecular Weight

Abstract The viscosities of solutions of chlorinated rubber in chloroform and in toluene and of mixed solutions of chlorinated rubber and anhydroformaldehyde urethan in toluene were measured. From the data it was possible to determine in an approximate way the mean molecular weight of chlorinated rubber and the mean molecular weights, determined viscometrically, of the mixtures. From the results it was, in turn, possible to derive the α coefficient in the relation of Kuhn. The action of anhydroformaldehyde urethan on chlorinated rubber could then be considered on a quantitative basis.

The Structure of Elastomers and Their Reactivity

1951 ◽  
Vol 24 (1) ◽  
pp. 95-98
Author(s):  
A. S. Kuz'minskii ◽  
N. N. Lezhnev
Keyword(s):  
Molecular Weight ◽  
Methyl Groups ◽  
Side Chains ◽  
Double Bonds ◽  
Gutta Percha ◽  
Different Temperatures ◽  
Spatial Configurations ◽  
The Mean ◽  
Kinetics Of ◽  
Mean Molecular Weight

Abstract It has not yet been ascertained what constituent parts within the structure of various elastomers have the greatest influence on the reactivity of the elastomers. There are indications that the side chains, the presence of methyl groups acting as substitutes, and differences in spatial configurations, etc., all have definite effects. The present authors have investigated the oxidation of several different elastomers at different temperatures. The experiments were carried out both in the presence and in the absence of an inhibitor (phenyl-β-naphthylamine). The elastomers and the inhibitor were first carefully purified. The kinetics of autoxidations were studied volumetrically by means of an apparatus already described by one of the authors. A chainless molecular introduction of oxygen into the double bonds of the elastomer in the presence of the inhibitor was studied with the aid of our own previously described inhibitor methods. The study included the oxidation of butadiene elastomers containing different distributions of double bonds in the main and side chains, divinylstyrene rubber, and the hydrocarbons of natural rubber and gutta-percha. These products are distinguished by their different degrees of unsaturation, the number of side chains, the number of double bonds in both their main and side chains, the length of their molecular chains (the mean molecular weight), and their spatial configurations.

Chromatographic Fractionation of Some Synthetic Elastomers

1948 ◽  
Vol 21 (3) ◽  
pp. 682-683 ◽  
Author(s):  
Ivan Landler
Keyword(s):  
Molecular Weight ◽  
Cellulose Acetate ◽  
Active Carbon ◽  
Low Molecular Weight ◽  
High Polymer ◽  
Acrylonitrile Copolymer ◽  
Molecular Weights ◽  
The Mean ◽  
Mean Molecular Weight ◽  
Poor Solvent

Abstract Mark and Saito were the first to fractionate a high polymer (cellulose acetate) by chromatographic adsorption on blood carbon. They found that molecules of low molecular weight were adsorbed first, and that the mean molecular weight of the product which remained unadsorbed was higher than the original molecular weight. Levi and Giera confirmed this result, but did not succeed in fractionating Buna-S or polyisoprene, for these polymers were eluted by the solvent during the washing operation in the column. The present authors have carried out further experiments in this field with a study of three commercial synthetic elastomers, viz., GR-S (butadienestyrene copolymer), Perbunan-N (butadiene-acrylonitrile copolymer), and Visitanex (polyisobutylene). The polymer was adsorbed by starting with a poor solvent composed of a mixture of toluene and methanol ; the quantity of alcohol added was just below the threshold of precipitation. The adsorbent used was a mixture of 75 per cent of lamp black (80 square meters per gram) and 25 per cent of coarse active carbon. The latter served to prevent agglomeration of the lamp black. The adsorbent was divided into three layers, of 10 grams each. At the end of the tube was a filter of fritted glass. Filtration was carried out under pressure, the rate of flow thereby being maintained constant, The polymers were characterized by their intrinsic viscosities. The molecular weights which were estimated by means of the relation, found experimentally between the molecular weight and viscosity, are only approximate, for this relation holds true only for narrow fractions.

scholarly journals Which physics determines the location of the mean molecular weight minimum in red giants?

2014 ◽  
Vol 443 (2) ◽  
pp. 977-984 ◽  
Author(s):  
Ross P. Church ◽  
John Lattanzio ◽  
George Angelou ◽  
Christopher A. Tout ◽  
Richard J. Stancliffe
Keyword(s):  
Molecular Weight ◽  
Red Giants ◽  
The Mean ◽  
Mean Molecular Weight
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