A Study of Particle Settling in Non-Newtonian Fluids—Part II: Rheological Characterization of Polymer Solutions

1994 ◽  
Vol 116 (1) ◽  
pp. 16-21 ◽  
Author(s):  
L. Jin ◽  
M. E. Chenevert
Keyword(s):  
Relaxation Times ◽  
Maxwell Model ◽  
Cellulose Derivatives ◽  
Rheological Characterization ◽  
Frequency Pattern ◽  
High Molecular Weight Polymer ◽  
Molecular Weight Polymer ◽  
Shear Thinning Fluids ◽  
Viscous Shear ◽  
Frequency Sweeps

Aqueous solutions of different concentrations of three polymers: a synthetic high molecular weight polymer, partially hydrolyzed polyacrylamide (PHPA), a xanthantype biopolymer (Xanvis), and a cellulose-type polymer (HEC) were investigated in this study. It was found that the steric arrangement of molecules or interactions between molecules can be detected by a systematically designed strain and frequency sweep measurement, and is reflected by the different relaxation times of the solutions. The degree of elasticity can be quantified by G′/|G*| in linear viscoelastic range. The responses of the fluids to frequency sweeps are displayed in a normalized moduli versus normalized frequency pattern derived from the Maxwell model. Results show that within the tested concentration ranges, PHPA solutions are highly elastic with moderate relaxation times that are strain and concentration insensitive. Xanvis solutions are also highly elastic, but with high relaxation times that are both strain and concentration sensitive, indicating a different mechanism of elasticity compared to PHPA solutions. HEC (cellulose derivatives) are mostly viscous shear thinning fluids with weak elasticity and short relaxation times that are insensitive to strain, but sensitive to concentration.

Computational steering in Monte Carlo simulations of thin film polystyrene

2005 ◽  
Vol 363 (1833) ◽  
pp. 1961-1974 ◽  
Author(s):  
Daniel R Mason ◽  
Adrian P Sutton
Keyword(s):  
Thin Film ◽  
Monte Carlo ◽  
Relaxation Times ◽  
Polymer System ◽  
Atomic Scale ◽  
Computational Steering ◽  
High Molecular Weight Polymer ◽  
Molecular Weight Polymer ◽  
Current State ◽  
Mc Simulation

High molecular weight polymer systems show very long relaxation times, of the order of milliseconds or more. This time-scale proves practically inaccessible for atomic-scale dynamical simulation such as molecular dynamics. Even with a Monte Carlo (MC) simulation, the generation of statistically independent configurations is non-trivial. Many moves have been proposed to enhance the efficiency of MC simulation of polymers. Each is described by a proposal density ( x ′; x ): the probability of selecting the trial state x ′ given that the system is in the current state x . This proposal density must be parametrized for a particular chain length, chemistry and temperature. Choosing the correct set of parameters can greatly increase the rate at which the system explores its configuration space. Computational steering (CS) provides a new methodology for a systematic search to optimize the proposal densities for individual moves, and to combine groups of moves to greatly improve the equilibration of a model polymer system. We show that monitoring the correlation time of the system is an ideal single parameter for characterizing the efficiency of a proposal density function, and that this is best evaluated by a distributed network of replicas of the system, with the operator making decisions based on the averages generated over these replicas. We have developed an MC code for simulating an anisotropic atomistic bead model which implements the CS paradigm. We report simulations of thin film polystyrene.

Intrinsic viscoelasticity in thin high-molecular-weight polymer films

2014 ◽  
Vol 89 (6) ◽  
Author(s):  
Xiaoyuan Sheng ◽  
Frédéric Wintzenrieth ◽  
Katherine R. Thomas ◽  
Ullrich Steiner
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Polymer Films ◽  
High Molecular Weight Polymer ◽  
Molecular Weight Polymer

scholarly journals The Food Additive Xanthan Gum Drives Adaptation of the Human Gut Microbiota

2021 ◽  
Author(s):  
Matthew P. Ostrowski ◽  
Sabina Leanti La Rosa ◽  
Benoit J. Kunath ◽  
Andrew Robertson ◽  
Gabriel Pereira ◽  
...  
Keyword(s):  
Gut Microbiota ◽  
Xanthan Gum ◽  
Enrichment Culture ◽  
Food Additives ◽  
Food Additive ◽  
Glycoside Hydrolase Family ◽  
Human Gut ◽  
High Molecular Weight Polymer ◽  
Molecular Weight Polymer ◽  
Uncultured Bacterium

SummaryThe diets of industrialized countries reflect the increasing use of processed foods, often with the introduction of novel food additives. Xanthan gum is a complex polysaccharide with unique rheological properties that have established its use as a widespread stabilizer and thickening agent1. However, little is known about its direct interaction with the gut microbiota, which plays a central role in digestion of other, chemically-distinct dietary fiber polysaccharides. Here, we show that the ability to digest xanthan gum is surprisingly common in industrialized human gut microbiomes and appears to be contingent on the activity of a single bacterium that is a member of an uncultured bacterial genus in the family Ruminococcaceae. We used a combination of enrichment culture, multi-omics, and recombinant enzyme studies to identify and characterize a complete pathway in this uncultured bacterium for the degradation of xanthan gum. Our data reveal that this keystone degrader cleaves the xanthan gum backbone with a novel glycoside hydrolase family 5 (GH5) enzyme before processing the released oligosaccharides using additional enzymes. Surprisingly, some individuals harbor a Bacteroides species that is capable of consuming oligosaccharide products generated by the keystone Ruminococcaceae or a purified form of the GH5 enzyme. This Bacteroides symbiont is equipped with its own distinct enzymatic pathway to cross-feed on xanthan gum breakdown products, which still harbor the native linkage complexity in xanthan gum, but it cannot directly degrade the high molecular weight polymer. Thus, the introduction of a common food additive into the human diet in the past 50 years has promoted the establishment of a food chain involving at least two members of different phyla of gut bacteria.

scholarly journals Activated Flooded Jets and Immiscible Layer Technology Help to Remove and Prevent the Formation of Bottom Sediments in the Oil Storage Tanks

2021 ◽  
Author(s):  
Georgii V. Nesyn
Keyword(s):  
Crude Oil ◽  
Bottom Sediments ◽  
External Heat ◽  
Storage Tanks ◽  
High Molecular Weight Polymer ◽  
Molecular Weight Polymer ◽  
Oil Storage ◽  
Screw Propeller ◽  
Fit For Purpose ◽  
Tank Bottom

Two flooded jet methods of tank bottom sediments caving based on either screw propeller generation or nozzle jets generated with entering crude head oppose each other. The comparison is not advantageous for the first one. Exceptionally if crude oil contains some concentration of high molecular weight polymer which can perform Drag Reduction. In this case, the jet range increases by many times, thus, upgrading the capability of caving system. Preventing the sedimentation of crude oil heavy components may be put into practice with Immiscible Layer Technology. Before filling the tank with crude oil, some quantity of heavy liquid, that is immiscible with all the components of crude oil, is poured into the tank. The most suitable/fit for purpose and available liquid is glycerin. Neither paraffin and resins, nor asphaltenes can penetrate through the glycerin layer to settle down at the tank bottom because of its density, which is equal to 1.26 g/cm3. Instead, sediments are concentrated at/on the glycerin surface and when it is heated in external heat exchanger all the sediments ought to move upwards with the convection streams. Thus, no deteriorate sediment is formed in the tank bottom.

scholarly journals Polymethylmethacrylate (PMMA) Encapsulated Graphene Oxide Nanocomposite: Pre-modification, Synthesis, and Latex Stability

2020 ◽  
Author(s):  
Hui Wang ◽  
Letian Wang ◽  
Shanyu Meng ◽  
Hanxue Lin ◽  
Melanie Correll ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Graphene Oxide ◽  
Critical Role ◽  
Miniemulsion Polymerization ◽  
Sem Analysis ◽  
High Molecular Weight Polymer ◽  
Molecular Weight Polymer ◽  
Transmission Electron ◽  
Composite Production ◽  
Uniform Particle Size

The compatibility of graphene or graphene oxide with its dispersion medium (polymer) plays a critical role in the formation nanocomposite materials with significant property improvements. Environmentally friendly miniemulsion polymerization, which allows a formation of nanoencapsulation in an aqueous phase and high molecular weight polymer/composite production is one promising method. In this study, we screened a series of amphiphilic modifiers and found that the quaternary ammonium (ar-vinyl benzyl) trimethyl ammonium chloride (VBTAC) pending carbon double bonds could effectively modify the graphene oxide (GO) to be compatible with the organophilic monomer. After that, free radical miniemulsion polymerization could successfully synthesize stable latex of exfoliated poly (methyl methacrylate) (PMMA)/ GO nanocomposite. The final latex had an extended storage life and a relatively uniform particle size distribution. X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) analysis of this latex and its films indicated successful encapsulation of exfoliated nano-dimensional graphene oxide inside a polymer matrix.

Structural studies of the capsular polysaccharide from Haemophilus pleuropneumoniae serotype 2

1987 ◽  
Vol 65 (5) ◽  
pp. 414-422 ◽  
Author(s):  
Eleonora Altman ◽  
Jean-Robert Brisson ◽  
Malcolm B. Perry
Keyword(s):  
Molecular Weight ◽  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
High Molecular Weight ◽  
Capsular Polysaccharide ◽  
Structural Studies ◽  
High Molecular Weight Polymer ◽  
Molecular Weight Polymer ◽  
Structure Formula ◽  
Nuclear Magnetic

The capsular polysaccharide of Haemophilus pleuropneumoniae serotype 2 (ATCC 27089) is composed of D-glucose (two parts), D-galactose (one part), glycerol (one part), and phosphate (one part). Hydrolysis, dephosphorylation, methylation, enzymic studies, and 1H and 13C nuclear magnetic resonance experiments showed that the polysaccharide is a high molecular weight polymer of a tetrasaccharide repeating units, linked by monophosphate diester and having the following structure:[Formula: see text]

Visco-Elastic Property Studies on Polymer Flooding Systems with High Concentrations

2012 ◽  
Vol 550-553 ◽  
pp. 834-837
Author(s):  
Ji Gang Wang ◽  
Quan Qing Du ◽  
Peng Wu ◽  
Shao Li Hu ◽  
Pan Niu
Keyword(s):  
Elastic Property ◽  
Oil Recovery ◽  
Elastic Characteristic ◽  
Polymer Flooding ◽  
Oil Field ◽  
High Concentration ◽  
Improved Oil Recovery ◽  
High Molecular Weight Polymer ◽  
Molecular Weight Polymer ◽  
Asp Flooding

Keywords: Visco-elastic property; polymer flooding; oil recovery Abstract. Polymer flooding and ASP flooding has improved oil recovery a lot in Daqing oil field. In ASP flooding, the existence of alkali decreases the visco-elastic characteristic of polymer, which decreases the oil recovery of polymer flooding. The aim of this paper was to study the visco-elastic characteristic, shear resistance in high concentration and high molecular weight polymer flooding, and analyzed the suitable parameter of it .They can provide the theory of polymer flooding development and application research.

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