Kinetics of change in polymer concentration in spinning viscose yarn

1987 ◽  
Vol 18 (6) ◽  
pp. 452-454
Author(s):  
Yu. I. Rzhevtseva ◽  
V. P. Kim
Keyword(s):  
Polymer Concentration ◽  
Viscose Yarn ◽  
Kinetics Of

Study of Film Structure and Adsorption Kinetics of Polyelectrolyte Multilayer Films: Effect of pH and Polymer Concentration

Langmuir ◽  
2008 ◽  
Vol 24 (19) ◽  
pp. 10887-10894 ◽  
Author(s):  
Akhilesh Garg ◽  
James R. Heflin ◽  
Harry W. Gibson ◽  
Richey M. Davis
Keyword(s):  
Adsorption Kinetics ◽  
Polymer Concentration ◽  
Multilayer Films ◽  
Film Structure ◽  
Polyelectrolyte Multilayer ◽  
Effect Of Ph ◽  
Kinetics Of

scholarly journals Recombination of Poly(Acrylic Acid) Radicals in Acidic Aqueous Solutions: A Pulse Radiolysis Study

2021 ◽  
Vol 11 (21) ◽  
pp. 10142
Author(s):  
Małgorzata Matusiak ◽  
Sławomir Kadłubowski ◽  
Piotr Ulański
Keyword(s):  
Acrylic Acid ◽  
Aqueous Solutions ◽  
Ph Dependence ◽  
Polymer Concentration ◽  
Second Order ◽  
Order Kinetic ◽  
Initial Number ◽  
Linear Charge Density ◽  
Kinetics Of ◽  
Poly Acrylic Acid

Carbon-centered radicals have been randomly generated on the chains of poly(acrylic acid), PAA, the simplest synthetic anionic polyelectrolyte, by pulse-irradiating its dilute, oxygen-free aqueous solutions by 6 MeV electron beam. In some experiments, oligo(acrylic acid), OAA, and propionic acid, PA, were used as PAA models. Recombination kinetics of PAA radicals has been followed by fast spectrophotometry. A strong pH dependence of radical lifetime on pH, and thus on the linear charge density due to deprotonated carboxylate groups, has been confirmed, while a weaker amplitude of pH dependence was observed for OAA and PA. Decay kinetics of PAA radicals in the protonated state, at pH 2, have been studied in some detail. At moderate doses of ionizing radiation, resulting in a moderate average initial number of radicals per chain, ZR0, the decay can be satisfactorily described by a second-order kinetic model, but a somewhat better fit is obtained by using a dispersive kinetics approach. While for a constant polymer concentration the reciprocal half-lives are proportional to the initial radical concentrations, such a data series for different PAA concentrations do not overlap, indicating that the overall radical concentration is not the decisive factor controlling the kinetics. Arranging all data, in the form of second-order rate constants, as a function of the average initial number of radicals per chain allows one to obtain a common dependence. The latter seems to consist of two parts: a horizontal one at low ZR0 and another one of positive slope at higher ZR0. This is interpreted as two kinetic regimes where two distinct reactions dominate, intermolecular and intramolecular recombination, respectively. Comparison of the low ZR0 data with calculations based on the translational diffusion model indicate that the latter is not the rate-controlling process in intermolecular recombination of polymer radicals; segmental diffusion is the more likely candidate.

scholarly journals Prediction of Viscoelastic Properties of Enzymatically Crosslinkable Tyramine–Modified Hyaluronic Acid Solutions Using a Dynamic Monte Carlo Kinetic Approach

2021 ◽  
Vol 22 (14) ◽  
pp. 7317
Author(s):  
Filippos F. Karageorgos ◽  
Costas Kiparissides
Keyword(s):  
Molecular Weight ◽  
Monte Carlo ◽  
Hyaluronic Acid ◽  
Kinetic Model ◽  
Average Molecular Weight ◽  
Polymer Concentration ◽  
Polymer Chains ◽  
Finite Sample ◽  
Dynamic Monte Carlo ◽  
Kinetics Of

The present study deals with the mathematical modeling of crosslinking kinetics of polymer–phenol conjugates mediated by the Horseradish Peroxidase (HRP)-hydrogen peroxide (H2O2) initiation system. More specifically, a dynamic Monte Carlo (MC) kinetic model is developed to quantify the effects of crosslinking conditions (i.e., polymer concentration, degree of phenol substitution and HRP and H2O2 concentrations) on the gelation onset time; evolution of molecular weight distribution and number and weight average molecular weights of the crosslinkable polymer chains and gel fraction. It is shown that the MC kinetic model can faithfully describe the crosslinking kinetics of a finite sample of crosslinkable polymer chains with time, providing detailed molecular information for the crosslinkable system before and after the gelation point. The MC model is validated using experimental measurements on the crosslinking of a tyramine modified Hyaluronic Acid (HA-Tyr) polymer solution reported in the literature. Based on the rubber elasticity theory and the MC results, the dynamic evolution of hydrogel viscoelastic and molecular properties (i.e., number average molecular weight between crosslinks, Mc, and hydrogel mesh size, ξ) are calculated.

scholarly journals Controlled Shape and Porosity of Polymeric Colloids by Photo-Induced Phase Separation

Polymers ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1225
Author(s):  
Elad Hadad ◽  
Eitan Edri ◽  
Hagay Shpaisman
Keyword(s):  
Phase Separation ◽  
Polyethylene Glycol ◽  
Chemical Composition ◽  
Particle Shape ◽  
Polymer Concentration ◽  
Continuous Phase ◽  
Uv Curable ◽  
Profound Influence ◽  
Acetone Water ◽  
Kinetics Of

The shape and porosity of polymeric colloids are two properties that highly influence their ability to accomplish specific tasks. For micro-sized colloids, the control of both properties was demonstrated by the photo-induced phase separation of droplets of NOA81—a thiol-ene based UV-curable adhesive—mixed with acetone, water, and polyethylene glycol. The continuous phase was perfluoromethyldecalin, which does not promote phase separation prior to UV activation. A profound influence of the polymer concentration on the particle shape was observed. As the photo-induced phase separation is triggered by UV radiation, polymerization drives the extracted solution out of the polymeric matrix. The droplets of the extracted solution coalesce until they form a dimple correlated to the polymer concentration, significantly changing the shape of the formed solid colloids. Moreover, control could be gained over the porosity by varying the UV intensity, which governs the kinetics of the reaction, without changing the chemical composition; the number of nanopores was found to increase significantly at higher intensities.

Rheological Monitoring of the Formation of Polyacrylamide/Cr+3 Gels

1983 ◽  
Vol 23 (05) ◽  
pp. 804-808 ◽  
Author(s):  
Robert K. Prud'homme ◽  
Jonathan T. Uhl ◽  
John P. Poinsatte
Keyword(s):  
Metal Ions ◽  
Storage Modulus ◽  
Shear Viscosity ◽  
Polymer Concentration ◽  
Gelation Time ◽  
Three Dimensional ◽  
Reducing Agent ◽  
Chromium Ion ◽  
Kinetics Of

Abstract The formation of polyacrylamide/chromium-ion gels has been followed rheologically. The time dependence of the storage modulus has been used to analyze the kinetics of the gelation process. The kinetic theory of rubber elasticity has been used to determine the crosslink density in the gel from the measured value of the storage modulus. The effects of changing polymer, chromium ion, and reducing agent concentrations have been studied. polymer, chromium ion, and reducing agent concentrations have been studied. Introduction Water-soluble polymers of high molecular weight, such as polyacrylamides, polysaccharides, and hydroxyl ethyl celluloses, have been studied as polysaccharides, and hydroxyl ethyl celluloses, have been studied as water flooding additives since the late 1950's. These polymers are added to control fluid movement in reservoirs to improve sweep efficiencies. In addition to enhanced fluid mobility control in porous media by increased viscosities of polymer solutions, the injection of dilute (250 ppm) polyacrylamide solutions causes permeability reductions that persist after polyacrylamide solutions causes permeability reductions that persist after the mobile polymer is flushed from the pore space by water. This reduction in permeability to water is a result of the retention of polyacrylamide in the porous rock by adsorption and mechanical entrapment. Rock permeability also can be reduced deliberately by crosslinking a polyacrylamide solution in situ to form a three-dimensional (3D) gel. The polyacrylamide solution in situ to form a three-dimensional (3D) gel. The gelled polymer is capable of shutting off fractures and zones of high permeability. The rate at which this 3D gel is formed determines how far permeability. The rate at which this 3D gel is formed determines how far the solution can be pushed into the rock formation away from the injection well before gelation occurs. Polyacrylamides are known to form gels in the presence of Cr+3 ions. The process involves the reduction of Cr+6 to Cr+3 with a reducing agent such as sodium bisulfite or thiourea. When Cr+6 is reduced to Cr+3, the trivalent chromium ion and polymer react slowly to form a 3D gel structure. The mechanism by which polyacrylamide or partially hydrolyzed polyacrylamide forms gels in the presence of metal ions is not well polyacrylamide forms gels in the presence of metal ions is not well understood. One idea is that Cr+3 serves as a crosslinking agent between the polyacrylamide molecules. Another suggestion is that Cr+3 forms a stable dispersion in the polymer solution, resulting in either a highly viscous liquid or a gel. Only a limited amount of data has been published on the kinetics of the polyacrylamide/chromium ion gelation process. Terry et al. followed the increase of the steady shear viscosity with time after the introduction of a reducing agent to a polyacrylamide/Cr+6 solution. Gelation time was defined as the time required for the shear viscosity to reach an arbitrary value. The effects of varying polymer type and concentration, Cr+6 concentration, and reducing agent type and concentration were investigated. A linear relationship was found between the reciprocal of the gelation time and the reciprocal of the polymer concentration for a given polymer reducing agent system. The gelation time decreases both with increasing polymer concentration and with increasing Cr+6 and reducing agent polymer concentration and with increasing Cr+6 and reducing agent concentrations. An Arrhenius-type relationship was shown between gelation time and temperature by Willhite and Jordan. During the buildup of a 3D gel network, the shear viscosity increases, but the shearing motion imposed on the sample also tends to break down the network being formed. SPEJ p. 804

scholarly journals Solubility, Rheology, and Coagulation Kinetics of Poly-(O-Aminophenylene)Naphthoylenimide Solutions

Polymers ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 2454
Author(s):  
Ivan. Y. Skvortsov ◽  
Valery G. Kulichikhin ◽  
Igor I. Ponomarev ◽  
Lydia A. Varfolomeeva ◽  
Mikhail S. Kuzin ◽  
...  
Keyword(s):  
Rheological Properties ◽  
Time Window ◽  
Polymer Concentration ◽  
Effect Of Temperature ◽  
Coagulation Bath ◽  
Continuous Polymerization ◽  
Coagulation Kinetics ◽  
The Stability ◽  
First Time ◽  
Kinetics Of

The effect of temperature and storage time at a constant temperature on the stability of poly-(o-aminophenylene)naphthoylenimide solutions in N-methylpyrrolidone has been analyzed using rotational rheometry. A temperature–time window beyond which an irreversible change in the viscoelastic properties of solutions due to cumulative reactions of continuous polymerization and possible intramolecular cyclization has been detected. The influence of polymer concentration and its molecular weight on the rheological properties of solutions determining the choice of methods for their processing into fibers and films has been investigated. The effect of non-solvents (water and ethanol) additives on the rheological properties of solutions and the kinetics of their coagulation has been studied. Dosed addition of non-solvent into the solution promotes a significant increase in the viscoelasticity up to gelation and phase separation. Non-solvent presence in the polymer solutions reduces the activity of the solvent, accelerates the movement of the diffusion front at coagulation, and minimizes the number of macro defects. The combination of parameters under investigation renders it possible for the first time to develop new principles modifying dopes for wet spinning into aqueous or ethanol coagulation bath and finally to obtain a heat- and fire-resistant polynaphthoylenebenzimidazole fibers.

Chemical grafting of silane end-functionalized polymer on silicon surfaces

1993 ◽  
Vol 304 ◽  
Author(s):  
A Karim ◽  
S. K. Satija ◽  
W. Orts ◽  
J. F. Ankner ◽  
C. F. Majkrzak ◽  
...  
Keyword(s):  
Concentration Profile ◽  
Polymer Concentration ◽  
Silicon Surfaces ◽  
Low Molecular Weight ◽  
Neutron Reflectivity ◽  
Exponential Behavior ◽  
Kinetics Of Adsorption ◽  
Chemical Grafting ◽  
Kinetics Of ◽  
Poor Solvent

AbstractX-ray and neutron reflectivity was used to determine the kinetics of adsorption and characterize the concentration profile of a low molecular weight trichlorosilane endfunctionalized polystyrene adsorbed onto polished silicon wafers. Higher adsorbed amounts were obtained from a cyclohexane solution of the polymer rather than toluene, with kinetics that followed a stretched exponential behavior. For moderately high grafting densities the polymer concentration profile in deuterated toluene (a good solvent) was best modelled using a small tailed parabola. In deuterated cyclohexane (a poor solvent) the brush profile steepened but was substantially smoother than a step, while in D20 (a non-solvent) it became step-like.

Direct observations of radiation-enhanced transformations in glass

1983 ◽  
Vol 41 ◽  
pp. 354-355
Author(s):  
J. F. DeNatale ◽  
D. G. Howitt
Keyword(s):  
Glass Matrix ◽  
Diffusion Mechanism ◽  
Bubble Formation ◽  
Silicate Glasses ◽  
Phase Decomposition ◽  
Direct Observations ◽  
Thin Foils ◽  
Oxygen Bubble ◽  
Electron Energy Loss ◽  
Kinetics Of

The electron irradiation of silicate glasses containing metal cations produces various types of phase separation and decomposition which includes oxygen bubble formation at intermediate temperatures figure I. The kinetics of bubble formation are too rapid to be accounted for by oxygen diffusion but the behavior is consistent with a cation diffusion mechanism if the amount of oxygen in the bubble is not significantly different from that in the same volume of silicate glass. The formation of oxygen bubbles is often accompanied by precipitation of crystalline phases and/or amorphous phase decomposition in the regions between the bubbles and the detection of differences in oxygen concentration between the bubble and matrix by electron energy loss spectroscopy cannot be discerned (figure 2) even when the bubble occupies the majority of the foil depth.The oxygen bubbles are stable, even in the thin foils, months after irradiation and if van der Waals behavior of the interior gas is assumed an oxygen pressure of about 4000 atmospheres must be sustained for a 100 bubble if the surface tension with the glass matrix is to balance against it at intermediate temperatures.

Irradiation behavior of pyrolytic silicon carbide

1983 ◽  
Vol 41 ◽  
pp. 72-73
Author(s):  
R. J. Lauf
Keyword(s):  
Silicon Carbide ◽  
Fission Products ◽  
Thermodynamics And Kinetics ◽  
Neutron Fluences ◽  
Fuel Particles ◽  
Sic Coatings ◽  
Irradiation Behavior ◽  
Kinetics Of ◽  
Htgr Fuel

Fuel particles for the High-Temperature Gas-Cooled Reactor (HTGR) contain a layer of pyrolytic silicon carbide to act as a miniature pressure vessel and primary fission product barrier. Optimization of the SiC with respect to fuel performance involves four areas of study: (a) characterization of as-deposited SiC coatings; (b) thermodynamics and kinetics of chemical reactions between SiC and fission products; (c) irradiation behavior of SiC in the absence of fission products; and (d) combined effects of irradiation and fission products. This paper reports the behavior of SiC deposited on inert microspheres and irradiated to fast neutron fluences typical of HTGR fuel at end-of-life.

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