Thickness Of Polymer Adsorption Layer Research Articles

Adsorption behavior and shear degradation of ultrahigh‐molecular‐weight hydrolyzed polyacrylamide in a capillary flow

ABSTRACTUltrahigh‐molecular‐weight partially hydrolyzed polyacrylamides (HPAMs) are commonly used in polymer flooding to enhance oil recovery. However, the viscosity of the HPAM solution is susceptible to shear action. Viscosity change affects sweep range and displacement efficiency of the displacement fluid. Here, a macromolecular adsorption model in microcapillary is proposed to reveal the shear variation mechanism at low flow rates. The rheological behaviors of HPAMs with three different molecular weights are investigated using a stainless steel capillary. The shear rate distributions near contraction and within capillary are compared by numerical calculation using the laminar flow model. Experimental and numerical results show that the polymer solution was mechanically degraded at low flow rates, which is in agreement with the results predicted by the adsorption theory model. A new calculation method for the thickness of polymer adsorption layer at lower flow rates is proposed based on the adsorption model proposed in this study. It is found that the viscosity and adsorption of HPAM were changed with flow rate, and their changes are closely related to the displacement efficiency in the micropores of reservoirs. This study provides new perspectives for the selection of polymer injection flow rates and the water shutoff in reservoirs. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48270.

Impact of polyacrylamide with different contents of carboxyl groups on the chromium (III) oxide adsorption properties in aqueous solution

The main goal of experiments was determination of solution pH and contents of anionic groups in polyacrylamide (PAM) macromolecules on the stability mechanism of chromium (III) oxide suspension. The spectrophotometry, potentiometric titration, microelectrophoresis, viscosimetry and turbidimetry were applied. They enabled determination of polymer adsorbed amount, surface and diffusion charges of solid particles with and without PAM, thickness of polymer adsorption layer, macromolecule dimensions in the solution and stability of the Cr2O3 – polymer systems, respectively. It was found that adsorption of anionic PAM decreases and thickness of polymeric adsorption layer increases with the increasing pH. Slightly higher adsorption was obtained for the PAM samples containing a greater number of carboxyl groups. At pH 3 and 9 insignificant deterioration of stability conditions of Cr2O3 particle covered with polyacrylamide was observed (neutralization of solid positive charge by the adsorbed polymeric chains (pH 3) and single polymeric bridges formation (pH 9)). The electrosteric repulsion between the solid particles covered with PAM layers at pH 6, is the main reason for significant improvement of Cr2O3 suspension stability in the polymer presence.

Effect of the presence of cationic polyacrylamide on the surface properties of aqueous alumina suspension-stability mechanism

The effects of solution pH and the content of cationic groups in polyacrylamide (PAM) macromolecules on the stability mechanism of aqueous alumina suspension were investigated. The following experimental techniques were applied: spectrophotometry, potentiometric titration, microelectrophoresis, viscosimetry and turbidimetry. They enable determination of polymer adsorbed amount, surface charge density and zeta potential of solid particles in the presence and absence of PAM, as well as thickness of polymer adsorption layer, size of macromolecules in the solution and stability of the Al2O3–polymer systems, respectively. The obtained results indicate that adsorption of PAM increases with the increasing pH, whereas the thickness of polymeric adsorption layer decreases. Additionally, the greater the number of cationic groups in the PAM chains is, the higher adsorption was found. The polymer presence influences on the alumina suspension stability. At pH 3 and 6 the slight deterioration of stability conditions of solid particle covered with polyacrylamide was observed. At pH 9 the systems containing polymer are unstable, similarly to the suspension without PAM, but the mechanism of their destabilization is different.

Effect of the type of polymer functional groups on the structure of its film formed on the alumina surface – Suspension stability

The effects of polymer functional group and solution pH on stability of colloidal Al2O3 water suspension were studied. Both the nonionic polymers: polyethylene glycol (PEG), polyethylene oxide (PEO) and the ionic ones: polyacrylic acid (PAA), polyacrylamide (PAM), polyvinyl alcohol (PVA) were used in the experiments. The following methods were applied: turbidimetry (stability measurements), spectrophotometry (determination of polymer adsorption), viscosimetry (thickness of polymer adsorption layer), potentiometric titration (solid surface charge density) and microelectrophoresis (potential zeta). It was shown that anionic polyacrylic acid is both the most effective stabilizer (at pH 9) and flocculant (at pH 3) of the alumina suspension. Its carboxyl groups have the greatest affinity for the surface active sites (the largest adsorption) of all functional groups present in the other examined polymers. The latter, i.e. hydroxyl (PEG, PEO, and PVA) and acetate (PVA) show a much lower affinity for the Al2O3 surface (negligible adsorption) and minimally affect the stability of the alumina-solution system.

Influence of solution pH on stability of aluminum oxide suspension in presence of polyacrylic acid

The effect of solution pH and molecular weight of polyacrylic acid (PAA) on its adsorption as well as on stabilization-floculation properties of the colloidal Al2O3 and electrolyte solution systems was studied. The measurements showed that at pH = 6, the presence of the polymer of molecular weight 2 000 and 240 000 does not change stability of Al2O3 suspension. However at pH =3 and 9 the effect of polyacrylic acid is significant. At pH = 3 it creates destabilization of the suspension while at pH = 9 PAA it improves significantly the stability of Al2O3. It was shown that the increase in solution pH affects conformation of adsorbed macromolecules which causes the decrease in PAA adsorbed amount and thickness of polymer adsorption layer. By comparing the values of diffusion layer and surface charges, main effects responsible for the decrease in surface charge and ζ potential of the solid in the presence of the polymer as well as suspension stability were determined.

Studies of temperature influence on adsorption behaviour of nonionic polymers at the zirconia–solution interface

The temperature influence (15–35 °C) on the adsorption mechanism and conformation of nonionic polymers (polyethylene glycol (PEG), polyethylene oxide (PEO) and polyvinyl alcohol (PVA)) on the zirconium dioxide surface was examined. The applied techniques (spectrophotometry, viscosimetry, potentiometric titration and microelectrophoresis) allowed characterization of the changes in structure and thickness of polymer adsorption layers with the increasing temperature. The rise of temperature favours more stretched conformation of polymer chains on the ZrO2 surface, which results in higher adsorption and thicker adsorption layer. Moreover, these conformational changes of adsorbed macromolecules affect the electric (solid surface charge density) and electrokinetic (zeta potential) properties of the zirconia–polymer interface. The obtained data indicate that the polyvinyl alcohol adsorption has a greater influence on zirconia properties in comparison to that of PEG and PEO. It is due to the presence of acetate groups in the PVA macromolecules (degree of hydrolysis 97.5%), which undergo dissociation.

Adsorption and thermodynamic properties of the alumina–polyacrylic acid solution system

Free energies of polyacrylic acid (PAA) adsorption (ΔG ∘) on an alumina (Al 2O 3) surface in the temperature range 15–35 °C were estimated on the basis of adsorption–desorption measurements of the inorganic radioactive ions 36Cl, 45Ca, and 55Fe. Adsorbing polymer macromolecules caused the desorption process of previously adsorbed radioactive ions. The free energy of Ca-PAA surface complex formation (ΔG ∘) was estimated to be close to the free energy of Ca 2+ ions adsorption (polymer causes about 50% desorption of these ions). Moreover, a free energy of polymer molecule adsorption increase with the increasing temperature was observed. The obtained values of ΔG ∘ were compared with those calculated from the adsorption data. Additionally, the amount of polymer adsorbed and the thicknesses of polymer adsorption layers were determined in the temperature range 15–35 °C. The changes of polymer chain conformation with the temperature increase are responsible for the increase of PAA adsorption as well as thickness of polymer adsorption layers in the studied temperature range.

Temperature Study of Nonionic Polymers Adsorption at the Alumina—Solution Interface

The temperature influence of the structures of polyvinyl alcohol (PVA) and polyethylene glycol (PEG) adsorption layers on the alumina surface was studied. The amount of polymer adsorbed, the surface and diffuse layer charge of Al2O3 particles in the absence and presence of the polymer, and the thickness of polymer adsorption layers were determined in the 5°–40°C temperature range. An increase of PVA and PEG adsorption with an increase of temperature was observed. It is caused by conformation changes of polymer macromolecules from the coil structure to more and more stretched conformation when the temperature increases. Such a behavior was confirmed by the parameters calculated from the experimental data (Rh—hydrodynamic radius of a polymer coil in the solution, δ—thickness of the polymer adsorption layer, Rs—radius of a sphere equivalent to the volume that falls per a macromolecule in the adsorbed layer). From the comparison of the values of diffuse layer charge and surface charge, the main factor influencing the ζ potential changes was determined. The free energy of PVA and PEG adsorption was calculated using the ζ potential data.

The temperature influence on the adsorption and electrokinetical properties in the nonionic polymer/controlled porosity glass (CPG) system

The temperature influence of the structure of polyvinyl alcohol (PVA) and polyethylene glycol (PEG) adsorption layers on the controlled porosity glass (CPG) surface was studied. Adsorption, surface charge, zeta potential and viscosity measurements were carried out in the 5–40 °C temperature range. Applied methods allowed determination of the amount of polymer adsorbed, the surface and diffuse layer charge of CPG particles in the absence and presence of the polymer as well as the thickness of polymer adsorption layers. The adsorption measurements indicated the increase of PVA and PEG adsorption with the rise of temperature. Such behavior is caused by conformation changes of polymer macromolecules. Moreover, the increase of temperature causes the increase of the thickness of polymer adsorption layers on solid surface. It is due to the fact that the increase of temperature favors more stretched conformation of polymer chains on CPG surface. From the adsorption and viscosity data were calculated parameters, which characterize changes of the polymer chains conformation on their way from liquid phase to the solid surface.

Study of the Thickness of Polymer Adsorption Layers on the Fibre Surface

The adsorption and thickness of the polymer adsorption layer on a fibre surface varies symbatically. The great thickness of the adsorption layer on fibre sorbents is due to the specificity of the reaction of the polymer (PVC) with the surface of the sorbent. The increase in the thickness of the adsorption layer with an increase in the temperature is due to a change in the conformation of the macromolecules in the layer.