Polyacrylamide-treated kaolin: A fabric study

Particle interactions, and in turn fabric, determine the behavior of clay mineral particle systems. Polymers with deliberately chosen characteristics, such as molecular mass and ionic type, can be utilized to manipulate clay fabric. The purpose of this study is to understand fabric development in a clay–polymer system, specifically kaolin–polyacrylamide systems over a wide range of solids content. Methodologies include sedimentation tests (low solids content), viscosity measurements (moderate solids content), and liquid limit measurements (high solids content), and are conducted to determine variation in fabric for kaolin–polyacrylamide systems at various concentrations, molecular mass and ionic types of polyacrylamide. Fabric development is verified using scanning electron microscopy (SEM). Results show that the polymer charge type impacts the resulting fabric formation only at polymer concentrations above a threshold concentration. Floc/aggregate size and density tend to increase with increasing polyacrylamide concentration, while high molecular-mass polyacrylamides tend to induce the formation of open flocculated structure. The most likely particle association in the presence of nonionic polyacrylamides is face-to-face association due to polymer bridging. A relationship is found between polymer characteristics, solids contents, and micro-scale particle arrangement. This study is relevant to the emerging field of engineered soil fabrics.     

Aging characteristics of protein precipitates produced by polyelectrolyte precipitation in turbulently agitated reactor

The relationship between aging and aggregation mechanism of solid lysozyme precipitates produced by polyacrylic acid (PAA) with a high molecular weight of 4.0×10⁶ was experimentally investigated in a semi-batch reactor. As feeding the PAA, the aggregation mechanism between lysozyme and PAA was found to be determined by the aging history, which was shifted from charge neutralization to polymer bridging with increasing the agitation level. The lysozyme precipitates generated through a high bridging effect of PAA at a high mixing speed were broken up with aging, i.e. additional agitation of the product suspension after the feeding time. In contrast, the particle size of the precipitates formed at a low mixing intensity through a poor polymer bridging increased due to aging-induced aggregation, except for the extremely long aging time. Based on the largest particle size of the precipitates after aging, the aggregate strength was clearly confirmed to be enhanced by the bridging effect. Regardless of the mixing level, the lysozyme precipitates exhibited a steady particle size when the Camp number approached about 5×10⁵ by adjusting the aging time with the same agitation speed as that used during the PAA feeding. However, the steady particle size was not observed when the Camp number was controlled by the aging intensity for the fixed aging time. The precipitates underwent the phenomenon of infilling at a high aging intensity, which appeared to participate, along with the shear stress, in the particle fragmentation that occurred during the aging process.     

Water soluble acrylamide polymers, 2. Aging and viscous flow of aqueous solutions of polyacrylamide and hydrolyzed polyacrylamide

The aging of aqueous solutions of polyacrylamide which appears experimentally as a decrease of solution viscosity and which is probably caused by microorganisms may be prevented by the addition of a small amount (0.02 wt.-%) of an antimicrobial agent such as sodium azide. Aluminium chloride causes a very strong decrease of the viscosity during a prolongated storing time. The addition of aluminium ions to the polymer solution leads to a complexing of amidic groups with aluminium cations and probably also to decrease of the dimensions of individual polymer coils. The viscous flow of aqueous solutions of polyacrylamide and hydrolyzed polyacrylamides was studied as a dependence of the shear gradient D on the shear stress τ and was described by the relation D = k · τⁿ, where k and n denote constants. Both constants depend on the polymer concentration, the degree of polymerization and the content of carboxylic groups in the polymer. The greatest deviations from the Newtonian behaviour were found in the range of molecular weights over 2 · 10⁶ g/mol and practically no deviations were observed for polyacrylamide with molecular weights below 1 · 10⁶ g/mol. The dependence of the viscosity on the shearing time at different shear rates (300, 600 and 1200 s^?1) which was observed in solutions of polyacrylamide, hydrolyzed polyacrylamide and poly-(N,N-dimethyl)-acrylamide was explained by an entanglement model.     

Factors effecting a loss of flocculation activity of polyacrylamide solutions: Shear degradation,cation complexation,and solution aging

Polyacrylamide and poly(acrylamide-co-acrylic acid) flocculant solutions were subjected to shear degradation in a rotating cone instrument. At constant shear rate, shear degradation was minimized (highest limiting intrinsic viscosity) by the use of a lower solution concentration and high ionic strength of the polymer solution. Resistance to shear degradation also increased with increasing anionic character of the polyacrylamide. Sheared polymers showed reduced performance as flocculants of coal preparation plant tailings, their major commerical application in the U.K. Partially anionic polyacrylamide solutions were completely inactivated in the presence of certain multivalent cations. Aluminium, iron_III, lead, copper, and zinc ions formed complexes with the carboxyl groups on the polymer, resulting in zero flocculation activity. Nonionic polyacrylamides were unaffected. Viscosity–aging of polyacrylamide solutions was observed over a period of several months, but was insufficient to affect the flocculation activity. In the presence of 3% ethanol or methanol, no aging was observed in solutions stored for over a year.     

Rheological Behaviour of Poly (Acrylamide-G-Propylene Oxide) Solutions: Effect of Hydrophobic Content,Temperature and Salt Addition

Abstract

The viscosity of hydrophobically modified polyacrylamide was investigated as a function of polymer concentration in aqueous and in salt solutions, and also as a function of temperature. The graft copolymers were constituted of polyacrylamide backbone and different amount of hydrophobic polypropylene oxide) graft chains. Measurements of intrinsic viscosities have been performed by using a Contraves low-shear LS-40 rheometer. From these results, a dependence of the intrinsic viscosity of the polymer solution with the molecular weight was observed, where an increase of the latter resulted in higher intrinsic viscosity. In this case, the effect of the molecular weight was more emphasized than the effect caused by the slightly different degrees of hydrophobic incorporation. When enhancing the temperature, it was not verified a significant change on the reduced viscosities of the copolymer solutions and the graft chain length was also observed.     

Polyacrylamides revisited: flocculation of kaolin suspensions and mature fine tailings

A series of acrylamide‐based water‐soluble (co)polymers was synthesized and they were investigated as flocculants of model kaolin suspensions and mature fine tailings of oil sands. The effects of molar mass, charge density, and polymer concentration on flocculation efficiency were studied by monitoring the initial settling rate during sedimentation. Hydrolyzed polyacrylamide (HPAM) with high molar mass and intermediate acrylic acid contents (0.14–0.41 mol/mol (14–41 mol%)) performed better in flocculation tests on kaolin suspensions requiring lower dose for maximum initial settling rate than native polyacrylamide (PAM). Surface force measurements showed that at low polymer concentrations (1 ppm), the partially‐adsorbed polymer induced a bridging attraction between the mica surfaces. Increasing the polymer concentration to 10 and 50 ppm caused purely repulsive forces. The presence of anionic groups in HPAM led to stronger repulsion, which was also demonstrated by the higher viscosity and larger hydrodynamic radius of the charged polymer. The charge‐induced increase in the viscosity of polymer solutions was suppressed by the screening effect of salts in a buffer solution and reducing the viscosity is desirable in the injection of flocculants in the industrial process.     

“水包水”聚合物乳液特性粘数测定方法的研究

本文采用两种方法,一种是采用沉淀再溶解法配制聚丙烯酰胺"水包水"乳液的水溶液,采用乌氏粘度计用五点稀释法来测定聚丙烯酰胺"水包水"乳液的特性粘数[η];另一种是以第一种方法得出的结果为标准试验并总结出的一套既简便误差又不大的测定聚丙烯酰胺"水包水"乳液特性粘数的方法,即用直接稀释乳液法配制聚丙烯酰胺"水包水"乳液的水溶液,采用乌氏粘度计用一点法来测定聚丙烯酰胺"水包水"乳液的特性粘数[η]。通过对一系列的阳离子型"水包水"聚丙烯酰胺乳液在每隔一段时间内测定其特性粘数的变化趋势,得出了"水包水"聚丙烯酰胺乳液的稳定性的有关信息:乳液的特性粘数[η]先随时间的增加而急剧下降,然后下降幅度又趋于平缓,最后达到一个稳定值。     

Viscosity and retention of sulfonated polyacrylamide polymers at high temperature

The viscosity and retention of several copolymers of acrylamide (AM) with sodium salt of 2‐acrylamido‐2‐methylpropane sulfonic acid (PAMS), and also hydrolyzed polyacrylamide (HPAM) have been studied under aerobic condition with and without the sacrificial agent, isobutyl alcohol (IBA) added at a temperature of 80°C. Parallel experiments have been performed in synthetic seawater (SSW) and 5 wt % NaCl. The viscosity at high temperature has been studied as a function of aging time, shear rate, sulfonation degree, molecular weight, and concentration of IBA. The retention in porous medium for sulfonated polyacrylamide polymers was measured in core floods using outcrop Berea sandstone. For the studied polymer sacrificial agent may protect polymer structure at high temperature. Higher sacrificial agent concentration gives better thermal stability in both 5 wt % NaCl and SSW solvents. Sulfonation degree also has a direct effect on thermal stability, i.e., higher sulfonation degree lead to better thermal stability in terms of viscosity. By increasing temperature, less relative reduction in polymer solution viscosity was observed for the polymer with lower molecular weight. The presence of divalent ions at high temperature leads to strong reduction of HPAM polymer solution viscosity, but the viscosity is better maintained for PAMS copolymer solution at high temperature. The precipitation of HPAM first occurred after 3 months at 80°C and for PAMS copolymer with lowest sulfonation degree precipitation started after 7 months. For the studied polymers the retention was found to be relatively independent of temperature and compared to HPAM a much lower retention is observed for the sulfonated copolymers. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Particle dimensions in polystyrene/polyethylene blends as a function of their melt viscosity and of the concentration of added graft copolymer

Apparent particle dimensions in blends of low density polyethylene (PE) and polystyrene (PS) made by mixing in the molten state have been measured and have been shown to depend on the viscosity of the mixed system. At a certain shearing rate small particles of the dispersed polymer are obtained if the polymer in excess has a high viscosity. At a higher concentration however this effect is counteracted completely if the dispersed phase has a low viscosity and thus lowers the overall viscosity. Coalescence is affected in the same way and the size of the particles increases greatly with increasing concentrations. If a highly viscous polymer is dispersed in a low viscosity polymer matrix relatively large particle sizes will be found at the preset shearing rate mentioned above. With increasing concentration of the highly viscous dispersed phase the particle size decreases due to the increasing viscosity. This effect is counteracted by coalescence leading to a relatively slow increase of particle size with concentration. Addition of surfactants such as graft copolymers based on PS and PE leads to smaller particle sizes as expected.     

磷矿酸解渣与聚丙烯酰胺絮凝动力学

通过激光粒度仪在线监测搅拌槽内聚丙烯酰胺与磷矿酸解料浆的絮凝过程 ,研究了絮凝剂加入量、絮凝温度、搅拌速度和酸解渣原始平均粒径对絮凝动力学的影响 .用电泳试验测定酸解渣的表面电性 ,合成不同荷电类型的絮凝剂及通过絮凝剂加入量对絮凝过程的影响实验可以判定磷矿酸解渣与聚丙烯酰胺的絮凝过程符合架桥机理     

Adsorption characteristics of polyacrylamide and sulfonate-containing polyacrylamide copolymers on sodium kaolinite

Polyacrylamide and its copolymer containing 6.8 mole % 2-acrylamido-2-methylpropane sulfonic acid were prepared by an irradiation-initiated precipitation polymerization technique. The polymer was characterized by intrinsic viscosity under conditions similar to those used during adsorption measurements. Hydrolytic degradation of the polyacrylamide was found to be negligible under conditions used. The adsorption substrate, sodium kaolinite, was prepared by extensive ion exchange treatment. Equilibrium adsorption of the polymers on the sodium kaolinite was made as a function of polymer concentration, solution pH, ionic strength, and temperature.     

The flocculation of kaolin by cationic polyacrylamides and the effect of cationic surfactant on this process

The flocculation of kaolin suspended in a dilute salt solution was studied as a function of the addition of cationic surfactant and cationic polyacrylamide (CPAM) added separately, consecutively, or simultaneously. Cationic polyacrylamide caused flocculation by bridging when added in low concentrations, but at higher concentrations, charge neutralization became the dominant mechanism and the flocculation rate was highly dependent on the charge density of the polymer. Adsorption of sufficient polymer or surfactant (cetyl pyridinium chloride) prevented immediate adsorption of the other, although surfactant could replace polymer after extended agitation. The adsorption of polymer was greatest when small flocs were formed by charge neutralization or by prolonged shaking. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2382–2389, 2002     

Low Temperature Non‐Isothermal Aging of Nitrocellulose

Slow multi‐sample thermal ramp aging experiments were performed on high viscosity lacquer grade nitrocellulose over the temperature range 30–80 °C. Nitrocellulose was used in the fibrous state, in solution and as the gelatinous nitro‐plasticized binder used to bind high explosive crystals (HMX) in a polymer‐bonded explosive (PBX) formulation. Samples were subjected to a slow, stable heating rate (dT/dt) of 10 °C per day with periodic sample withdrawal for analysis by triple detector size exclusion chromatography (SEC). Molecular weight and intrinsic viscosity data indicate inter‐chain recombination/aggregation for fibrous material or highly concentrated solutions, when dry. When in fibrous or gelatinous binder form, little degradation was observed, aside from apparent recombination/aggregation. As a concentrated solution complex behavior was noted; fast eluting peaks formed with increased temperature, accompanied by rapid molecular weight reduction and a marked decrease in light scattering peak area. Progressive dilution of nitrocellulose solutions and/or addition of very small quantities of water reduced the recombination/aggregation effects but did not appear to significantly affect the overall rate of nitrocellulose degradation. Activation energies for nitrocellulose chain scission have been estimated from the molecular weight and intrinsic viscosity data obtained by the thermal ramp method.     

Modification induced by alpha particle irradiationin Makrofol polycarbonate

Makrofol DE 1‐1 CC polycarbonate samples were exposed to alpha particles of initial energies at levels between 5.1 and 34 MeV. The modifications induced in polycarbonate samples due to the alpha particle irradiation have been studied through different characterization techniques such as X‐ray diffraction (XRD), infrared spectroscopy, intrinsic viscosity, and color difference studies. The infrared spectroscopy indicated that the intensities of the characteristic absorption bands decrease with increasing the deposited alpha energy in the range 5.1–8.4 MeV, indicating that the degradation is the dominant mechanism at this range. At the same time, an increase in the ? OH groups was observed at the same energy range 5.1–8.4 MeV due to the degradation of carbonate group and the ? H abstraction from the polymer backbone to form hydroxyl groups. The degradation reported by IR spectroscopy enhanced the degree of ordering in the degraded samples as revealed by XRD technique. Additionally, this degradation decreases the intrinsic viscosity from 0.56 to 0.43 at 35°C, indicating a decrease in the average molecular mass. The non irradiated Polycarbonate polymer is nearly colorless. It showed significant darkness sensitivity towards alpha particle irradiation, indicated by an increase in the color intercept L* from 33.6 to 36.7. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Interparticle and particle-matrix interactions in polyethylene reinforcement and viscoelasticity

Composites of surface treated and untreated non-colloidal CaCO₃ particles and high-density polyethylene (HDPE) with different filler loading (0-30 vol%) were prepared. Their viscoelastic properties were studied by dynamic strain sweep and small amplitude oscillatory shear and correlated to the particle-particle and particle-matrix interactions. The results gave insight into the mechanism of polymer reinforcement by solid inclusions and the factors that lead to the often observed solid-like response in the terminal zone. With increasing filler volume fraction, the particles tend to agglomerate and build clusters (local structures) that can be disintegrated by shearing. Up to 30 vol% no evidence for a space-filling particle network could be found. The presence of clusters increases the viscosity, the moduli and the viscoelastic non-linearity of the composites. Coating the filler surface by a stearic acid monolayer reduces its tendency to agglomerate as well as the adhesion between the particles and the polymer, leading to lower viscosity and interfacial slippage with increasing strain amplitude. Solid inclusions increase the storage modulus more than the loss modulus, hence decrease the material damping. The hydrodynamic reinforcement is frequency independent and dominates at high frequency. Polymer adsorption on the particles surface results in a transient filler-polymer network, which together with the topological restraints exerted by the inclusions on the polymer chain reptation leads to slow relaxation. These slow relaxation processes are sensitive to the oscillation frequency and strongly contribute to the polymer reinforcement at low frequencies. Agglomerates differ in shape and packing from the nearly spherical primary particles, and exert strong restraints on the polymer chain relaxation, hence offer an additional contribution to the composite's moduli. The sum of these effects results in higher moduli and a shift of the crossover (liquid-like to solid-like) frequency to lower values with increasing filler volume fraction. They also lead to the often-observed tendency towards a solid-like response in the terminal zone before a space-filling filler network is formed. Hydrodynamic and micromechanical models can only predict the hydrodynamic reinforcement, provided that the polymer strongly adheres to the inclusions.     

无机矿物对三元复合驱中聚合物吸附性能影响

三元复合驱过程中，聚合物会发生吸附现象，导致黏度降低，波及体积变小。研究了新疆油田三元复合驱实验中，无机矿物对聚合物吸附的影响因素。结果显示，对聚合物吸附最强的是蒙脱石，其次是绿泥石、伊利石，长石和石英砂最小；聚合物在松散岩心上的吸附大于胶结岩心上的吸附；随着渗透率的降低，聚合物的动态吸附量逐渐减小。与纯聚合物驱相比，三元复合驱中聚合物的黏度和吸附量要小的多，这主要是因为三元复合驱中高浓度的碱相当于增大了无机盐的浓度，压缩了聚合物导致吸附变小；而表面活性剂与聚合物产生了竞争吸附，降低了聚合物的吸附量。     

Control of rheology of water-borne paints using associative thickeners

Water-borne decorative topcoats generally show inferior leveling and open time compared to solvent-based paints. Basically, this behavior is caused by the divergent viscosity–solid content relationship for dispersions and emulsions and by the relatively high evaporation rate of water. Employment of associative thickeners may improve leveling and open time of latex paints only if they introduce a substantial amount of ‘network viscosity,' characterized by a short relaxation time and little dependence on solid content. This network viscosity enables one to formulate a paint with sufficient high-shear viscosity at a particle-packing density far below the value where low-shear viscosity starts to diverge. Addition of an associative thickener not only affects rheology, but also the interaction between latex particles: Associative HEUR thickeners may induce undesired phase separation by strong bridging between the latex particles. The influence of HEUR thickeners on latex particle interaction has been studied by turbidity measurements. The experimental results could qualitatively be interpreted very well by two-particle interaction potentials computed using the Self-Consistent-Field theory of Scheutjens and Fleer. It is demonstrated how viscosity, created by the addition of an associative thickener to a highly concentrated latex, can be split up into a polymer network viscosity and a contribution to (relative) dispersion viscosity. According to these analyses, reduction of the molecular weight of tri-block HEUR thickeners yields an increase of the favorable network viscosity and a reduction of the unfavorable dispersion viscosity. However, reduction of the molecular weight of the HEUR thickener is limited by the introduction of undesired phase separation (bridging flocculation) below a certain molecular weight.     

Investigation of Polymer Adsorption on Rock Surface of Highly Saline Reservoirs

Blocking or reducing water production from oil wells is a serious problem in oil industry. Two types of polymers, namely, polyacrylamide (PAA) and polysaccharides (xanthan) have been investigated in this paper. The viscosity of both polymer solutions was first evaluated at different salinities, shear rates and concentrations. Afterwards, the solutions were injected into core samples to examine the adsorption on the rock surface by calculating the resistance factor as well as the residual resistance factor. Also, the effect of the injection rate of the polymer solutions has been studied. The results show that xanthan solution is tolerant of high salinity (20 %), while PAA solution is very sensitive to salt. Both polymer solutions show a pseudoplastic flow as a function of the shear rate. The core sample experiments show that both polymer solutions suffer a reduction in the adsorption rate with salinity increase. However, xanthan shows acceptable values even with a salinity up to 20 % and a temperature of 60 °C. Therefore, xanthan can be recommended to shut off water in high salinity and high temperature reservoirs. It was also found that the lower the injection rate the higher the adsorption on the rock surface.     

Asymmetric Polymer Bridging Between Starch‐Coated Colloidal Particles and Pulp Fibres by Cationic Polyacrylamide

Internal sizing agents are commonly used as additives in papermaking to impart hydrophobicity to paper. They are commonly added in the form of colloidal particles, stabilized by cationic starch. As an example we studied the deposition of micron‐sized Alkyl Ketene Dimer (AKD) particles on pulp fibres by cationic polyacrylamide (cPAM), a common flocculent. It was found that cPAM did not adsorb on AKD particles stabilized by cationic starch. Despite this inability to adsorb, cPAM was found to drastically improve the deposition of AKD particles on pulp fibres. This deposition was ascribed to asymmetric polymer bridging, a phenomenon observed by us before, while studying clay deposition on fibres by polyethylene oxide. In asymmetric polymer bridging between two types of particles, the bridging polymer first adsorbs on one type of particle, since it is unable to adsorb on the second type. Asymmetric polymer bridging occurs when the enthalpy gain on both surfaces exceeds the entropy loss. The kinetics of AKD deposition on fibres was found to agree with the predictions of the asymmetric bridging theory. In addition, an increase in bond strength with time was found, due to starch and cPAM reconfiguration. The increase in AKD retention by cPAM is also observed in experiments on a laboratory twin‐wire sheet former. Asymmetric polymer bridging by cPAM between starch‐coated AKD particles and fibres is compared with classical polymer bridging by cPAM between fibres and AKD particles coated by carboxymethylcellulose.     

Evaluation of hydrophobically associated polyacrylamide‐containing aqueous fluids and their potential use in petroleum recovery

Acrylamide and tridecyl acrylate copolymers were synthesized by micellar copolymerization to obtain water‐soluble, hydrophobically modified polymers. Rheological properties of the obtained polymer solutions were evaluated and compared to those of solutions of a commercial polyacrylamide currently used in the petroleum industry. The behavior of the copolymer solutions was studied as a function of the variation of hydrophobic monomer content incorporated in the copolymer as well as the salt content of the aqueous medium, for diluted and semi‐diluted regimens. Comparative studies of such effects on the intrinsic viscosity and the critical concentration of those polymers were conducted. The increase in hydrophobic monomer content produced a sudden increase in the bulk and absolute viscosity of the polymeric solutions, a trend that was more intense from a certain concentration typical for each polymer. Salt addition led to lower bulk viscosity caused by a stronger interaction among hydrophobic groups, resulting from minimized exposure of such groups and water. The same effect was observed for the critical concentration. A comparison of the synthesized polymers with industrial polyacrylamide showed that the synthesized polymers were characterized by advantageously high shear strength and high salt resistance. However, in the absence of salts, higher copolymer amounts were needed to prepare solutions whose viscosity was the same as that of commercial polyacrylamide. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3686–3692, 2004