Water Soluble Polymers

Hydrophobically modified poly(acrylic acids) (HMPAA’s) are commonly used as primary, pH sensitive, stabilizers for oil-in-water emulsions. It has been shown that electrosteric stabilization is one of the mechanisms. An important factor in steric stabilization is the breadth of the extension of stabilizing molecules from the discontinuous phase interface into the continuous phase. It must be substantial. This dictates that the stabilizing molecules be of substantial hydrodynamic volume. However, polymers with large hydrodynamic volumes diffuse slowly through solution (Brownian diffusion coefficients on the order of 10⁻¹² to 10⁻¹³ m²/s). This can be a restriction to their use as emulsifiers, since the kinetics of emulsion coalescence begin to compete with the kinetics of interfacial adsorption of the stabilizing species. With these things in mind, we have developed a technique, based on drop volume tensiometery, which can be used to determine the “adsorption/diffusion” coefficients that characterize the kinetics of polymers adsorbing at oil/water interfaces. We have previously used this technique to show that increased hydrophobic content and increased crosslink density enhance adsorption efficiency for HMPAA’S. The current work is a pH dependence study which shows that neutralizing HMPAA in aqueous solution decreases its adsorption efficiency.

The effect of solids concentration on the adsorption and conformation of polymers at solid/liquid interface was investigated using depletion adsorption and fluorescence techniques. The fluorescence of pyrene labeled polyethylene oxide at silica/water interface as a function of solids concentration revealed a surprisingly measurable change in polymer conformation as the solids content was increased. Adsorption density as well as coiling of the polymers was found to decrease with increase in solids concentration. These changes are correlated with the rheological behavior of the suspensions.

Poly(vinyl alcohol) (PVA) is a water soluble polymer whose water solubility depends on its degree of hydrolysis, molecular weight, and tendency to hydrogen bond in aqueous solutions. PVA exhibits both upper and lower critical solubility temperatures and can be readily solubilized in water. For long-term dimensional stability, a new method involving freezing and thawing of aqueous PVA solutions was used to prepare insoluble PVA gels held together by physical crosslinks formed predominantly by crystallites. Solutions containing 15% PVA were frozen at −20 °C for, 1, 8, and 18 hours and thawed at room temperature for 30 minutes to 6 hours. These cycles were repeated for up to 10 times. The ensuing gels were analyzed by equilibrium swelling studies. Each cycle led to further crystallization of PVA leading to stable gels. Differential scanning calorimetry was used to analyze the gel morphology. Degrees of crystallinity varied from 4 to 16% on a swollen basis. Upon exposure to swelling temperatures of up to 37 °C, the crystallites of these gels remained remarkably stable for a period of several weeks. However at 60 °C relatively fast crystal melting occurred. The dissolution process was followed using complexation with boric acid.

Expressions describing the influence of additives and impurities on the kinetics of mineralization and demineralization have been derived from an interfacial tension point of view. In aqueous solution, the Lifshitz-van der Waals interfacial tension component changes very little, but the Lewis base (or electron-donicity) surface tension parameter varies markedly as a function of additive and impurity concentrations. The inhibiting effects of simple cations on crystal growth in solution may result from the increase in interfacial tension accompanying their adsorption on the surfaces. In the case of polymers or macromolecules, the kinetics of crystallization will not only depend upon the substrata but also the surface properties of the additives. Nucleation of calcium phosphate phases was observed only on surfaces having low solid/solution interfacial tension and relatively high electron-donicity of the solid surfaces. Such properties were found for human serum albumin immobilized on polymer solid surfaces of poly(methyl methacrylate) (PMMA) and poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP), and following radiofrequency glow discharge (RFGD) treatment which mimicked the adsorption of impurity OH⁻ ions on the surfaces.

The influence of several natural and synthetic additives containing hydroxy and/or carboxyl groups on the kinetics of crystal growth of hydroxyapatite (HAP) at sustained supersaturation has been investigated using the constant composition method. Addition of low levels (0.25 to 5 parts per million) of fulvic acid, tannic acid, benzene hexacarboxylic acid, and poly(acrylic acid) to supersaturated calcium phosphate solutions has an inhibitory influence upon the rate of crystal growth of HAP. Salicyclic acid, under similar experimental conditions, is an ineffective HAP growth inhibitor. Kinetic analysis suggests Langmuir-type adsorption of added ions on the HAP surfaces with a relatively high affinity for the substrate in the concentration range investigated.

Sodium polyvinylphosphonic acid (SPVPA) was synthesized using vinyl phosphonyl dichloride and azobisisobutyronitrile (AIBN) as a radical initiator. The homopolymer obtained was characterized by molecular weight, purity and impurities by using gel permeation chromatography and NMR. The pure polymer was used to assess the influence on crystal growth kinetics of hydroxyapatite (HAP) in vitro. Briefly, the experimental solution supersaturated with respect to hydroxyapatite (HAP) was prepared from stock solutions of CaCl₂, K₂HPO₄, KH₂PO₄, and NaCl. The crystal growth was initiated by adding pure seeds of HAP at 37 °C. The precipitation kinetics was followed using a pH-stat and measuring calcium phosphate in the solution. The effect of the polymer on the crystal growth kinetics was assessed, and it was found that the polymer inhibited the growth at 10⁻⁵ M. The inhibitory effect of the polymer was related to its adsorption onto the growing crystals. The adsorption parameters were derived from an adsorption isotherm-yielding a K value of 1,950 m1/mM and the N value of 0.038 mM/m². A topical application of 1% solution of the polymer onto teeth was effective in reducing calculus formation by 18% in rat model system. SPVPA was also very effective in reducing adsorption (>90%) of radiolabelled bacteria, Streptococcus mutans, and Actinomyces viscosus, onto saliva-coated hydroxyapatite beads and disks. The polymer was also tested in short-term human clinical studies and showed that 1% and 3% solutions significantly (P = 0.05) reduced bacterial plaque film on teeth by 21 to 36%, respectively. Collectively, the data indicated that the sodium polyvinylphosphonic acid has the potential to prevent soft and hard dental deposits on teeth.

Adsorption of hydroxypropylcellulose (HPC) on hydroxyapatite (HAP) in the presence of sodium dodecylsulfate (SDS) and its effect on stability of the HAP suspension were studied. Although the adsorption amount of HPC was low in the absence of SDS, it increased with the amount of SDS after the formation of the intermolecular complex between them on the surface of HAP. The adsorption of SDS by HAP is due to electrostatic attractive force between dodecylsulfate anion (DS-) and Ca²⁺ on the surface and due to isomorphous substitution of the sulfate group of DS- for the surface phosphate ion. Formation of the surface complex is by virtue of hydrophobic interaction between hydrophobic groups of DS- thus adsorbed and those of HPC captured from the bulk solution. Adsorption of SDS by HAP was reversible with respect to dilution with its solvent (a NaCl solution). As for HPC, however, the desorption was rather complicated, depending on the dilution procedure whether with water or with an aqueous solution of a given concentration of SDS. This observation suggests that the adsorbed SDS is offering the adsorption sites for HPC on the surface after implantation of the hydrophobic groups on the surface. Mean diameter (d) of the secondary particles of HAP was determined by means of a Coulter counter as a function of concentrations of SDS and HPC. The d-value decreased after attaining a maximum with an HPC concentration when an SDS concentration was kept constant. This result suggests that an SDS-HPC complex plays a role of a dispersing/flocculating agent against the HAP suspension. In fact, the behavior of the complex is quite similar to that of a polyelectrolyte as a dispersing/flocculating agent.

Calcium carbonate scale formation in geothermal wells and other industrial processes is a persistent problem. Remediation of this problem may be achieved through the addition of water soluble polymers which may influence nucleation, crystal growth and the particle characteristics of the precipitated calcium carbonate. In the present work we have investigated the effect of water soluble copolymers of maleic acid with N-Vinyl Pyrrolidone, Vinyl Acetate, Methyl Methacrylate and Styrene groups on the kinetics of calcium carbonate crystal growth. The effectiveness of the polymers tested on the kinetics of calcium carbonate scale formation was evaluated using the constant supersaturation methodology. The water soluble copolymers tested, were all found to be effective inhibitors of calcium carbonate formation at concentration levels lower than 1 ppm. The crystal growth rates of calcite showed a drastic decrease, while for inhibitor concentrations exceeding 0.25 ppm crystal growth was completely suppressed. It is suggested that the activity of the inhibitors is due mainly to the presence of the maleic acid entity in the copolymer, which promoted the adsorption of the copolymer onto the growing solid particles. Kinetics analysis of the rates measured in the presence and in the absence of the polymers, provided additional evidence that adsorption of the macromolecules on the active growth sites of calcite seed crystals was responsible for the inhibition of crystal growth.

Addition of carboxylate-containing polymeric materials to a metastable supersaturated calcium carbonate solution greatly reduced calcite crystal growth rates at constant supersaturation and pH = 8.5. Calcite crystallization rates were decreased to half their value in pure solutions by a tannic acid concentration of about 0.3 ppm (parts per million); a fulvic acid concentration of about 0.2 ppm; and a poly(acrylic acid) concentration of about 0.0175 ppm. An equation relating the calcite crystallization rate and the additive concentration follows an expression based on a Langmuir adsorption model. However, the Langmuir isotherm plot has two linear segments suggesting that these polyelectrolyte inhibitors may selectively adsorb initially at the fastest growing crystal faces. This relation between polyelectrolyte concentration and calcite growth rates implies inhibition by carboxylate-containing polymeric materials involves blockage of crystal growth sites on the calcite surface.

Phosphate based chemical treatment programs are used in several industrial applications in order to control corrosion on low carbon steel metal surfaces. In cooling systems, for example, phosphates are added to the cooling water to prevent corrosion on low carbon steel heat exchangers and pipes. Because there is a tendency to run cooling systems at higher cycles and process operation at higher temperatures, calcium phosphate scale has become more common in cooling water systems. A new terpolymer able to provide calcium phosphate scale control and dispersion of suspended solids has been developed. The inhibitor has been shown to be effective in highly cycled cooling water and at relatively high temperatures. The efficacy of the new terpolymer at different monomer ratios and molecular weight was also established.

The inhibitory efficiency of polymeric inhibitors against the precipitation of common mineral scales in industrial processes could be described quantitatively using a semi-empirical model based on nucleation theory and laboratory experimental observations. The minimum effective inhibitor concentration (C_inh, mg/1) which is needed to prevent precipitation at a given degree of supersaturation can be estimated by: C_inh = (l/b_inh) log (f_St_p/t₀), where b_inh is the efficiency of the inhibitor (l/mg), t_p is the inhibition time or protection time needed for the system (seconds), t₀ is the nucleation induction period for the mineral at a given condition in seconds, and f_S is the safety factor (e.g., 2). Model parameters have been measured for typical scale minerals such as calcite and barite with eight scale inhibitors which have been commonly used in industrial processes, including polyacrylates and their derivatives (PAA, SPA, and PPCA) and poly-phosphonates (HEDP, NTMP, HDTMP, DTPMP, and BHPMP). This semi-empirical model has been demonstrated to be accurate in predicting the minimum effective inhibitor concentrations needed to protect a system from scaling comparing to both laboratory experimental simulation results using a high-temperature/high-pressure flow-through apparatus and preliminary observations in oil and gas production systems.

Waters containing high levels of silica can result in severe fouling of a water treatment system. In certain cases, high silica levels may become the limiting factor as to the level of RO recovery achievable. The recent usage of polymeric antiscalants has resulted in the attainment of silica levels far in excess of the generally recognized maximum of 150 parts per million (ppm) as SiO₂. The results of comparative tests incorporating the usage of two polymeric antiscalants for control of silica deposition in reverse osmosis (RO) systems are presented.

The formation and adherance of calcium sulfate dihydrate, hemihydrate, and anhydrite scales is a problem in many heat exchanger applications where the equipment is fed with waters containing high levels of calcium and sulfate. Industrial processes are affected by the deposition of sulfate scales including cooling, boiler, desalination (i.e., flash distillation), and oil recovery. Historically, polymeric and non-polymeric additives have been used in these processes to prevent the formation and deposition of scaling salts. In the present study, the influence of polymeric additives on gypsum (CaSO₄•2H₂O) scale on heat exchanger surfaces has been investigated. It has been observed that polymer composition, molecular weight, ionic charge and charge density, and polymer dosage have a significant impact on the performance of the polymeric additive.

High molecular weight water-soluble topologically structured copolymers of acrylamide (AMD) and 2-(acryloyloxy)ethyltrimethylammonium chloride (AETAC) were synthesized by inverse emulsion polymerization process. Copolymers with various structures were attained by introducing appropriate amounts of branching and chain-transfer agent in the monomer feed. Polymer structure was characterized by solution rheological properties comprising the measurements of the viscosity of a 0.2% polymer solution in de-ionized water (Bulk Viscosity, BV) and the viscosity of a 0.1% polymer solution in 1.0 N NaCl (Standard Viscosity, SV). The synthesized polymers were then subject to flocculation test with several types of sludge. De-watering rate, filtrate turbidity, and percent cake solids were used to ascertain the efficiency of flocculation. It was found that the polymer with a high BV and a low SV had exceptional performance on certain types of sludges. A statistically designed experiment was conducted to reveal the quantitative relationships between the structure parameters (BV and SV) and the performance characteristics.

The drive for increased water conservation in industrial plants has expanded the use of non-traditional sources of makeup water for cooling towers. Studies of the use of recycled wastewater for tower makeup usually focus on process changes, but the focus of this paper is on the design process of custom water treatment programs for many kinds of water sources. Special problems unique to each type of non-traditional source water are identified and discussed. The use of computer software in guiding the formulation process is also discussed in detail. The components of cooling water formulations, including water soluble polymers, must be selected to deal with the unique set of problems presented by each type of water. Formulations must also be compatible with process changes, and not interfere with other processes downstream. As with other more traditional programs, cost and performance factors are critical.

Alkaline hair relaxers used to straighten excessively curly hair, usually African-American hair, often cause considerable hair damage. One of the effects of straightening the hair with relaxers is a loss in tensile strength due mainly to breakage of disulfide and hydrogen bonds. This loss in tensile strength leaves the hair more susceptible to breakage and cuticle erosion from subsequent grooming. The damaging effects of relaxer treatment are not limited to disulfide bond breakage alone. Another cause of hair damage during relaxing is swelling of hair fibers during the highly alkaline treatment. During a conventional hair relaxer treatment, the hair swells by 50% or higher, and another 20% upon rinsing. When hair swelling is not controlled, the hair develops radial and longitudinal cracks again rendering the hair susceptible to breakage from combing and brushing. This study presents results on the application of cationic polymers to strengthen hair during relaxing, and non-ionic polymers which control hair swelling.

Ultra-high molecular weight (5–17 × 10⁶ daltons) amphoteric copolymers prepared from acrylamide, acrylic acid, N-(dialkylaminomethyl)- and/or N-(trialkylammoniomethyl)-acrylamide are shown to be excellent finishing agents for natural fibers and superior to the finishing agents prepared from natural resources such as hyaluronate and xanthan gum. The detergents containing the copolymer, inorganic builders and a small amount of penetrating agent showed detergency comparable to commercial detergents.