Different Degrees Of Neutralization Research Articles

Study of new commercial collectors for the recovery of coarse quartz particles in iron ore flotation

Currently, a small range of commercial collectors is available for the use in reverse iron ore flotation at Vale. This input represents a considerable unit cost, being essential for the concentration of low content itabiritic iron ores. The present work evaluated the reverse cationic flotation of an itabiritic ore with low iron content (39.6 % Fe) from the Iron Quadrangle (BR) in bench scale tests, focusing on the use of new collectors to remove coarse quartz. The sample presents 19% of its particles as oversize in the 0.150 mm sieve. The poor flotation of coarse quartz particles (>0.150 mm) causes significant problems in various iron ore flotation circuits by contaminating the concentrate. The study evaluated the performance of 10 new collectors from the etheramine family with different degrees of neutralization and at different collector dosages. The flotation process variables were set as industrially practiced at the Cauê iron ore plant (BR). In tests varying the specific collector dosage, the non-neutralized etheramines showed improved performance compared to the current 50% neutralized etheramine used in the plant, achieving industrial targets: concentrate SiO2 content rate lower than 4.5% (1.4%), tailings iron content lower than 23% (18.94%), metallurgical recovery greater than 66% (74,8%), and Gaudin Selectivity Index greater than 6.6 (10.5). The 0.150 mm oversize in the concentrate, mostly coarse quartz particles, was reduced from 5.7% down to 1.2%, indicating the potential for the industrial application of non-neutralized etheramines in the recovery of coarse quartz.

Effect of neutralization on physicochemical/mechanical properties of hydroxypropylmethylcellulose acetate succinate

Hydroxypropylmethylcellulose acetate succinate (HPMCAS) as an enteric coating polymer, has been used in organic solvent system due to its poor water solubility. A facile and effective method was proposed to prepare aqueous HPMCAS polyelectrolyte coating from granule grade HPMCAS particles without using any emulsifier or plasticizer. Aqueous HPMCAS solutions and their corresponding films with various types of neutralizers and different degrees of neutralization have been prepared. NH4HCO3 was found to be the most efficient neutralizer for HPMCAS and not only the solutions displayed long-term stability but the films presented good enteric properties (dissolve at pH 5.2) and high tensile strength of 52 MPa. This study facilitates the understanding of the effect of neutralization on aqueous HPMCAS solutions and their corresponding films, in addition to developing a stable aqueous enteric coating formulation.

Polymer conformation in supramolecular complexes with wedge-shaped ligands: Exploring the impact of the liquid-crystalline organization

The chain conformation of poly(2-vinylpyridine) (P2VP) complexed by 4-((4-((3,4,5-tris(dodecyloxy)benzoyl)oxy)phenyl)diazenyl)benzenesulfonic acid at different degrees of neutralization (DN) was addressed by small- and wide-angle neutron scattering technique. To get information on the conformation of P2VP chains spatially confined within lamellar and columnar mesophases at different DNs, the complexes were prepared from a blend of protonated and deuterated P2VP. The 2D scattering patterns of extruded fibers show that at low DN the complex self-organizes in a lamellar phase. The inertial mean distances in the direction parallel and perpendicular to the fiber axis reveal the formation of compact disc-like globules of individual P2VP chains at DN = 25 and 33%. With the increase of DN the interaction between the neighboring side groups along the backbone increases. This results in formation of hexagonal columnar phase at DN = 50%, in which the P2VP macromolecules are confined within cylindrical channels forming most probably a disordered helical conformation. At DN = 1.0, the enhanced rigidity of the complex hinders the accommodation of the ligands at the interface with polymer chain. This results in appearance of non-bonded side groups in the columns giving rise to a poorly-ordered structure. In contrast to more rigid chains of poly(4-vinylpyridine), the transition from lamellar to columnar mesophase in P2VP occurs at lower DNs, indicating a significant role of the chain flexibility in the formation of ordered structures.

PePC-SAFT: Modeling of polyelectrolyte systems 2. Aqueous two-phase systems

This work considers aqueous two-phase systems (ATPS) containing one polymer–polyelectrolyte as well as one salt. To model the liquid–liquid equilibria (LLE) of these systems, the recently presented model pePC-SAFT has been employed. ATPS containing poly(acrylic acid) of different degrees of neutralization or poly(vinyl pyrrolidone), respectively, were considered. The binary interaction parameters used between water–poly(acrylic acid) and water–poly(vinyl pyrrolidone) were adjusted to vapor–liquid equilibrium (VLE) data of these systems. ATPS consisting of poly(vinyl pyrrolidone)–water–sodium sulfate were predicted as function of temperature as well as of molar mass of the polymer. For poly(acrylic acid) systems, ATPS were predicted as function of charge density (degree of neutralization) for different types of salt. For these calculations, the polyelectrolyte model parameters were determined from the non-charged polymer whereas the effect of increasing charge density has been purely predicted by the model. Using this approach, it is possible to predict the shrinking of the liquid–liquid equilibrium region with increasing charging of the polyelectrolyte.

Electrochemical synthesis of perfluoropolyethers by the Kolbe method

Electrochemical dimerization of hexafluoropropylene oxide dimer and trimer acids on SU-2000 glassy carbon, bulk platinum, and SU-2000 electrodes modified with platinum-group metals in acetonitrile in the presence of water was studied at various concentrations of the starting substance and different degrees of neutralization of the starting acid. Also, the possibility was examined of obtaining some perfluoropolyethers in a single process by cross-condensation of several starting perfluorocarboxylic acids, followed by separation of the products by physicochemical methods.

Thin Film Morphologies of Block Copolymers Complexed with Wedge-Shaped Liquid Crystalline Amphiphilic Molecules

Wedge-shaped molecules with a sulfonic group at the tip have been incorporated into a poly(2- vinylpyridine)-b-poly(ethylene oxide) (P2VP-b-PEO) diblock copolymer via proton transfer at different degrees of neutralization. The protonation of P2VP was monitored by means of Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The thin film morphology of the complexed block copolymers has been studied by scanning force microscopy and X-ray reflectivity. The complexes exhibit strongly microphase-segregated patterns comprising smectic layers of the complexed P2VP blocks, oriented parallel to the substrate throughout the whole film with the embedded PEO domains. For the complex with a degree of neutralization of 0.50 ordered amorphous PEO cylinders are observed oriented perpendicular to the substrate. For a degree of neutralization equal to 0.25 initially also perpendicular PEO cylinders are formed, but upon solvent-vapor annealing they partially merge, resulting in a mixed lamellar-cylindrical morphology. In all cases an extra surface layer is formed at the substrate. Thus, for the first time we have demonstrated that a block copolymer thin film structure can easily be controlled by the degree of neutralization of one of the blocks.

Formation of wormlike micelle in a mixed amino-acid based anionic surfactant and cationic surfactant systems

Formation of wormlike micelles in mixed anionic/cationic system without the addition of any salt has been studied. Amino-acid based anionic surfactant N-dodecylglutamic acid (LAD), which is practically immiscible with water at 25 °C upon neutralization by 2 , 2 ′ , 2 ″ -nitrilotriethanol (TEA) forms small micellar aggregates and the solution behaves like a Newtonian fluid. The rheological behavior of LAD/water/hexadecyltrimethylammonium bromide (CTAB) and LAD/water/dodecyltrimethylammonium bromide (DTAB) systems were investigated at different degrees of neutralization of the LAD depending on the concentration of the cationic surfactants and on temperature. Addition of CTAB to the dilute aqueous solution of the LAD–TEA- x (the neutralized product, where x represents the mole ratio of TEA) causes one dimensional micellar growth. After certain concentration the elongated micelles entangle forming a rigid network of viscoelastic wormlike micelles. Thus formed viscoelastic solutions follow Maxwellian behavior over a wide range of frequency and thus are considered to consist of transient network of wormlike micelles. By varying the degree of neutralization from 1:1 via 1:1.5 to 1:2 (molar ratio) phase and rheological behavior were modified in that the highly viscous region of viscoelastic wormlike micelles shifted to higher CTAB concentrations and no maxima in the zero-shear viscosity could be observed for the higher degree of neutralization of the LAD (1:1.5 and 1:2). However, the obtained rheological parameters showed scaling relationships that were consistent with the living polymer model. The zero-shear viscosity decays exponentially with temperature following Arrhenius behavior. The flow activation energy calculated from the Arrhenius plot is very close to the value reported for the typical wormlike micellar solution. In contrast to CTAB no formation of viscoelastic wormlike micelles could be observed with DTAB, although, the solution viscosity increases. The elongated micelles could not entangle to form a rigid network of wormlike micelles in this system. For the first time viscoelastic wormlike micelles could be obtained in salt-free mixed anionic/cationic surfactant systems.

Morphological Transformation of [60]Fullerene-Containing Poly(Acrylic Acid) Induced by the Binding of Surfactant

Water-soluble pH-responsive [60]fullerene end-capped poly(acrylic acid) (PAA85-b-C60) was synthesized using atom-transfer radical polymerization (ATRP) technique. The unusual morphological transformation of the polymer induced by the binding of nonionic surfactant Triton X-100 (TX100) at different degrees of neutralization (alpha) was investigated using isothermal titration calorimetry (ITC), UV-vis spectroscopy, dynamic light scattering (DLS), and transmission electron microscopy (TEM). For the 5 mM (monomer concentration) polymer solution at pH < 4, approximately 1.3 mM TX100 binds specifically to C60 domains of the polymeric micelles driven by hydrophobic interaction, which induces a structural transformation of the polymer from a large compound micelle with a radius of 110 nm to a dense precipitated spherical polymer/surfactant complex (PSC) with a radius of 500 nm. The precipitates are resolubilized by a wetting layer of TX100 in excess surfactant (> 1.7 mM in the polymer solution). The binding is significantly weakened and the complexation is disrupted with increasing pH, where the interaction completely ceased at pH > 6.

Dynamic mechanical and thermal characteristics of homopolymers and copolymers containing arylene ether ketone units with carboxylic side groups and their salts

Properties of a poly(arylene ether ketone) with carboxyl side groups, copolymers containing units of this homopolymer, and their salts with different degrees of neutralization by alkali metals were studied by the methods of dynamic mechanical analysis, thermogravimetric analysis, and differential scanning calorimetry. By varying the nature of a metal atom and the degree of neutralization of carboxylic groups of a homopolymer and their content in copolymers, one may change the properties of polymers, including their ability to form ion pairs and, hence, their glass transition temperatures. For polymer salts at the 100% neutralization of carboxylic groups, the storage modulus and the glass transition temperature are shown to increase with decreasing the radius of the metal ion. The thermal stability of poly(arylene ether ketone) with carboxylic side groups and copolymers with different contents of such groups may be controlled by varying the nature and content of the introduced metal.

Binding of Dodecyltrimethylammonium Bromide to pH-Responsive Nanocolloids Containing Cross-Linked Methacrylic Acid−Ethyl Acrylate Copolymers

The binding of dodecyltrimethylammonium bromide (DoTab) to cross-linked methacrylic acid-ethyl acrylate (MAA-EA) copolymers with various MAA/EA molar ratios at different degrees of neutralization (alpha) was quantitatively studied using isothermal titration calorimetry, dynamic light scattering, surfactant selective electrode, and electrophoresis techniques. The surfactant binds to the polymers at all degrees of neutralization, but via different mechanisms. When alpha is sufficiently high, the binding is primarily electrostatic interaction between the surfactant and ionized polymer chains, which is reinforced by the micellization of electrostatically bound surfactant molecules. The saturation takes place at charge ratio ([DoTa(+)]/[ approximately COO(-)]) close to 1, indicating that the binding is a one-to-one charge neutralization between the cationic surfactant headgroups and anionic carboxylate sites of the polymers. When alpha is low, the binding of DoTab to the unneutralized polymers is driven by the hydrophobic interaction. The onset of hydrophobic binding takes place at DoTab concentration as low as 0.01 mM in 0.05 wt % polymer solution, where the saturation occurs at C(DoTab) approximately 0.19 mM and the amount of bound surfactant is approximately 0.09 mmol of DoTab/(g of polymer) at saturation concentration. The binding results in the formation of the polymer-surfactant complex. For the polymer with low MAA/EA molar ratio, the complex coagulates at a higher DoTab concentration that leads to phase separation; however, for polymers with high MAA/EA molar ratio, the complex remains dispersed and the mixture is stable even at high DoTab concentration.

Interaction between Polyelectrolyte and Oppositely Charged Surfactant: Effect of Charge Density

The binding of dodecyltrimethylammonium bromide (DoTab) to poly(acrylic acid) (PAA) at different degrees of neutralization (α) was investigated using isothermal titration calorimetry (ITC) and laser light scattering (LLS) techniques. The surfactant binds to the polymer at all α; however, the mechanism varies. When α is lower than a critical value (αC), the hydrocarbon chains of DoTab cooperatively bind to the apolar segments of PAA driven by hydrophobic interaction at very low DoTab concentration (CDoTab ≤ 0.2 mM). In this binding region, the ITC profile exhibits a significant exothermic peak and the mixture precipitates, which is attributed to the interchain complexation via hydrogen bonding induced by the binding. The precipitation is soon resolubilized with further addition of surfactant as more DoTab micelles are bound to the polymer backbones with their ionic headgroups extending outward. When α > αC, the hydrophobic binding ceases as the polymer is progressively ionized and DoTab binds to the charged polymer chains driven by electrostatic attraction. The condensed counterions on the charged polymer chains are released via the ion-exchange process, resulting in an endothermic maximum on the ITC profile. The value of αC determined from ITC is approximately 0.3, which is reasonably close to the theoretical value derived from the Manning's counterion condensation theory (approximately 0.35).

Physicochemical Properties of Acidic Ammonium Phosphate Slurries

Acidic ammonium phosphate slurries with different degrees of neutralization were obtained by neutralizing dilute phosphoric acid with ammonia. They were then concentrated to different water contents. The effects of the degree of neutralization and water content on the density, boiling point, fluorine volatility, thermal conductivity, and viscosity were studied. The results indicate that the density of the slurry increases with decreasing water content and/or neutralization degree. The density of acidic ammonium phosphate slurries can be calculated by the formula ρ = k[ρSxv + ρL(1 − xv)]. The experiments show that the boiling point of an acidic ammonium phosphate slurry increases with decreasing water content and/or neutralization degree. When the water content is below 40%, the boiling point strongly depends on the water content. The fluorine in the slurry, brought in with wet-process phosphoric acid, volatilizes when the slurry is heated. The volatility increases with increasing concentration of the slurry. The volatilization is significant in low range of neutralization degrees. It increases sharply with decreasing neutralization degree. Increasing the degree of neutralization above 0.6 causes the volatility to drop to a rather low level. The thermal conductivity of acidic ammonium phosphate slurries varies from 0.471 to 0.608 W·m-1·K-1. For an acidic ammonium phosphate solution, the thermal conductivity increases with increasing water content or neutralization degree. However, for such a slurry, the presence of a crystalline phase makes the thermal conductivity increase with decreasing water content. The viscosity is the lowest for a slurry with a neutralization degree of 0.52. The viscosity increases with decreasing water content. The slurry behaves as a Newtonian fluid when its water content is above 40%. However, it switches to act as a pseudoplastic fluid when its water content decreases below 40%. Increasing the temperature can reduce the viscosity.

Self-Assembly in SomeN-Lauroyl-l-glutamate/Water Systems

Acylglutamate is a divalent anionic surfactant whose properties are affected by its degree of neutralization. In this study, we present phase maps for aqueous systems of the potassium (LGP) and triethanolamine salts (LGT) of N-lauroyl l-glutamic acid, at different degrees of neutralization. A cubic phase forming between the isotropic micellar and the hexagonal phase was detected in both LGP/water and LGT/water systems. The stability of this cubic phase was promoted by increasing the degree of neutralization. The lattice parameters of the phase were determined by small-angle X-ray scattering (SAXS). SAXS spectra from samples of this cubic phase could be indexed to the crystallographic space group Pm3n. 1H NMR self-diffusion measurements have also been performed in the isotropic micellar and cubic regions. The self-diffusion coefficient of the surfactant decreases with increasing its concentration. In the cubic phase, the self-diffusion is of the order of 10-13 m2 s-1, demonstrating that the cubic phase consists of discrete micelles.

Thermal stability and bonding in the silver complexes of ethylenediaminetetraacetic acid

The solid silver-EDTA complexes AgH 3Y·(3/4)H 2O; Ag 2H 2Y; Ag 3HY and Ag 4Y·(1/2)H 2O (Y −4 is ethylenediaminetetraacetate anion) obtained by reaction of the Ag + ions with sodium salts of EDTA in different degrees of neutralization in aqueous media have been characterized by means of potentiometric titrations, IR spectrometry, elemental analysis and powder X-ray diffraction (XRD). Thermogravimetry (TG) and Differential Scanning Calorimetry (DSC) were used to investigated the thermal stability of the complexes as well as the decomposition pathways. The thermoanalytical results associated with infrared data lead to the conclusion that the silver-carboxylate group bonding is primarily ionic.

Stable aqueous dispersions of some cataphoretically applicable film-forming resins

Dispersion of two film-forming resins with amine functional groups in water was studied: a quaternary copolymer with 2-dimethylaminoethyl methacrylate as amine co-monomer (Trak) and an aminated epoxy resin (Romhydrol). Their concentrated solutions, about 72% by weight, in coupler solvents were dispersed in water containing formic or acetic acids to provide different degrees of neutralization and concentrations of 13–15%, as required for industrial electrodeposition, and of double concentration. The more diluted dispersions were characterized by viscosity, surface tension and turbidity and the concentrated dispersions, being gels, by rheological properties. Trak, having a higher content of amine groups, gives stable 15% dispersions, while Romhydrol, with a lower content of such groups, gives less stable 13% dispersions. Concentrated dispersions are of interest especially for storing Romhydrol. In both cases dilution can be done by gentle stirring.

Effect of the degree of neutralization on the micellization of block ionomers

The effect of neutralization on the micellization of polystyrene-b-poly(acrylic acid) (PS-b-PAA) was investigated by static light scattering (SLS) and small-angle X-ray scattering (SAXS). The block copolymers, present initially in single chain form in either dioxane or benzene–methanol (90/10 (v/v)), were neutralized to different degrees by the addition of cesium hydroxide dissolved in methanol. The solutions were simultaneously monitored by SLS. It was found that micelle formation began near 5% neutralization. The normalized scattered light intensity at 90° (I90/c) increased dramatically in the neutralization range between ca. 10 and 60%. For neutralization degrees between 60 and ca. 100%, I90/c did not change significantly with a further increase in the percent of neutralization. In the second part of the study, two block copolymers, PS(600)-b-PAA(34) and PS(600)-b-PAA(45) (the number of monomer units is given in parentheses), were prepared from benzene–methanol (90/10 (v/v)) with different degrees of neutralization: 5, 25, 60, 100, and 150%. The resulting solutions were freeze-dried and the dried samples were redissolved in toluene. These samples were investigated by SLS and SAXS. By SLS, the aggregation numbers (f) were found to be the same between 5 and 60% neutralization. An increase in f was observed in going from 60 to 100%; i.e., f increased from 82 to 92 for PS(600)-b-PAA(34), and from 79 to 110 for PS(600)-b-PAA(45). The f values for the two block copolymers at 150% neutralization were found to be the same as those for 100% neutralization. The core radii values (Rcore) were measured for the neutralized PS(600)-b-PAA(45) samples at 0.05 g/mL in toluene by SAXS. The Rcore values increased from 5 to 60% neutralization, remained constant from 60 to 100%, and increased again in the range from 100 to 150%. The results are explained by dynamic considerations. For low percent neutralization, between 5 and 60%, the micelles and single chains are proposed to be in a dynamic equilibrium state. For higher percent neutralization, between 60 and 100%, the dynamics are probably much slower. Keywords: block copolymers, micelles, ionomers, light scattering, small angle X-ray scattering (or SAXS).

A quantitative description of the viscometric behaviour of partially neutralized poly(acrylic acid) in aqueous solutions studied by the isoionic dilution method

The intrinsic viscosity, [η], and the Huggins constant, κ′, of a poly(acrylic acid) (PAA) sample have been measured at different degrees of neutralization, i, ranging from i=0.25 to i=1.00 and different ionic strengths, I, in the region 1.0 × 10 −4 M< I<1.0 × 10 −1 M, using the isoionic dilution method in aqueous solutions. The results show that the variations of [η] and κ′ as a function of I are given by scaling laws characterized by constant exponents irrespective of the i value of the PAA sample investigated. An empirical equation giving the reduced viscosity of the PAA sample as a function of its concentration for various values of i and I has been obtained.

Phase Separation Phenomena and Viscosity Enhancements in Aqueous Mixtures of Poly(styrenesulfonate) with Poly(acrylic acid) at Different Degrees of Neutralization

Interactions between poly(styrenesu1fonate) (PSS) and poly(acry1ic acid) (PA) in aqueous solution have been studied, with and without added salt, and at various degrees of neutralization (a) of PA. Equilibrium phase diagrams have been determined, and the viscosities of monophasic mixtures have been measured. Both types of experiments reveal striking effects of a on the PA-PSS interactions. Salt-free mixtures with fully or partially neutralized poly(acry1ic acid) phase separate segregatively, except at very low a where, instead, an association between PA and PSS occurs. The association is evidenced by a dramatically increased viscosity, relative to solutions of PA or PSS alone, in semidilute mixtures. Addition of salt (1 M NaC1) results in an increased two-phase area at all a, and in the appearance of an associative phase separation for non-neutralized PA. The qualitative phase behavior observed in the presence of salt can be generated by calculations using the Flory-Huggins theory, if it is assumed that both the PSS-PA and the PA-solvent interactions change monotonically with a in a specified fashion. All experimental observations, and the theoretical modeling, suggest that the effective PA-PSS interaction changes (over a narrow interval of a) from an attraction at very low a to a repulsion at higher a. (Less)

EPR Study of Chain Rotational Dynamics in Dilute Aqueous Solutions of Spin-Labeled Poly(acrylic acid) at Different Degrees of Neutralization

EPR Study of Chain Rotational Dynamics in Dilute Aqueous Solutions of Spin-Labeled Poly(acrylic acid) at Different Degrees of Neutralization

Dissolution of Dental Zinc Phosphate Cement in Organic Acid Solutions

Dissolution of dental zinc phosphate cement was investigated in acetic, lactic, oxalic and citric acid solutions with different degrees of neutralization (α). The dissolution process was discussed based on the ion equilibrium in acid solution. Dissolution was controlled by H+ ion concentration and/or complexing ability of the acid anions. The release of Zn, Mg and P decreased with increasing α except for oxalic acid. In acid solutions with low complexing ability such as acetic acid, the unreacted ZnO and/or MgO particles dissolved preferentially by the attack of H+ ion and most of the dissolved Zn or Mg existed as hydrated ions. While in acids with high complexing ability such as citric acid and oxalic acid, both of the phosphate matrix and the unreacted ZnO particles simultaneously dissolved at lower degrees of neutralization. Zn and Mg dissolved to form stable complexes with those acid anions. At high degrees of neutralization, a driving force for the dissolution was complexing ability of acids. The extent of the cement matrix erosion increased, with increasing tendency of the stable complex formation. Hopeite, Zn3(PO4)2⋅4H2O crystallized on the surface of the cement immersed in acetic acid with α from 0 to 0.9 and zinc oxalate monohydrate, Zn(COO)2⋅H2O did in oxalic acid with α from 0 to 0.6.