Commercial Dispersants Research Articles

Stabilization of PCC dispersions prepared directly in the mother-liquid after synthesis through the carbonation of (hydrated) lime

Various CaCO 3-based products are often used in the form of concentrated aqueous dispersions. This study investigates the stabilization of PCC dispersions prepared directly in the mother-liquid after the carbonation of (hydrated) lime through the adsorption of a commercial sodium polyacrylate dispersant. The results demonstrate that the composition of the mother-liquid, particularly the Ca 2 + activity, profoundly influences virtually all processes pertinent to dispersion stabilization—from the initial charging of the CaCO 3 surface in base PCC dispersions, to the surface charge regulation and dispersion stabilization efficiency of the polyacrylate dispersing agent. Rising prominence of the counterion condensation effects in Ca 2 + rich solutions limits the conditions conducive to the surface charge regulation through dispersant adsorption to an optimum pH range of about 8–11. Furthermore, dispersion stability analysis, based on the classical DLVO theory of colloid stability, and corroborated by experimental evidence in the form of particle size distribution analyses, also indicates that optimum stability conditions for such PCC dispersions are established with small dispersant doses (0.25–0.5% per dry weight) in the pH range of about 9–11.

Influence of silicon and carbon excesses on the aqueous dispersion of SiC nanocrystals for optical application

The dispersion behaviour of laser-synthesized silicon carbide nanoparticles (npSiC) in water is investigated by photon correlation spectroscopy (PCS). With regard to previous studies and due to an application in the processing of optical materials, this paper concerns low npSiC contents (from 0.05 to 10 wt.%). The role played by the particle surface state is be pointed out through the consideration of stochiometric (C/Si = 1), carbon-rich (C/Si > 1) and silicon-rich (C/Si < 1) nanopowders. Suspensions made from stoichiometric and silicon-rich nanopowders are easily dispersed and stable with time. The PCS measurements reveal in this case more than 95% of isolated nanoparticles, pointing out the key role of the oxidized layer covering the grain of silicon-rich samples. At the opposite, the carbon-rich powders are hardly dispersed in pure water, correlated with the presence of a relatively inert graphitic carbon layer at the grain surface. However, by addition of a commercial polymeric dispersant, all nanopowders induce high quality suspensions. In particular, the carbon-rich samples are easily dispersed, and possible dispersion mechanisms of npSiC in presence of a polymeric surfactant are discussed. The influence of the npSiC loading and the time evolution of the suspension are also presented. By considering stoichiometric, as well as carbon- and silicon-rich samples, this paper demonstrates the possibility to achieve high quality dispersions of SiC nanoparticles, whatever the chemical composition of the powder, as an easy step for optical material processing.

Amphoteric water‐soluble copolymer for barium titanate slurries. I. Synthesis and dispersing ability

AbstractAn amphoteric water‐soluble copolymer, polyacrylamide/[α‐N,N‐dimethyl‐N‐(3‐(β‐carboxylate)acrylamino)propyl] ammonium ethanate (PAM/DAE) was synthesized and used as a dispersion agent for BaTiO3 particles. PAM/DAE was prepared from acrylamide and [α‐N,N‐dimethyl‐N‐(3‐(β‐carboxylate)acrylamino)propyl] ammonium ethanate in a basic condition through a free‐radical polymerization. The structure of this copolymer was verified by IR and 1H‐NMR spectra. The dispersing effects of PAM/DAE were examined by measuring the viscosity and sedimentation of BaTiO3 suspensions, and by analyzing the particle size. The results indicate that this copolymer could uniformly disperse the particles, and the resulting suspensions were less viscous, more stabilized, and contained powder with smaller particle size. The dispersing/stabilizing ability of PAM/DAE is close to, or slightly better than, that of a commercial dispersant, ammonium salt of poly(methacrylic acid). © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1443–1450, 2005

Dispersion Properties of BaTiO3 Colloids with Amphoteric Polyelectrolytes

An amphoteric water‐soluble copolymer, i.e., poly(acrylamide/(α‐N,N‐dimethyl‐N‐acryloyloxyethyl) ammonium ethanate) (PAAM/DAAE), was evaluated as a novel dispersant for aqueous BaTiO3 (BT) slurries. The dispersing property of this copolymer was examined by means of rheology, sedimentation, particle size, green density, zeta potential, and leached Ba2+ concentration measurements. The results indicate that PAAM/DAAE could reduce the viscosity of slurries greatly, cause BT particle sizes to shift to smaller values, and make green compacts more consolidated. Compared with a commercial dispersant, ammonium salt of poly(methacrylic acid) (PMAA‐NH4), it is as effective or even better in preparing stabilized suspensions. More importantly, PAAM/DAAE could lessen the leached Ba2+ concentration. This is related to the adsorption behavior of this copolymer onto BT particles, and the interaction between the adsorbed dispersant and dissolved barium ions.

Dispersant Adsorption during Asphaltene Aggregation Studied by Fluorescence Resonance Energy Transfer (FRET)

Fluorescence resonance energy transfer (FRET) is used to study the adsorption of a commercial dispersant on asphaltenes in a toluene−heptane solution. We induce the asphaltene aggregation process by changing the heptane volumetric fraction, where heptane plays the role of a precipitant agent. The dispersant and asphaltenes are naturally fluorescent, and no special labeling was performed to use this fluorescent technique. Low concentrations of asphaltene and dispersant were used in this work0.007 and 0.055 g/L, respectivelyto avoid self-association of the dispersant and to induce asphaltene aggregation only by the presence of heptane in the solution. The results show different behavior of the energy transfer below and above the precipitation onset of the asphaltenes, corresponding to a heptane volumetric fraction of 0.6. The dispersant adsorption was followed during the induced aggregation by measuring the resonance energy transfer from the dispersant (energy donor) to the asphaltenes (energy acceptor) above a heptane volumetric fraction of 0.7, where aggregates are formed and stabilized by the dispersant. The fluorescent experiments presented here also give information about the asphaltene stability in the solvent below the asphaltene precipitation onset.

A study and comparative assessment of the thinning effect in deflocculants. Part 1. Bauxite-based highly concentrated ceramic binding suspensuons (HCBSs)

The thinning efficiency of deflocculants (dispersing aluminas ADS, ADW-1, M-ADS1, M-ADW1and their binary mixtures; commercial dispersants Giessfix, Dollafax, Costament, and organomineral additives) was tested on bauxite-based HCBS specimens. The thinning efficiency of additives (measured by the decrease in viscosity at low shear rates) is different; the best effect was observed in Giessfix 162 and M-ADS1 dispersants.

Effects on aqueous barium titanate tape properties of passivation of barium ion leaching by using dispersants

To passivate a barium titanate (BaTiO 3) ceramic powder surface from Ba 2+ ion leaching in water, passivation agent layer (PAL) was formed by drying the slurry after adding a commercial polymeric dispersant. By following the several characteristic steps of actual MLCC production process, slip and green properties were compared for two different polymer-adding modes; one is the PAL and the other is the conventional dispersant mode. Compared to the conventional dispersant adding method, PAL mode was the only effective way in reducing the amount of Ba 2+ leaching. However, slip viscosity and green body properties were not a function of adding mode but a function of dispersant itself, which means using PAL did not deteriorate any of slip and green properties of BaTiO 3.

Amphibious water‐soluble copolymer. I. Its synthesis and dispersing ability on barium titanate

AbstractAn amphibious water‐soluble copolymer, polyacrylamide/(α‐N,N‐dimethyl‐N‐acryloyloxyethyl) ammonium ethanate (PAAM/DAAE), was synthesized and used as a dispersion agent for BaTiO3 particles. PAAM/DAAE was prepared from acrylamide and (α‐N,N‐dimethyl‐N‐acryloyloxyethyl) ammonium ethanate under basic conditions through a free‐radical polymerization. The structure of this copolymer was verified with IR and 1H‐NMR spectra. The dispersing effects of PAAM/DAAE were examined through the measurement of the viscosity and sedimentation of BaTiO3 suspensions and the green density. The results indicated that this copolymer could uniformly disperse the particles, reduce the viscosity, stabilize the suspensions, and produce high‐density green compacts. In comparison with a commercial dispersant, the ammonium salt of poly(methylacrylic acid), PAAM/DAAE was clearly more effective. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2232–2239, 2004

A Thermo-Chemical Surface Treatment of AlN Powder for the Aqueous Processing of AlN Ceramics

Dense aluminum nitride ceramics were prepared by sintering green bodies at 1750 °C for 2 h. These green bodies were prepared by aqueous slip-casting from a powder that was surface-treated to prevent hydrolysis. The surface treatment of the aluminum nitride (AlN) powder consisted of dispersing the powder in warm-water solutions of aluminum dihydrogenphosphate Al(H2PO4)3. Different treatment temperatures in the range 30–80 °C were tested. For all the tested temperatures, the surface-treated AlN powder was found to be water-resistant, even after drying and/or redispersion. Various commercial dispersants were tested for their effectiveness, and the amount of dispersant was optimized in terms of a high solids loading of the suspension and an acceptable viscosity for slip casting. Based on these studies, a stable aqueous suspension of AlN powder, treated at 60 °C, with a total solids loading of 50 vol%, was prepared using CaF2 as a sintering additive. The well-dispersed powder made it possible to prepare green samples with close particle packing and relatively high sintered densities; that is, more than 96% of the theoretical density.

Rational Design of Dispersants for Colloidal Processing of Barium Titanate Suspensions by Molecular Modeling

A molecular modeling based approach to design/selection of dispersants in colloidal processing for advanced ceramics applications is presented. The validity and utility of the proposed approach is illustrated with an example of the dispersion of nano-particles of barium titanate by a variety of commercial dispersants including fatty acids and phosphate esters.

Electrokinetic Characterization of Asphaltenes and the Asphaltenes−Resins Interaction

The electrophoretic mobility of asphaltene particles formed by precipitation induced by the addition of n-heptane to asphaltene solutions in toluene was measured in water and in nonpolar media. Dispersed in water, the particles presented a negative electrophoretic mobility, whereas in toluene their mobility was positive and around 2.0 × 10-9 m2/V s. When resins were present in the precipitating medium, a coprecipitation of these fractions occurred, indicating an adsorption or binding process of the resins on the nascent asphaltene particles. This interaction, however, did not significantly change the electrophoretic mobility of the asphaltene particles. In contrast with commercial dispersants, resins fail to stabilize asphaltene dispersions. This result indicate that the descriptions representing asphaltenes as a solid phase intrinsically insoluble in hydrocarbon media dispersed by adsorbed resins molecules does not accurately represent the structure of these fractions

処理剤による干潟漂着油除去および多環芳香族炭化水素類（ＰＡＨｓ）の生分解促進の検討

Large-scale oil spills have significant impacts on the both natural environment and society. The purpose of this study is to determine the optimum composition of a dispersant for removal of oil and clarify the effects of dispersants on biodegradation of PAH. The optimum composition of the dispersant for sandy beach sediments contaminated by 5 wt. % fuel oil C is 22% Brij 30 as the surfactant and 78% decaline as the solvent. The dispersant at its optimum composition remove greater amounts oil than commercial dispersant. Both dispersants could accelerate biodegradation of PAH in oil. The acceleration of biodegradation of PAHs is more significant for the dispersant with an dispersant at its optimum composition than for commercially available dispersant of the third generation. The acceleration of biodegradation of PAH appear to be due to washout of oil by the dispersant.

Toxicity of Biosurfactants and Synthetic Surfactants on Marine Organisms

This paper presents results of toxicity testing series, in which four synthetic surfactants, two commercial oil dispersants, and six bio surfactants have been examined.

Optimization of the rheological properties of alumina slurries for ceramic processing applications Part I: Slip-casting

Aqueous powder slurries are widely employed in ceramic manufacturing processes like slip-casting and spray-drying. The aim of the present work was to identify the conditions for the preparation of stable alumina slurries with high solids content for the production of slip-cast objects with improved properties, as well as to correlate the slurry properties to the final object properties. For slurry stabilization, three commercial dispersants were compared. It was found that for each dispersant there exists an optimum concentration range within which low viscosity is achieved for a slurry of high solids content. In addition to the slurry solids content, the choice of a particular dispersant also affects the slurry viscosity and through that the casting rate. The combination of high slurry solids content and slower casting rate results in objects with higher densities both in the green and fired state.

Fabrication of porous calcium polyphosphate implants by solid freeform fabrication: A study of processing parameters andin vitro degradation characteristics

Solid freeform fabrication (SFF) involves the creation of a solid 3-D object of desired shape by successively adding raw materials in particles or layers. Its use in fabricating surgical implants is being explored. The objective of this study was to determine the feasibility of using SFF to build porous parts of calcium polyphosphate (CPP), a linear condensed phosphate that has been suggested as a material for forming bioresorbable skeletal replacement implants. CPP powders (<25 microm in particle size) were added to an UV curable monomer (SOMOS 6110) at a solids loading of 25 vol %, with the addition of a commercial dispersant to prevent particle agglomeration and settling. Viscosity and cure depth measurements were performed to insure that CPP suspension met the requirements deemed necessary for use in SFF. The CPP suspension was bulk cured and sintered in molds in order to assess binder removal and sintering parameters. Using a three-point bend test, the ultimate bending strength and energy-to-fracture of sintered CPP samples simulating parts to be formed by this strategy were characterized. In vitro degradation studies using 0.1M of tris-buffered solution were performed to assess the effect of aging on mechanical properties of the samples as a function of the processing route and resulting structures. The polymer binder successfully was removed from the cured ceramic suspension by developing a procedure that combined slow heating rates with low temperature dwells. Sintering CPP at 585 degrees C for 1 h produced amorphous material samples with average porosity of 27.7 +/- 2.0%. Sintering CPP at 600 degrees C for 1 h produced a crystalline material with samples having an average porosity of 22.9 +/- 1.3%. Crystalline CPP was found to exhibit superior bend strength and toughness compared with amorphous CPP. Both samples experienced a decline in mechanical properties during in vitro degradation; however, the effects were more pronounced with the amorphous CPP samples. Amorphous CPP was found to degrade four times faster than crystalline CPP, as shown by high levels of phosphate present in the degradation solution and a noticeable increase in the porosity of the samples. Crystalline CPP was more resistant to attack as dissolution was limited to surface features of the sintered particles.

Comparison of Test Methods and Early Toxicity Characterization for Five Dispersants

The acute toxicities of a commercial dispersant (Corexit 9527) and four experimental dispersant formulations were evaluated using the 96-h mysid (Mysidopsis bahia) test and two rapid screening tests, Microtox and the Mysid IQ Toxicity Test. During 96-h toxicity tests, survival observations were recorded at 3, 6, 9, 12, and 24 h to document mortalities from short-term exposures more consistent with field exposure times and more approximate to exposure times used in Microtox and the Mysid IQ Toxicity Test. At nominal concentrations (6.25 and 12.5 mg/liter) and exposure times (3–24 h) near the upper range of predicted field conditions, mysid mortalities were ≤5% for all test materials. Microtox and Mysid IQ Toxicity Test were evaluated for their ability to differentiate test materials compared with that of the 96-h mysid test. Dispersant formulations were ranked by relative toxicities based on LC50or EC50values and ranks compared among test methods. Microtox ranked the test materials similar to the 96-h mysid test. Ranks from the Mysid IQ Toxicity Test were dissimilar to those of the other tests. Early mortality observations during 96-h tests did not provide a better basis for comparing results of the rapid screening tests.

Development of Ceramic Inks for Direct Continuous Jet Printing

A ceramic ink that contains 30 vol% of zirconia in butyl acetate and 2 wt% of a commercial oligomeric dispersant is considered. The dispersion and viscosity of this ink was optimized in previous work; however, its conductivity is too low for continuous ink‐jet printing. The conductivity has been improved by the addition of ethanol and ammonium nitrate, but this addition detrimentally affects the dispersion, viscosity, and surface tension of the ink. This problem has been largely overcome by reducing the amount of ceramic in the ink. The ceramic inks that have been developed are tested in a pressurized, continuous ink‐jet printer, and, depending on their performance, the ink composition is modified further.

Direct Ink-Jet Deposition of Ceramic Green Bodies: I - Formulation of Build Materials

AbstractA conventional rapid prototyping technology has been used to build prototypes using direct deposition through a drop-on-demand ink-jet printing system. Al2O3- filled waxes have been developed with viscosity values close to those of the materials used in commercial printing systems. Commercial dispersants based on stearic acid and sterylamine have been studied and stable ceramic suspensions with ceramic volume fractions in the range 20–40 volume% produced with suitable viscosity. A suspension of 20% Al2O3in an alkane wax has been successfully printed.

Bacterial degradation of emulsified crude oil and the effect of various surfactants.

A Rhodococcus sp. 094 bacterium was tested for its ability to oxidize alkanes in crude oil emulsified by nonionic chemical and biological surfactants. Oxidation rates were measured in a 3-h period by Warburg respirometry. 14CO2 recovery was measured from the [1-14C]hexadecane spiked crude oil. Response to emulsified oil depended on the physiological state of the bacteria (i.e., cells harvested in the exponential and stationary growth phases) were tested. Oxidation rates by cells in the exponential growth phase were negatively affected by surfactant amendment. Oxidation rates by cells in the stationary growth phase were in some cases stimulated by surfactants. The stimulatory effect depended on both the chemical structure and the physicochemical properties (i.e., hydrophilic-lipophilic balance (HLB)) of the surfactants. Surfactants with intermediate HLB values (8-12) gave the best results. Neither the biosurfactants nor the commercial oil-spill dispersants tested had any significant stimulatory effect.

Polymeric additives for improving the flow properties of waxy distillate fuels and crudes

Propenoxylated tetraethylenepentamine adduct was prepared by the reaction of tetraethylenepentamine (TEPA) with propylene oxide (PO). Four α-olefin-maleic anhydride copolymers (OMACs) previously synthesized were esterified with the synthesized adduct successively. They were also subjected to esterification with saturated long-chain alcohol blend NAFOL 20 + and amidation with TEPA. The prepared polymeric products were purified and characterized, then evaluated for improving the cold flow properties of a waxy gas oil blend and Umbarka waxy crude. In addition, they were compared with a commercial wax dispersant. The results show the high efficiency of these additives in improving the flowability of both distillate fuel and crude, while the filterability of the gas oil blend was slightly ameliorated. The results are interpreted on the basis of the structure of the additives and distillate composition.