Concentration Of Dispersed Phase Research Articles

Flow of a dispersed phase in the Laval nozzle and in the test section of a two-phase hypersonic shock tunnel

An unsteady gas-particle flow in a hypersonic shock tunnel is studied numerically. The study is performed in the period from the instant when the diaphragm between the high-pressure and low-pressure chambers is opened until the end of the transition to a quasi-steady flow in the test section. The dispersed phase concentration is extremely low, and the collisions between the particles and their effect on the carrier gas flow are ignored. The particle size is varied. The time evolution of the particle concentration in the test section is obtained. Patterns of the quasi-steady flow of the dispersed phase in the throat of the Laval nozzle and the flow around a model (sphere) are presented. Particle concentration and particle velocity lag profiles at the test-section entrance are obtained. The particle-phase flow structure and the time needed for it to reach a quasi-steady regime are found to depend substantially on the particle size.

PIV measurement of mean and pulsating velocities in a gas-droplet jet with low concentration of dispersed phase

A Particle Image Velocimetry (PIV) system was used to perform an investigation into the effect of low concentration of dispersed phase on time-average and pulsating characteristics of the flow over the self-similar part of a two-phase jet emanating into ambient space filled with the same fluid. A phase discrimination procedure based on reflected intensity was introduced into routine practice. Distributions of mean and pulsating velocities in the carrier and dispersed phases of the gas-droplet jet were obtained. In spite of low concentration of the dispersed phase, large droplets present in the flow were found to reduce the intensity of velocity pulsations in the gas phase.

Microwave-assisted modification of starch for compatibilizing LLDPE/starch blends

Modification of activated cassava starch (S) was performed by using octenyl succinic anhydride (OSA) at different starch/OSA ratios under microwave radiation. FTIR and titration results indicated that, within a reaction time of 7 min, degrees of substitution (DS) of about 0.045 may be achieved with 20% OSA. Subsequently, linear low density polyethylene/starch (LLDPE/S) blends were prepared employing succinylated starches (S- g-OSA) as compatibilizers. The morphology and mechanical properties of LLDPE/S blends with and without compatibilizer were compared. It was observed that the addition of 10% of compatibilizer with respect to the dispersed phase content led to a reduction of the starch phase size and to an improvement of the blends mechanical properties.

Synthesis, characterization, and electrorheological properties of polyindene/calcium carbonate composites

AbstractIn this study, synthesis, characterization, and electrorheological (ER) properties of polyindene (PIn) and PIn/calcium carbonate (PIn/CaCO3) conducting composites were carried out by free radical polymerization. In the experiments, FeCl3 was used as oxidizing agent and the ratio of salt:monomer was 2:1. First, PIn was synthesized and obtained with 70% yield. Then, PIn/CaCO3 composites containing various amounts of PIn were prepared. PIn and PIn/CaCO3 composites were characterized by FTIR spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), dynamic light scattering (DLS) methods, Gouy Balance, and dielectric measurements. Suspensions of PIn and PIn/CaCO3 composites were prepared in silicone oil (SO), at a series of concentrations (c = 10–25%, m/m) and their sedimentation stabilities were determined. The effects of dispersed particle concentration, particle size, shear rate, external electric field strength, frequency, and temperature onto ER activities of suspensions were investigated. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers

Use of N,N-dimethyl-N,N-diallylammonium chloride-maleic acid copolymer for recovery of butadiene-styrene rubber from a latex

The flocculating effect of a cationic polyelectrolyte, N,N-dimethyl-N,N-diallylammonium chloride-maleic acid copolymer, in the recovery of rubber from SKS-30 ARK butadiene-styrene latex at various concentrations of the dispersed phase and H2SO4 and at various temperatures was studied.

Morphology of Different Epoxy‐Amine Systems Modified with a Thermoplastic: Influence of Temperature, Thermoplastic Concentration and Molecular Structure of Epoxy Systems

AbstractThe morphologies generated by polymerization induced phase separaron (PIPS) in different epoxy‐amine systems modified with a thermoplastic, polystyrene (PS), were studied by SEM. The amino groups of the epoxy‐amine systems were provided by a monoamine and a diamine in different proportions, so that the resulting polymer would vary from a linear polymer (epoxy‐MA) to a highly crosslinked polymer (epoxy‐DA). The effects of reaction temperature, initial modifier concentration and degree of crosslinking of epoxy‐amine system on the morphology were discussed and trends for the size, distribution and concentration of dispersed particles were deduced. Different types of morphologies were obtained depending on the initial PS content. Typical morphologies of compositions close to critical point were observed for the 9 and 12 wt. % of PS in all the studied systems.

Controlled production of oil-in-water emulsions containing unrefined pumpkin seed oil using stirred cell membrane emulsification

Membrane emulsification of unrefined pumpkin seed oil was performed using microengineered flat disc membranes on top of which a paddle blade stirrer was operated to induce surface shear. The membranes used were fabricated by galvanic deposition of nickel onto a photolithographic template and contained hexagonal arrays of uniform cylindrical pores with a diameter of 19 or 40 μm and a pore spacing of 140 μm. The uniformly sized pumpkin seed oil drops with span values less than 0.4 were obtained at oil fluxes up to 640 L m −2 h −1 using 2 wt.% Tween 20 (polyoxyethylene sorbitan monolaurate) or 2–10 wt.% Pluronic F-68 (polyoxyethylene–polyoxypropylen copolymer) as an aqueous surfactant solution. Pumpkin seed oil is rich in surface active ingredients that can be adsorbed on the membrane surface, such as free fatty acids, phospholipids, and chlorophyll. The adsorption of these components on the membrane surface gradually led to membrane wetting by the oil phase and the formation of uniform drops was achieved only for dispersed phase contents less than 10 vol.%. At high oil fluxes, Pluronic F-68 molecules present at a concentration of 2 wt.% could not adsorb fast enough, on the newly formed oil drops, to stabilise the expanding interface.

Characterisation of the thickness of transition layer and its relation to mechanical properties of polypropylene/poly(ethylene-co-octene) blends

Poly(ethylene-co-octene) (POE) was mixed into polypropylene (PP) by an internal mixer, which was installed on on-line small-angle laser light scattering (SALLS) device. A new parameter called the thickness (d) of transition layer was introduced to describe the compatibility of PP/POE blends in both dynamic and static states. Using the correlation distance, ac (it was indicative of the dimension of the dispersed phase pellets), d was calculated for the PP/POE blends based on the SALLS theory. The results indicated that the average values of d increased with increasing concentration of dispersed phase and had a maximum value at 40/60(PP/POE) for the blends. And the values of d showed much more violent fluctuation and were much larger at the early stage of mixing, but at a later stage d leveled off and approached to steady state. In addition, the relationships between the thickness of transition layer and mechanical properties were studied. It showed that the notched Izod impact strength and the average values of d of PP/POE blends increased with increasing of POE concentration, while the Young's modulus and flexural modulus decreased. The results indicated that SALLS method was an effective method to deal with diffuse transition layer of PP/POE blends and d was indeed a valid parameter to describe compatibility.

Coupling of various methods for the investigation of the morphology of blends of natural rubber and polybutadiene

AbstractThe aim of this work is to develop a set of experimental methods to investigate the morphology of blends of two immiscible elastomers, namely natural rubber (NR) and polybutadiene (PB). Selective extraction, dynamic mechanical spectroscopy in the melt, and transmission electron microscopy (TEM) were used to get information on the structure of unfilled and uncured blends. 1,2‐dichloroethane and 4‐methyl‐2‐pentanone (MIBK) were employed to dissolve selectively NR and PB in specific conditions to assess the continuity of the phases. In oscillatory shear flow at low frequencies and low volume fractions of the minor phase, the storage modulus shows an excess of elasticity that increases with the dispersed phase content. At higher concentration of the minor phase, the elasticity decreases in relation to the morphology. Samples were also ultra cryo‐microtomed and then analyzed by TEM. The superposition of the three methods highlights the existence of a phase‐inversion point for these systems. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers

Electrorheological Properties of Polyaniline/Red Mud Composite

In this study, electrorheological (ER) properties of polyaniline (PANI) and polyaniline/red mud (RM) composites were investigated. Polyaniline and polyaniline/red mud (PRM) composites were prepared by oxidative polymerization. PANI and PRM particle-based ER suspensions were prepared in silicone oil (SO) and their ER behavior was investigated as a function of concentration, shear rate, electric field strength, frequency, and temperature. Sedimentation stabilities of these suspensions were determined. ER activities of all the suspensions were observed to increase with increasing electric field strength, dispersed particle concentration, and decreasing shear rate. The suspensions show shear thinning non-Newtonian viscoelastic behavior, in which viscosity of suspension decreases with increasing shear rate. Shear stress of composite suspensions increases linearly with increasing applied electric field strength and concentration of the particles. Effect of high temperature on ER activity of ER fluids system was also investigated.

On the phase inversion process in an oil–water pipe flow

An experimental study of the phase inversion process in an oil–water flow through a pipe was carried out. Special attention was paid to the critical concentration of the dispersed phase at which phase inversion occurs and to the change in morphological structures during inversion. To that purpose two different types of experiments were performed: (1) continuous experiments during which the dispersed phase fraction was gradually increased and (2) direct experiments whereby oil and water were injected simultaneously into the pipe at a certain concentration. During the experiments detailed pictures were taken of the phase inversion process and simultaneously the electrical conductivity of the mixture was measured to determine which liquid formed the continuous phase and which the dispersed phase. Also the pressure gradient over several parts of the pipe was measured. For continuous experiments the critical concentration was found to depend on the injection phase volume fraction. The critical concentration was significantly higher for continuous experiments than for direct experiments. The change in morphological structures during phase inversion was the same for the two types of experiments. During inversion the concentration of drops of the (originally) dispersed phase becomes so high, that they coalesce at certain places in the flow field and form relatively large, rather complex, morphological structures. With a further increase in concentration of the (originally) dispersed phase these morphological structures grow in size and start to form the new continuous phase in which again complex structures are present, but this time consisting of the (originally) continuous phase.

Preparation and characterization of aceclofenac microspheres

The objective of the present study was to microencapsulate the anti-inflammatory drug (aceclofenac) to provide controlled release and minimizing or eliminating local side effect by avoiding the drug release in the upper gastrointestinal track. The drug was targeted to the colon and their aligned area for their local effect. Aceclofenac was microencapsulated with Eudragit (S 100, RL 100, and RS 100), using an O/W emulsion-solvent evaporation technique. Aceclofenac microspheres were subjected to micromeritic properties including angle of repose, bulk density, tapped density, Carr’s index, Hausner’s ratio, and particle size determination. Microspheres were subjected to drug loading, in vitro drug release as well as for scanning electron microscopy.The prepared microspheres were white, free-flowing, and almost spherical in shape.The drug- loaded microspheres show 60-82% drug entrapment, angle of repose was in the range of 16.13 ± 0.621-24 ± 0.590, bulk and tapped densities respectively were in the range of 0.311 ± 0.006-0.562 ± 0.012 and 0.373 ± 0.01-0.735 ± 0.02, Carr’s index ranges from 14.04 ± 0.026 to 27.25 ± 1.405, Hausner’s ratio was 1.14 ± 0.026-1.37 ± 0.03, and particle size was in the range of 79.7016-144.840 μm. In vitro drug release studies were carried out up to 24 h in three different pH media, i.e., 0.1 N HCl (pH 1.2), phosphate buffer (pH 6.8), and phosphate buffer (pH 7.4). The drug-polymer concentration of dispersed phase influences the particle size and drug release properties. All the formulations at higher pH were followed by the Matrix-Higuchi model.

Electrorheological properties and creep behavior of polyindole/poly(vinyl acetate) composite suspensions

In this study, electrorheological (ER) properties of polyindole (PIN) and polyindole/poly (vinyl acetate), (PIN/PVAc) conducting composites having different compositions were investigated. Conductivities and dielectric properties of these composites were determined. The particle sizes of the composites were determined by dynamic light scattering method. Suspensions of PIN and PIN/PVAc composites were prepared in silicone oil, at several concentrations (c = 5–25%, m/m) and their sedimentation stabilities were determined. Then the effects of dispersed particle concentration, shear rate, electric field strength, frequency, and temperature onto ER activities of suspensions were investigated. The flow times of these suspensions at various dc electric field strengths were measured. Further, creep tests were applied to the composite suspensions and a reversible viscoelastic deformation was observed.

Drop deformation in sheared polymer blends

Drop deformation in equiviscous polymer blends with dispersed phase volume fraction ranging from 0 to 10% has been investigated by video microscopy and image analysis in a parallel plate shear apparatus. Under steady external flow conditions the shape of individual drops, as measured by the three main axes, the orientation angle and the deformation parameter, showed marked time fluctuations around an average value depending on dispersed phase concentration and on drop capillary number. At small volume fractions the deformed shape was essentially coincident with the isolated drop case, whereas the higher the concentration, the larger the observed drop deformation at a given capillary number. Such deviations from the isolated drop case can be attributed to hydrodynamic interactions, mainly due to flow-induced collisions among drops. The experimental results can be conveniently described by a mean field approximation whereby the forces causing drop deformation are taken as proportional to blend viscosity rather than to continuous phase viscosity. By using this correction, i.e., by calculating the capillary number from blend viscosity, all the data collapsed to the isolated drop case, thus allowing one to exploit the small-deformation theoretical analyses available from the literature to predict the morphology of concentrated polymer blends.

In vitro Release Characteristics of Nitroglycerin from Microemulsion-Based Hydrogel System for Anal Fissure Treatment

To develop topical nitroglycerin (NTG) preparation far chronic anal fissure treatment, the release rate of NTG should be controlled carefully. For this, microemulsion was prepared from the phase diagram construction with Cremophor ELP, ethanol and Labrafil and the topical gel was prepared by dispersing NTG containing microemulsion into hydrophilic polymers. in viかo release characteristics were evaluated with Franz diffusion cell using cellulose membrane and compared with control hydrogels. The release rate of NTG was followed order kinetics and, when comparing the NTG release from control hydrogel with that from the microemulsion-based hydrogel, the NTG release rate was controlled by the content of polymers within continuous phase and the concentration of dispersed phase.

Influence of turbulence intensity on particle drag coefficients

The effect of turbulent eddies on the motion of the dispersed phase is often ignored by assuming a standard drag coefficient as applied to quiescent flow. Such an assumption can lead to large errors when predicting the dispersed phase concentration profile of an industrial flow under turbulent conditions. Recently, [G.L. Lane, M.P. Schwarz, G.M. Evans, Numerical modelling of gas-liquid flow in stirred tanks, Chem. Eng. Sci. 60 (2005) 2203–2214] developed a model relating the drag coefficient to fluid turbulence characteristics through the dimensionless group Stokes number. Their model has been successfully applied to predict gas holdups of a mechanically stirred tank over the range of St < 0.7. The present study focused on broadening the analysis by Lane et al. Specifically, the aim was to examine the effects of dispersed phase density and size on the applied drag force under turbulent conditions and to extend the much needed experimental data on particle drag coefficients in free-stream turbulence, as a function of solid particles characteristics. This was achieved by a systematic experimental approach using particles of different sizes and densities in two distinct turbulent flow fields generated by oscillating grids. The results indicated that the reduction in settling velocity is a function of both particle size and density and turbulent characteristics with maximum interaction between the continuous and dispersed phases occurring at low ratios of particle density to liquid density and high turbulence intensities. Richardson number , a dimensionless group, was employed to capture the effects of these parameters on the drag coefficient.

Electrorheological properties of kaolinite, polyindole, and polyindole/kaolinite composite suspensions

AbstractIn this study, polyindole (PIN) and polyindole/kaolinite (PIN/KAO) composite were synthesized by free radical polymerization using FeCl3 as an initiator. Average particle sizes (d50) of PIN and PIN/KAO composite were determined by dynamic light scattering (DLS) as 7.2 and 6.2 μm, respectively. The samples were characterized by FTIR, elemental analysis, DSC/TGA and SEM measurements. Suspensions of KAO, PIN, and PIN/KAO composite were prepared in silicone oil (SO) and the sedimentation stabilities were determined. Electrorheological (ER) properties of these suspensions were studied as a function of dispersed phase concentration, shear rate, shear stress, and temperature; and yield stresses and excess shear stresses determined. Further, dielectric properties of KAO, PIN, and PIN/KAO composite were investigated. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007

Aggregate morphology and aggregation rate constants for silica dispersions in the presence of salt and polyelectrolyte

It is shown that the addition, over suitable concentration ranges, of mixtures of (nonadsorbing) sodium poly(styrene sulfonate) and potassium chloride, to dispersions of silica particles in water, can lead to very large changes in the sediment height of the resulting aggregates, reflecting similarly large changes in particle packing density within the aggregates. It can also lead to aggregation rates which are considerably faster than the diffusion-controlled rates (by as much as a factor of 2.5), although this enhancement is reduced as the dispersion particle concentration is reduced.

Rheological behavior of poly(methyl methacrylate)/polystyrene (PMMA/PS) blends with the addition of PMMA-ran-PS

In this work, the dynamic behavior of poly(methyl methacrylate)/polystyrene blend to which P(S0.5-ran-MMA0.5) was added was studied. Several blend (ranging from 5 to 20 wt% of dispersed phase) and copolymer (up to 20 wt% with respect to dispersed phase) concentrations were studied. The rheological behavior of the blends was compared to Bousmina’s (Rheol Acta 38:73–83, 1999) and Palierne’s (Rheol Acta 29:204–214, 1990) generalized models. The relaxation spectra of the blends were also inferred, and the results were analyzed in light of the analysis of Jacobs et al. [J Rheol 43:1495–1509, 1999]. The relaxation spectra of the blends with smaller dispersed phase (below 10 wt%) and larger copolymer concentrations (above 0.4 wt%) showed the presence of four relaxation times, two corresponding to the blend phases, τ F , corresponding to the relaxation of the shape of the dispersed phase of the blend and $$ \tau _{\beta } $$ that can be attributed to the relaxation of Marangoni stresses tangential to the interface between the dispersed phase and matrix. The experimental values of $$\tau _{F} $$ and $$ \tau _{\beta } $$ were used to infer the interfacial tension (Γ) and the interfacial complex shear modulus (β) for the different blends, Γ decreased with increasing copolymer concentration. β decreased with increasing blend dispersed phase concentration and decreasing copolymer concentration. The predictions of Palierne’s generalized model were found to corroborate the experimental data once the values of Γ and β, found analyzing the relaxation spectra, were used in the calculations. Bousmina’s model was found to corroborate the data only for larger dispersed phase concentration.

Countercurrent plug flow mass exchange with internal particle diffusion

The model for countercurrent steady state mass transfer between uniform dispersed phase particles and a continuous phase, both assumed to move in plug flow, with diffusion resistance inside the particles, and film resistance around the particles, is solved analytically for three particle geometries: infinite plates, infinite cylinders and spheres. In the solution, the direct relation between the local continuous phase concentration, and the average dispersed phase concentration is accounted for in the boundary condition. Concentration profiles in the mass exchanger are derived from the analytical solution, as well as asymptotic Sherwood numbers. The analytical solution requires the determination of roots of the characteristic equations, which is cumbersome for spherical particles. Correlations are provided for the asymptotic Sherwood numbers for easy computation. The model can easily be used for the analogous direct heat exchange problem.