Diameter Of Dispersed Particles Research Articles

Eulerian-Eulerian Modeling of the Features of Mean and Fluctuational Flow Structure and Dispersed Phase Motion in Axisymmetric Round Two-Phase Jets

The features of the local mean and fluctuational flow structure, carrier phase turbulence and the propagation of the dispersed phase in the bubbly and droplet-laden isothermal round polydispersed jets were numerically simulated. The dynamics of the polydispersed phase is predicted using the Eulerian–Eulerian two-fluid approach. Turbulence of the carrier phase is described using the second-moment closure while taking into account the presence of the dispersed phase. The numerical analysis was performed in a wide range of variation of dispersed phase diameter at the inlet and particle-to-fluid density ratio (from gas flow laden with water droplets to carrier fluid flow laden with gas bubbles). An increase in the concentration of air bubbles and their size leads to jet expansion (as compared to a single-phase jet up to 40%), which indicates an increase in the intensity of the process of turbulent mixing with the surrounding space. However, this makes the gas-droplet jet narrower (up to 15%) and with a longer range in comparison with a single-phase flow. The addition of finely dispersed liquid droplets to an air jet suppresses gas phase turbulence (up to 15%). In a bubbly jet, it is found that small bubbles (Stk < 0.1) accumulate near the jet axis in the initial cross-sections, while concentration of the large ones (Stk > 0.2) along the jet axis decreases rapidly. In the gas-droplet jet, the effect of dispersed phase accumulation is also observed in the initial cross-section, and then its concentration decreases gradually along the jet axis. For gas bubbles (Stk < 0.1), small turbulence attenuation (up to 6%) is shown.

Composition and Physical Stability of the Colloidal Dispersion in Veiled Virgin Olive Oil

AbstractVeiled virgin olive oil (VOO) samples of nine different olive cultivars are chosen to have a wide range of physicochemical and biological properties of colloidal dispersions. The contents of proteins and phospholipids range from 40 to 190 mg kg−1 and from 70 to 200 mg kg−1, respectively. The effect of lab‐scale centrifugation on cloudy appearance is studied measuring the decrease of turbidity grade values. The time to obtain unveiled oils (20 NTU) is modeled by a logistic equation, and a clear relationship between the initial water content and the above time is observed with a different trend between two groups of the VOO samples. Four VOO samples are selected to study the aggregation phenomena of microdroplets of water, pulp particles, and olive stone fragments via optical microscopy and dynamic light scattering during lab‐scale gravity sedimentation. All VOOs are unstable with the cloudiness disappearing within the 230 days of investigation due to an overall diameter increase of cloudy components which is modeled by a power‐law equation. The VOO samples, characterized by both small diameter values of dispersed components (150–250 nm) and high values of water content, show the fastest aggregation kinetics, but they have the longest time of cloudiness stability.Practical Applications: Water content and size distribution of VOO cloudy components can be key factors to control the colloidal stability. If removal of cloudy appearance is required, centrifugation can be applied to obtain a fast oil clarification which shows a power law relationship of water content with time. Instead, if physical stability of the colloidal dispersion is required, the aggregation phenomena should be slow down through VOO processing to obtain small diameters of the cloudy components. Tuning both the water content and dispersed phase diameter in the VOO can be the first step towards the control of phenomena related to the colloidal dispersion for every olive oil processing organization, above and beyond the simple removal of cloudy appearance by filtration.

Settling dynamics of cohesive sediments in a highly turbid tidal river

An optical settling column was used in the Garonne Tidal River to estimate the settling velocity of suspended matter in surface waters over a period characterized by contrasting hydrological conditions. A time and space variability of settling velocity was observed during this study. The settling velocities of surface suspended matter ranged from 0.018 to 0.268 mm. s−1, and the median diameter of dispersed particles varied from 4.74 to 14.38 μm. The data revealed the physical processes influencing the sediment settling dynamics throughout different time scales in a highly turbid tidal river. On tidal and fortnightly time scales, resuspension, deposition and advection mechanisms were the major drivers of the settling velocity variability, while it is likely that the estuarine turbidity maxima (ETM) was responsible for seasonal variations. The findings of this work suggest that in tidal rivers, salinity is too low to promote flocculation, whereas ETM can play a key role in enhancing this process. The stronger variability in settling velocity occurs on a tidal timescale, with median values up to four times higher at the end of the ebb tide than at high water. These variations cannot be correlated to salinity or sediment concentration. On a seasonal timescale, flocculation appears to be strongly correlated with the presence of the ETM and associated fluid mud layer. A simple correlation based on tidal variations seems to be a better predictor than the relationships based on the sediment concentration.

Comparative mechanical, morphological, rheological, and thermal properties of polypropylene/ethylene‐propylene‐diene rubber blends

AbstractBecause of its weak durability at low temperatures and low strain rates, polypropylene's use as an engineering plastic is restricted. To make polypropylene more tougher, combine it with elastomeric particles in a cost‐effective manner is an excellent option. Internal melt blending was used to manufacture polypropylene (PP) and high‐molecular‐grade ethylene‐propylene‐diene rubber (EPDM) blends with varying constitutive ratios in this work. EPDM's lower portions have especially high impact strength ratings for PP/EPDM mixtures. (i.e., 2.5, 5, and 7.5 parts per hundred EPDM rubber). The mechanically generated cavitation behavior of impact cracked specimens is obvious from SEM morphology, showing to the strong impact resistance of PP/EPDM blends. Increased EPDM content reduces the amount of scattered EPDM rubber particles by increasing the average diameter of dispersed particles, as seen by HRTEM images of the samples. The tensile and flexural properties of PP/EPDM blends were analysed. The rheological tests demonstrate that as the frequency increases, the complex viscosity drops, indicating that the melt is in a pseudoplastic condition. Due to the destruction of polymer chain mobility at greater cooling rates, DSC analysis indicates that percentage crystallinity values decrease as the cooling rate of crystallization increases, resulting in an incomplete crystallization process. The fact that PP/EPDM mixes have two glass transition temperatures indicates that they are immiscible. An investigation using the TGA found that the maximum degradation temperature (Tmax) of the PP/EPDM rubber mixtures may be sustained for long periods of time at very high operating temperatures.

STRUCTURE FORMATION OF DISPERSED-REINFORCED BUILDING COMPOSITES

Abstract. The results of the study of the mechanism of structure formation of cement compositions reinforced with finely dispersed monofilament are presented in the article. The mechanism of microstructure organization of construction composites was studied on models of dispersed systems, with different qualitative and quantitative composition of linear and dispersed particles. At the same time, restrictions had been placed on particle size – fiber diameter and diameter of dispersed particles are proportional to each other. Study of cracking formation kinetics was carried out on disk-shaped samples made of water-clay and water-cement compositions. Physical and mechanical characteristics of dispersed-reinforced cement stone, including non-reinforced stone, have been defined on prisms-shaped samples of square section with size 40×40×160 mm. The analysis of physical models showed that cluster structures filling with particles of various nature and shape increases structural diversity of entire dispersed system. An inserting of linear particles changes nature of system structure formation. Depending on the characteristics, structural components of the system, substructures are formed, which differ in the periods of their formation and geometric parameters. It has been established that dispersed particles of different nature are structured in different ways into clusters with discrete fibers of different length. Linear particles were more active in the creation of structural aggregates (clusters) comparing to dispersed grains. The impact of highly dispersed fibers on the structure organization of the binder compositions was quantified by the damage coefficient determined on samples of different types. The presence of discrete fibers in the composition of the material leads to modify the qualitative characteristic of compositions cracking formation. Improvement of physical and mechanical properties of the dispersed-reinforced composite confirms the ability of the fiber to change a mechanism of material destruction due to a probable deposition of hydration products on monofilaments, to densify and strengthen the interfacial transitional zone.

Use of nanofiltration concentrates of buttermilk and whey for fermented dairy products with increased mass content of protein

Baromembrane methods, in particular, nanofiltration, open up broad opportunities in the field of obtaining dairy products with a high protein content in terms of quality and energy saving. This paper describes the feasibility of using buttermilk and cheese whey concentrates obtained by nanofiltration in the production of fermented milk products. The physicochemical, rheological and organoleptic studies of nanofiltration concentrates of buttermilk and cheese whey made it possible to select concentrates with a mass fraction of dry substances of 20% for further research. Electron microscopic studies of the microstructure of buttermilk, whey and their concentrates with a mass fraction of dry substances of 20% showed that when buttermilk was concentrated by nanofiltration, the average diameter of dispersed particles did not increase and amounted to (130 ± 30) nm. The grid cells size decreased by 3.2 times; in serum concentration, the particle size increased by 1.7 times with a decrease in the grid cells size by 1.3 times. The obtained data make it possible to predict the positive effect of this concentration method on the consistency of fermented milk products. The use of the combined milk base with a ratio of buttermilk concentrate (20% dry matter) to whey concentrate (20% dry matter) of 50:50 and 75:25 is substantiated, providing a complete protein content of 4.4–5.6% in fermented milk products. A high rate of acid formation and a good water-holding capacity of acid clots were established when fermenting with a starter culture containing thermophilic streptococcus and acidophilic bacillus in a ratio of 4:1. The obtained results make it possible to expand the range of fermented milk products with an increased mass fraction of protein for good nutrition of the population.

INVESTIGATION OF THE INFLUENCE TWO-PHASE FLOWS PARAMETERS ON THE EROSION WEAR OF THE GAS PIPELINES BENDS

CFD modeling (Computational Fluid Dynamics) Lagrangian approach (model DPM (Discrete Phase Model)) in ANSYS Fluent R19.2 Academic software complex investigates the influence of twophase gas flow velocity, size and flow rate of dispersed particles on the location and magnitude of gas pipeline bends erosion wear. The motion of the continuous phase was modeled by the solution of the Navier-Stokes equation and the continuity of the closed two-parameter k-ε turbulence model with the corresponding initial and boundary conditions. The motion trajectories of the dispersed particles were determined by integrating the force equations acting on each particle. The erosion wear of gas pipeline bends was modeled using the Finney equation. The studies were performed for gas flow velocities at the inlet of the bend from 4 m/s to 19 m/s, the diameters of the dispersed particles 0.005 mm, 0.01 mm, 0.05 mm, 0.1 mm, 0.5 mm and 1.0 mm and the flow rate of the dispersed particles from 0.0002 kg/s to 0.0022 kg/s. Natural gas was selected as the continuous phase, and sand was dispersed. The geometry of each of the simulated taps and the pressure at the outlet of the bend were assumed to be the same. The simulation results were visualized in the postprocessor software complex by constructing erosion rate velocity fields on gas pipeline bends. From the visualized results it is determined that the largest influence on the location of the erosion wear of the pipeline bends has the diameter of the dispersed particles and the least concentration. The influence of the two-phase gas flow parameters on the location of the field of their maximum erosion wear is determined. The graphical dependences of the maximum velocity of erosion wear of gas pipeline bends on each of the studied parameters of the two-phase gas stream are constructed. It has been determined that the diameter of the dispersed particles and the velocity of the gas stream have the greatest influence on the erosion wear of the erosion of the bends. Keywords: bend, dispersed particle diameter, dispersed particle rate, dispersed phase, erosion wear, Finney equation, gas flow rate, Lagrange approach.

Insights on physicochemical aspects of chitosan dispersion in aqueous solutions of acetic, glycolic, propionic or lactic acid.

Chitosan is a polysaccharide well-known for its applicability as a biocompatible, biodegradable, and non-toxic material to produce drugs excipients and food coatings. Acidic media are required to disperse chitosan, and aqueous solutions of acetic acid have been typically used for this purpose. However, this acid has several sensory drawbacks. In this study, chitosan was dispersed [0.1 g·(100 mL)-1] in aqueous media containing acetic (AA), glycolic (GA), propionic (PA), or lactic (LA) acid, at 10, 20, 30, 40, or 50 mmol·L-1. The increase of acid concentration reduced pH and viscosity of the dispersions, and |ζ potential| of dispersed particles. Conversely, it increased electrical conductivity and density of the dispersions, and hydrodynamic diameter of dispersed particles. At a given concentration, these effects were slightly more pronounced for dispersions formed with GA or LA, compared to AA or PA. FT-IR data suggested more intense attractive interactions of chitosan chains with glycolate and lactate anions, than with acetate and propionate. Chitosan chains interacted more strongly with hydroxylated acids counter-anions than with their non-hydroxylated counterparts, leading to slight quantitative changes of physicochemical properties of these systems. Then, in physicochemical terms, GA, LA or PA are suitable to replace AA when preparing aqueous chitosan dispersions for technological applications.

Cost-effective way to improve the optical properties of poly(methyl methacrylate)/poly(ethylene terephthalate) light scattering materials: drop coalescence.

Herein, the dependence of the dispersed phase diameter on the shear history during melt processing is verified experimentally. We fabricated different kinds of poly(methyl methacrylate) (PMMA)/poly(ethylene terephthalate) (PET) blends by modifying the shear rate and shear time in a torque rheometer. Light-scattering sheets (LSSs) were then prepared by compression molding with the above blends. The total transmittance of the LSS with a shear history of 8min at 30rpm and then 20min at 5rpm achieves 84.8% due to the drop coalescence and larger diameters of the PET scatterers in the PMMA matrix, while the total transmittance of a sheet with a shear history at only 30rpm is just 70.8%. In addition to high total transmittance, the sheet also features high haze (beyond 92.5%) and tiny direct transmittance (less than 5%), which is vital for uniform illumination and glare protection from lasers and light-emitting diodes.

Effect of montmorillonite and chain extender on rheological, morphological and biodegradation behavior of PLA/PBAT blends

The effect of montmorillonite clay (MMT) and/or chain extender (CE) on rheological, morphological and biodegradation properties of PLA/PBAT blend was investigated. The biodegradation behavior was evaluated by CO2 evolution in soil burial. CE incorporation resulted in an increase in the complex viscosity of PLA/PBAT blends, an increase in PLA crystallinity and a decrease in the dispersed phase diameter. MMT incorporation resulted in an increase in the complex viscosity, more pronounced shear-thinning behavior and a decrease in the dispersed phase diameter. CE incorporation resulted in a slight effect in the rheological properties of PLA/PBAT blend in the presence of MMT. Unfilled PLA/PBAT blend presented the highest amount of evolved CO2, and the micrographs indicated that degradation tends to occur on the surface. MMT delayed biodegradation of PLA/PBAT blends even although their surfaces presented some cracks and holes in a few localized regions. PLA/PBAT + CE blend presented the lowest amount of evolved CO2.

Role of Humic Acid in Enhancing Dissolved Air Flotation for the Removal of TiO2 Nanoparticles

The particle separation efficiency by flotation sharply decreases or even completely fails when the diameter of dispersed particles falls into the nanoscale. In the present laboratory work, humic acid was used to enhance the removal of TiO2 nanoparticles from suspension in a chemical coagulant-free dissolved air flotation process. Without humic acid, merely 63.8% of TiO2 nanoparticles were removed. For the humic acid-assisted dissolved air flotation, the pH of humic acid solution significantly influenced the removal efficiency: more than 90% of nanoparticles could be separated when the pH of the humic acid stock solution was acidic; however, the basic solutions resulted in rather poor performance. In the acidic solution, the fiberlike humic acid might form colloids through the attraction between hydrophobic moieties. They possibly acted as a fishnet and trapped nanoparticles, leading to the great measured bubble–particle attachment efficiency. In all the effluents, a low residual dissolved organic carbon ...

硬質な球状微細粒子を含む二相合金の加工硬化に関する数理モデリング

Plastic deformation and dislocation accumulation in dispersion hardening alloys are numerically analyzed by a crystal plasticity finite element technique and work hardening characteristics are discussed. The critical resolved shear stress for slip system is given by the extended expression of the Bailey-Hirsch type model which include the Orowan stress as size effect of microstructure. Work hardening of slip system is estimated by statistically stored dislocation (SSD) density. Increment of the SSD density is evaluated by slip strain and the mean free path of dislocations (the Kocks-Mecking model). The mean free path depends on the average spacing of dispersed particles, which is also used to estimate the Orowan stress. The average spacing of dispersed particles is calculated from the volume fraction and average diameter of dispersed particles. As a result, flow stress level at the initial stage of deformation agreed very well with experimental result but work hardening rate was higher than that of experiment. From this fact, it is considered that the mean free path and the average spacing of dispersed particles are different spacing factors. When we assume that the mean free path is two to three times larger than the average spacing of dispersed particles, numerical result of the strain hardening agrees very well with experimental one.

Preparation and properties of polyurethane‐modified epoxy cured in different simulated gravity environments

ABSTRACTGreat attention has been paid to the composites with interpenetrating polymer networks (IPNs) because of their special performance. However, the influence of sedimentation and convection from different gravity environments on the formation of IPNs and the properties of IPNs blends has received little attention. To understand their influence, environments with different gravity accelerations of 0g, 1g, and 2g were simulated with a superconducting magnet, and tests, including differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), coefficient of thermal expansion (CTE), scanning electron microscopy, and three‐point bending, of the IPNs blends cured in different gravity environments were conducted and analyzed. Fourier transform infrared spectroscopy, DSC, and DMA proved the formation of IPNs during the reaction between the polyurethane prepolymer (PUP) and epoxy resin (E51). The curves of DSC also certified the differences in the curing degree between the different parts along the direction of gravity of a sample. With the increase of mass fraction of PUP, the change trends of the storage modulus presented a linear decrease when samples cured in microgravity environment, but presented a parabolic trend when samples were cured in terrestrial environment. The damping properties of samples cured in simulated microgravity environments are better than those cured in terrestrial environment. With the increase in the simulated acceleration of gravity, the diameter of dispersed phase in a sea‐island structure increased, but their number decreased and the bending stress and CTE of the IPN blends all decreased. These results show the formation of IPNs was affected by different gravity values, and the thermal and mechanical properties of the IPN composites were influenced by the changed IPN components. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42063.

Mathematical Model for Determinating the Efficiency of Separation of Aerosols in Dry and Sprayed Channels

Turbulent fl ow of aerosols in a cylindrical channel has been investigated. Differential equations of transfer of dispersed particles have been considered, and a two-dimensional equation with a mass source has been solved. Different numerical experiments have been conducted on the basis of the model proposed. Air with water droplets was used as a gas-liquid mixture in the calculations. The influence of the spraying of the channel, the fl ow velocity, the diameter of dispersed particles, and the water concentration on the separation efficiency of an aerosol have been studied. Agreement with experimental data has been shown. A mathematical model has been developed that can be used in designing gas-cleaning apparatuses for enterprises of various industries.

Investigations on structure and properties of blends of polypropylene with polyamide 1010 by Rayleigh scattering

The phase structure and morphology of polypropylene (iPP) blends with poly(decamethylene sebacamide (polyamide 1010, PA1010) and the part-compatible alloys (iPP/PA1010/iPP-g-MAH) are investigated by Rayleigh scattering, i.e. small angle light scattering (SALS). The structure parameters of SALS, i.e. correlation distance, a c and average chord lengths, $$\bar l$$ , are calculated. Their variation with the composition of the blends and alloys is discussed. The morphology and structure of fracture surfaces in the blends and alloys are studied by SEM images. The average diameter of dispersed phase in the blends and alloys is calculated by graph processing. The variation of average diameter is similar as that of average chord lengths of dispersed phases. The mechanical properties of the blends and alloys are analyzed and the relation of modulus and yield stress with the composition is studied. It is confirmed that the correlation between the modulus and the structure parameters is non-linear, while the correlation between the yield stress and the composition or structure parameters is linear.

Effect of maleated EVA on compatibility and toughness of PETG/EVA blend

AbstractMaleic anhydride (MAH) grafted onto ethylene vinyl acetate copolymer (EVA), mEVA (modified EVA) was blended with poly(ethylene glycol‐co‐cyclohexane‐1,4‐dimethanol terephthalate) (PETG) with various mEVA and EVA (unmodified) content in the internal mixer. The effect of reactive compatibilizer to decrease the dispersed particle diameter was observed. The brittle–ductile transition was found at about dn: 0.37 µm and dv: 0.55 µm of particle diameter, a critical particle diameter, regardless of EVA content, and the blend was also toughened at above the critical particle diameter regardless of dispersed EVA content and compatibility. The toughening mechanism and the effect of the particle diameter on the impact strength of the blend were investigated by morphological observation, and it was found that the toughening of the PETG/EVA blend system resulted from the shear deformation, induced by cavitation of dispersed EVA particles. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

The Preparation and Property of Organic Solvent Lignin and PVC Composite Materials

The organic solvent lignin in this paper was extracted from the scrap liquid of the reed ethanol pulping. The attained lignin was characterized by Scanning Electron Microscope（SEM）.On this basis，the lignin is blended with PVC and other auxiliaries, PVC/lignin composite material is prepared by pressure molding. The mechanical performance index of PVC/lignin composite material is detected and the impact fracture morphology of the PVC/lignin composite material is observed by SEM photograph. According to the research, it is indicted that the lignin and PVC has a certain degree of compatibility. The less dosage of lignin, the better compatibility lignin and PVC performances. With the increasing of dosage of lignin, the impact strength, tensile strength and bend strength of PVC/lignin composite material decrease. Compared with 5 phr PVC/lignin composite material, the dispersed phase diameter of the impact fracture morphology of 20 phr PVC/lignin composite material becomes bigger, and the uniformity of distribution becomes worse.

The effect of free radical reactions on structure and properties of poly(lactic acid) (PLA) based blends

The blending of PLA with poly(butylene-adipate-co-terephthalate) (PBAT) is a promising strategy to achieve a toughened multiphase material. The blends ductility could be further improved through reactive compatibilization, i.e. inducing the formation of comb PLA-PBAT copolymers during the melt blending. In the present work a non-selective strategy was adopted which consisted in the use of a peroxide, 2,5-Dimethyl-2,5-di(tert-butylperoxy)hexane. The phase morphology development and the final properties (torque, fluidity in the melt, tensile behaviour, thermal and dynamical–mechanical features) of the blends were studied as a function of the peroxide concentration. The elongation at break was improved up to a maximum value thanks to this approach and a corresponding minimum was observed in the value of the dispersed phase diameter. A structural characterization of the macromolecules formed during the reactive process was attempted by using size exclusion chromatography of the blends and comparison with the pure polymers obtained by processing in the presence of the peroxide.

Effect of Poly (Propylene-g-maleic Anhydride) on the Morphological, Rheological, and Mechanical Properties of PP/HDPE Blend

In this study, the morphological, rheological, and mechanical properties of PP/HDPE blend compatibilized with poly (propylene-g-maleic anhydride) were studied. Necessary blends were prepared using a counter current twin-screw extruder. The blend composition ranged from 10 to 50 wt% of dispersed phase (HDPE) and compatibilizer (MAPP) with two Concentration ranges 10, 20 wt% were used for PP/HDPE (80/20) blend with respect to the dispersed phase (HDPE). The results of morphological studies shows a droplet dispersion morphology in the composition to 50wt% HDPE content, which indicates that HDPE forms a dispersed phase and PP forms a continuous phase in these composition region. Addition of the MAPP compatibilizer decreases the dispersed phase diameter. Rheological studies show that addition of the MAPP compatibilizer increases the melt viscosity, complex viscosity, storage, and loss modulus of the blends. Mechanical studies show that with increasing of HDPE concentration the tensile and impact strength first increase, and then decrease. The elongation at break decreases with increasing of HDPE concentration. Addition of the MAPP compatibilizer increases the elongation at break, tensile, and impact strength.

Microcompounding of organoclay–ABS/PA6 blend‐based nanocomposites

AbstractIn this study, acrylonitrile–butadiene–styrene (ABS) and polyamide‐6 (PA6) were blended in the presence of an olefin‐based compatibilizer and organoclays. The effects of ABS to PA6 ratio, clay content, and screw speed of the microcompounder were examined by performing morphological (i.e., XRD, SEM, and TEM) and tensile tests. The average aspect ratio of the clay platelets after processing was obtained by applying semiautomatic image analysis method. SEM analysis showed that addition of the compatibilizers to the ABS/PA6 blend system resulted in a decrease in diameter of dispersed phase when one of the phases was continuous. The addition of 5 wt% compatibilizer altered the dispersed morphology to cocontinuous morphology when the weight percentage of ABS was equal to that of PA6. The results of XRD analysis implied that clays were exfoliated in the presence of PA6. It was observed in TEM micrographs that clays were selectively dispersed in PA6 phase. Aspect ratio of the platelets increased as the PA6 content increased. Moduli of the nanocomposites were improved by enriching blend with PA6 and increasing screw speed. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers