High Shear Mixer Research Articles

Continuous Production of Water-Based UV-Curable Polyurethane Dispersions Using Static Mixers and a Rotor-Stator Mixer.

UV-curable polyurethane dispersions (UV-PUDs) have applications in coatings for a variety of materials. Historically, the neutralization and dispersion steps of the UV-PUD production process have been performed in batch. However, continuous processing might reduce capital and operating costs, improve the dispersion characteristics, and facilitate scale-up. Static mixers and inline high-shear mixers are able to provide the necessary shear forces to obtain miniemulsions. The production of a UV-PUD is therefore studied in a continuous setup, whereby the neutralization step is performed in static mixers and the dispersion step is performed either in static mixers or in a high-shear mixer. The influence of the prepolymer temperature, mixing energy, and feed flow rate on the particle size and stability of the UV-PUD particles in water is explored. The results show that the neutralization step is mixing-sensitive, and the temperature of the neutralized prepolymer influences the particle size in the dispersion process. The amount of shear force applied during the dispersion step has a limited effect on the particle size. UV-PU dispersions with an average particle size below 80 nm and PDI below 0.1 are obtained with static mixers or in an inline rotor-stator mixer, at flow rates of 5.2 and 7.2 L/h, respectively. This research demonstrates that continuous processing using static mixers and high-shear mixing is a viable option for the neutralization and dispersion of UV-PUDs.

Nanoparticle de-agglomeration in viscous fluids using different high shear mixer geometries

In the present work, the effect of batch high shear mixer (HSM) geometries is studied on nanoparticles deagglomeration and power draw in water and aqueous glycerol solutions. The kinetics and mechanism of cluster break-up are investigated for disintegrated (less number of larger stator holes), and mesh (higher number of smaller stator holes) heads at different rotor speeds. Mesh head geometry is found to be more efficient for fines generation than disintegrated head. A bi-modal particle size distribution and erosion as dominant break-up mechanism is found. The size of the smallest fines is found to be ≈30 nm for mesh head and ≈50 nm for the disintegrated head. Z-average ranges from 180 to 310 nm for given operating and process conditions. The power draw is more in mesh head and increased with an increase in viscosity. Further, power draw increased with an increase in viscosity of continuous media and rotor speed.

CFD analysis of flow field and power consumption of in-line high shear mixers with different stator structures

As a new type of process enhancement equipment, the high shear mixer (HSMs) has very complicated structure, high strain rate, and very complicated internal flow, makes it more difficult to understand the flow and mixing characteristics. Although the relationships between the power consumption and operating parameters of HSMs have been obtained, there are too many factors to be considered, and there is still a lack in how the model parameters depend on the design parameter size, such as the geometric structure sizes of the rotor and stator. In this study, Computational fluid dynamics (CFD) is used to study the effect of different number of stator slots and stator tooth thicknesses on the flow field and power characteristics of in-line HSMs under the same stator opening area. Through the CFD simulation of Newtonian fluid and shear thinning power-law fluid, the functional relationship between power consumption constant KP , strain rate constant Ks , stator tooth thickness and the number of stator slots is studied. The results show that with the decrease of the number of stator slots ns and the thickness of stator teeth Ts, the jet intensity from the outermost stator tooth slots increases, and the circulating flow behind the jet increases, so the influence of the jet on the tangential movement is more obvious. With the increase of stator tooth thickness, KP decreases and Ks increases. With the increase of the number of stator slots, KP and Ks increase. Based on the correlation between KP and Ks and stator structure parameters, a new correlation with tip-to-base clearance, shear gap width, stator thickness and the number of stator slots for the power number is established. A new correlation can be provided as a unified correlation for viscous fluid in the laminar regime.

Comparison and estimation on deagglomeration performance of batch high shear mixers for nanoparticle suspensions

The deagglomeration performance of batch HSM was investigated including the effect of major operating and structural parameters through the experiments assisted with CFD simulation, as well as deagglomeration mechanism and the smallest attainable size of the agglomerates. The deagglomeration mechanism in batch HSM was dominated by erosion, and the smallest attainable size is stable at 131 nm under all the experimental operating and structural parameters of rotor–stator head. The results indicate that the optimization on the operating and structural parameters including increasing rotor speed, rotor teeth number and rotor teeth height, as well as reducing shear gap, can usefully intensify the deagglomeration performance of batch HSM. The rotor–stator head with the standard vertical teeth is more suitable than forward and backward bending teeth for promoting deagglomeration process due to its strong collision and shear effect and ability to provide high turbulent kinetic energy dissipation in the stator side slotting. At last, establishing the ANN model is a useful approach to estimate the d32 for the whole suspension correlated with the major operating and structural parameters.

Strengthening effect of Ti3C2Tx in copper matrix composites prepared by molecular-level and high-shear mixings and SPS

MXene (Ti3C2Tx) reinforced copper matrix composites with weight fractions of MXene from 1 to 4 wt.% were fabricated based on molecular-level and high-shear mixings and spark plasma sintering (SPS) method. The mechanical properties of the composites with different weight fractions of MXene were studied, and X-ray photoelectron spectroscopy (XPS) was used to track the state of MXene in the composite preparation process. Chemical state and interface transitions would result in an interesting ductile-brittle transition phenomenon of the composite. The Vickers hardness and compressive strength of the composites prepared by the molecular-level mixing and high-shear mixing methods have been improved (the maxima are 44.9% and 41.8%, respectively), where the addition of 1wt.% MXene results in a tensile strength increase of 29.9%. The results show that molecular-level mixing and high-shear mixing methods are hopeful to be applied to produce many kinds of MXene composites.

Optimasi Penggunaan High Shear Mixer pada Pembuatan Fraksi Alkaloid dari Daun Awar-awar (Ficus septica) dengan Desain Faktorial

Awar-awar (Ficus septica) is an Indonesian anticancer plant that contains alkaloids as the active compound. The n-hexane insoluble fraction (FTLH) is alkaloid-containing fraction obtained from the ethanolic extract of F. septica leaves (EEDFS) by fractionation using n-hexane. High shear mixer (HSM) can be used to optimize the separation processes, including fractionation. The application of HSM in the fractionation of EEDFS is affected by fractionation duration, amount of solvent per gram extract, and strirring strength. Thus, these parameters must be optimized to obtain the optimum condition for the production of FTLH with the highest alkaloid content. This study aimed to optimize the production of FTLH using HSM with factorial designs. The single factor experimental design was employed to determine the influence of the individual variable on the alkaloid content and to define the optimum range value of each variable. A full factorial design was used to determine the presence of interaction among the factors and to determine the optimal fractionation condition. The results showed that all investigated factors independently affected alkaloid contents. The solvent volume of 14-18 mL per gram extract, the fractionation duration of 2.5-5.0 minutes, and the stirring strength of 3000 rpm are the optimal range value of each factor. The optimal conditions were solvent volume of 14.0-14.4 mL/gram extract, fractionation duration of 2.5-2.7 minutes, and strirring strength at 3000 rpm. At the optimal condition, the total alkaloid content in the FTLH reached 0.1466% or 1.3 times higher than the extract (0.1128%).

Solventless-mixing layering using a high shear mixer for preparing drug pellets: A feasibility study using acetaminophen

Our aim was to investigate the feasibility of mechanical-mixing layering using a high shear mixer, which can produce drug pellets by simply mixing drug crystals and inactive seed particles without the need for solvents or binders. Acetaminophen crystals and microcrystalline cellulose spheres were mechanically mixed using various impeller speeds and the resulting composite particles were characterized. Acetaminophen particles were separated from the spheres using a low impeller speed and deposited on the surface of the spheres at a higher impeller speed. The diameter of the acetaminophen crystals in the composite particles decreased as the impeller speed increased, due to increased collision impact between the spheres. The correlation between drug content and drug particle diameter in the composites indicates that acetaminophen particles were layered on the cellulose spheres due to their pulverization during the mixing treatment. We examined additional mixing treatments to enhance drug loading: after mechanically mixing acetaminophen crystals and cellulose spheres, fresh acetaminophen crystals were added and mechanically mixed with the composite particles. Additional mixing increased the loading of acetaminophen particles without lowering the layering efficiency. In conclusion, mechanical-mixing layering can be accomplished using a high shear mixer.

Effect of stator geometries on flow fields and mixing performance for viscous fluids

High shear mixers (HSMs) find wide applications in industrial processes where intense mixing and dispersion of fluids play a vital role. In this work, the flow fields and mixing performance is analyzed in different batch HSMs with varying stator heads, such as disintegrated, slotted, and mesh. Further, the effect of viscosity, flow behavior and rotor speed on hydrodynamics and mixing performance is assessed through numerical investigations. The turbulent flow fields and mixing enhancement are characterized using standard k-ɛ turbulence model with multiple reference frames approach for various HSMs. The turbulent statistics like turbulent kinetic energy are found to be maximum in the stator hole region and varied with flow behavior. The energy dissipation within the rotor vicinity is found higher for mesh head geometry followed by disintegrated and slotted heads. The effect of tracer injection locations is evaluated to gain comprehensive information on the mixing performance inside the mixing tank. Mixing time (t95) was evaluated and correlated with the existing results. For viscous fluids, complete mixing is hard to achieve due to the presence of cavern effect in smaller stator holes HSM. Moreover, the results provided guidance for further selection, design and development of HSMs for process industries.

Mechanical properties of graphene nanoplatelets-reinforced concrete prepared with different dispersion techniques

In this paper, an experimental investigation is carried out to study the effects of graphene nanoplatelets (GNPs) on the mechanical properties of cementitious composites with coarse aggregates. The concrete mixtures with GNPs concentrations ranging from 0.025% to 0.10% by weight of the cement are prepared, where a wet dispersion technique that employs high shear mixing and polycarboxylate-based superplasticizer to disperse GNPs in water. The effects of various dispersion parameters including different high shear mixing durations as well as the use of ultrasonication together with high shear mixing on the dispersion of GNPs are studied. The dispersion quality of GNPs is assessed through optical microscopy, Raman spectroscopy, and Scanning Electron Microscopy tests. Compressive strength and flexural strength tests are conducted to assess the effects of GNPs on mechanical properties of the fabricated GNP-reinforced concrete specimens. Results show that all the dispersion procedures considered in this study can disperse GNPs in water without causing any basal or vacancy defects in graphene sheets and reduce the size of graphene flakes. The use of ultrasonication together with high shear mixing leads to the smallest size graphene sheets. When the GNPs are added to the concrete mixture at a dosage of 0.025%, a maximum increase of 17% in compressive strength is observed, while no significant effect of GNPs on the flexural strength is noticed.

Fig seed oil‐loaded nanostructured lipid carriers: Evaluation of the protective effects against oxidation

The aim of this study was to develop a carrier system that protects fig seed oil (FSO) from oxidation by encapsulating into nanostructured lipid carriers (NLCs). NLCs were prepared by high shear mixing technique and the effects of solid lipids and surfactants on the formulation parameters were investigated. The formulations were characterized in terms of particle size, polydispersity index, and zeta potential, and fatty acid and tocopherol amounts were determined by GC and HPLC, respectively. NLC loaded with FSO was obtained at a particle size of 241 nm with low polydispersity (0.259) and a negative electrical charge (−13.6 mV). The antioxidant capacity has been evaluated by accelerated oxidation storage tests, radical and hydrogen peroxide scavenging activity tests. The stability of the final formulation with high concentration of gamma tocopherol and unsaturated linoleic acid content of FSO was increased by loading into NLCs. Novelty impact statement NLC formulations loaded with FSO were prepared for the first time at a dimension of 241 nm with low polydispersity. FSO was protected against lipid oxidation by encapsulation into NLC as revealed by lipid peroxidation, hydrogen peroxide, and radical scavenging activity tests. FSO-loaded NLC formulations were shown to be valuable carriers for encapsulation of bioactive food materials for stability.

Micromixing performance of the teethed high shear mixer under semi-batch operation

Micromixing performance of the teethed high shear mixer under semi-batch operation

Influence of Graphene Nanoplatelet Lateral Size on the Electrical Conductivity and Electromagnetic Interference Shielding Performance of Polyester Nanocomposites.

Polyester nanocomposites reinforced with graphene nanoplatelets (GnPs) with two different lateral sizes are prepared by high shear mixing, followed by compression molding. The effects of the size and concentration of GnP, as well as of the processing method, on the electrical conductivity and electromagnetic interference (EMI) shielding behavior of these nanocomposites are experimentally investigated. The in-plane electrical conductivity of the nanocomposites with larger-size GnPs is approximately one order of magnitude higher than the cross-plane volume conductivity. According to the SEM images, the compression-induced alignments of GnPs is found to be responsible for this anisotropic behavior. The orientation of the small size GnPs in the composite is not influenced by the compression process as strongly, and consequently, the electrical conductivity of these nanocomposites exhibits only a slight anisotropy. The maximum EMI shielding effectiveness (SE) of 27 dB (reduction of 99.8% of the incident radiation) is achieved at 25 wt.% of the smaller-size GnP loading. Experimental results show that the EMI shielding mechanism of these composites has a strong dependency on the lateral dimension of GnPs. The non-aligned smaller-size GnPs are leveraged to obtain a relatively high absorption coefficient (≈40%). This absorption coefficient is superior to the existing single-filler bulk polymer composite with a similar thickness.

Thermo-Physics characterization of polypropylene/multi-walled carbon nanotube nanocomposites for rapid replication using hot embossing process

This study presents a comprehensive review of the thermophysical, rheological, and mechanical characteristics of nanocomposites reinforced with carbon nanotubes (CNTs). The high-loaded polypropylene (PP) nanocomposites with multi-walled carbon nanotube loadings ranging from 0.01 wt.% to 5 wt.% were elaborated via high-shear mixing using a twin-screw mixer. The structural and rheological properties of the neat polypropylene in the molten state and those of the elaborated composites were determined. The thermophysical properties of the nanocomposites were investigated via differential scanning calorimetry and thermogravimetric analysis. The mechanical properties were determined through quasi-static tensile testing at room temperature. The results clearly indicate that the incorporation of CNTs in a thermoplastic polymer matrix significantly improves the final thermophysical and mechanical properties of the nanocomposites, through excellent dispersion of CNTs in the thermoplastic matrix and an improvement in interfacial interaction. The produced nanocomposites were granulated and used in a hot embossing process to manufacture micro-structured components. These micro-shapes on the surface of a metal mould were successfully transferred to a CNTs/PP nanocomposite substrate.

Healing characterisations of waste-derived bitumen based on crack length: Laboratory and modelling

The accumulations of waste plastics and municipal solid wastes from the resident groups and industrial companies have been causing serious environmental issues in the UK, due to difficulties in logistics, sorting, and reuse. In this sense, this paper is stimulated to develop novel approaches to convert some wastes into eco-friendly infrastructural materials, which provides a new way of waste reduction and reuse and extending the service life of asphalt pavement. This study aims to characterise the healing performance of waste-derived bitumen before and after pressure ageing vessel (PAV) ageing based on the crack length. One waste-derived bitumen was fabricated by blending the bio-oil pyrolysed from the organic fraction of municipal solid waste (5 wt%) with a control bitumen (X70) using a high shear mixer at a speed of 150 revolutions per minute (RPM) for 30 min at 150 °C under nitrogen atmosphere. A second waste-derived bitumen was fabricated using the low-density polyethene (LDPE) and mixed with the control bitumen at a concentration of 6 wt% at a speed of 900RPM for 90 min at 180 °C under nitrogen atmosphere. Crack length-based healing index and Ramberg-Osgood model were employed to characterise the healing rate and healing capability of the bitumen, respectively. Material properties (e.g., relaxation modulus and surface energy) of the bitumen used in the healing models were calibrated by linear amplitude sweep test (10 Hz and 20 °C), frequency sweep test (10 Hz, 10–70 °C), and time sweep fatigue-healing test (10 Hz and 20 °C) at a controlled strain level of 5% with different rest durations. Advancing contact angles used in the healing models of the bitumen were measured by a sessile drop tensiometer based on the tilting cradle method. Results show that the bio-oil productively promotes the healing potential and capability of the unaged bitumen, and the LDPE slightly strengthens them. The PAV ageing process evaporates most of the modifier bio-oil; hence, the PAV-aged bio-oil modified bitumen does not show better healing performance than that of the PAV-aged control bitumen. The PAV-aged LDPE modified bitumen has much better healing performance than those of the PAV-aged control bitumen and the PAV-aged bio-oil modified bitumen. The short-term healing rate and healing potential dominate the healing behaviours of the bitumen. The unaged bio-oil modified bitumen heals the fastest (having the highest short-term healing rate) and most (having the highest healing potential), followed by the unaged LDPE modified bitumen, and the unaged control bitumen heals the least and slowest. The PAV-aged LDPE modified bitumen heals the fastest and most, followed by the PAV-aged bio-oil modified bitumen and the PAV-aged control bitumen. The fundamental reason for LDPE's enhancement to bitumen's healing is that the LDPE increased the deformation recovery ability of the bitumen, leading to a higher wetting rate of the cracked surfaces and thus a higher short-term healing rate. However, the LDPE in bitumen cannot accelerate the molecular diffusion to increase the intrinsic healing or the long-term healing rate.

Numerical Simulation of Particle Mixing Behavior in High Speed Shear Mixer and Cylinder Mixer

Numerical Simulation of Particle Mixing Behavior in High Speed Shear Mixer and Cylinder Mixer

Preparation and characterization of experimental oily wastewater: effect of rotor speeds and oil/water ratios in an in-line high-share mixer

ABSTRACT Multiple oily wastewaters are necessary for scientific research and technological development. Experimental oily wastewater is prepared with an in-line high shear mixer at a constant flow rate. Rotor speeds have a significant effect on pressure drops across shear mixer, while oil/water ratios have less effect. With the increase of rotor speeds, most of the oil droplet size (D50, D90) show a downward trend. D10 of oil droplets may increase at low oil/water ratios while those decrease at high ones. Oil droplet sizes (D50 and D90) change slowly and emulsibility values decrease with the increase of oil/water ratios, and 0.06% is most favorable for fine emulsion. Higher rotor speeds prepare the turbulent environment easily, and higher oil/water ratios are available to improve droplets coalescence. Rotor stirring changes the drop size, and in turn influences the Zeta potential and stability of the emulsion. As oil/water ratios increase, absolute Zeta potential tends to decrease and coalesce easily. The oil contents of prepared wastewater measured with polyacrylamide addition are more than those without polyacrylamide addition respectively, and all of them are lower than their theoretical counterparts respectively. The results can provide necessary parameter references for the laboratory to prepare the character-specific oily wastewater.

The mechanical and thermal properties of graphitic carbon nitride (g‐C3N4)‐based epoxy composites

AbstractNumerous ways to reinforce epoxy resin and improve its thermomechanical properties have been attempted using organic and inorganic nanoparticles. In this paper, graphitic carbon nitride (g‐C3N4) nanoparticles were synthesized and used to improve the mechanical properties and thermal stability of epoxy composites. The g‐C3N4 was synthesized from cheap melamine powder using a simple one‐step thermal treatment, then was used to reinforce the resin at different weight percentages (wt%). X‐ray diffraction, scanning electron microscopy (SEM), and Fourier infrared spectroscopy were used to characterize the g‐C3N4 and ensure its successful synthesis by studying the changes in its crystal structure, morphology, and chemical structure. The filler was dispersed in the resin using a combination of ultrasonication and high shear mixing. The results showed that the mechanical properties were optimum when 0.5 wt% g‐C3N4 was used. The tensile strength and fracture toughness of the resulting epoxy composite improved by 21.8% and 77.3%, respectively. SEM was used to investigate the morphologies of cracks formed in epoxy composite specimens after the tensile testing. The SEM micrographs of the fracture surface showed a transition from a brittle to a rough morphology, signifying the enhancement in the composites' toughness. Thermogravimetric analysis showed a good improvement in degradation temperature of up to 8.86% while dynamic mechanical analysis showed that the incorporation of g‐C3N4 did not affect the material's glass transition temperature.

Green solvent-based extraction of chlorophyll a from Nannochloropsis sp. Using 2,3-butanediol

Chlorophyll acts as a beneficial antioxidant for the human body; however, only a few studies have reported the chlorophyll extraction using the non-toxic solvents. In this study, we used a green solvent, 2,3-butanediol (2,3-BDO), for extraction of chlorophyll a from Nannochloropsis sp. for the first time. Levo-isomer of 2,3-BDO exhibited remarkable chlorophyll extraction properties compared to its meso-isomer, and other conventional solvents such as ethanol. Hydrogen bonding between the solvent and chlorophyll was a detrimental factor for evaluating the extraction efficiency. The extraction yield reached 91.8% with the maximum specific antioxidant activity at 10,000 rpm for 20 min, using 25 mL solvent/g dry cell with assistance of a high shear mixer (HSM). The scalability was verified upon comparing the lab- and bench-scale tests, which demonstrated similar extraction yields and antioxidant activities, reducing process time and specific energy consumption.

Expanded vermiculite-filled flexible polymer composites

This study focuses on the fabrication and characterization of vermiculite-filled flexible polymer composites. Exfoliated vermiculite was incorporated into triblock thermoplastic elastomer copolymer, styrene- b-(ethylene- co-butylene)- b-styrene (SEBS), at various levels from 1 to 15 wt% by a high shear mixer. The composite films were obtained by the combination of solvent casting and compression molding. The morphological, structural, thermal, and mechanical properties and contact angle of the composites were determined. Some micro-morphological differences were observed between the samples and the difference was assumed to be caused by high shear mixing and filler concentration. High shear mixing was found effective in terms of the detachment of vermiculite layers at all concentrations. However, at low filler loading, that behavior was more obvious. At 1 wt% filler concentration, mechanical properties increased that was probably caused by good filler-matrix interaction stemmed from smaller particle size. At higher vermiculite concentrations, fillers found to show agglomerations that led to a decrease in mechanical strength and strain at break. Elastic and secant modulus showed an increasing trend. Contact angle measurements were carried out to determine the oleophilic character of the samples. An increase in the vermiculite content resulted in higher oleophilic character and the lowest contact angle was obtained at 15 wt% VMT loading. In addition to these, thermal stability, thermal dimensional stability and flame retardancy were improved by the incorporation of VMT. 15 wt% vermiculite-filled sample showed the best performance in terms of thermal stability and flame retardancy.

Impact of high-intensity ultrasound on the chemical and physical stability of oil-in-water emulsions stabilized by almond protein isolate

Lipid and protein oxidation always causes the deterioration of foods and their shortened shelf lives. The aim of the present work was to evaluate the effect of high-intensity ultrasound on the chemical and physical stabilities of oil-in-water emulsions comprising a plant-based oil (walnut oil) and protein (almond protein isolate). Emulsions were produced using a three-step procedure: high-shear mixing, sonication, and homogenization. The sonication step was carried out for 30 min at three different energy densities: 0, 200, or 400 J/cm3. Increasing sonic energy densities resulted in much smaller particle size and more droplet charge of the freshly made emulsions. The sonication step also improved the physical stability of emulsified lipids during storage by suppressing the changes in the droplet size and charge. Meanwhile, sonication also inhibited the oxidation of emulsified lipids by decreasing the generation of lipid hydroperoxides and 2-thiobarbituric acid-reactive substances as well as protein by reducing the gain of carbonyls, the loss of free sulfhydryl groups and intrinsic tryptophan fluorescence, and the modification of molecular weights. The highest sonication energy density (400 J/cm3) gave the best results. This study is expected to broaden the application of high-intensity ultrasound in protein emulsion production to improve their quality and acceptability.