Effect Of Mixing Conditions Research Articles

Effects of mixing conditions and activator anionic species on the rheology of silicate-activated slag concrete

The proper control of the rheological performance of silicate-based alkali-activated slag (AAS) mixtures is problematic, as the conventional superplasticizers become less effective in alkaline media. Nevertheless, several methods have been proposed to improve the workability of silicate-activated AAS, such as by extending the mixing time, and replacing sodium silicate with sodium carbonate activators. However, the underlying fluidizing mechanism is not yet well understood in the literature, which is crucial knowledge to achieve proper rheology control of silicate-activated AAS.In this study, the effects of mixing conditions and activator anionic species on the rheology of silicate-activated AAS concrete have been assessed. The reaction products, particle size and interparticle interactions, as well as the reaction kinetics in AAS, have been further investigated to understand the distinct fluidizing mechanisms. By using a longer mixing time, it was found that the solid particles formed at early ages are broken down into smaller particles, accompanied by a slight increase in the amount of reaction products to improve the fluidity. With the sodium carbonate substitution, the calcium ions dissolved from slag particles are entrapped into calcium carbonate precipitates to slow down the accumulation of C-(A)-S-H phases, leading to a better dynamic flow. However, the interparticle interactions are intensified due to the formation of larger particles and the declined dispersing effect induced by silicate activators.

Effect of Mixing Conditions on Dispersion and Degradation Behavior of HDPE/UHMWPE Blends

High density polyethylene (HDPE) / ultra high molecular weight polyethylene (UHMWPE) blend is expected as an all-polyolefin recycle material that can achieve both mechanical properties and a continuous melt-mixing process. In order to improve the mechanical properties of polymer blends, optimal mixing is required to achieve both good dispersibility and low degradation. In this study, the effect of mixing conditions on the dispersion and degradation behavior of HDPE/UHMWPE blends were investigated. Neat HDPE and HDPE with 5% UHMWPE were obtained by melt mixing in internal batch mixer. Time of mixing, Specific Energy Input (SEI), and rotation speed of the rotors were changed. From the results of microscopic observation and a differential scanning calorimetry (DSC), the dispersibility progressed with the increase in SEI regardless of the rotor speed. The results of Gel Permeation Chromatography (GPC) show the molecular chain scission was also promoted by the increase in SEI. In the other hands, the results of oscillatory shear test show the increase in storage modulus G’ were promoted by increase in not only SEI but rotor speed. Furthermore, the molecular chain scission and increase in G’ were significantly suppressed by the nitrogen atmosphere.

Effect of mixing conditions and polymer particle size on the properties of polypropylene/graphite nanoplatelets micromoldings

Abstract In this study, properties of polypropylene/graphite nanoplatelets (PP/GNP) composites and corresponding micromoldings were systematically studied in terms of filler loading concentrations and mixing methods. PP of different forms, i.e., PP pellets and powders, were adopted to fabricate PP/GNP composites. Additionally, a comparative study of precoating GNP and PP powders using solvent-based solution blending and ultrasonication-assisted mixing was performed. Results showed that PP/GNP composites prepared using powder form PP resulted in at least one order of magnitude higher electrical conductivity than using pellet form PP and further reduced the percolation threshold from 12.5 to 10 wt%, which was related to the state of filler distribution within corresponding moldings. Morphology observations revealed that microparts prepared with powder-PP/GNP composites exhibited less preferential alignment of GNP particles along the flow direction when compared with those molded using pellet-PP/GNP counterparts, which was helpful in improving the overall electrical conductivity for PP/GNP micromoldings.

Effect of mixing conditions on the density, morphology, thermal and mechanical properties of mineral foam

Mineral foam concretes are classified as lightweight concretes, which are characterized by the presence of air voids in the materials due to the use of a suitable foaming agent. Their physical and mechanical properties are strongly governed by microstructural properties, which depend on several factors such as foam quantity, water/binder ratio (W/B), and the mixing process. In this study, mineral foams were prepared with a mixed foaming method. Gypsum is used as a binder, flax shives as vegetative aggregates, and Betomouss as the foaming agent (sodium lauryl ether sulfate as the main tensioactive molecule). The impact of mixing conditions (stirring rate, stirring time, and W/B ratio) on the performances of foams is investigated. The results show that varying these mixing conditions will induce high variation of foam performances at the fresh and hardened states. Furthermore, increasing the stirring rate and stirring time generates an increase of the air-void system, finally causing materials to decrease foam density. Consequently, this entails an improvement in thermal conductivity and a reduction of mechanical properties. In addition, increasing the W/B ratio leads to an increase in spreadability, density, and mechanical properties. In contrast, foams with a low W/B ratio have the best thermal properties.

Effects of mixing conditions on floc breakage and re-growth formed by magnesium hydroxide and polyacrylamide

Effects of mixing conditions on floc breakage and re-growth formed by magnesium hydroxide and polyacrylamide

Effect of Mixing Conditions and Montmorillonite Content on the Mechanical Properties of a Chloroprene Rubber

Effect of Mixing Conditions and Montmorillonite Content on the Mechanical Properties of a Chloroprene Rubber

The Effect of Mixing Conditions on the Mechanical Properties of Polymer Mixtures of Low-Density Polyethylene and Rubber Powder Based on Ternary Ethylene–Propylene–Diene Elastomer

The effect of mixing conditions on the properties of polymer mixtures of low-density polyethylene with vulcanizates and rubber powder based on ternary ethylene–propylene–diene elastomer was studied. Polymers were mixed by two techniques: using a rotor disperser by high-temperature shift deformations and in a Brabender mixer. The analysis of mechanical characteristics of rubber plastics manufactured using different types of equipment showed that deformation and strength properties of rubber plastics mixed in a rotor disperser are higher compared to those made in a Brabender mixer.

Effects of Mixing Conditions on Floc Properties in Magnesium Hydroxide Continuous Coagulation Process

Magnesium hydroxide continuous coagulation process was used for treating simulated reactive orange wastewater in this study. Effects of mixing conditions and retention time on the coagulation performance and floc properties of magnesium hydroxide were based on the floc size distribution (FSD), zeta potential, and floc morphology analysis. Floc formation and growth in different reactors were also discussed. The results showed that increasing rapid mixing speed led to a decrease in the final floc size. The floc formation process was mainly carried out in a rapid mixer; a rapid mixing speed of 300 rpm was chosen according to zeta potential and removal efficiency. Reducing retention time caused a relatively small floc size in all reactors. When influent flow was 30 L/h (retention time of 2 min in rapid mixer), the average floc size reached 8.06 μm in a rapid mixer; through breakage and re-growth, the floc size remained stable in the flocculation basin. After growth, the final floc size reached 11.21 μm in a sedimentation tank. The removal efficiency of reactive orange is 89% in the magnesium hydroxide coagulation process.

Improved tableting behavior of paracetamol in the presence of polyvinylpyrrolidone additive: Effect of mixing conditions

Monoclinic paracetamol (PA) is notorious as a poorly compactible model drug. Polyvinylpyrrolidone (PVP) is a polymer that can act as an effective binder to improve the mechanical properties of PA. It is surprising however that the role of mixing conditions on the physicochemical and mechanical properties of PA–PVP mixtures has not been reported previously. The results of this work showed that PA–PVP mixtures containing 5% (w/w) PVP prepared using high energy mixing conditions had considerably smaller particle size distributions and higher cohesivities than mixtures prepared using low energy mixing conditions. Solid-state analysis did not detect any change in the monoclinic crystalline form of PA after mixing with PVP. The following rank order of tabletability for PA–PVP mixtures was obtained according to the mixing condition: low shear∼medium shear<dry high shear<wet high shear<high-speed homogenization. A higher level of hydrogen bonding was detected in the mixtures prepared via high energy mixing conditions than in those prepared using low energy mixing conditions. Mixing is therefore a critical process that needs to be optimized during the preparation of interactive mixtures for tableting.

Effect of mixing conditions on the wet preparation of ceramic foams

Ceramic foams are a promising alternative to conventional catalyst supports due to their macro-porosity, which should enhance mass transport properties during reactions. Whilst direct foaming is a straightforward production method, the use of kitchen mixers commonly reported in the literature to initially froth the ceramic slurry limits understanding of scale-up. This study reports a systematic experimental investigation of the impact of mixing parameters on the properties of the foams produced in an agitated baffled vessel of diameter, T=175mm, equipped with an up-pumping pitch blade turbine with diameter of either D=0.23T or 0.51T and a bottom round sparger with a diameter of 45mm. The flow conditions in the present study were in the low to mid transitional regime (50<Re<1000). Design of Experiments (DoE) was employed to generate a series of screening experiments by variation of sparging time, air flow rate, impeller speed and impeller diameter. The mixing behaviour was described as a function of relevant dimensionless groups (Re, Fr, Flg, etc.) whilst the gas–liquid flow regime was estimated by examination of a ceramic particles free system. The properties of the foams obtained were correlated with key dimensionless numbers, though the exponents obtained deviated from values in the published literature. In addition, the rheology of the foam was correlated to the bubble size distribution showing that rheology measurements have potential for at-line measurement to control the structure of the produced material.

Structural, thermal, rheological and mechanical properties of polypropylene/graphene nanoplatelets composites: Effect of particle size and melt mixing conditions

Graphene nanoplatelets (GNP) of various sizes were mixed with polypropylene (PP) in an internal mixer to prepare composites. The effects of mixing conditions, GNP size and concentration in composites were investigated. The composites were characterized at different scales, using electron microscopy, X‐ray diffraction, thermogravimetric analysis, and rheometry. It was shown that the PP/GNP composites had to be considered as non‐intercalated and non‐exfoliated microcomposites. However, the thermal, rheological and mechanical properties of the PP/GNP microcomposites were improved with respect to that of the matrix and similar to those of thermoplastic/organoclay or reduced graphene nanocomposites. In the best cases, storage modulus plateau in the glassy domain was increased by 30% and onset of degradation temperature by 40°C. Finally, in the investigated range of this study, the mixing conditions applied in the internal mixer did not affect the structural and rheological properties of the PP/GNP composites. POLYM. ENG. SCI., 58:1937–1944, 2018. © 2017 Society of Plastics Engineers

Effect of Mixing Time and Temperature on Cracking Resistance of Bituminous Mixtures Containing Reclaimed Asphalt Pavement Material

The use of reclaimed asphalt pavement (RAP) in bituminous mixtures is considerably increasing due to the environmental and economic benefits of recycled materials. However, stiffer mixes, usually resulting from RAP addition, have raised concern about long-term properties of the pavement; a mechanical characterization of these mixes is thus needed. In this study, the effect of mixing condition on bituminous mixtures containing RAP was evaluated. Volumetric and mechanical properties were analyzed. An experimental program, with the aim of measuring stiffness modulus, water sensitivity, and cracking resistance, was conducted. Cracking resistance was evaluated according to the Fenix test because it has proved to be a convenient and effective method for characterizing cracking behavior of bituminous mixtures at different temperatures. Mixtures containing 20 or 40% of RAP material were tested; virgin aggregates and RAP mixing temperatures as well as mixing time were varied and comparisons with a reference mix were conducted to characterize fracture energy and mechanical performance.

Characterization of re-grown floc size and structure: effect of mixing conditions during floc growth, breakage and re-growth process

The impact of mixing speed in three stages-before breakage, during breakage, and after breakage-on re-grown floc properties was investigated by using a non-intrusive optical sampling and digital image analysis technique, respectively. And then, on the basis of different influence extent of mixing speed during each stage on size and structure of re-grown flocs, coagulation performance with varying mixing speed was analyzed. The results indicated that the broken flocs could not re-grow to the size before breakage in all cases. Furthermore, increasing mixing intensity contributed to the re-formation of smaller flocs with higher degree of compactness. For slow mixing before breakage, an increase in mixing speed had less influence on re-grown floc properties due to the same breakage strength during breakage, resulting in inconspicuous variation of coagulation efficiency. For rapid mixing during breakage, larger mixing speed markedly decreased the coagulation efficiency. This could be attributed that mixing speed during breakage generated greater influence on re-grown floc size. However, as slow mixing after breakage was elevated, the coagulation efficiency presented significant rise, indicating that slow mixing after breakage had more influence on re-grown floc structure upon re-structuring and re-arrangement mechanism.

A strategy to simulate radio frequency heating under mixing conditions

A computer simulation model was developed using finite element-based commercial software, COMSOL, to simulate temperature distributions in wheat samples packed in a rectangular plastic container and treated in a 6kW, 27.12MHz RF system with and without mixing conditions. The developed model was then experimentally validated by temperature distributions of three layers without mixing condition, and surface and interior temperature distributions of wheat samples under one, two and three times mixing conditions. Both simulation and experiment showed similar heating patterns in RF treated wheat samples under both conditions, in which corners and edges were overheated and the temperatures were higher in the lower sections of the container. The uniformity index (UI) was used to evaluate effects of mixing on RF heating uniformity. Both experimental and simulated UI showed decreasing trend with the increasing mixing times. The developed model can help to understand the RF heating patterns and effects of mixing conditions on RF heating uniformity and provide valuable strategy for developing effective industrial-scale RF treatments with mixing processes.

Effect of Mixing Condition on the Mechanical Properties of Magnesium Based Composites

The effects of mixing conditions, i.e; mixing speed and mixing duration on the mechanical properties of the magnesium based composites were investigated. The hardness, tensile strength and microstructure of composites were studied. It was found that increase of the mixing speed and prolong the mixing time can improved the distribution of SiC particle and mechanical properties of magnesium based composites.

Effect of mixing conditions on the selective localization of graphite oxide and the properties of polyethylene/high-impact polystyrene/graphite oxide nanocomposite blends

We develop here a new and effective strategy for compatibilizing immiscible polymer blend nanocomposites of polyethylene/high impact polystyrene/graphite oxide (PE/HIPS/GO) by combination of solution intercalation and melt mixing method.

Effect of mixing conditions on the morphology and performance of fiber-reinforced polyurethane foam

Polyol derived from soybean oil was used as a natural source preparation to create an environmentally friendly polyurethane foam. In order to stiffen these foams, wood fibers were added to provide reinforcement at low cost, while preserving the environmental friendly nature of the material. Mixing is a crucial step in the manufacture of reinforced foams and determines the fiber distribution and cell structure and hence the performance of the material. In this study, the effect of stirring variables on the mechanical properties of polyurethane foams was investigated and foams made using hand mixing were compared to foams made with a mechanical stirrer. Cell morphologies of the reinforced foams were characterized using scanning electron microscopy, X-ray computed tomography, and 3D stereo microscopy. The mechanical performance of the reinforced foam was essentially independent of stirring time and mainly depended on the variation in stirring rate. For foams made with high fiber fractions using a mechanical stirrer, the fibers were not as effective in increasing the compressive strength and modulus as they were in foams prepared by hand stirring. This suggests that mechanical stirring causes damage to the fibers, particularly at high fiber content.

Effect of mixing condition on the physical properties of gel including the bubble

Effect of mixing condition on the physical properties of gel including the bubble

Formation, breakage and re-formation of flocs formed by cationic starch

The efficiency of flocculation can be significantly improved through floc breakage and re-formation under appropriate conditions. To obtain a better understanding of the mechanisms involved and to relate floc properties to separation efficiency, the effects of mixing conditions on the formation, breakage and re-formation of flocs formed by kaolin and cationic starch were investigated through conventional jar test procedure and continuous optical monitoring. It has been found that the breakage of flocs was fully reversible and the polymer flocculant could resist strong shear; even having been sheared for four times, the flocculation index (FI) value would be higher than that of the original flocs. The results indicated flocs formed at neutral and alkaline conditions had better shear resistance than those at acidification conditions, and the mode of floc rupture was large-scale fragmentation.

Effect of Mixing Conditions on Phase Morphology of NR/EPDM Blends

A number of mixing parameters including mixing temperature, rotor speed, fill factor, mixing time, and loading sequence have strong influences on mixing quality. In this work, an in-house developed co-rotating batch mixer equipped with the MX2 rotors, which providing a combination of shear and extensional flows, was used to prepare NR/EPDM blends under various mixing temperatures, rotor speeds, and mixing times. Phase morphology and magnitude of coefficient of dispersive mixing (CDM) were used as qualitative and quantitative determination of mixing quality, respectively. It was found that the lower the mixing temperature, the greater the mixing quality would be obtained. The optimum rotor speed was observed at 60 rpm which was probably caused by the counter-balancing effect of shear stress and shear heating.