Increase In Apparent Viscosity Research Articles

Influence of the alkaline solution and temperature on the rheology and reactivity of alkali-activated fly ash pastes

The aim of the present research is to ascertain the effect of the nature and concentration of the alkaline activator and temperature on the rheological behaviour of alkali-activated fly ash (AAFA) pastes. Furthermore, the reaction process of fly ash has been investigated from rheological measurements.Results have shown that the increase of the activator concentration and the temperature leads to an increase of yield stress and apparent viscosity, mainly at temperatures above 65 °C when dissolution of fly ash and precipitation of hydration products is raised. In general, similar activation energies were determined for alkali-activated fly ash pastes, regardless of the concentration and silica modulus of the activator, concluding that the underlying reaction mechanism is the same independently on the nature of the activating solution.

Finite-sized rigid spheres in turbulent Taylor–Couette flow: effect on the overall drag

We report on the modification of drag by neutrally buoyant spherical finite-sized particles in highly turbulent Taylor–Couette (TC) flow. These particles are used to disentangle the effects of size, deformability and volume fraction on the drag, and are contrasted to the drag in bubbly TC flow. From global torque measurements, we find that rigid spheres hardly decrease or increase the torque needed to drive the system. The size of the particles under investigation has a marginal effect on the drag, with smaller diameter particles showing only slightly lower drag. Increase of the particle volume fraction shows a net drag increase. However, this increase is much smaller than can be explained by the increase in apparent viscosity due to the particles. The increase in drag for increasing particle volume fraction is corroborated by performing laser Doppler anemometry, where we find that the turbulent velocity fluctuations also increase with increasing volume fraction. In contrast to rigid spheres, for bubbles, the effective drag reduction also increases with increasing Reynolds number. Bubbles are also much more effective in reducing the overall drag.

EFECTO DE LA ADICIÓN DE GRENETINA EN LAS PROPIEDADES REOLÓGICASY DE TEXTURA DE UN PANQUÉ REDUCIDO EN MARGARINA

To increase the concentration of gelatin in a formulation for pound cake reduced in margarine and partially replaced by canola oil, there is a proportional increase in specific gravity, apparent viscosity and viscoelastic modules, decreasing the size and number of bubbles formed in the batter. In pound cake, there is a proportional decrease in volume and uniformity of the crumb and increase in the firmness, however, the addition of 1.25% of gelatin was the most accepted sensory formulation due to perceived a crumb more consistent and wet, so, the functionality of the gelatin as hydrocolloid, is limited to the final texture of the pound cake, concluding that it may be an alternative to improve the acceptability of a pound cake reduced in margarine, which is also of lower cost.

Two Distinct Morphologies for Semicrystalline Isotactic Polypropylene Crystallized after Shear Flow

Application of shear flow to molten, highly isotactic polypropylene (iPP) results in two different morphology transitions: (1) above a certain shear rate but below a critical shear stress σ*, flow-induced precursors nucleate many small crystallites; (2) for shear stress above σ*, shish precursors nucleate highly oriented shish-kebab morphology. Herein we study flow-induced crystallization (FIC) in iPP with different molecular weights, using rotational and capillary rheometry. Since precursors created by shear are quite stable, we can also use differential scanning calorimetry (DSC) and polarized optical microscopy (POM) to study crystallization, melting, and morphology of iPP samples with different shear histories. Above a critical shear rate (inverse of long-chain relaxation time 1/τ), the onset of crystallization on cooling shifts to higher temperatures compared to unsheared samples. POM micrographs see a clear border between the regions affected by FIC (with γ̇ > 1/τ) and regions crystallizing as though they had not been sheared. FIC results in much smaller crystallites, so-called rice grains of order 1 μm in size. Above a critical shear stress (σ* ∼ 0.11 MPa) in the rotational rheometer, the morphology transitions to a shish-kebab structure. Shish appear in micrographs as highly aligned birefringent regions; in DSC, flow-induced shish further accelerate the onset of crystallization. In the rheometer, sheared samples with σ < σ* at 170 °C (above Tm) behave as a viscoelastic liquid identical to unsheared samples, whereas strongly sheared samples with σ > σ* behave as weak gels, revealing the presence of a percolating network of shish. In capillary rheometry, samples sheared above this threshold stress likewise show an abrupt increase in apparent viscosity.

Effect of Different Gums on Features of 3D Printed Object Based on Vitamin-D Enriched Orange Concentrate

This study examined the effects of different gums viz. gum arabic (GA), guar gum (GG), k-carrageenan gum (KG), and xanthan gum (XG) on rheological and 3D printing characteristics of vitamin D (Vit D) enriched orange concentrate (OC) wheat starch (WS) blends. The textural and microstructural properties of printed objects from above mixture were evaluated and compared. The addition of gums induced an increase in apparent viscosity, storage modulus (G′), and loss modulus (G″) of the OC-WS mixtures, while GA decreased the apparent viscosity and G′. Nuclear magnetic resonance (NMR) analysis of 3D printed samples revealed that the movement of transverse time (T2) toward closer to 0 ms indicated an increase in immobilized and bound water populations suggesting the gel formation. The slight shift toward shorter wavelength in FT-IR results for the broadband centered around 3400 cm−1 after addition of gums possibly caused an increase of G′ and load bearing capacity of the blends. 3D printing characteristics revealed that the objects printed using KG containing blend possessed maximum fidelity to the target geometry and good loading bearing capacity, preventing collapsing over time due to the proper G′ value. At tanδ of 0.238, OC-WS-KG mixture achieved the best printing condition. Higher tanδ of GA (0.038) containing samples led to an unwanted collapse of the printed constructs. The objects printed using KG also exhibited the smoothest visible surface as well as microstructure and best mastication properties. Considering the studied features, vitamin D enriched OC with WS-KG was found to be the best match for orange fruit concentrate-based 3D food printing. This work demonstrates the novel ways to develop fortified 3D printed foods.

Rheological behavior of lithium grease with CNTs/GNPs hybrid nanocomposite as an additive

PurposeThe purpose of this paper is to investigate the rheological characteristics of graphene nanoplatelets (GNPs) and hybridized nanocomposite consisting of multi-walled carbon nanotubes (MWCNTs) and GNPs as an additive on lithium-based grease. The experiments of nanogrease are examined in different values of shear stress, apparent viscosity, temperature and shear rate using Brookfield Programmable Rheometer DV-III ULTRA and characterized by high-resolution transmission electron microscope (HRTEM) and X-ray diffraction (XRD).Design/methodology/approachFirst, GNPs was mixed well with lithium grease using mechanical stirring at 3,500 rpm for 15 min at room temperature to form a homogenous composite at different concentrations (0.5, 1, 1.5, 2 and 2.5 Wt.%). Afterwards, MWCNTs and GNPs are mixed and dispersed well in the lithium grease using a sonication path for 30 min and mechanical stirring at 3,500 rpm for 15 min at 28°C to form a homogenous nanocomposite.FindingsThe results indicated that 1 Wt.% of GNPs is the optimum concentration. Subsequently, the weight percentage of additives varying between MWCNTs and GNPs are tested, and the result indicate that the grease containing GNPs had a 75 per cent increase in shear stress and 93.7 per cent increase in apparent viscosity over ordinary grease.Originality/valueThis work describes the inexpensive and simple fabrication of nanogrease for improving properties of lubricants, which improve power efficiency and extend lifetimes of mechanical equipment.

Changes on the rheological properties of pectin-enriched mango nectar by high intensity ultrasound

Effects of high intensity ultrasound (US, 5–40 min) on pectin-enriched mango nectar were evaluated, with regards to its rheological properties and related factors, including microstructure, particle size, and water-soluble pectin (WSP) changes. Results showed that the rheological properties of mango nectar exhibited a complex change, with an initial increase and subsequent decrease in apparent viscosity, storage modulus G’, and loss modulus G”. All these changes were ultrasonic time dependent. Ultrasound treatment caused significant degradation on suspended particles in mango nectar, as evidenced by optical microscopy, and particle-size distribution. The surface mean diameter (D[3, 2]) was reduced to 30.7 μm from an original value of 37.6 μm after ultrasound treatment. Moreover, US further caused the molecular degradation of WSP, with Mw being reduced from 3000 to 367 kDa in mango nectar. The interaction among them during processing determined the final rheological properties.

Evaluation of starch propionate as emulsion stabiliser in comparison with octenylsuccinate starch

Starch propionate (SP) with a degree of substitution (DS) of 0.21 was produced and its ability to stabilise emulsion was studied and compared with a commercial octenylsuccinate (OSA) starch (DS 0.03). The intrinsic viscosity values of SP and OSA were 0.9018 and 0.2514 (100 mL/g), respectively. Three different concentrations of SP and OSA at 12, 14 and 16 g/100 g of water phase and two different concentrations of oil at 35 and 45 g/100 g of water and oil phase were evaluated. Rheological properties, particle size and creaming index were assessed. Both SP and OSA emulsions produced shear thinning curve. Increase in concentration of starch stabilisers led to the increase in yield stress and apparent viscosity. SP emulsions demonstrated a significantly higher yield stress and apparent viscosity compared to OSA emulsions. SP emulsion showed G′> G″ values but OSA emulsions exhibited G″>G′ throughout the whole frequency range. As modified starch concentration increased, mean droplet diameter (d32) decreased. All SP emulsions were stable when stored at room temperature for 14 days. SP has great potential to be used in the preparation of cream-type emulsion such as mayonnaise, dermatological creams and cosmetic products.

Influence of processing conditions on apparent viscosity and system parameters during extrusion of distiller's dried grains-based snacks.

A combination of different levels of distillers dried grains processed for food application (FDDG), garbanzo flour and corn grits were chosen as a source of high‐protein and high‐fiber extruded snacks. A four‐factor central composite rotatable design was adopted to study the effect of FDDG level, moisture content of blends, extrusion temperature, and screw speed on the apparent viscosity, mass flow rate or MFR, torque, and specific mechanical energy or SME during the extrusion process. With increase in the extrusion temperature from 100 to 140°C, apparent viscosity, specific mechanical energy, and torque value decreased. Increase in FDDG level resulted in increase in apparent viscosity, SME and torque. FDDG had no significant effect (p > .5) on mass flow rate. SME also increased with increase in the screw speed which could be due to the higher shear rates at higher screw speeds. Screw speed and moisture content had significant negative effect (p < .05) on the torque. The apparent viscosity of dough inside the extruder and the system parameters were affected by the processing conditions. This study will be useful for control of extrusion process of blends containing these ingredients for the development of high‐protein high‐fiber extruded snacks.

Viscosity Models for Polymer Free CO2 Foam Fracturing Fluid with the Effect of Surfactant Concentration, Salinity and Shear Rate

High quality polymer free CO2 foam possesses unique properties that make it an ideal fluid for fracturing unconventional shales. In this paper, the viscosity of polymer free fracturing foam and its empirical correlations at high pressure high temperature (HPHT) as a function of surfactant concentration, salinity, and shear rate are presented. Foams were generated using a widely-used surfactant, i.e., alpha olefin sulfonate (AOS) in the presence of brine and a stabilizer at HPHT. Pressurize foam rheometer was used to find out the viscosity of CO2 foams at different surfactant concentration (0.25–1 wt %) and salinity (0.5–8 wt %) over a wide range of shear rate (10–500 s−1) at 1500 psi and 80 °C. Experimental results concluded that foam apparent viscosity increases noticeably until the surfactant concentration of 0.5 wt %, whereas, the increment in salinity provided a continuous increase in foam apparent viscosity. Nonlinear regression was performed on experimental data and empirical correlations were developed. Power law model for foam viscosity was modified to accommodate for the effect of shear rate, surfactant concentration, and salinity. Power law indices (K and n) were found to be a strong function of surfactant concentration and salinity. The new correlations accurately predict the foam apparent viscosity under various stimulation scenarios and these can be used for fracture simulation modeling.

Ultrasound impact on whey protein concentrate-pectin complexes and in the O/W emulsions with low oil soybean content stabilization

Consumers’ preference for products with reduced levels of fat increased in the last years. Proteins and polysaccharides have an important role due to their functional and interaction properties because, when combined in ratios and pH of higher potential for electrostatic interactions they may act as emulsifiers or stabilizers. This study evaluated the ultrasound impact on the electrostatic interaction between pectin (PEC) and whey protein concentrate (WPC) at different WPC:PEC ratios (1:1 to 5:1), and its effect on the emulsification and stability of emulsions formulated with WPC:PEC blends (1:1, 4:1) at low soybean oil contents (5 to 15%). Zeta potential analysis showed greater interactions between biopolymers at pH 3.5, which was proven in FTIR spectra. Rheology and turbidimetry showed that the ultrasound reduced the suspension viscosity and the size of the biopolymer complexes. Suspensions were Newtonian, whereas the emulsions showed shear-thinning behavior with slight increase in apparent viscosity as a function of oil content, and remained stable for seven days, with small droplets (<8 μm) stabilized and entrapped in a pectin network evidenced by confocal laser microscopy. Sonication was successfully applied to emulsion stabilization, improving the functional properties of WPC:PEC blends and enabling their application as low-fat systems, providing healthier products to consumers.

Experimental investigation of associative polymer performance for CO2 foam enhanced oil recovery

Polymer addition amplifies the foam flood performance by providing a substantial mobility control during the enhanced oil recovery (EOR). A conventional anionic polymer i.e. hydrolyzed polyacrylamide (HPAM) is widely used for polymer enhanced foam (PEF) flooding. In this study, the foam stability and viscosity performance of the conventional HPAM polymer were compared with a relatively new associative polymer. An associative polymer (i.e. Superpusher B 192) and the conventional polymer of same molecular weight were considered and the foam generation was performed using a widely used foamer i.e. alpha olefin sulfonate (AOS) and a foam stabilizer (betaine). FoamScan was used to measure the foam stability whereas, for foam viscometric measurements, a high-pressure high-temperature foam rheometer was utilized. An associative polymer showed an interesting combination and both the apparent viscosity and foam stability were found to be significantly high. The conventional polymer failed to provide a high foam strength in rheometric analysis whereas, an associative polymer showed an interesting viscosity profile and a two-fold increase in the foam apparent viscosity was observed. This study shows that the associative Superpusher B192 holds a bright potential in increasing the foam flood performance during EOR.

Design and Study of a Novel Thermal-Resistant and Shear-Stable Amphoteric Polyacrylamide in High-Salinity Solution.

Water-soluble polymers are widely used in oilfields. The rheological behaviors of these polymers in high-salinity solution are very important for stimulation of high-salinity reservoirs. In this work, a novel thermal-resistant and shear-stable amphoteric polyacrylamide (PASD), prepared from acrylamide (AM), sodium styrene sulfonate (SSS), and acryloxyethyl trimethylammonium chloride (DAC) monomers, was prepared by free-radical polymerization in high-salinity solution. The amphoteric polyacrylamide was characterized by Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance spectroscopy (1H NMR), elemental analysis, thermogravimetric analysis (TG), and scanning electron microscopy (SEM). The amphoteric polyacrylamide exhibited excellent salinity tolerance. The slow increase in apparent viscosity of the polymer with increase in salinity was interesting. The amphoteric polyacrylamide showed perfect temperature resistance in high-salinity solution. The viscosity retention reached 38.9% at 120 °C and was restored to 87.8% of its initial viscosity when temperature was decreased to room temperature. The retention ratio of apparent viscosity reached 49.7% at 170 s−1 and could still retain it at 25.8% at 1000 s−1. All these results demonstrated that PASD had excellent thermal-resistance and shear-stability in high-salinity solution. We expect that this work could provide a new strategy to design polymers with excellent salinity-tolerance, thermal-resistance, and shear-stability performances.

Determination of optimum experimental conditions for preparation and functional properties of hydroxypropylated, phosphorylated and hydroxypropyl-phosphorylated glutinous rice starch

Optimization of the preparation of hydroxypropylated, phosphorylated and hydroxypropyl-phosphorylated glutinous rice starch was performed using a response surface methodology comprising three variables at three levels. Multi-linear regression was used to fit the degree of substitution and molar substitution against. Optimal reaction conditions were 9h, 42°C, 10% (hydroxypropylated), 148min, 150°C, 7% (phosphorylated) and 95min, 140°C, 7.8% (hydroxypropyl-phosphorylated). For hydroxypropylated, predicted optimal and experimental molar substitution values were found to be identical: 0.20. Both the phosphorylated and hydroxypropyl-phosphorylated, the predicted optimal and experimental degree of substitution values was 0.02. Static rheological analysis revealed a pseudoplastic nature for native and modified starches and an increase in apparent viscosity following modification. Dynamic rheological analysis indicated an entanglement network system for native glutinous rice starch suspension, but weak elastic gel-like structure for modified starches as the storage modulus (G’) exceeded the loss modulus (G”). Additionally, chemical modification improved the freeze-thaw stability, swelling power, solubility and paste clarity.

Short communication: Effect of whey protein addition and transglutaminase treatment on the physical and sensory properties of reduced-fat ice cream

The effects of whey protein addition and transglutaminase treatment, alone and in combination, on the physical and sensory properties of reduced-fat ice cream were investigated. Adding whey protein with or without enzyme treatment decreased melting rate, overrun, and hardness of the reduced-fat ice cream; however, the enzyme-treated sample had a higher melting rate and overrun and softer texture. Whey protein-fortified samples showed higher melting resistance, but lower overrun and firmer texture compared with the enzyme-treated sample without added whey protein. Whey protein addition with or without transglutaminase treatment caused an increase in apparent viscosity and a decrease in flow index of the reduced-fat ice cream; nevertheless, the flow behavior of full-fat sample was most similar to the enzyme-treated reduced-fat sample with no added whey protein. Descriptive sensory analyses showed that neither whey protein addition nor transglutaminase treatment significantly influenced the flavor and odor of reduced-fat ice cream, but they both noticeably improved the color and texture of the final product. The results of this study suggest that whey protein addition with transglutaminase treatment improves the physical and sensory properties of reduced-fat ice cream more favorably than does whey protein addition or transglutaminase treatment alone.

Effects of slurry composition on the properties of 3-1 type porous PZT ceramics prepared by ionotropic gelation

In this study, 3-1 type lead zirconate titanate (PZT) ceramics with one-dimensional pore channels were produced by ionotropic gelation process of alginate/PZT suspensions. By increasing the sodium alginate concentration from 1.0wt% to 3.0wt%, the alginate/PZT suspensions turned from Newtonian to non-Newtonian behavior with substantial increase in apparent viscosity. Accordingly, 3-1 type PZT ceramics with porosity decreasing from 56.78% to 41.44% were obtained, while the pore size distribution became non-uniform gradually. Based on the structural features, the 3-1 type PZT ceramics possessed much higher relative permittivity (εr) than that of 3-0 or 3-3 type PZT ceramics with similar porosities. Increase in the porosity led to a moderate decline in the longitudinal piezoelectric strain coefficient (d33), a reduction in the dielectric loss factor (tan δ), and a high value of hydrostatic strain coefficient (dh). As a result, the 3-1 type PZT ceramics possessed a maximal hydrostatic figure of merit (HFOM) value of 5597×10–15Pa−1 when the porosity was 56.78%, which may be of help for low frequency hydrophones applications.

A novel approach to thickening characterization of an acrylic latex thickener

Abstract Alkali-soluble latex thickeners are extensively used in activities such as coating manufacturing, cosmetics, and textile industry. They increase apparent viscosity as a result of neutralization of carboxyl groups present in latex particles. Rheometry is the main method used to monitor the rheological activity of these substances. In this manuscript, we propose the use of dynamic light scattering (DLS) to get quantitative parameters and correlate them to apparent viscosity increase, confirming the results using more traditional methods. More specifically, we monitored by DLS the characteristic and average relaxation rates, as well as the width of the relaxation rate distributions. Critical changes of these parameters were observed during thickening; drastic changes at the same point were confirmed by rheometry, conductometry, and turbidimetry.

The rheological and thickening properties of cationic xanthan gum

ABSTRACTIn the present study, cationic xanthan gum (CXG) was synthesized to enhance the rheological property of xanthan gum (XG) by attaching quaternary amine groups to the backbone of XG. The efficacy of the substitution was confirmed by FT-IR spectra and 13C NMR. The surface morphology was changed considerably as demonstrated by SEM. The examined rheological properties of XG and CXG include steady-state and dynamic rheological properties. The results show that quaternary amine groups are successfully grafted onto the XG molecule. Apparent viscosity, storage modulus, and loss modulus of CXG solutions are greater than those of XG solutions under the same conditions. It is moreover found that apparent viscosity and viscoelasticity increase with the degree of substitution. The data indicate that the modified XG has much better heat resistance.

Effect of whey protein concentrate, sodium caseinate, Cheddar cheese, and milk fat on sensory and functional properties of cheese dip

Cheese dip was prepared using sodium caseinate, WPC-70, Cheddar cheese, carboxy-methyl cellulose, and glycerol mono stearate. The response surface methodology was employed for the optimization of level of protein blend, Cheddar cheese, and milk fat by studying the responses namely flavor, body & texture, color & appearance, firmness, stickiness, and apparent viscosity. An increase in protein blend and Cheddar cheese content was associated with decrease in flavor, body & texture, and color & appearance score and increase in firmness, stickiness, and apparent viscosity. The optimized conditions for the cheese dip were 8.82% protein blend, 6% Cheddar cheese, and 9.72% milk fat with desirability value of 0.929. Principal component analysis applied to data matrix has identified protein blend, Cheddar cheese/apparent viscosity, and milk fat as three principal components which explained 83.18% of variance in total. Color & appearance score was found dependent on Cheddar cheese content added to cheese dip. Practical application This study could successfully be utilized in preparing a new cheese product with high nutritional and functional properties owing to the presence of whey proteins. The product formulation and technology can be scaled up for commercial manufacturing. Introduction of such a healthy product as food adjunct in the market will be inline with the growing consumer demand of new and healthy convenience products.

Impact of Thermal and Pressure-Based Technologies on Carotenoid Retention and Quality Attributes in Tomato Juice

The aim of this study was to investigate the impact of thermal processing (TP) (90 °C, 90 s), high-pressure processing (HPP) (600 MPa, 46 °C, 5 min), and high-pressure homogenization (HPH) (246 MPa, 99 °C, <1 s) on product quality parameters, specifically carotenoid content, and physicochemical attributes of particle size, color, viscosity, total soluble solids, and pH in tomato juice. Unprocessed tomato juice was used as control. The four major species of carotenoids (lycopene, β-carotene, phytoene, and phytofluene) in tomato juice were analyzed by HPLC. The content of total lycopene, all-trans-lycopene, cis-lycopene isomers, phytoene, and phytofluene, in TP-, HPP-, and HPH-treated tomato juice did not significantly differ from that in unprocessed (control) juice. Significant reduction in β-carotene content was observed after TP treatment but not after HPP and HPH treatments. HPH significantly reduced tomato juice particle volume mean diameter from ∼330 μm in control, HPP-, and TP-treated tomato juices to ∼17 μm. A concomitant increase in apparent viscosity was observed in HPH-treated juice versus control. HPH-treated juice had increased redness (a*) and yellowness (b*) than that in control and HPP-treated tomato juices. These results indicate that high-pressure-based technologies (HPP and HPH) can preserve carotenoids as well as improve physicochemical properties.