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The challenge of insufficient proppant transportation capacity in slick water remains unresolved. To tackle this concern, a hydrophobically associating water-soluble polymer (HAWP), characterized by a low molecular weight (MW) of 8.11 × 105 g/mol, was successfully synthesized via a photo-initiation method. The drag reduction mechanism of the material was characterized through nuclear magnetic resonance and rheological performance testing. The drag reduction mechanism of the material was characterized through nuclear magnetic resonance and rheological performance testing. The results show that in comparison to conventional drag reducers in slick water with an average MW of approximately 1 × 107 g/mol, HAWP demonstrates significantly reduced MW. The rheological test results indicate that upon addition of sodium dodecyl benzene sulfonate (SDS, 200 mg/L) to the HAWP solution (0.3 wt%), the storage modulus experienced a substantial increase from 0.14 Pa to 7.42 Pa, demonstrating enhanced mechanical properties. Meanwhile, drag reduction (DR) tests showed that the efficiency of drag reduction achieved by the polymer system (PS) drag reducer was comparable to that of conventional linear polymers. This research achievement effectively addresses the challenges of low molecular weight and resistance reduction encountered in previous endeavors. [ABSTRACT FROM AUTHOR]

Research has shown that reversible phenomena such as non-linearity, self-heating and thixotropy occur during laboratory fatigue testing on bituminous mixes. This work aims to develop a test protocol to separate and quantify the recovery of reversible phenomena and the restoration of damage. Besides proposing some adjustments to the protocol, in the present paper, its repeatability is evaluated by comparing the results obtained for several samples of the same bituminous mixture. The test procedure is composed of two parts: short complex modulus tests (200 cycles at 10 Hz) at temperatures ranging from 8°C to 14°C with strain amplitudes ranging from 50 to 110 µm/m are used and five partial fatigue tests (at 10°C) are carried out at 100,000 cycles, 100 µm/m and 10 Hz. Each fatigue lag is followed by a 48-h rest period which consists of short complex modulus tests. The test protocol appears to show reliability and provide repeatable results. [ABSTRACT FROM AUTHOR]

Cracks in coal goaf provide air leakage pathways and therefore increase the likelihood of coal spontaneous combustion, thus strongly affecting the safety of mining operations. Herein, an inorganic thixotropic gel (ITG) was proposed for inhibiting coal spontaneous combustion by blocking this leakage. The orthogonal experiments were designed to examine the effects of gel composition on gelation time and rheological/thixotropic properties. The three interval thixotropy test of the optimal-composition gel (4 wt% sodium bentonite, 3 wt% laponite, and 0.46 wt% silicate cement) revealed its good thixotropic recovery. The viscoelasticity test indicated that this gel retained elasticity-dominated behavior before being completely transformed into a sol and was not easy to break into pieces under pressure. By testing the characteristics of the ITG, it was proven that the ITG had an excellent water retention capacity, and high-temperature resistance and the apparent effects on blocking air leakage and extinguishing coal fire. By the thermogravimetric test, the influence of ITG on coal activation energy was calculated based on the ignition activation energy theory. FTIR was also introduced to analyze the effect of ITG on active groups of coal. In addition, structural characterization showed that ITG featured a tight surface and a stable overall structure, which further agreed with its prominent ability to block air leakage. [ABSTRACT FROM AUTHOR]

This research aims to perform a comparison of the mechanical response and the fatigue behaviour of two Ultra-High Performance Concrete (UHPC) mixtures subjected to bending loads: a regular UHPC and a high-thixotropy UHPC. The same materials were used in both mixtures and the only difference was the proportions of water and additive. Rheological tests were performed to validate the thixotropy of mixtures in fresh-state. Additionally, image analysis was applied to get fibre distribution and orientation from beam-cut slices. Thus, the Image pixel complete colour structure (RGB) was analysed to avoid greyscale transformations because of its loss of information. Finally, three-point bending tests were conducted over pre-cracked beams to establish a fatigue equation for the mixtures. Experimental results showed that high-thixotropy UHPC has mechanical properties comparable to regular UHPC. [ABSTRACT FROM AUTHOR]

The mechanical characteristics of the soil–structure interface have a crucial impact on the bearing capacity of offshore foundations. The thixotropy-induced strength recovery of remolded soils has a significant effect on the increase in the stability of the foundation. To explore the effects of thixotropy on the recovery characteristics of the soil–structure interfacial shear strength, a self-designed interfacial mechanical characteristic apparatus is designed in this study to perform a series of soil–structure interface tests on clays from the South China Sea and offshore Dalian, respectively. The relationship between the recovery of undrained shear strength and the change of interfacial shear strength is analyzed by the index of shear-resistant coarseness. And the effect mechanism of thixotropy on interfacial shear strength is discussed from the microscopic view. The test results indicated that the rate of increase of the soil–structure interfacial shear strength is higher than that of the undrained shear strength. The particle size index of the soil was found to significantly influence the strength recovery characteristics of the soil–structure interface. A higher clay content will accelerate the development of the interfacial shear strength. This article provides a deep insight into the thixotropic effect on the mechanical properties of the marine soil–structure interface. [ABSTRACT FROM AUTHOR]

Cappadocia Region (World Heritage Site registered by UNESCO) carries thousands of rock-cut structures, masonries and fairy chimneys, which have been used in every aspect of daily life. Damages occurred during their working life, and restoration with inappropriate materials are threatened these structures. Moreover, an enormous amount of waste material is excavated throughout the carving process, passing approximately 10 million cubic meters per annum, creating pollution in the region, and not being used efficiently. This study aims to use Cappadocia waste earth (CWE) in the grout for consolidation and strengthening rock-cut structures, masonries and fairy chimneys located in Cappadocia region. The utilization of this waste earth in the grout prevents the destruction of these valuable structures and provides a solution to a critical environmental problem. The experiments were conducted employing by 30%, 40%, and 50 wt% of Cappadocia waste earth with natural hydraulic lime in the existence of chemical admixtures. The influence of ambient temperatures (5°C, 20°C, and 40°C) and time-dependent behavior on the rheological performance of grouts were investigated. The findings revealed that dosages of Cappadocia waste earth, different environmental temperatures, and constant shearing (time-dependent) have critical roles in determining the optimum requirements for injection. [ABSTRACT FROM AUTHOR]

The purpose of this study is to determine the rheological properties of cross-linked inulin solutions in two different polymerization degrees (native and degree of polymerization of >23%). Thus, the effect of cross-linking, a new approach applied to support a specific property (stabilization) of inulin, which has many benefits, has been demonstrated. Sodium hexametaphosphate was used as a cross-linking agent at three different ratios (0.375%, 0.500%, and 0.750%). The cross-linked inulin solutions were lyophilized, and the lyophilized mixture was then reconstituted at 25 °C and 45 °C to obtain cross-linked inulin solutions with 1% and 5% (w/v) concentrations. The control samples (native and with a high degree of polymerization) were treated similarly without a cross-linking agent. The samples were subjected to a dynamic frequency sweep test in the range of 0.01–10 Hz as well as shear viscosity measurements at 1–500/s shear rates for the determination of rheological properties. The thixotropic curves were analyzed as the shear rate increased from 0.1/s to 300/s in the first 120 s (up curve), and then decreased to the same point in the subsequent 120 s. Results indicated that cross-linking increased inulin solution viscosity, particularly at 5% concentration, and solubility. Solutions with 5% inulin containing 0.750% and 0.375% cross-linker yielded the highest viscosities at 45 °C and 25 °C, respectively. Samples with 5% inulin concentration exhibited solid-like behavior in the oscillation test. Thixotropic curves revealed antithixotropy at low shear rates and thixotropy at high shear rates. The study demonstrated the impact of cross-linking on inulin stabilization, providing insights for future applications. Results indicated that cross-linking increased inulin solution viscosity, particularly at 5% concentration, and solubility. Solutions with 5% inulin containing 0.750% and 0.375% cross-linker yielded the highest viscosities at 45 °C and 25 °C, respectively. Samples with 5% inulin concentration exhibited solid-like behavior in the oscillation test. Thixotropic curves revealed antithixotropy at low shear rates and thixotropy at high shear rates. The study demonstrated the impact of cross-linking on inulin stabilization, providing insights for future applications. [ABSTRACT FROM AUTHOR]

Tunnel excavation, pile driving and pipe cutting will cause different degrees of disturbance to the surrounding soil, which brings great potential risks to the safe operation of the project. In this study, the influence law of thixotropy on the compression characteristics, stress-strain relationship and shear strength index of soft clay in the Binhai area of Tianjin is investigated by using one-dimensional compression and triaxial tests, combined with two factors, which are the degree of initial perturbation and the resting time. The study shows that the mechanical properties of the soil will be greatly improved after 1d of resting, while the enhancement effect will be weakened in the later stage. The larger the initial disturbance degree, the worse the mechanical properties of the soil. Finally, based on the data analysis, the prediction models of soft clay shear strength index c and φ value are established respectively. [ABSTRACT FROM AUTHOR]

The thixotropy of water-in-waxy crude emulsion is the basic data used for flow safety studies of oil-water mixed pipelines. This work studied the shearing rate of a water-in-waxy crude oil emulsion under constant shear stress loading conditions. A relative shear rate was defined. A prediction method was developed to estimate the thixotropy of a waxy crude oil emulsion under constant shear stress loading conditions. The method only requires the thixotropy data of 3 water content emulsions and dehydrated crude oil, it can estimate the thixotropic characteristics of the oil-water-waxy crude oil emulsion of any volume of water content. [ABSTRACT FROM AUTHOR]

Drilling fluids are used in the process of drilling wellbores. They are formulated by a combination of solubles and suspended solids. During drilling, cuttings of rock formation may get in the mix. Some of them are too small and light to be removed from the fluids. They are called low-gravity solids (LGS). In no drilling situations, both solids may settle due to gravity. This project aimed to characterize the physical and rheological properties of synthetic-based drilling fluids and monitor the distribution of solids concentration in batch gravity settling experiments. The interplay of solid content and mud rheology was evaluated by pycnometry, retort, and rheological analysis. The Gamma-ray Attenuation Technique was applied to monitor the solid concentration along the test tube as a function of time. We analyzed two similar muds that slightly differed by the presence LGS The fluids presented non-Newtonian behavior, clear separation of solids in two phases and apparent viscosity changes. After 90 days, the clarified liquid region was formed between 16 and 22 cm from the bottom of the tube. This region took shape between 7 to 80 days, and the maximum solid concentration was approximately 9%. Finally, the LGS increased the fluid resistance of settling. [ABSTRACT FROM AUTHOR]

Semisolid metal processing is a well-known technology that can be used to enhance manufacturing product quality in broad industries. The technology controls the thixotropic properties of alloys within their solidus and liquidus temperature ranges. In general, most known alloys can generate semisolid slurries at high solid fractions, and the remaining can form slurries at low solid fractions. This has provided opportunities for many metals and alloys to be processed as semisolid slurries in today's casting industry. However, only a few researchers studied this technology potentially for a new metal-based additive manufacturing or 3D printing process. This article reviewed literature and findings from thixotropy rheology and semisolid metal processing methods, finally to thixotropic metal 3D printing. The survey shows that more future work is needed, including the investigation of thixotropic metal flow mechanics, the modelling and simulation of semisolid metal extrusion and further development of a fully thixotropic 3D printing system. [ABSTRACT FROM AUTHOR]

The disposal processes like dewatering and anaerobic digestion (AD) are commonly utilized to reduce the volume of sludge and recover energy. Thermal hydrolysis process is widely used as a pretreatment for sludge AD, which can change rheological properties and dehydration of sludge irreversibly. The experiment was designed to evaluate the effect of high-temperature thermal hydrolysis (120, 130, 145, 160 and 170°C) for 60 min on sludge rheological properties, as well as its dewaterability. Rheological tests were performed at (20 ± 0.1)°C with a HAAKE Viscotester 550 Rotary Viscometer. Both raw and thermal hydrolysis sludge has a considerable reduction on apparent viscosity and yield stress, but a somewhat increase in thixotropy. With the increase of temperature, the sludge flow behaviour index n increases linearly, while the consistency coefficient k follows the law of linear decline, showing that thermal hydrolysis can weaken the non-Newtonian fluid properties and then improve sludge fluidity. The dewaterability increases linearly with the temperature. Besides, the dewaterability of high-temperature thermal hydrolysis processes sludge was always significantly better than raw sludge as its mud cake has a much larger solid content. Notably, the increase in flow performance index n and the decrease of thixotropy kinetic coefficient K caused by thermal hydrolysis are all linear with the enhancement of dewaterability, which demonstrates that rheological indicators can be a new tool to evaluate the dewaterability of sludge. [ABSTRACT FROM AUTHOR]

Using a Viskomat XL mortar rheometer, parameters related to the rheological properties of machine-sprayed mortar were studied, and the effects of cement, fly ash (FA), and additives such as hydroxypropylmethylcellulose (HPMC) and starch ether (SE) on the rheological properties of cement mortar were studied. The results show that τc, Δτ, g, and h can be used to characterize the rheological properties of machine-sprayed mortar, where τc and Δτ reflect the sagging resistance properties, thixotropy, and plasticity of the mortar in the previous stage during the process of mortar changing from plastic structure to plastic fluid. Together, g and h determine the flowability of mortar in the later stage, and h is positively correlated with the stability and water retention of the mortar. Cement, FA, and HPMC have different effects on the rheological properties of cement mortar. SE changes the fluid properties of mortar from Bingham plastic fluid to the thixotropic fluid. [ABSTRACT FROM AUTHOR]

Objective: Novel niosomal formulation may be successfully applied to treat a systemic disease such as migraine through transdermal drug delivery system (TDDS), moreover, the treatment of topical diseases such as mycotic infections by targeting and localizing the drug to the stratum corneum. The current study aims to formulate zolmitriptan (Zt) in niosomal vesicles to potentiate its transdermal effect. Significance: The development of a promising niosomal formulation will push the scaling up of pharmaceutical industry in this field. Methods: Design- Expert 10 was used to design twelve formulations using Box-Behnken. Zt loaded niosomes were prepared by the thin film hydration method using Span 60(S 60), Span 80(S 80) along with cholesterol(Ch) at three different levels. The optimized formulation (F11) was formulated in Emulgel (1:1 emulsion/gel ratio). Results: The vesicles revealed vesicle size (VS) ranging from 133.1 to 851.3 nm, zeta potential (ZP) −43.8 to −82.8 mV, entrapment efficiency (EE%) from 66.7 to 88.7%, and Zt release after 4 h up to 67%. Optimized niosomal formulation (F11) depicted the smallest VS (133.1 nm), highest EE (88.7%), high ZP (−80.6 mV) and satisfactory release after 4 h (61.5%). There was a significant difference (p <.05) in drug permeation after 8 h for niosomal F11(460.98 ug/cm2) and niosomal F11 loaded Emulgel (336.92 ug/cm2) compared to plain Zt loaded emulgel (160.83 ug/cm2). Niosomal F11 loaded emulgel showed thixotropic behavior of rapid recovery, significant bioavailability and pharmacokinetic parameters as compared to the plain Zt-loaded Emulgel. Conclusion: Optimized F11 represents a promising formulation for transdermal drug delivery system to treat both topical and systemic diseases. [ABSTRACT FROM AUTHOR]

The thixotropic characteristics of xanthan solutions and their emulsions with crude oil were investigated experimentally. Understanding these characteristics are required for the crude oil displacement mechanism by polymer solution during the enhanced oil recovery phase. RS100 rheometer with a cone and plate device was employed for this examination using controlled-rate mode. Two crude oil concentrations of 25% and 75% by volume were examined. A wide range of xanthan gum concentration of 500–104 ppm was covered. This study results that the aqueous solutions of xanthan gums showed thixotropic behavior. The high concentrations of xanthan solutions provide higher hysteresis loop than the solutions of lower concentrations. The existence of crude oil within the xanthan emulsions considerably elevates the thixotropic rheograms profile. [ABSTRACT FROM AUTHOR]

Gelatinized starch paste was prepared by gelatinizing rice starch at 95 °C in a water bath. Then, the rice starch (both normal rice starch and waxy rice starch) paste was subjected to high-pressure homogenization at homogenizing pressure of 20, 40, 60, 80 MPa. The rheological properties (including shear stress versus shear rate, apparent viscosity versus shear rate and thixotropy) of starch paste were studied. The high-pressure homogenization was able to improve the flow properties of starch paste. The shear stress increased with the increasing shear rate, and the Power law equation was capable of fitting the shear stress versus shear rate quite precisely. High-pressure homogenization treatment sharply decreased the thixotropy of starch paste, and the thixotropy of rice starch (both NRS and WRS) paste decreased with the increasing homogenous pressure. [ABSTRACT FROM AUTHOR]

Rheological behaviour of pharmaceutical semisolid preparations significantly affects manufacturing process, administration, stability, homogeneity of incorporated drug, accuracy of dosing, adhesion in the place of application, drug release, and resulting therapeutic effect of the product. We performed test of consistency by penetrometry, rotational, oscillation and creep tests, and squeeze and tack tests of model samples to introduce methods suitable for characterization and comparison of semisolids in practice. Penetrometry is a simple method allowing sorting the semisolids to low and high stress-resistant materials but deficient for rheological characterization of semisolids. Value of yield stress, generally considered to be appropriate feature of semisolids, is significantly influenced by the method of testing and the way of evaluation. The hysteresis loops of model semisolids revealed incomplete thixotropy, therefore, three-step thixotropy test was employed. Semisolids showed nonlinear response in the creep phase of tests and partial recovery of structure by storing energy in the recovery phase. Squeeze and tack tests seem to be convenient ways for comparison of semisolids. Our study can contribute to a better understanding of different flow behaviour of semisolids given by different physicochemical properties of excipients and can bring useful approaches to evaluation and comparison of semisolids in practice. [ABSTRACT FROM AUTHOR]

A novel photorheological fluid composed of cationic Gemini surfactant N, N’-bis (octadecyl dimethyl)-1, 2-dichloride-propyl ammonium salt (C18-3-C18) and trans-ortho-methoxycinnamic acid (trans-OMCA) was investigated. When C18-3-C18 and trans-OMCA are mixed in equimolar quantities, the result is a low-viscosity Newtonian fluid with no thixotropy. After irradiation by UV light (365 nm), trans-OMCA is converted to cis-OMCA, and in turn, the solution undergoes more than 50 fold increase in the relative viscosity and exhibits shear thinning and thixotropy. The viscosity rise is associated with the formation of wormlike micellar network in the solution, which was confirmed by cryo-scanning electron microscopy (cryo-SEM). Furthermore, the rheokinetics process of the C18-3-C18/trans-OMCA solutions during UV irradiation was studied and rheokinetics equation was established, which can well describe the dynamic changing of the rheological properties. Critical packing parameter was introduced to explain the mechanism of photo-induced micelle transition. [ABSTRACT FROM AUTHOR]

To broaden the application of clean fracturing fluid based on surfactant, a gemini cationic C25-tailed surfactant, called FL-25, was synthesized. FL-25 can form a wormlike viscoelastic fluid in aqueous solution without adding any organic or inorganic salts. The rheological properties and thermal stability of the novel gemini micelle solutions were further investigated. The results show that the gemini micelle solution possesses viscoelasticity, thixotropy, and shear-thinning properties. The apparent viscosity of the viscoelastic gemini micelle solution at a shear rate of 170 s−1 remains approximately 69 mPa · s at 110°C for 90 minutes, showing good high-temperature-resistance property. FL-25 may be a novel gemini surfactant applied in clean viscoelastic surfactant fracturing fluids in the oil and gas field. [ABSTRACT FROM AUTHOR]

A novel amphoteric xanthan gum (AXG) containing anionic carboxyl groups and cationic quaternary ammonium substituents was prepared from xanthan gum (XG) and 3-chloro-2-hydroxypropyltriethanolammonium acetate. The rheological and microrheological properties of AXG and XG solutions were studied in this work. The rheological results showed that the apparent viscosity of the 0.4% AXG solution was 5.26 times that of the 0.4% XG solution, and the AXG solution exhibited more obvious thixotropy and much stronger viscoelasticity than the XG solution. Both experiment and numerical simulations were adopted to investigate the gel-breaking process of the AXG solution, and the rheokinetics equations can well describe the evolution of complex viscosity. Moreover, the optical microrheology method was also adopted to investigate the microrheological behavior of AXG and XG solutions. The microrheological results showed that the AXG solution exhibited higher viscosity index at zero shear and a more obvious solid-like behavior than the XG solution. Good agreement is found when comparing the results obtained from microrheology to classical rheology, which verifies the feasibility of the microrheology method for measuring the solution properties, especially some properties not well described by the current rheological approach. [ABSTRACT FROM AUTHOR]

To meet requirements of fracturing fluid thickener, triethanolamine was used to modify carboxymethyl hydroxyethyl cellulose (CMHEC) to obtain product called T-CMHEC of high viscosity. Rheological properties of CMHEC and T-CMHEC solutions were investigated to compare its structure and rheological performance, including viscosity, flow curve, thixotropy, and viscoelasticity. Viscosities of CMHEC and T-CMHEC solutions are, respectively, 19.0 and 63.2 mPa · s for the same concentration of 0.3%. Viscosity of T-CMHEC solutions is 3.3 times of CMHEC ones. Besides, the thixotropy and viscoelasticity of T-CMHEC system are both getting stronger than before. In summary, the T-CMHEC system shows better rheological performance after modification. Crosslinking process of T-CMHEC system is investigated under steady shear under different conditions, containing shear rates, concentrations of crosslinking agent, concentrations of pH adjuster, and temperature. Viscosity curves changing with time are obtained during crosslinking process. Four-parameter crosslinking rheokinetics equation is suitable to fit the viscosity curves under different conditions. Study on crosslinking process of T-CMHEC solutions is helpful to deepen the understanding on gel formation, and provides a theoretical basis for its application. [ABSTRACT FROM AUTHOR]

Herein, the influence of temperature (10°C, 30°C, 50°C, 70°C, and 90°C) on the dynamic (using amplitude sweep, frequency sweep, and temperature sweep tests), steady-shear, thixotropy (using hysteresis loop, single shear decay, and in-shear structural recovery tests), yield stress (static and dynamic yield stresses), and dilute solution (intrinsic viscosity ([η]), voluminosity (vs), shape factor (v), Berry number (C[η]), and chain flexibility) properties of sage seed gum (SSG) have been studied. In this way, the effect of type of thermal procedure (iso-thermal and non-isothermal), temperature program (temperature gradient and temperature profile sweeps), and the rate of thermal program (1, 5, and 10°C/min) on the structural changes during heating and cooling stages were also investigated. Furthermore, the time-temperature superposition and Cox-Merz rules were tested on dynamic and steady shear rheological data. [ABSTRACT FROM AUTHOR]

A mixture of fumed silica and nitrile butadiene rubber (NBR) is used to improve the viscosity and thixotropy of ethyl 2-cyanoacrylate (ECA) and to reduce the internal stress of ECA. Rheological characteristics of ECA/silica, ECA/NBR, and ECA/silica/NBR are measured using a rheometer and are presented using the viscosity and thixotropic index. The pristine and modified ECA were characterized using Fourier transform infrared spectrometer (FT-IR) and Thermal gravity analysis (TGA). The impact of additives on curing internal stress of ECA is measured and analyzed. Results shown that addition of fumed silica and NBR effectively improve the viscosity of ECA blends, which increases with an increased content of both additives. Thixotropic ECA/silica/NBR shows an apparent shear-thinning character and is well fitted by a power law equation. FT-IR spectra and TGA analysis indicated that the thixotropy of the obtained ECA/silica/NBR blends is mainly attributed to silica via the creation of hydrogen bonds between silica particles and between silica and polymers, and a synergistic effect between silica and NBR is shown to improve viscosity. The modified ECA showed considerable stability and their viscosity were slightly increased after 30 days. The presence of NBR is beneficial for silica dispersion in the ECA matrix and for a smooth surface of cured ECA. The added silica and NBR can alleviate the internal stress of the cured adhesive layer, and NBR plays a significant role in reducing internal stress. This work is devoted to developing thixotropic and low-shrinkage cyanoacrylate-based adhesives. [ABSTRACT FROM PUBLISHER]

Results of experimental determination of Yaregskoe field degassed oil's rheological characteristics are given in the article. Modern methods of viscoelastic and thixotropic properties research are described and results of these method's application while abnormal oil research are shown. As a result an improved data of Yaregskoe field's oil is obtained and there is a recommendation to extend a number of enhanced oil recovery methods, including physicochemical and wave methods application. [ABSTRACT FROM PUBLISHER]

Effects of tara gum (TG) at different TG concentrations (0.2-0.6% w/w) on the rheological and pasting properties of rice starch (RS) pastes (5% w/w) were studied. Confocal laser scanning microscopy (CLSM) observation was also conducted to investigate the possible interaction between RS and TG. All RS-TG mixture pastes exhibited a pseudoplastic shear-thinning characteristic (n = 0.17-0.26). RS alone displayed a highly thixotropic behaviour as compared to RS-TG mixtures, showing that the thixotropic loop area markedly decreased in the presence of TG. Consistency index (K), apparent viscosity (ηa,100), storage moduli (G'), and loss moduli (G'') values increased with increasing TG concentration. Viscous characteristics in the RS-TG mixture system were more pronounced compared to the control (0% TG) as evidenced by their higher tan δ values. Rapid visco-analysis showed that the addition of TG resulted in a significant increase in the peak, breakdown, final, and setback viscosities, and their viscosities also increased with an increase in TG concentration. These results suggested that the synergistic effect of TG addition on rheological and pasting properties of RS pastes appeared to be due to phase separation process that occurred as a result of incompatibility between TG and amylose component in starch, as confirmed by CLSM micrographs. [ABSTRACT FROM AUTHOR]

Viscosity determination of thixotropic emulsions with good repeatability has always been a major challenge. Currently, Saybolt Furol viscometer (SFV) is used to determine the viscosity of the emulsion, but the main drawback of the SFV is that it cannot simulate the behaviour of emulsion under different shear rate. Rotational viscometer (RV) can measure viscosity at different shear rates. Due to the thixotropic behaviour of the emulsions, getting repeatable results by following the hot binder specification is a problematic task. In this study, a new multiple shear step approach is used to determine the viscosity of the emulsified asphalt using RV. Three low viscous (SS-1, SS-1H and SS-1L) and two high viscous (CRS-2 and CRS-2P) emulsions were used in this study. Shear stress is gradually stepped up to different levels after certain time interval to determine the viscosity. In this manner, emulsion undergoes a known shear state and each reading is preceded by a certain repeatable shear history. It was observed that with the progression of time and simultaneous increase in shear rate, the viscosity results are much more stable and repeatable with less than 5% coefficient of variance. The final specifications proposed are 220–730 and 5–90 cP at 50 rpm and 30 °C for high and low viscous emulsions, respectively, which are based on 98% probability. Viscosity measured by this approach also showed strong correlation with water content (R2 > 0.94). The correlation between viscosity and water content is even stronger after dilution. With different dilution water content, viscosity of CRS-2 and CRS-2P exhibitedR2values of 0.97 and 0.98, respectively. [ABSTRACT FROM AUTHOR]

In this paper, effect of emulsification processes on the properties of Pickering emulsions stabilized by organomontmorillonites (OMts) was studied. Results of micro-morphology and X-ray diffraction showed that the structure of OMt in emulsion depended on the emulsification processes and had an effect on the stability of emulsion. We propose a schematic diagram to reveal the relationship between emulsification processes-OMt laminates structure-stability of Pickering emulsion. In emulsion prepared by ultrasonic, OMt showed uniform dispersion, loose structure, and irregular crystalline. In emulsion prepared by vortex mixing method, OMt illustrated stacking and coagulation structure. In emulsion prepared by microwave method, OMt showed interacting structure and had a little interaction with oil/water interface, and thus the properties of emulsion prepared by microwave was weakly related to oil/water ratios. Emulsification processes had a profound effect on the structure of OMt and stability of Pickering emulsion, which can be used as a trigger to prepare emulsion for various applications. [ABSTRACT FROM AUTHOR]

Aiming at synergistic interaction between carboxymethyl hydroxyethyl cellulose (CMHEC) and cetyltrimethyl ammonium bromide (CTAB), mixtures of CMHEC and CTAB solutions were investigated, employing relative viscosity and rheological measurements. The effects of mass ratio of CMHEC and CTAB solutions, temperature, and polysaccharide concentration on relative viscosities of CMHEC/CTAB systems were studied. Rheological method was used to study rheo-kinetics of the isothermal crosslinking process for CMHEC/CTAB synergistic fracturing fluid, and the novel crosslinking rheo-kinetics equation was established. The results showed the strong synergism between CMHEC and CTAB, resulting in a higher relative viscosity, storage modulus G, and loss modulus G' than that of separate ones. CMHEC/CTAB systems behave as pseudoplastic fluids with considerable thixotropy and viscoelasticity, and the flow behavior can be well described by Carreau-Williamson model. The crosslinking rheo-kinetics equation can well describe the isothermal crosslinking process at different shear rates. The model parameters are well-defined and reasonable. [ABSTRACT FROM AUTHOR]

This study describes the investigation about the physicochemical behavior of methylene blue (Mb) addition to systems containing poloxamer 407 (Polox), Carbopol 934P (Carb), intended to be locally used by photodynamic therapy. A factorial design 23(plus center point) was used to analyze the rheological, mucoadhesive and textural properties of the preparations. Systems containing the lower concentrations of Polox (15 and 17.5%, w/w) exhibited pseudoplastic flow and low degrees of rheopexy. On the other hand, at higher Polox concentration (20%, w/w) the systems display plastic flow and thixotropy. Carb and Mb exhibited a negative influence for the consistency and flow behavior index, due to the interaction between them. For most of the formulations, the increase of Polox and Mb content significantly increased storage modulus, loss modulus and dynamic viscosity. The systems display a sol–gel transition temperature, existing as a liquid at room temperature and gel at 29–37 °C. Increasing the temperature and the polymer concentration, the compressional properties of systems significantly increased. The mucoadhesion was noted to all formulations, except to systems composed by 15% (w/w) of Polox. The analyses enabled to understand and predict the performance of formulations and the polymer–Mb interactions, tailoring to the suit systems (Polox/Carb/Mb): 17.5/0.50/0.20 and 20/0.15/0.25. [ABSTRACT FROM AUTHOR]

Ethanolamine is considered to be an environmentally friendly propellant system because it has low toxicity and is noncarcinogenic in nature. In this article, efforts are made to formulate and prepare ethanolamine gel systems, using pure agarose and hybrids of paired gelling agents (agarose + polyvinylpyrrolidine (PVP), agarose + SiO2, and PVP + SiO2), that exhibit a measurable yield stress, thixotropic behavior under shear rate ranges of 1–1,000 s−1and a viscoelastic nature. To achieve these goals, multiple rheological experiments (including flow and dynamic studies) are performed. In this article, results are presented from experiments measuring the apparent viscosity, yield stress, thixotropy, dynamic strain, frequency sweep, and tan δ behaviors, as well as the effects of the test temperature, in the gel systems. The results show that the formulated ethanolamine gels are thixotropic in nature with yield stress between 30 and 60 Pa. The apparent viscosity of the gel decreases as the test temperature increases, and the apparent activation energy is the lowest for the ethanolamine-(PVP + SiO2) gel system. The dynamic rheology study shows that the type of gellant, choice of hybrid gelling materials and their concentration, applied frequencies, and strain all vitally affect the viscoelastic properties of the ethanolamine gel systems. In the frequency sweep experiment, the ethanolamine gels to which agarose, agarose + PVP, and agarose + SiO2were added behave like linear frequency-dependent viscoelastic liquids, whereas the ethanolamine gel to which PVP + SiO2was added behaves like a nearly frequency-independent viscoelastic solid. The variation in the tan δ of these gelled propellants as a function of frequency is also discussed. [ABSTRACT FROM PUBLISHER]

Context: Garlic oil and Eruca oil have been reported to have excellent antimicrobial activity. However, the exact knowledge of their required hydrophilic–lipophilic balance (rHLB) values to facilitate their emulsification are still not reported in the literature. Objective: The objective of this study is to determine rHLB values of Garlic and Eruca oils to formulate an elegant stable cream formulation enriched with both oils. Materials and methods: Emulsions of both oils were prepared by the bottle method using water, Tween 80 and Span 80. Formulated emulsions were evaluated for creaming index (CI), droplet size, and turbidity to determine rHLB. Utilizing determined rHLB, creams were formulated using a combination of two surfactants, Span 60:Brij 58 (1:2.333) at three different concentrations (2, 4, and 6%). Results: rHLB of Garlic oil and Eruca oil was determined to be 7.92 ± 0.27 and 9.76 ± 0.32, respectively. Stable cream (F1) developed with 2% surfactant blend showed elegant rheological properties, the best antimicrobial activity againstStaphyococcus aureusATCC29737, Escherichia coliATCC25299 S. aureus (MRSA), Malassezia fufur AUMC No. 5173with no skin irritation. In addition, its texture parameters and pH were found to be consistent over 12 months at 25 ± 1 °C and 60% relative humidity. Discussion: The lowest CI, smallest droplet size, and highest turbidity were obtained at the optimum surfactant concentration in the prepared emulsions. Increasing surfactant blend concentration in cream formulations leads to increasing viscosity and consequently decreasing antimicrobial activity. Conclusion: Determination of the rHLB of Garlic and Eruca oils allows the ease of preparation of stable, consistent, and non-irritant cream. [ABSTRACT FROM PUBLISHER]

An evaluation method combined with an experiment and theoretical analysis was proposed to study the effect of thermal history on the thixotropy of waxy crude, and the damage extent and recovery extent are the two crucial parameters in the evaluation. The results indicate the longer thermostatic time is, the higher heat-treatment temperature is, the faster the cooling rate is, and the more repeated heating times would cause a bigger damage extent and a smaller recovery extent. Moreover, the variation of damage extent and recovery extent are closely related to the state of structure (i.e., the more stable structure would cause bigger damage extent and a smaller recovery extent). [ABSTRACT FROM PUBLISHER]

Purpose: Localized mechanical vibration, applied directly to a muscle, is known to have powerful, duration-dependent effects on the muscle spindle’s reflex arc. Here, the conditioning of the function of the spindle reflex arc via vibration was examined with considerations for use as a non-invasive, sensorimotor research tool. Methods: Muscle spindle function was examined with patellar tendon taps prior to and following exposure to muscle vibration applied to the quadriceps femoris for acute (<5 s) and prolonged (20 min) durations. Surface electromyography (sEMG), torque, and accelerometry signals were obtained during the taps to quantify various measures of reflex magnitude and latency. Results: Our findings suggest that acute vibration had no effect on normalized reflex torque or sEMG amplitude (p > 0.05), but increased total reflex latency (p = 0.022). Alternatively, prolonged vibration reduced normalized reflex torque and sEMG amplitude (p < 0.001), and increased reflex latency (p < 0.001). Conclusions: Our findings support the use of prolonged vibration as a practical means to decrease the function of the muscle spindle’s reflex arc. Overall, this suppressive effect was evident in the majority of subjects, but the extent was variable. This approach could potentially be used to help delineate the muscle spindle’s role in various sensory or motor tasks in which more direct measures are not feasible. Acute vibration, however, did not potentiate muscle spindle function as hypothesized. Rather, our results suggest that acute vibration increased total reflex latency. Accordingly, potential mechanical and neurophysiological mechanisms are discussed. [ABSTRACT FROM PUBLISHER]

In this work, the flow characteristics of heavy crude oil were investigated by using a rheometer and a lab scale flow loop, respectively. In the experiments of rheometer, there is an approximate linear relationship between the yield stress and the area of thixotropic loop independent to the system temperature and crude oil types. A comparison between the experimental data of yield stress versus start-up rate obtained in the pipe start-up flow with those measured in the rheometer reveals that the transport characteristics of heavy crude oil can be predicted well by the rheological measurements. [ABSTRACT FROM AUTHOR]

The effect of high hydrostatic pressure-750 on rheological properties of rice starch-water system was examined. The starch dispersions (20% w/v) were pressurized at 120, 240, 360, 480, and 600 MPa for 30 min. The storage modulus and loss modulus increased with the pressure increase. A yield stress was generated at a low shear rate. The high hydrostatic pressure-treated starch gels performed shear thinning and the apparent viscosity dropped sharply at 480 MPa. Hysteresis loop area increased with the pressure increased and reached the maximum at 600 MPa. High hydrostatic pressure-treated starch gels were found to be weak gels and thixotropic. [ABSTRACT FROM PUBLISHER]

Application of novel natural surfactant for enhancing rheological properties including pour point, viscosity, thixotropic behavior, yield stress, and interfacial tension of Indian heavy crude oil was investigated. The surfactant was prepared in the laboratory using extracts fromSapindus mukorossi(soapnut) plant. Viscosity reduced by 80%, thixotropic area by 94.64%, yield stress by 98%, and interfacial tension by 97%. The study also provides the possible mechanism behind improvement of the rheological properties through FTIR spectroscopic analyses. They showed lowering of concentration of C˭O and C˭C groups in surfactant-crude mixture indicating the effectiveness of the surfactant. [ABSTRACT FROM PUBLISHER]

The objective of this study was to evaluate the effect of high pressure treatment on rheological properties of various egg components (i.e., egg white, egg yolk, and whole liquid egg). A five-level central composite design with three independent variables (pressure, 281.8–618.2 MPa; temperature, 8.2–41.8°C; pressure holding time, 1.6–18.4 min) was employed. Samples were packed in plastic pouches, heat sealed, and subjected to pressure treatment in an isostatic press. Shear and time-dependent rheological properties were evaluated using a 3-segment (each 5 min) program with the shear rate initially increasing from zero to 100 s−1(upward curve), then held at 100 s−1(hold curve), and finally decreasing from 100 to 0 s−1(downward curve) using a parallel plate rheometer. Power law model was fitted to the upward (virgin) and downward curves while Weltman time dependency model was fitted for the hold curve (R2> 0.90). Rheological properties were most significantly affected by pressure followed by holding time and temperature for all egg components. In general, they showed thixotropic shear thinning behavior and reduction in time dependency, which was dependent on the level of processing treatment used (combination of pressure, time, and temperature level). The high pressure treatment resulted in a progressive transition of egg components from flowable liquid-like behavior (218–350 MPa) to semi-viscous (350–500 MPa) to highly-viscous (500–618 MPa) behavior. Rheology-based optimal conditions satisfying HP pasteurization needs were identified. [ABSTRACT FROM AUTHOR]

Stressing the importance of diet in the prevention of certain diseases, nutritional scientists have emphasized on the reduction of calories in consumers’ diets. The steady-shear flow behavior of three optimized low-calorie pistachio butter formulations containing fat replacers (xanthan gum, Reihan seed gum, and Balangu seed gum) and sweeteners (sucrose and isomalt) were investigated at different temperatures. All three samples presented a non-Newtonian shear thinning flow behavior. Bingham, power law, and Moore models were selected as the appropriate time-independent rheological ones. Increasing the temperature resulted in lower values of Bingham viscosity, Bingham yield stress, and consistency coefficient. Increasing the amount of pistachio paste and isomalt led to higher and lower viscosity values, respectively. All data were reasonably fitted by Arrhenius model and formula containing xanthan gum showed the highest temperature dependency. The structural recovery evaluation revealed a weak thixotropic behavior for all samples. [ABSTRACT FROM PUBLISHER]

The thixotropy of three waxy crude oils was measured to evaluate different measurement methods using RheolabQC. The results showed that the average relative deviation using the hysteresis loop method was 24.4%, the lowest among the methods evaluated. The method of stepwise-increase in shear rate was able to obtain several rheological characteristics from a single experiment, and such a thixotropic experiment can be performed with any rheometer. This makes the stepwise-increase in shear rate the method of choice when considering convenience. However, the method of hysteresis loop is preferable when it comes to the reliability of measuring thixotropic parameters. [ABSTRACT FROM AUTHOR]

Due to their exceptional rheological properties, bentonites are used in different branches of industry, such as in drilling fluids, dyes, pharmaceuticals, paper, cement, nanocomposites, polymer composites, and ceramics. In the use of bentonite in different applications, the addition of carboxymethyl cellulose (CMC) sodium salt is recommended to optimize the rheological properties of the suspension. In this study, the effect of carboxymethyl cellulose on the rheological properties of Na-bentonite suspensions was investigated in the polymer concentration range of 0.02–0.50 wt%. The addition of carboxymethyl cellulose to the bentonite dispersions resulted in significant increase in the dispersion viscosity. The advantage of carboxymethyl cellulose is that the desired rheological properties can be obtained with less bentonite by adding carboxymethyl cellulose polymer and the undesirable effects of high bentonite concentrations can be avoided. The viscosity of 8.0 wt% pure bentonite dispersions was achieved by adding 0.10 wt% carboxymethyl cellulose to 4.0 wt% bentonite dispersions. The combined flow behaviors of Bingham and shear thickening observed for the 4.0 wt% pure bentonite dispersion was shifted toward the shear thinning profile with a yield stress in the presence of the carboxymethyl cellulose. This yield stress increased substantially with carboxymethyl cellulose concentration. In addition, the thixotropic behavior of bentonite dispersions was significantly enhanced by adding carboxymethyl cellulose polymer. [ABSTRACT FROM PUBLISHER]

The structural characteristics of low-temperature waxy crude are important to the pipeline transportation, especially the destruction of the structure and the recovery of the structure. The authors experimentally studied them with the strain-controlled rheometer, and the experimental data indicated the effect of isothermal holding time on the structure was little, and it verified Wardhaugh and Boger's view about the yielding behavior of waxy crude, but it also showed the yielding behaviors strongly depend on the strain rate. In addition, some typical characteristics about the recovery of the structure were obtained. [ABSTRACT FROM PUBLISHER]

The thixotropic behaviors of Daqing waxy crude were studied experimentally with the help of the advanced strain controlled rheometer (ARES-G2). The experimental results indicated the decrease in viscosity can be divided into two continuous steps, and the recovery of viscosity consists of three continuous processes. Then a new method was used to model the thixotropic behavior combined with the experimental data, and the new method was based on a potential function that can characterize the recovery capability of the inner structure, it is reasonable for to describe the thixotropic behavior of Daqing waxy crude properly. [ABSTRACT FROM PUBLISHER]

Background: Hydrogels are widely used for cutaneous formulations; thereby comparing the bioadhesive properties of polymers with a view to prolong the residence time of topical drugs on the skin would be very useful to design novel topical drug delivery systems. Aim: The objective of this study was to correlate data from rheological studies and texture profile analysis, with bioadhesion on the skin. Methods: Polyacrylic acid polymers used were carbomer homopolymer type A (C971) and type B (C974), and polycarbophil (PP) dispersed in water at various concentrations (0.1, 0.5, 1.0, 1.5, 2.0, 3.0, 5.0%, w/v). Rheological, texture, and bioadhesive properties were determined to compare the hydrogels. Results: Rheological analysis showed that all samples exhibited pseudoplastic behavior with thixotropy. Texture profile analysis showed that compressibility, hardness, and adhesiveness of the hydrogels were dependent on the polymer concentration, and the cohesion values were high. Bioadhesion of C974 and PP at 0.5 and 2% was of the same magnitude, while all samples of C971 had lower values. The bioadhesion of 5% C974 was the highest, while that 5% PP was lower, possibly because PP showed the greatest hardness and this rigidity may decrease the interaction of the polymer with the skin. Conclusion: A comprehensive comparative rheological and textural analyses of several polymers for topical systems were undertaken in terms of their bioadhesion. Therefore, it is possible to conclude that these polymers can be used for optimization of drug delivery systems on the skin. [ABSTRACT FROM AUTHOR]

The rheology behavior of water bentonite suspensions has been studied through recording the viscosity measurements to study the thixotropy of the suspensions using local Egyptian bentonite at 5.0%, 6.40%, and 7.5.0% concentrations in the a presence of different salt concentration as 0.0 M, 0.01 M, and 0.1 M NaCl according to API stander, rheological data was calculated by viscometer, deriving first the D0 curve, from 600 to 3 rpm, followed by a typical thixotropic loop, getting the U curve from 3 to 600 rpm, and then the D curve from 600 to 3 rpm. Three rheograms have been derived for each suspension after intensive preshearing, from high to low, from low to high, and from high to low shear rates. Positive thixotropy is observed for all suspensions at 0.0 M and 0.01 M but not at 0.1 M salt concentrations. Thixotropic indexes computed from the normal thixotropic loop, low to high to low shear rates, have been computed and vary from positive to negative. The higher the bentonite concentration, the higher the index for the suspensions with no salt, while in the presence of salt, variations of the thixotropy index are obtained with the degree of variation dependent on bentonite concentration and salt concentration The suspension with no salt and 0.01 M salt exhibited thixotropy, estimated from the D0-U curves, while the 0.1-M suspensions showed no thixotropy. Thixotropy indices vary and depend on bentonite type and concentration and on the presence and amount of salt. [ABSTRACT FROM PUBLISHER]

Zinc(II)-orotate complex (ZnOA)has been synthesised, and it is used to produce supramolecular complex with melamine (M) at 1:1 molar ratio. During sonication for 5–6 min, the supramolecular complex is transformed into a bi-component hydrogel (S-gel). The spectroscopic tools such as FTIR and UV–vis spectra suggest that the H-bonding interaction betweenMandZnOAproduces a supramolecular complex which further forms J-aggregates during gelation. The circular dichroism spectra indicate the change in ellipticity with temperature that arises from the molecular dissymmetry during stacking of theZnOAMcomplexes. The microscopic images indicate that the hydrogel network is formed with short helical nano-fibres. The energy-minimised structure ofZnOAMcomplex exhibits a well-defineddvalue of 11.3 Å obtained from X-ray scattering of the xerogel. The frequency-dependent rheological experiment (storage modulus (G′) is greater than loss modulus (G″)) characterises it as a gel. The gel shows thixotropic and stimuli-responsive behaviour. [ABSTRACT FROM AUTHOR]

The knowledge of rheological characteristics can indicate the emulsions properties, thus, nowadays rheology is used in the cosmetic and pharmaceutical industries, even to study the influence of rheological additives on them. Ten emulsions were prepared with 5% and 10% of nonionic emulsifier. Two of them were used as controls while in the others were added thickening agents. Rheological analyses were performed. The results showed that all emulsions are non-Newtonian, thixotropics and viscoelastics fluids. The thickening agents could modify the rheological characteristics of the emulsions and knowing the influence of them is easy to adopt one to reach the desirable performance. [ABSTRACT FROM AUTHOR]

The thixotropic property of waxy crude is of great importance for oil pipeline restart. In previous studies, several mathematic models have been published for describing the thixotropic behaviors. However, no comparison of the prediction accuracy among these models has been carried out. In this work, thixotropic behaviors of four waxy crudes were studied experimentally using stepwise shearing measurements. The stepwise shearing method is proved to be a convenient method to obtain thixotropic experimental data. Seven published thixotropic models were evaluated based on these experimental data. A model with two structure parameters (Zhao's model) provides the calculation results mostly close to the experimental data. [ABSTRACT FROM AUTHOR]

The thixotropic behavior of Mg-Al hydrotalcite-like compound (HTlc)/cationic starch (CS) suspensions was investigated as a function of the mass ratio (> 0.08) of HTlc to CS, the electrolyte and the temperature, respectively. The thixotropy was studied by monitoring viscosity (η) change during the recovery process as a function of time (t) after the cessation of intensive shear. The results showed that the strength of negative thixotropy of the CS solution decreased with the increasing of electrolyte (NaCl, CaCl2, or AlCl3) concentration and the temperature. The thixotropic type of the HTlc/CS suspensions could transform from negative to complex, positive, complex, and then to negative thixotropy with the increasing of HTlc content if CS was the main component of the suspensions. In addition, the thixotropic type of the HTlc/CS suspensions transformed from original type to positive thixotropy with the increasing of electrolyte concentration and the temperature. [ABSTRACT FROM AUTHOR]

Native water in crude oil emulsions, stabilized by indigenous surfactants, exhibit both positive thixotropy (PT) and negative thixotropy (NT) in Couette flow. PT is associated with microscopic processes, local break-up of droplet clusters in emulsions with low and moderate volume fractions of water φ, or fracturing of emulsion-gels with φ > 0.7. The latter process involves the coalescence of water droplets along a fracture plain, which results in vorticity banding of emulsion flow. NT reflects evolution of the macroscopic radial banding in flow of emulsions with 0.18 < φ < 0.58 and is dictated by the displacement of the interface between the sheared and unsheared regions. [ABSTRACT FROM AUTHOR]

The properties of solid surface on oil-wax gel are one of the most important factors which decide the quality of products such as cosmetics. The thixotropic property of solid surface depends on the velocity gradient and it is increased with higher velocity gradient as controlling the morphology on solid surface of oil-wax gel. The morphological change of oil-wax gel in compliance with surface properties of wax matrix can cause different rheological behaviors. Rheological behavior of oil-wax gel regarding the surface transition range in accordance with shear strain was observed to characterize surface properties. In an earlier article, the morphological mechanism of causing surface transition range and the factors of influencing surface transition range were examined by studying the rheological behaviors of a solid-state emulsion. Here, we investigated, in the lattice structure terms, the morphological change of oil-wax gel by measuring surface transition range depending on velocity gradient, which could influence the hardness and sweating phenomenon. We confirmed that the morphological change of oil-wax gel was accompanied by crystal size, crystal conformation, the degree of crystallinity. Surface transition range depending on velocity gradient was shown in large and regular lattice structure of oil-wax gel better than small and irregular one. [ABSTRACT FROM AUTHOR]