Thickener Concentration Research Articles

The mechanism of solifenacin release from a pH-responsive ion-complex oral suspension in the fasted upper gastrointestinal lumen

The main objective of this study was to investigate the mechanism of solifenacin release from a pH-responsive ion-complex oral resinate suspension under conditions simulating the environment in the upper gastrointestinal lumen. A secondary objective was to propose an appropriate in vitro methodology for evaluating the quality of orally administered solifenacin suspensions. The mechanism of solifenacin release from polacrilin potassium resin (Amberlite® IRP88) was investigated using biorelevant media and compendial setups (USP Apparatus 2 and USP Apparatus 4) and using newer, recently validated in vitro methodologies [biorelevant gastrointestinal transfer (BioGIT) system]. We evaluated the impact of particle size and concentration of the resin; thickener concentration (carbomer homopolymer, type B); and the impact of pH, cationic strength, agitation intensity and level of simulation of contents in the upper gastrointestinal lumen. Data suggested that solifenacin release from the resinate was determined by the resin particle size, the medium pH, cationic strength (when the conditions in the upper small intestine are simulated) and the level of simulation of contents in the upper small intestine. The interaction of solifenacin with taurocholic acid/lecithin aggregates was significant, but unlikely to affect the degree of solifenacin absorption, as a BCS Class I compound. Under acidic conditions, solifenacin was dissociated and released from the pH-responsive resin rapidly. Under conditions simulating the contents of the upper small intestine, solifenacin was replaced by cations from the testing media and diffused through the resin matrix. All three in vitro systems with or without a pH gradient are useful in distinguishing solifenacin release characteristics from resinate suspensions with different particle sizes. Because of this drug release mechanism, USP Apparatus 2 with fixed pH media demonstrated equivalent or slightly higher discriminative sensitivity than the other setups and appears to be appropriate for product quality control.

Pretreatment of silk for digital printing: identifying influential factors using fractional factorial experiments

PurposeThe purpose of this study is to identify the most influential factors affecting the printing properties and print quality of digitally printed silk fabrics in terms of colour strength and fixation percentage.Design/methodology/approachIn this study, five factors (concentration of thickener, concentration of urea, concentration of alkali, pH of pretreatment liquor and steaming duration) were investigated using a blocked 25−1 fractional factorial experiment. The type of thickeners [polyacrylic acid and polyacrylamide (PAM)] were considered as a block.FindingsLinear models were obtained and statistically tested using both analysis of variance and coefficient of determination (R2), and they were found to be accurate at 90 per cent confidence level. It was revealed that concentration of alkali, concentrations of urea and pH of the pretreatment liquor had an increasing effect on colour strength, whereas concentration of thickener and steaming duration showed decreasing effect on colour strength of digitally printed silk fabrics. Furthermore, concentration of alkali, concentrations of urea had increasing effect on dye fixation percentage, whereas steaming duration showed decreasing effect on dye fixation percentage of digitally printed silk fabrics. In addition, PAM thickener based pretreatment recipe exhibited better printing properties for the digitally printing of silk fabrics.Originality/valueThe main influences and significant two-factor interactions were discussed in detail to gain a better understanding of the printing properties of digitally printed silk fabrics. The findings of this study are useful for further optimisation of pre- and post-treatment processes for digital printing of silk fabrics.

The Role of Grease Composition and Rheology in Elastohydrodynamic Lubrication

Grease lubrication is inherently complicated due to its non-Newtonian flow dynamics. The flow behavior of grease is difficult to determine under tribological shear rates as these shear rates are often extremely high, and therefore, are not accessible on a regular rheometer. In this work, we demonstrate the use of shear rate-concentration superposition method to extrapolate the data measured with a rheometer to tribologically relevant shear rates. This method is similar to the other superposition methods routinely employed by rheologists for predicting flow behavior beyond the measurement range of rheometer. In this method, a data master curve, which extends over a broad range of shear rates, is constructed by superposing individual flow curves for greases with different thickener concentrations. The master curve is utilized to determine infinite shear viscosity of grease which is then used for the film thickness estimation. Furthermore, the grease samples are tribologically tested using a four-ball tester to identify the individual and interactive roles of the thickener type, concentration and base oil in lubrication behavior. A change in thickener concentration or type influences frictional torque and wear scar size through modification in infinite shear viscosity and structural stability of grease. The SEM images show deposition of thickener particles on the contact surface, which also apparently affect friction and wear during the test. The lubrication performance is strongly influenced by base oil, which points towards the importance of its role in dictating flow resistance and film-forming behavior of grease inside elastohydrodynamic contact.

Synthesis and Er3+ spectroscopic property of Er3+/Yb3+-codoped CaIn2O4 nano-fibers for thermometry

Er3+/Yb3+-codoped CaIn2O4 nano-fibers with good morphology were synthesized by electrospinning technique. X-ray diffraction was performed on the synthesized phosphor of nano-fibers to confirm that the CaIn2O4 crystalline phase is dominant in it. The morphology of the nano-fibers was characterized by scanning electron microscopy. Optimal power supply voltage and thickener concentration for the synthesis were obtained. Er3+ 980-nm-upconverted emission characteristics of the nano-fibers were investigated. The results show that two-photon process is the dominant mechanism for the upconversion emissions. The nano-fibers doped with 5 mol% Er3+ display the strongest upconversion fluorescence. Temperature characteristics of the green 530 and 550 nm upconversion fluorescence of the nano-fibers were also studied for thermometry purposes. The results reveal that the nano-fibers show thermally stable spectral structure and the ones doped with 5 mol% Er3+ display the highest thermal sensitivity of green fluorescence intensity ratio. We conclude that there exists an optimal Er3+ concentration of 5 mol%, and the CaIn2O4 nano-fibers doped with this optimal Er3+ concentration display some spectroscopic properties favorable for ratiometric thermometry in the high-temperature regime.

Evaluation of Thickened Fluids Used in Dysphagia Management Using Extensional Rheology.

Recent studies show that understanding the rheological properties of thickened fluids, such as viscosity and yield stress, is advantageous in designing optimal thickened fluids for the treatment of dysphagia. To date, these studies have focused on the rheological behavior of thickened fluids in shear deformation, while limited information is available on the surface tension of thickened fluids or their rheological behavior in extensional deformation. Knowledge of the extensional properties of thickened fluids (extensional viscosity and cohesiveness) is important to fully understand the behavior of such fluids while swallowing. Our aim in this work, therefore, was to characterize water and skim milk thickened with a commercial thickener (xanthan gumbased) to determine extensional deformation and surface tension properties. It was observed that the surface tension decreases as the thickener concentration increases due to the accumulation of the biopolymer at the surface of the fluid when it dissolves in water. In addition, the extensional viscosity of the fluid increased over time as the filament thinned (i.e., as the Hencky strain increased) until it reached a plateau. It was observed that the maximum extensional viscosity, which is related to the cohesiveness of the fluid, increases with the higher concentrations of thickener. However, the cohesiveness of thickened skim milk was lower than that of the thickened water at a given thickener concentration due to lower surface tension. This study confirms that by increasing the concentration of thickener, it will not only increase the shear viscosity (i.e., bolus thickness) of the fluid, but also the extensional viscosity (i.e., bolus cohesiveness).

A modified Ester-branched thickener for rheology and wettability during CO2 fracturing for improved fracturing property.

The thickening performance of CO2 fracturing fluid was poor because of the low apparent viscosity. In this paper, the thickening performance of a modified silicone on liquid CO2 is measured, and a rheology was investigated according to the consistency coefficient K and rheological index n. Meanwhile, a reservoir model was established to evaluate the fracturing property. Results showed that the modified silicone contributes to improve the apparent viscosity of liquid CO2 and decrease the rheology of liquid CO2. With the thickener content or pressure increase, the apparent viscosity of liquid CO2 increases, and the rheological index n decreased obviously. A reduced apparent viscosity is shown as the flow rate or temperature rises, but the rheology increased gradually. The fracturing simulation herein shows that thickened CO2 fracturing fluid could improve obviously the fracture property. This modified thickener possesses the potential as a thickener and could be a reliable alternative to the thickener in CO2 fracturing technology, and the large contact angle improved the backflow property of this CO2 thickener from rock surfaces. The development of CO2 fracturing technology provides basic data for the improvement of greenhouse effect and clean mining of energy.

On the Shear Stability of Dry and Water-Contaminated Calcium Sulfonate Complex Lubricating Greases

Calcium sulfonate complex greases have excellent extreme pressure, antiwear, and anticorrosion properties and are widely applied in rolling bearings, particularly in humid environments. In this article, the shear stability of dry and water-contaminated lubricating calcium sulfonate complex greases is described using a novel aging method. Unlike lithium and polyurea greases, no shear softening is observed for the dry greases due to the good mechanical stability of the particle-like thickener structure. For water-contaminated greases, no water separation was found during the prolonged aging. Instead, a homogeneous water–calcium sulfonate thickener micellar structure is generated. These micelles function as apparent thickeners and effectively increase the thickener concentration, which thickens the grease. This may explain why calcium sulfonate complex grease has excellent water absorption properties.

Effect of thickener and reservoir parameters on the filtration property of CO2 fracturing fluid

ABSTRACTSome drawbacks of the hydraulic fracturing technology included the water pollution and reservoir destruction, hindered its development and application in shale reservoirs. CO2 fracturing fluid is considered to be an excellent substitution to conduct the fracturing operation because of its cheapest, enhance gas production and environment friendly. However, the low viscosity and high filtration property of pure CO2 are viewed as a huge challenge to develop CO2 fracturing technology. In this paper, we synthesize a modified silicone as a CO2 thickener to investigate the effect of different thickener parameters, temperature, and pressure on the CO2 filtration property in low permeability reservoirs. This is a working theory which is based on the organic synthesis and unconventional oil and gas exploration. We carry out several studies which have demonstrated that the CO2 filtration coefficient deceased as an increase of CO2 thickener and carbonyl group content, molecular weight, and pressure. When the temperature rises, an increasing filtration coefficient of liquid CO2 was presented. Physical parameters of thickener display a significant impact on CO2 filtration coefficient. A thickener with a reasonable chemical structure significantly was not only improving the CO2 viscosity but also the filtration coefficient has. It was also found that fracturing fluid viscosity is the ultimate factor that changes the CO2 filtration property.

Effect of a Modified Silicone as a Thickener on Rheology of Liquid CO₂ and Its Fracturing Capacity.

The low viscosity of pure liquid CO2 hindered the development of CO2 fracturing technology. A modified silicone polymer was prepared as a CO2 thickener to investigate the effect of temperature, pressure, shear rate and thickener content (wt.%) on the apparent viscosity and rheology of thickened liquid CO2. In addition, CO2 fracturing capacity was evaluated with the numerical simulation of extended finite element. The results displayed that an apparent viscosity of up to 1.3 mPa·s at 303 K and 18 MPa was attained over liquid CO2 using the thickener of 3 wt.% and Toluene of 9 wt.% as additives. Compared to the commercial linear polydimethylsiloxane, a better apparent viscosity was obtained from the mixture of this prepared thickener, Toluene and CO2. The apparent viscosity decreases with increasing temperature and shear rate. By contrast, an improving apparent viscosity was revealed with an increase in the pressure from 8 to 14 MPa and thickener content from 1 to 3 wt.%. The rheological index decreased with increasing thickener content with pressure but the rise in temperature led to an increasing rheological index. The mesh structure theory of the thickener, CO2 and Toluene molecules was in this paper gives a good explanation for the discrepancy between CO2 viscosity with the thickener content, temperature, pressure, or shear rate. Compared to pure CO2, the numerical simulation of CO2 fracturing demonstrated an excellent fracturing capacity by using the thickened CO2 fracturing fluid in shale reservoirs. This investigation could provide the basic reference for the development of CO2 fracturing technology.

An application of thickener to increase viscosity of liquid CO2 and the assessment of the reservoir geological damage and CO2 utilization

ABSTRACTIn comparison to hydraulic fracturing, CO2 fracturing technology is more efficient and effective in solving environmental problems caused by the fracturing process. However, the low viscosity caused by pure CO2 under high pressure hinders the development of the entire fracturing technology. Given that, a siloxane that can significantly improve the liquid CO2 viscosity is prepared and the excellent performance to thicken CO2 by silicone polymer is shown. Polymerization that occurs under water conditions presents a trend and is more likely to trigger reaction than ring-opening polymerization under anhydrous conditions. The thickening performance test is conducted by capillary viscometer self-designed at 35°C and 10 MPa. Moreover, a rising trend in viscosity is demonstrated with increase in thickener concentration. Smaller damages and chemical residue exists in the stratum after CO2 fracturing. In addition, there are no changes that occur in the quality of crude oil. A fine conclusion for thickening performance provides a basis for the synthesis of the polymer to thicken CO2.

Standard Recipes for the Preparation of Thickened Barium Liquids Used in the Diagnosis of Dysphagia.

Barium sulfate is commonly used to prepare contrast media for videofluorograpy. The flow characteristics of thickened liquids formulated for oropharyngeal imaging are known to be greatly affected by the addition of barium. In this study, thickened barium liquids were prepared by mixing a commercial xanthan gum (XG)-based thickener (Visco-up®) at different concentrations (0.1%–3.0%) with barium powder (Baritop HD®), and differences in the viscosity between thickened non-barium and thickened barium liquids were investigated. In addition, the thickness levels of thickened barium liquids, which are based on the National Dysphagia Diet (NDD) and International Dysphagia Diet Standardization Initiative (IDDSI) guidelines, were classified by measuring the viscosity (NDD) and gravity flow through a syringe (IDDSI) with 0.1%–3.0% thickener concentrations. The apparent viscosity (ηa,50) values of thickened barium liquids were much higher than those of thickened non-barium liquids, indicating that the addition of barium to the XG-based thickener resulted in further thickening. Standard recipes for preparing thickened barium liquids with desirable thickness levels were also established, showing the different thickener concentrations corresponding to the different NDD and IDDSI levels.

Microstructure and frictional properties on biological mucosa

Swallowing disorder has been becoming a serious issue with increasing in elderly people. Disorder sometimes appears with an decrease in saliva, because saliva has an important role in lubrication over the oral cavity and throat. Though the structure of biological mucosa has been studied physiologically, there are only few studies that examined the influence of its micro structure on fluid lubrication. Therefore, we investigated the friction characteristics by reproducing the micro structure of oral cavity and pharynx. As an example of the oral cavity mucous membrane, the tongue of a pig was subjected to observation by microscope and laser surface shape and roughness measuring machine. As a result, roughness properties of a pig tongue differed from root part to tip part, and it was confirmed that hemispherical protrusions were observed on the tip part by irregular arrangement. An imitation tongue was produced using a high-precision 3D printer. Furthermore, the concentration of thickener was determined from the measurement of the viscous characteristic by the rotational viscometer to have the same viscosity as that of saliva. We measured friction coefficients on the imitation tongue lubricated by artificial saliva. The friction coefficients were changed depending on the lubrication condition and the moving speed.

INFLUENCE OF BASIC OIL VISCOSITY ON QUALITY INDICATORS RECYCLING PLASTIC LUBRICANTS

The results of laboratory research on determination of dependence between quality indicators of plastic oils and kinematic viscosity of base oil on the example of recycling lubricants obtained from spent lubricating oils are presented. As a thickener, secondary polyethylene of low pressure was used at a concentration of 5 % (w / w). It was established that the obtained dependences between the determined quality parameters of the lubricant and the kinematic viscosity of the base oil are adequately described by the polynomial of the second degree, as evidenced by the very high (0.93-0.99) values of the coefficients of reliability of the approximation of R2. Therefore, the kinematic viscosity of the base oil significantly affects the evaporation of the lubricant, the loss of oil during storage of lubricants and its rheological properties. When added the same concentration of thickener, the best properties were the lubricant obtained from high-viscosity transmission oil. The worst rheological properties differed from the lubricant with a little viscous hydraulic oil. In this regard, the kinematic viscosity of the base oil acts as a factor in the process of production of plastic lubricants, which controls, it is possible to form its structure, to predict the properties and reduce the cost, due to the rational use of the thickener.

Application of the building block approach to characterize the pressure loss of water and fracturing fluid in contraction-expansion pipe

In the fracturing pipeline, the contraction-expansion pipe structure is various. Accurate calculation of pressure loss can provide a theoretical support for the design of high sand ratio fracturing process parameter and tools selection. In this paper, the building block approach is used to describe the general framework for calculating the pressure loss of water in contraction-expansion pipe [D1≠D2、Ld/(D1/2 + D2/2)＜2.00] and expansion-contraction pipe (d1≠d2、LD/D＜3.75). The drag ratio method was used to describe the pressure loss of the fracturing fluid based on the pressure loss of water in the contraction-expansion pipe and the expansion-contraction pipe. Finally, the calculation methods for the pressure loss of water and fracturing fluid were described. The data from the experimental test showed that the relative error was less than 15%. The experimental study of water in the contraction-expansion pipe showed that the pressure loss was positively correlated with the flow rate, but it was negatively correlated with the ratio of inlet-outlet diameter and the ratio of flow path length. And for the expansion-contraction pipe, pressure loss was positively correlated with the flow rate and ratio of flow path length. When the ratio of flow path length was close to 3.75, the ratio of inlet-outlet diameter was positively correlated with the pressure loss, and when the ratio of flow path length was close to 0.05, the ratio of inlet-outlet diameter was negatively correlated with the pressure loss. Analysis of fracturing fluid in contraction-expansion pipe and expansion-contraction pipe showed that the flow rate, proppant concentration and thickener concentration were positively correlated with pressure loss, and the drag rate of fracturing fluid reached 72%.

Eco-Friendly Tamarind Kernel Thickener for Printing of Polyester Using Disperse Dyes

Printing is a form of dyeing in which colors are applied to specified regions instead of the entire fabric. To restrict the coloring matter to the design area, the dyes and other auxiliaries are pasted with a natural or synthetic thickening agent. Finding alternatives to the used thickeners has gained importance lately due to the several limitations associated with toxicity, availability, and cost of the currently used thickeners. Tamarind kernel powder has the potential to be explored as a textile thickener whilst providing economic benefits. Tamarind kernel, derived from the seeds of Tamarindus indica Linn., is a byproduct of the tamarind fruit and pulp industry. It is a low cost, non toxic, biodegradable, cold water soluble thickener. In the present study, an effort has been made to explore the suitability of tamarind kernel thickener for printing of polyester using disperse dyes. On the basis of the qualitative and quantitative analysis, 25 % concentration of tamarind kernel powder, steaming temperature of 130 °C for 30 min with carrier was optimized as printing conditions. The samples printed using the given conditions exhibited brighter and sharper lines with uniformity of color. No change in whiteness of the ground and handle of the fabric was seen. Haloing and flushing was observed in samples printed with lower concentrations (5-15 %) of tamarind kernel thickener. Color value (K/S) of the samples was increased with increase in steaming time and temperature indicating better fixation of dye at high temperatures. All the printed samples irrespective of the varying thickener concentration, steaming time and temperature gave excellent fastness to washing and rubbing.

Osmolality analysis of human milk and an infant formula with modified viscosity for use in infants with dysphagia

ABSTRACT Purpose: to evaluate the effects of a thickening agent on the osmolality of human milk and on an infant formula, with respect to concentration and time. Methods: six trials were performed to evaluate the osmolality of a natural and thickened infant formula, raw human milk, and pasteurized human milk. Rice cereal was used as a thickening agent (at concentrations of 2%, 3%, 5%, and 7%). Osmolality was measured using the Advanced Micro Osmometer Model 3300 after sample preparation periods of 0-60 minutes. Statistical evaluations were performed using ANOVA. Results: pasteurized human milk exhibited time- and concentration-dependent variation in osmolality. The osmolality of raw human milk differed among time points and between the samples with 5% and 7%, when compared to the non-thickened milk. The infant formula did not show differences in osmolality with respect to time. At time zero, there were differences in osmolality between the infant formula samples with 2%, 3%, and 5% thickener. At other time points, there were differences in osmolality between the sample with a 5% thickener and the non-thickened formula. Conclusion: the osmolality of diets varied over time and according to the concentration of thickener in human milk and the infant formula. However, the observed variation remained within the recommended parameters, indicating that rice cereal is a safe thickener for the feeding of infants presented with mild or moderate oropharyngeal dysphagia.

Tribological performance of paraffin grease with silica nanoparticles as an additive

The present study deals to evaluate the physical properties, frictional behavior, and extreme pressure performance of paraffin grease dispersed with silica (SiO2) nanoparticles. The paraffin grease was developed using paraffin oil as a base oil and 12-lithium hydroxy stearate was chosen as a thickener. The concentration of thickener was fixed at 14% w/w. The SiO2 nanoparticles were synthesized by the modified sol–gel method and dispersed in paraffin grease by the in-situ method. The various analytical tools were used to ensure the formulation of SiO2 nanoparticles. The extreme pressure and frictional characteristics of SiO2 doped in paraffin grease were studied in four-ball tester as per ASTM D2596 and D2266, respectively. The physical properties of paraffin greases such as cone penetration, drop point, water washout, leakage tendency, and evaporation loss were also evaluated according to ASTM standards. The experimental results showed that the addition of SiO2 nanoparticles in paraffin grease enhances its tribological performances as compared to pure paraffin grease. The maximum reduction in coefficient of friction and mean wear volume was ~ 20% and ~ 42% at a concentration of 0.03 and 0.05% w/w, respectively.

Composition, Properties, and Structure of Low-Temperature Lubricating Greases Based on Polymeric Thickener

The dependence of the colloidal stability, effective viscosity, penetration, and yield stress of low-temperature polymeric greases on the composition and characteristics of the dispersion medium was investigated. Various types of low-viscosity oil with known fractional and group composition were used as base oils. The effect of the concentration of the two-component thickener of high- or low-molecular polypropylene and the proportions of its components on the main physicochemical characteristics of the polymer greases was determined. The dependence of the structure and properties of the polymer greases on the concentration of lithium stearate was established.

Shear and extensional rheological characterization of thickened fluid for dysphagia management

Thickened fluids are used in the medical management of individuals who suffer from swallowing difficulties (known as dysphagia). Recent studies show that understanding the rheological properties of thickened fluids is advantageous in designing better-controlled fluids. Whilst the rheological behavior of thickened fluids in shear deformation has been studied by several authors, studies on their extensional behavior are limited, despite their critical importance in influencing bolus flow and swallowing. Our aim in this work was to rheologically characterize extensional deformation of dysphagia fluids thickened with different types of commercial thickeners at varying concentrations using a filament stretching and break-up device. It was observed that the extensional viscosity increased and became more cohesive as the thickener concentration was increased. Additionally, it was observed that for similar shear viscosity at 50 s−1, the extensional viscosity of the fluid was dependent on the type of thickener. This study confirms that by thickening fluid with different types of thickeners, the cohesiveness of the fluid may be very different even at the same shear viscosity. Therefore, both shear and extensional rheology of thickened fluids should be considered for the management of dysphagia.

The effect of supercritical CO2 fracturing fluid retention-induced permeability alteration of tight oil reservoir

Supercritical CO2 (SC-CO2), as a non-aqueous material of fracturing fluid, receives widely attention in the development of unconventional reservoirs. In this study, permeability regain (Krg) was introduced to characterize the permeability alteration on tight cores by SC-CO2 fracturing fluid. Meanwhile, scanning electron microscope (SEM), microscope system, nuclear magnetic resonance (NMR) were used to reveal the mechanisms of permeability alteration at different scales.The results showed that the composition of SC-CO2 fracturing fluid, fluid filter loss, and reservoir permeability were all responsible for permeability alteration. With the increasing thickener contents and filter loss of fracturing fluid, core permeability regains turned to be declined. Comparatively, tight cores which consist of more micro-nanometer sized pores were more likely to receive more formation damage of permeability, as well. The retention of thickener in microchannels (micro pores) were confirmed to be the main mechanisms on permeability alteration.