Lower Viscosity Values Research Articles

Effect of treatment type of natural fibers on the rheological and micromechanical behavior of polyvinyl alcohol composites

AbstractThe viscoelastic and mechanical performance of sustainable raw materials on biodegradable matrices provide insights into how to develop and improve materials that contribute to the circular economy. Thus, we aim to evaluate the effect of conventional (acid or alkali) and dual (alkali/acid‐ultrasound) treatment on Agave fibers, as well as their rheological and micromechanical performance on polyvinyl alcohol (PVA)‐based composites. TGA results indicate that the treatments promote the removal of moisture, waxes, pectin, hemicellulose, and lignin from the fibers to different extents. PVA matrix containing modified fibers exhibits low viscosity, flux index, and critical shear values, indicating a high interaction and dispersion of the filler in the matrix. Furthermore, tensile tests and theoretical predictions of micromechanics‐based finite element analysis show evidence that the modified fiber type provides a different stress transfer ratio () than in the matrix, which changes Young's modulus values. The results indicate that Agave fibers modified by dual treatment are a useful filler to produce soft or stiff PVA composites when looking for potential applications in the mobility industry or other fields like the packaging.

Iso-propyl caprylate and iso-propyl linolenate synthetic fluids as novel alternatives in deep-water drilling operations: Critical fluid properties and aerobic biodegradability assessments

Present drilling fluids for deep water wells have severe degenerative effect on the environment with high operational and disposal costs. Thus, making them less desirable in recent times. Ester synthetic drilling fluid provides a novel environmentally friendly alternative but conventional ester-based drilling fluids exhibit high viscosities in deep-water wells causing excessive equivalent circulating density (ECD) and increased risk of lost circulation owing to narrow mud density window. This study experimentally investigates the critical fluid properties and aerobic biodegradability potentials of two newly developed deep-water synthetic ester drilling fluids namely: iso-propyl caprylate (COIPE) and iso-propyl linolenate (LOIPE) synthetic fluids and their comparison with synthetic-paraffin (SP-SBF) and isomerized-olefin (IO-SBF) synthetic hydrocarbon fluids. The esters of iso-propyl caprylate and iso-propyl linolenate were produced from the isolation of ester mixtures that were obtained from the homogeneous catalytic transesterification of coconut and linseed plant oil biomass respectively. The COIPE was isolated from the coconut oil iso-propyl ester mixture by low-pressure fractional distillation technique. While fractional distillation and crystallization were used to isolate the LOIPE ester from the linseed oil iso-propyl ester mixture. Meanwhile, the aerobic biodegradation investigation was conducted by a modified oxygen consumption respirometry technique. The GC-MS analysis of the COIPE and LOIPE showed that the former contains essentially of lower saturated carbon compounds (C8). Whereas the latter contains higher molecular weight and unsaturated carbon compounds (C18+). The COIPE and LOIPE kinematic viscosity values are in good agreement with that of the reference synthetic hydrocarbon fluid samples (SP-SBF and IO-SBF). Although, the COIPE synthetic ester has lower viscosity value owing to the presence of shorter chain and saturated carbon atoms (C8 esters). Similarly, the linolenic oil iso-propyl ester has excellent cold flow characteristics for deep-water well drilling owing to lower values of cloud and pour points as a result of higher concentration of poly-unsaturated linolenic esters. The iso-propyl caprylate and the iso-propyl linolenate ester synthetic fluids are readily biodegradable in the sea water inoculum under aerobic condition. However, the iso-propyl caprylate is inherently biodegradable because its degradation level and that of the reference chemical sample were already above 60% during the 10-day window period. The SP-SBF and the IO-SBF synthetic fluids have lower aerobic biodegradation values because they contain little quantity of poly aromatic hydrocarbons as evident in their GC-MS profiles. Finally, esters and unsaturated synthetic-based fluid are more rapidly biodegradable than paraffinic synthetic fluids and the rate of biodegradation of organic compounds decreases as molecular weight increases

Binary glycerol-based deep eutectic solvents containing zinc nitrate hexahydrate salt for rechargeable zinc air batteries applications with enhanced properties

Deep eutectic solvents (DESs) have attracted interest due to their unique and favorable electrochemical characteristics. This study reported a novel binary glycerol-zinc salt deep eutectic solvents were prepared with a combination of hydrogen bond donor (glycerol (Gly)) and hydrogen bond acceptor (Zinc nitrate hexahydrate (ZNH)) at different molar ratios of 1:2, 1:3, 1:4, 1:5, and 1:6. The various physicochemical properties including viscosity, refractivity index, conductivity, thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), cyclic voltammetry (CV) and electrochemical impedance (EIS) were measured. The results showed that among the various combinations tested, DES 1:2 resulted in a low viscosity value of 690, 500, 310, 220, and 160 mPa (mPa s) at shear rate (S−1) values of 20, 30, 60, 100, and 200 respectively. Moreover, DES 1:2 resulted in more electrochemically stable solvents with a lower refractive index value of 1.446, and a higher conductivity (σ) of 4.41 mS/cm. The findings found disclose the features, nature and of properties of prepared DESs as a potential solvents for different electrochemical storage applications.

Polymeric Surfactants Bearing Divalent Carboxy Pendants for Stable Color Dispersions with High Redispersibility

Inkjet printing of ink requires dyes or pigments insoluble in water but uniformly dispersing as fine particles for a long period. In addition, redispersibility after solidification by solvent vaporization around the jetting heads is also important for performance. In this study, thus, a series of amphiphilic copolymers were prepared for a dispersant of inkjet using reversible addition fragmentation chain-transfer copolymerization of styrene (St), benzyl acrylate (BnA), and phenoxyethyl acrylate (PEA) as a hydrophobic monomer with acrylic acid (AA) and itaconic acid (IA) as a hydrophilic monomer. To understand the fundamental properties and potentials as a polymer dispersant, the surface parameters and rheology of the copolymers and their color dispersions in aqueous media were investigated. The aqueous solutions were typical Newtonian fluids, whereas the color dispersions were non-Newtonian fluids with shear-thinning properties and yield values ranging from 0.57 to 1.04 Pa. Although the surface parameters, such as surface tension (γ), molecular occupied area (Amin), and zeta potential (ζ), did not show clear correlation with polymer structures, their behaviors as a dispersant were significantly different. The color dispersants containing the copolymer of St or BnA as a hydrophobic monomer and IA and AMPS as hydrophilic monomers exhibited sufficient redispersion both for yellow and cyan inks, even after the aging test at 60 °C for 5 days, whereas other copolymers did not exhibit such superior performances. In addition, the color dispersions of the copolymer of St, IA, and AMPS (St-IA-AMPS) showed lower viscosity and yield value and became closer to Newtonian fluid compared with that of St, AA, and AMPS (St-AA-AMPS). Thus, St-IA-AMPS provided good redispersibility and avoided sedimentation. These results suggest that the most suitable dispersant for inkjet inks among the polymers investigated was the copolymer of St, IA, and AMPS.

Effect of calcium hydroxide on pasting, thermal, and water‐adsorption behavior, and the flow properties of nixtamalized corn flour

AbstractNixtamalized corn flour (NCF) has gained favor worldwide due to the growing popularity of Mexican cuisine. This research evaluates the effect of the amount of calcium hydroxide (Ca(OH)2) employed during the nixtamalization on the water‐adsorption, thermodynamic, and flow properties of NCF. In addition, NCF pasting and thermal properties were evaluated to relate bulk‐powder properties to wet‐dispersion conditions. Ca(OH)2 amounts of 1.5 and 2.0% induced higher ash and calcium content as well as lower fat and protein content. Also, pasting properties and gelatinization enthalpy (ΔHgel) values, in addition to yellowish NCF, were related to Ca(OH)2 concentration. With the independence of the Ca(OH)2 amounts employed, no important differences in the equilibrium's moisture content, as well as a negligible effect of temperature on adsorption behavior, were observed. For prepared NCF, the moisture content corresponding to minimum integral entropy was not observed within the range of the aw analyzed; thus, GAB parameters are more reliable for suggesting the storage conditions. NCF with a low amount of Ca(OH)2 exhibited higher values of mean caking strength (≈1.81 N) and cohesiveness index (≈13.99 × 10−5 N m g−1), in addition to higher resistance to flow. Therefore, the amount of Ca(OH)2 positively influenced flow properties, whereas wet‐dispersion properties such as lower maximal peak viscosity and ΔHgel values were obtained.Practical applicationsThis study contributes useful information to the manufacturers of NCF concerning the amount of Ca(OH)2 needed to obtain NCF with desirable physical properties while attempting to affect thermal and pasting properties to a lesser extent. In addition, this study characterizes and provides the adequate amount of Ca(OH)2 employed the during the nixtamalization process to improve the flowability of NCF in industry during handling. Finally, the absence of a moisture content corresponding to minimum integral‐adsorption entropy provides clarification for NCF producers regarding the long‐term storage stability of NCF.

On the Absence of Cyclic Structures in Branched Polystyrenes Synthesized by Living Three-Dimensional Radical Polymerization in the Medium of a Deteriorating Thermodynamic Quality Solvent

Branched polystyrenes are synthesized by the radical copolymerization of styrene and divinylbenzene with reversible inhibition (in the presence of 2,2,6,6-tetramethylpiperidine-1-oxyl) under deteriorating thermodynamic quality of the solvent. The resulting polymers are studied by size-exclusion chromatography combined with static light scattering, ozonolysis, NMR spectroscopy, and differential scanning calorimetry. The branched polymers synthesized by living radical polymerization are characterized by lower intrinsic viscosity values than their linear analogs. Kuhn–Mark–Houwink parameters for these polymers in a tetrahydrofuran solution (а = 0.29) confirm the nonlinear architecture of macromolecules and a high content of pendant double bonds comparable in the order of magnitude with their theoretical content in the absence of the cyclization reaction indicate their branched structure. The glass transition temperature of the branched polystyrenes is 20–35°С lower than the glass transition temperature of the linear polystyrene.

Quality Characteristics of Rice-Based Ice Creams with Different Amylose Contents

Ice cream consumption has increased over the years. In this study, we investigated the potential of using rice varieties with varying amylose contents for ice cream production. We analyzed the physical and chemical properties and sensory quality characteristics (appearance, taste, texture, chewiness, aroma, and rice flavor) of rice-based ice cream made from five varieties with low and high amylose levels. To make the ice cream, we ground rice into a fine powder and combined it with skim milk powder, butter, sugar, glycerin esters of fatty acids, locust bean gum, and water to form a gelatinized mixture. This mixture was then aged, frozen, and hardened. The ice cream's key quality characteristics, such as viscosity (2170-25,030 cP), hardness (4.27-49.55 N cm-2), and overrun (17.95-46.99%), showed a wide range. Ice cream made from Saemimyeon (high amylose content rice variety) exhibited the highest hardness value (49.55 N cm-2) among the varieties tested, but had relatively low viscosity (4030 cP), overrun (17.95%), and drip-through (0.75 g/min) values. These findings suggest that rice varieties with different amylose contents are suitable for making ice cream and have the potential to expand the rice processing market and increase its value.

Influence of Dynamic Viscosity of a Lubricant Material on the Parameters of Adhesion Bond in the Systems of Materials "12KH2H4 - STEEL 45", "45KHN2MFA - Steel 45" when Boring and Borocement Steel 45

In this work, the regularities of the change in the shear strength of the adhesive bond τ0 and the piezoelectric coefficient β in the metal systems "12Kh2N4 (45KhN2MFA) - steel 45 + B", "12Kh2N4 (45KhN2MFA) - steel 45 + VS" were obtained during physical modeling of the shear of surfaces of small-sized samples and changes in dynamic viscosity environment of their interaction with the use of additional equipment of the SMTs-2 friction machine. It has been established that borating and boron carburizing of the surface of steel 45 leads to the absence of adhesion to the surfaces of steels 12Kh2N4 and 45KhN2MFA in certain ranges of normal pressures, at which τ0> 0 and the dynamic viscosity of liquid and grease. It was found that the parameter τ0 when lubricating surfaces is determined to a greater extent for the system "12X2H4 - steel 45", and partially for borating steel 45 and low values of dynamic viscosity μ = 0.027 Pa•s. With an increase in the dynamic viscosity of the liquid phase of the lubricant in the "12X2H4 - steel 45" system, there is a tendency to an increase in the value of τ0. It was found that the absence of modification of steel 45 with boron and boron carbide predetermines the independence of the piezoelectric coefficient from the viscosity of the liquid lubricant and the shear rate. Boring and boron carburizing steel 45 predetermines an increase in the piezoelectric coefficient by an average of 1.6 times with an increase in dynamic viscosity from 0.027 Pa•s to 0.19 Pa•s at a shear rate of 10.16±0.8. At shear rate = 5.08±0.6 mm/s, the piezoelectric coefficient is relatively constant in the systems under study. With the transition to contact through a grease lubricant, there is an ambiguous manifestation of the rate of change of the piezoelectric coefficient.

YNAMIC VISCOSITY OF THE LUBRICANT AND ITS EFFECT ON STEEL MATERIALS WITH BORON

In this work, the regularities of the change in the shear strength of the adhesive bond τ0and the piezoelectric coefficient β in the metal systems "12Kh2N4 (45KhN2MFA) -steel 45 + B", "12Kh2N4 (45KhN2MFA) -steel 45 + VS" were obtained during physical modeling of the shear of surfaces of small-sized samples and changes in dynamic viscosity environment of their interaction with the use of additional equipment of the SMTs-2 friction machine. It has been established that boridingand boron carburizing of the surface of steel 45 leads to the absence of adhesion to the surfaces of steels 12Kh2N4 and 45KhN2MFA in certain ranges of normal pressures, at which τ0> 0 and the dynamic viscosity of liquid and grease. It was found that the parameter τ0when lubricating surfaces is determined to a greater extent for the system "12X2H4 -steel 45", and partially for borating steel 45 and low values of dynamic viscosity μ = 0.027 Pa•s. With an increase in the dynamic viscosity of the liquid phase of the lubricant in the "12X2H4 -steel 45" system, there is a tendency to an increase inthe value of τ0. It was found that the absence of modification of steel 45 with boron and boron carbide predetermines the independence of the piezoelectric coefficient from the viscosity of the liquid lubricant and the shear rate. Вoridingand boron carburizing steel 45 predetermines an increase in the piezoelectric coefficient by an average of 1.6 times with an increase in dynamic viscosity from 0.027 Pa•s to 0.19 Pa•s at a shear rate of 10.16±0.8. At shear rate = 5.08±0.6 mm/s, the piezoelectric coefficient is relatively constant in the systems under study. With the transition to contact through a grease lubricant, there is an ambiguous manifestation of the rate of change of the piezoelectric coefficient

Postglacial relative sea-level changes in the Gulf of Maine, USA: Database compilation, assessment and modelling

Relative sea level (RSL) reconstructions from paleo records are often the most valuable data set for testing and constraining glacial isostatic adjustment (GIA) models. In some regions, the amplitude and rate of the reconstructed RSL changes are large making the data difficult to fit. Arguably, the reconstructed RSL curve from Maine, USA, is the classic example of such a data set with peak values at about 120 m dropping to a low stand of around −40 m within a few thousand years. To our knowledge, no GIA model has captured these extreme variations and the record has been somewhat neglected by the GIA modelling community. Here we critically assess and present a revised pre-10 ka RSL data base for this region and combine it with two recent Holocene compilations. Based on our assessment, we conclude that the large and rapid changes, inferred in previous studies, are robust. To determine if a successful model fit can be found, we consider a GIA parameter set comprising five ice models and 440 spherically-symmetric, Earth viscosity models assuming a Maxwell rheology. Results show that none of the model parameter sets produce a good fit to the data set. The rapid RSL fall and lowstand can be simulated by Earth models with low values of upper mantle viscosity (∼5 × 1019 Pas). However, such low viscosity values result in a large mid-Holocene highstand (order 10 m) while the observations indicate a monotonic RSL rise throughout this interval. Our results indicate that Earth models able to simulate time-dependent viscosity (i.e., those that include transient and/or non-Newtonian deformation) might be required to fit the Maine RSL data set.

Numerical analysis of the fluid-solid interactions during steady and oscillatory flows of non-Newtonian fluids through deformable porous media

The flow of non-Newtonian fluids through evolving porous media is involved in important processes including blood flow and remediation of deformable aquifers. However, the effects of a moving solid boundary and the coupling between fluid rheology and solid deformation are still unclear. This study considers the steady and oscillatory flows of a yield stress fluid through a bundle of deformable channels. Simple semi-empirical expressions to predict the relationships between Darcy velocity and pressure gradient as a function of pore sizes, shear-rheology parameters and inlet pressure are developped, based on the results of innovative numerical simulations. The results show that channel deformation reduces the minimum pressure gradient required to induce the flow of a yield stress fluid through a porous medium, which results in lower values of Darcy-scale viscosity. For the considered conditions, macroscopic flow can be accurately predicted without a detailed knowledge of the hydraulic conductances of the deformed pores.

A review on viscoelastic behaviour of plasticizers in ap/al/htpb based composite solid propellant

Solid composite rocket propellant is commonly employed in military applications, such as in a rocket missile fuel engine. However, ongoing research is still being conducted on the material composition, fabrication process, and design of the grain structure to modify the performance of rocket motors. One of the most important parts of studying the solid rocket propellant is the propellant grain's fabrication process, which is the rheology and viscoelastic behaviour of the plasticizer as an additive material in the propellant slurry. Recent research indicates that the flowability of the propellant slurry has a substantial effect on grain quality. The plasticizer is an additive material that can improve the flowability of the propellant slurry by elongating the polymer chain structure. On top of that, most researchers have proven that the most crucial behaviour of the plasticizers is the particle migration that will affect the homogeneity of the propellant composition. This unwanted phenomenon was proven by the experimental work using chromatographic and Shore A hardness analysis of the propellant layer. The plasticizer concentration at 1 cm from the insulation layer decreased from 3 % to 2.087 % after the propellant was cured and aged. The Shore A hardness test shows the lowest value was at 3 cm from the insulation layer compared to 25 cm. Besides, it was also found that Isodecyl Pelargonate (IDP) can be a potential plasticizer for AP/AI/HTPB-based composite solid propellant application because it has the lowest viscosity value in the propellant slurry compared to the others. Thus, this paper focuses on reviewing the rheological behaviour of the plasticizers, influence of the curing temperature, plasticizer concentration, and curing time of the AP/AI/HTPB solid propellant slurry because all these factors affect the viscosity value of the plasticizers in the propellant slurry.

Overcoming the rheological performance and density limitations using a novel high density magnesium bromide based completion fluid in oil and gas reservoirs

Commonly used brine-based completion fluids are calcium chloride, sodium chloride, and potassium chloride. Our main objective for this study is to overcome the rheological performance and density limitations of existing brine-based completion fluid for workover and completion in oil and gas reservoirs. Magnesium Bromide-based completion fluid exhibits a high-density 13.41-lb/gal, with a specific gravity of 1.61. Existing, calcium chloride, potassium chloride, and sodium chloride-based completion fluid exhibit a density of 11.64-lb/gal (specific gravity 1.39), 9.6-lb/gal, (specific gravity 1.15), and 10.02-lb/gal (specific gravity 1.20), respectively. Results suggest that a high-density and solid-free novel magnesium bromide-based completion fluid show suitable optimum rheology avoid formation damage, plugging, and eroding of tubular and completion equipment. In this study, we have investigated the rheological properties such as apparent viscosity, plastic viscosity, yield point, and gel strength 10 sec and 10 min of formulated completion fluid at the varying temperature of 84 °F (28.8 °C) to 192 °F (88.8 °C). We have found that magnesium bromide-based completion fluid shows lower apparent viscosity and plastic viscosity as compared to calcium chloride-based completion fluid. A low value of apparent viscosity is desired for the design and development of the completion fluid.

Залежність «в’язкість – температура» вбирних олив різних виробників.

Coal tar wash oil is the main absorbent for removing benzene hydrocarbons from coke gas and is also used in various industries. Determination of oil viscosity is important primarily for precise regulation of the flow of the substance, given that a low viscosity value indicates less resistance to movement and higher movement speed. The value of the oil viscosity index in the process of its use for the recovery of benzene hydrocarbons from coke gas acquires the status of an integral criterion for evaluating the properties of the oil as an absorbent. For engineering and technological calculations of the viscosity of wash oil, coke chemists of Ukraine use two reference sources of information, although the conditions and materials for obtaining data are not specified in these sources. In the current period in Ukraine, in connection with the limitation of the production of wash oil, the issue of purchasing foreign samples of oil of a wide range of quality is being considered. To determine and interpret the temperature dependence of viscosity for samples of foreign and domestic oils of different composition, experiments were performed to measure dynamic viscosity using a Brookfield DV2T rotational rheometer with a controlled shear rate. β-methyl naphthalene was selected as the additive that most reduces oil viscosity, and diphenylene oxide as the additive that most increases oil viscosity. Among the experimentally obtained dependences, the maximum viscosity values are obtained by the oil produced in Ukraine on a single-column unit, and the minimum values by the oil produced abroad, artificially saturated with β-methyl naphthalene. The nature of the experimentally obtained curves is approximately the same, only the heavier domestic oil is more temperature-dependent at the beginning of the temperature range taken for research. Foreign samples of absorbent oil with a rather narrow boiling range have a lower viscosity level than oils of Ukrainian producers with a wider boiling range. Keywords: wash oil, viscosity, temperature dependence, aromatic components, viscous flow activation energy. Corresponding author: Artem L. Bannikov, e-mail: artiksmartik@gmail.com

Numerical Stability Analysis for a Stationary and Translating Droplet at Extremely Low Viscosity Values Using the Lattice Boltzmann Method Color-Gradient Multi-Component Model with Central Moments Formulation

Numerical Stability Analysis for a Stationary and Translating Droplet at Extremely Low Viscosity Values Using the Lattice Boltzmann Method Color-Gradient Multi-Component Model with Central Moments Formulation

Formula Optimization and Physicochemical Characterization of Tempe Drink Powder

Tempe is chosen as the main ingredient of tempe drink powder (TDP) due to its protein digestibility, phytochemical compounds, as well as vitamins and minerals. Previous studies had been conducted to develop TDP formula. The commercial TDP formula showed that improvement of quality aspects needs to be done so the product has better physical and chemical characteristics. In order to optimize the TDP formula, the viscosity, water solubility index (WSI), water absorption index (WAI), sedimentation index (SI), proximate, antioxidant activity, isoflavone content, GABA content, and physicochemical properties were analyzed. The optimized formula was done using the mixture experiment optimization method with optimization d-optimal to obtain the best formula. The optimization result showed that the best formula proportion consisted of 70% (w/w) Tempe flour, 18.23% (w/w) maltodextrin and 1.77% (w/w) guar gum. The best formula was chosen due to having better chemical characteristics compared with the commercial TDP and commercial soy drink powder (SDP), with protein content of 42.61%, antioxidant activity of 58.36 mgAEAC/100g, daidzein and genistein isoflavones of each 48.18 and 140.06 mg/100g and GABA of 21.24 mg/g. Based on the physical characteristics, the optimum formula had a lower viscosity value (18.67 cP) and WAI (2.58g/g) as well as a higher SI value (10.18%) and WSI (9.70%) compared with the commercial TDP. The optimum TDP formula has fulfilled the quality requirements based on the Indonesian National Standard (SNI 7612:2011) regarding soy drink powder.

On rheological properties of environmentally friendly inorganic systems and their modeling by artificial neural networks

This work aims to investigate the rheological properties, namely dependence of dynamic viscosity on temperature, chemical composition, and shear rate, of environmentally friendly inorganic systems using a high-temperature rotational viscometer up to 1550 °C. The liquidus and start and end softening temperatures of these systems were also studied. The environmentally hazardous calcium fluoride in the amount of up to 6 wt% was substituted by other components (B2O3, TiO2, and Na2O) to preserve the original utility properties of the investigated systems (low liquidus temperatures and viscosities). The effect of alternative additives ranging from 2 to 6 wt% on the required properties was more beneficial than that of fluoride. The most significant reduction in liquidus temperature of up to 185 °C was achieved by adding 6 wt% B2O3 while maintaining a low viscosity value. The addition of CaF2 (up to 6 wt%) had the least effect, lowering the liquidus temperature by only 22 °C as compared to the original system. In the case of TiO2 addition, the dependence of viscosity on chemical composition was non-linear and complex to predict with existing models. Therefore, it was modeled using artificial neural networks. The predicted viscosity values for a given temperature and chemical composition were in good agreement with the experimentally obtained values, as the maximum relative error between the measured and calculated viscosity values was less than 5%. The characterization of the internal structure of the investigated systems was performed by Energy Dispersive X-Ray (EDX), X-Ray Diffraction (XRD) analyses and Scanning Electron Microscopy (SEM).

Compositional and rheological analysis of carrageenan from the gametophyte phase of the red seaweed Chondrus crispus neutrally extracted at varying temperatures and time

Carrageenan-rich precipitate (CRP) was extracted from gametophyte Chondrus crispus at varying temperatures (22 °C, 45 °C, 90 °C) and time (0.25 h, 2 h, 8 h) at neutral conditions (i.e. without addition of alkali). Lower levels of 3,6-anhydrogalactose were detected in CRPs extracted at room temperature (22 °C) compared to extractions at 45 °C and 90 °C, suggesting a lower proportion of gelling units. Meanwhile, the CRPs obtained during the first period of extraction (0.25 h, at 45 °C and 90 °C) showed a higher amount of sulphate as compared to extractions for 2 or 8 h, suggesting a higher proportion of precursor units. These compositional differences were also supported by rheological studies. Gels made from CRP extracted at 22 °C had lower shear elastic modulus (G’) compared to gels made from CRP extracted at higher temperatures (45 °C, 90 °C). This was likely due to the lower 3,6-anhydrogalactose content in the extraction made at room temperature. In addition, the viscosity of gels made from CRP extracted at 0.25 h were higher compared to gels made from CRP extracted at 2–8 h for the same temperature (45 °C or 90 °C). This could be due to the higher amount of sulphate detected in the CRP of the former. Since 3,6-anhydrogalactse is an indicator of transformed (gelling) units, this result suggested that carrageenan chains with higher proportion of precursor units are more extractable under mild conditions. This knowledge may lead to the possibility for selective carrageenan extraction. • There are various carrageenan fractions in the seaweed cell walls that differ in terms of extractability in water. • Carrageenan fraction extracted at 22 °C contains lower amounts of 3,6-anhydrogalactose. • Gels made from carrageenan fraction extracted at 22 °C exhibits lower G’ values. • Carrageenan fraction obtained during the first period of extraction (0.25 h, at 45 and 90 °C) contains higher proportion of sulphate units. • Gels made from carrageenan obtained during the first period of extraction (0.25 h, 45 and 90 °C) exhibits lower viscosity values.

Preparation, Characterization, Stability and Thermophysical Properties of Bio, Non-Bio (Metallic and Non-Metallic) and Hybrids Nanofluids: A Review

Traditional heat transfer base fluids, such as ethylene glycol, ethanol, kerosene, oil, methanol, water etc. are normally used to enhance the heat transfer performance in many industrial applications. These traditional heat transfer fluids have many limitations. One of the limitations is the poor thermophysical properties of each of the base fluids and this results in a lower heat transfer rate in Thermal Engineering systems. Nanofluids are considered a new generation heat transfer fluid with higher thermal conductivity. Nanofluids have enhanced thermophysical properties compared to single-phase traditional heat transfer fluids. This paper highlights detailed reviews of the various methods of preparation, characterization, stability and thermophysical properties of bio, non-bio and hybrids nanofluids. Thermophysical properties such as density, viscosity, thermal conductivity and specific heat capacity from different works of literature were summarized, discussed and presented. There are many different parameters to be considered while investigating the thermophysical properties of nanofluids. Density and specific heat capacity are strongly dependent on the material type while the viscosity and thermal conductivity are highly affected by temperature and concentration. The most influential parameters on thermophysical properties of nanofluids are material type and temperature. The majority of the literature revealed that bio nanofluids have low viscosity values and hybrids have high thermal conductivity values. The novelty of this review paper is the presentation of the various methods of synthesizing, characterization, stability and factors affecting the thermophysical properties of metallic, non-metallic and hybrid nanofluids.

Compression-only behavior: Effect of prestress and shell rheology on bifurcation diagrams and parametric stability of coated microbubbles in an unbounded flow

Compression only is a counterintuitive response pattern of lipid coated microbubbles that are strain softening by nature and normally exhibit a bias towards expansion during volume pulsation. It is a result of shell viscoelastic behavior and arises for shells with low bending resistance and shear viscosity. During sonication such microbubbles buckle when the shell is prestressed, leading to oscillations around deformed shapes of lower volume. The latter are energetically favored and arise due to parametric mode excitation. Lower values of shear shell viscosity enhance this pattern that can be used to improve protocols for the acoustic characterization of shell mechanical properties.