Maximum Viscosity Research Articles

Relations Between Amylose Content and Physicochemical Properties of Starches from White and Red Sorghum Varieties

AbstractThis research aims to determine the relationship between amylose content and physicochemical properties in white and red sorghum starches. Five varieties of red sorghum and four varieties of white sorghum were evaluated. The chemical properties, the amylose content, the resistant starch content, scanning electron microscopy, the absorption and solubility index in water, the viscosity profile, the thermal properties, and the correlation between the amylose content were determined. Sorghum starches had an amylose content between 24.51% and 34.34%, but did not show any relationship with color. Regarding the microstructure, the starches that appear larger granules (20–30 µm) have lower amylose content. Sorghum red varieties shown higher values in gelatinization enthalpy, pasting temperature and water absortion index, this effect was attributed to the formation of complexes with phenolic compounds. Starches with a higher proportion of amylose shown lower viscosity profiles and a high thermal stability. Correlation matrix analysis reveals that amylose content had a negative correlation with water absorption index, water solubility index, maximum viscosity, minimum viscosity, and positive correlation with the resistant starch content. The amylose content can define the potential application of the sorghum starches.

Simulation of the Performance of Kevlar Impregnated Shear Thickening Fluid Ballistic Test Results (STF) Ballistic Test Results

This study explores the enhancement of Kevlar fabric’s ballistic performance through impregnation with Shear Thickening Fluid (STF) for potential application in soft body armor. The experimental approach often fails to elucidate mechanical phenomena critical for the development of lightweight and high-strength body armor designs. To address this limitation, the finite element method, specifically using ANSYS/LS-DYNA R.13, was employed for a comprehensive analysis. The simulation aimed to evaluate the impact of STF on Kevlar fabric by assessing projectile velocity, force exerted by the projectile onto the fabric, displacement, stress distribution, and fabric failure mechanisms. Kevlar yarn was modeled as a shell element formed into fabric with a sine wave profile, investigating two types of STF: SiO2-PEG200 (S0) and SiO2-PEG200-B4C (S1), differing in maximum viscosities. The addition of STF resulted in increased coefficients of friction on Kevlar, with the highest values observed for the SiO2-PEG200-B4C impregnated fabric ( =0.87 and =0.82). The incorporation of the second STF type (S1) significantly reduced the projectile’s velocity from an initial 200 m/s to 153.2 m/s upon impact. Additionally, the force on the S1 fabric surged to 121,556 N, a threefold increase compared to neat Kevlar. STF's influence was further evidenced by enhanced fabric displacement and more uniform stress distribution upon ballistic impact. The fabric's thickening upon failure indicated STF's ability to enlarge the deformation area, facilitating uniform distribution of ballistic kinetic energy across the impact zone. Notably, the fabric impregnated with the second type of STF, featuring boron carbide (S1), demonstrated superior ballistic performance. This study concludes that STF-impregnated Kevlar fabric, particularly the SiO2-PEG200-B4C variant, not only surpasses the ballistic performance of neat Kevlar but also meets the criteria for NIJ Level IIIA standards, highlighting its potential as a highly effective material for advanced soft body armor designs.

A constitutive model for shear thickening fluid (STF) impregnated Kevlar fabric subjected to impact loading

A constitutive model is presented herein to predict the response and failure of STF impregnated Kevlar fabric under impact loading on the basis of the progressive damage model for fibre reinforced plastic (FRP) laminates. In the constitutive model, the strain rate effect of shear strength is innovatively connected with the rheological property of STF. In order to verify the validity and accuracy of the model, numerical simulations of both ballistic and low-velocity impact experiments of STF impregnated Kevlar fabric are conducted. Furthermore, parametric study is carried out on the influences of impact velocity and rheological behavior of STF. It transpires that the numerical results using the constitutive model are in good agreement with the experimental data in terms of residual velocity, load-displacement curve, energy absorption, global deformation and failure patterns. It also transpires that, with the same impact energy, STF impregnated Kevlar fabric shows stronger resistance to lower velocity ballistic impact. In addition, the maximum viscosity and shear thickening interval of the STF have a significant effect on the ballistic performance of the STF impregnated Kevlar fabric.

Nonmonotonic Composition Dependence of Viscosity upon Adding Single-Chain Nanoparticles to Entangled Polymers.

Well-characterized single-chain nanoparticles (SCNPs), synthesized from a linear polystyrene precursor through an intramolecular [4 + 4] thermal cycloaddition cross-linking reaction in dilute conditions, were added to entangled polystyrene melts at different concentrations. Starting from the pure linear melt, which is much more viscous than the melt of SCNPs, the zero-shear viscosity increased upon the addition of nanoparticles and reached a maximum before eventually dropping to the value of the SCNP melt. Molecular simulations reveal the origin of this unexpected behavior, which is the interplay of the very different compositional dependences of the dynamics of the two components. The SCNPs become much slower than the linear chains as their concentration decreases because they are threaded by the linear chains, reaching a maximum viscosity which is higher than that of the linear chains at a fraction of about 20%. This behavior is akin to that of single-loop ring polymers when added to linear matrices. This finding provides insights into the design and use of SCNPs as effective entropic viscosity modifiers of polymers and contributes to the discussion of the physics of loopy structures.

Thermal and irreversibility analyses of a suspension embodying nano-encapsulated phase change materials using power-law and Darcy-Brinkman-Forchheimer models

The study of natural convection and heat transfer in a trapezoidal cavity finds a wide range of technological applications including thermal energy storage systems, building ventilation/insulation, waste heat recovery, electronic device cooling, controlling PV panel temperature, energy conservation, exchangers, nuclear reactors, furnaces, glass production, food processing, and drying technologies. The purpose of the current study is to explore the entropy and natural convection of non-Newtonian nano-encapsulated phase change material (NEPCM) suspension in a saturated porous medium enshrouded in a trapezoid-shaped domain with three heated blocks fitted with the bottom surface. The novelty of the present work is the introduction of power-law (Ostwald-de Waele) model subject to NEPCM suspension in trapezoidal enclosure emplacing three heated fins at its bottom surface embedded in Brinkman-Forchheimer extended Darcy medium with variant porosity. The finite element method is implemented to solve the governing equations numerically. The important findings of the present study include streamlines, isotherms, velocities, and apparent viscosity enhance while entropy generation whittles down with rise in Darcy number. Entropy generation ameliorates by 519.16 % for low to high porosity of Brinkman-Forchheimer extended Darcy medium. The maximum apparent viscosity augments by 1441.24 % when power law index ameliorates.

Synthesis of polymerizable betulin maleic diester derivative for dental restorative resins with antibacterial activity

ObjectiveBisphenol A glycidyl methacrylate (Bis-GMA) is of great importance for dental materials as the preferred monomer. However, the presence of bisphenol-A (BPA) core in Bis-GMA structure causes potential concerns since it is associated with endocrine diseases, developmental abnormalities, and cancer lesions. Therefore, it is desirable to develop an alternative replacement for Bis-GMA and explore the intrinsic relationship between monomer structure and resin properties. MethodsHere, the betulin maleic diester derivative (MABet) was synthesized by a facile esterification reaction using plant-derived betulin and maleic anhydride as raw materials. Its chemical structure was confirmed by 1H and 13C NMR spectra, FT-IR spectra, and HR-MS, respectively. The as-synthesized MABet was then used as polymerizable comonomer to partially or completely substitute Bis-GMA in a 50:50 Bis-GMA: TEGDMA resin (5B5T) to formulate dental restorative resins. These were then determined for the viscosity behavior, light transmittance, real-time degree of conversion, residual monomers, mechanical performance, cytotoxicity, and antibacterial activity against Streptococcus mutans (S. mutans) in detail. ResultsAmong all experimental resins, increasing the MABet concentration to 50 wt% made the resultant 5MABet5T resin have a maximum in viscosity and appear dark yellowish after polymerization. In contrast, the 1MABet4B5T resin with 10 wt% MABet possessed comparable shear viscosity and polymerization conversion (46.6 ± 1.0% in 60 s), higher flexural and compressive strength (89.7 ± 7.8 MPa; 345.5 ± 14.4 MPa) to those of the 5B5T control (48.5 ± 0.6%; 65.7 ± 6.7 MPa; 223.8 ± 57.1 MPa). This optimal resin also had significantly lower S. mutans colony counts (0.35 ×108 CFU/mL) than 5B5T (7.6 ×108 CFU/mL) without affecting cytocompatibility. SignificanceIntroducing plant-derived polymerizable MABet monomer into dental restorative resins is an effective strategy for producing antibacterial dental materials with superior physicochemical property.

Further Investigation of CO2 Quasi-Dry Fracturing in Shale Reservoirs—An Experimental Study

The physical properties of shale reservoirs are typically poor, necessitating the use of fracturing technology for effective development. However, the high clay content prevalent in shale formations poses significant challenges for conventional hydraulic fracturing methods. To address this issue, CO2-based fracturing fluid has been proposed as an alternative to mitigate the damage caused by water-based fracturing fluids. In this paper, the applicability of quasi-dry CO2 fracturing in shale reservoirs is examined from three key perspectives: the viscosity of CO2 fracturing fluid, the fracture characteristics induced by the CO2 fracture fluid, and the potential reservoir damage caused by the fracturing fluid. Firstly, the viscosity of CO2 fracturing fluid was determined by a rheological experiment. Rheological tests revealed that the viscosity of CO2 fracturing fluid was significantly influenced by the water–carbon ratio. Specifically, when the water–carbon ratio was 30:70, the maximum viscosity observed could reach 104 mPa·s. Moreover, increasing reservoir temperature resulted in decreased fracturing fluid viscosity, with a 40 °C temperature rise causing a 20% viscosity reduction. Secondly, matrix permeability tests were conducted to investigate permeability alteration during CO2 fracturing fluid invasion. Due to the weak acidity of CO2-based fracturing fluid, the permeability reduction induced by clay hydration was inhibited, and an increase in permeability was observed after a 3-day duration. However, the matrix permeability tends to decrease as the interaction time is prolonged, which means prolonged soaking time can still cause formation damage. Finally, triaxial fracturing experiments facilitated by a three-axis servo pressure device were conducted. The fracture properties were characterized using computed tomography (CT), and 3D reconstruction of fractured samples was conducted based on the CT data. The results demonstrate that CO2 fracturing fluid effectively activates weak cementation surfaces in the rock, promoting the formation of larger and more complex fractures. Hence, CO2 quasi-dry fracturing technology emerges as a method with significant potential, capable of efficiently stimulating shale reservoirs, although a reasonable soaking time is necessary to maximize hydrocarbon production.

The effect of microwave-assisted hydrothermal treatment on physicochemical and functional properties of wheat, barley, and rye flours

The aim of this study was to investigate the effect of microwave-assisted hydrothermal process on color, solvent holding capacity, damaged starch content, resistant starch content, gelation and textural properties of wheat, barley, and rye flours. The hydrothermal treatment was conducted by adjusting the moisture content of the flours to 20, 25, 30, 35% following drying of the hydrated flours using a modified microwave oven until the moisture content fell below 8%. As a result, a general increase was observed in solvent (water, lactic acid, sucrose, and sodium carbonate) holding capacity, damaged starch content, b* value, chroma (saturation), redness, ΔE value, and gelatinization temperature of the flours regardless of the cereal type. The variations were more pronounced at higher initial moisture contents. On the contrary, the resistant starch content, L* value, whiteness, and breakdown viscosity decreased as a result of the treatment. The hydrothermal treatment resulted in an increase in maximum viscosity, setback viscosity, and gel hardness for wheat flour, whereas it led to a decrease in these parameters for treated barley and rye flours. Moreover, the impact of the treatment varied depending on the initial moisture content, with a more significant effect observed at moisture contents exceeding 25%.

Crystal growth in oxide melts—From CALPHAD thermodynamic modeling to statistical prediction

Using a thermodynamic database approach (CALPHAD), thermodynamic parameters of crystal growth of 31 stoichiometric and non-stoichiometric glasses are calculated. Together with these parameters, the measured growth rates, taken from both literature and in-house measurements, are interpreted in the framework of four interface-controlled growth models: normal, screw-dislocation, 2D growth and a combination of the latter two. A multiple linear regression model is used to explain the maximum crystal growth rate and viscosity at the liquidus temperature with the above growth mechanisms. This finding seems to reflect a general trend and can therefore be used to avoid unintentional devitrification phenomena or to derive their temperature-time range based on the sole knowledge of glass viscosity and liquidus temperature. In future research, it can also help to reduce the experimental workload required for the development of novel glasses and glass-ceramics.

Genome-based approach to evaluate the metabolic potentials and exopolysaccharides production of Bacillus paralicheniformis CamBx3 isolated from a Chilean hot spring.

In the present study, a thermophilic strain designated CamBx3 was isolated from the Campanario hot spring, Chile. Based on 16S rRNA gene sequence, phylogenomic, and average nucleotide identity analysis the strain CamBx3 was identified as Bacillus paralicheniformis. Genome analysis of B. paralicheniformis CamBx3 revealed the presence of genes related to heat tolerance, exopolysaccharides (EPS), dissimilatory nitrate reduction, and assimilatory sulfate reduction. The pangenome analysis of strain CamBx3 with eight Bacillus spp. resulted in 26,562 gene clusters, 7,002 shell genes, and 19,484 cloud genes. The EPS produced by B. paralicheniformis CamBx3 was extracted, partially purified, and evaluated for its functional activities. B. paralicheniformis CamBx3 EPS with concentration 5 mg mL-1 showed an optimum 92 mM ferrous equivalent FRAP activity, while the same concentration showed a maximum 91% of Fe2+ chelating activity. B. paralicheniformis CamBx3 EPS (0.2 mg mL-1) demonstrated β-glucosidase inhibition. The EPS formed a viscoelastic gel at 45°C with a maximum instantaneous viscosity of 315 Pa.s at acidic pH 5. The present study suggests that B. paralicheniformis CamBx3 could be a valuable resource for biopolymers and bioactive molecules for industrial applications.

An energy perspective on the mechanism of crude oil electrorheological effect

Exposing a waxy crude oil to an electric field represents an emerging environmentally sound strategy for improving the cold flowability of oil. However, a substantial knowledge gap still exists regarding the quantitative relationship between the viscosity reduction and treatment parameters (field strength, treatment time, the volume of treated oil, etc.). This study endeavors to investigate the physical essence of the effect of these treatment parameters on the viscosity reduction and its duration. It was found when subjected to electric fields of varying strengths (0.5–5 kV/mm) for sufficient time, a same maximum viscosity reduction of approximately 40% can be achieved regardless of the applied field strength. Further research has elucidated that the factor determining the viscosity reduction is energy input, rather than the field strength as was reported previously, and the inputted energy may work in three stages: first, it works for initiating a decrease in viscosity. Subsequently, the continued energy input further reduces the oil viscosity and ultimately achieves a maximum reduction at that temperature. Then further inputted energy enhances the duration of the viscosity reduction. Fundamentally, the inputted energy density, i.e., the inputted energy per unit volume/mass of the oil, is the essential factor. These new findings facilitate further understanding of the negative electrorheological effect and its mechanism of crude oil and may help for the development of electric treaters for reducing crude oil viscosity.

Investigating the Age-Dependent behavior of MoS2-hBN nanohybrid additives on the rheological properties of diesel engine oil

This study utilizes Design of Experiment (DOE) to optimize the viscosity of MoS2-hBN nanolubricants, synthesized using a microwave synthesis platform that significantly reduces synthesis time and energy consumption compared to other methods. The investigation focuses on viscosity and aging characteristics, aiming to understand the relationship between nanolubricant viscosity and key factors: nanoparticle concentration, temperature, and shear rate. The study shows that the optimal concentration of MoS2-hBN nanoparticles is 0.05 wt%. At this concentration, when subjected to a shear rate of 200 (1/s) and a temperature of 100°C, the highest viscosity recorded is 12.87 mPa·s. In contrast, at 40°C and a shear rate of 50 (1/s), the lowest viscosity measured is 113.42 mPa·s. Experimental validation confirms the accuracy of the model predictions. The study also examines MoS2-hBN nanolubricant aging behavior under constant high-temperature conditions (100 °C for 120 h), providing insights into its thermal stability, tribological performance, oxidation resistance, and thermal conductivity properties. Compared to SAE20W40 base oil, the nanolubricant reduces friction and wear, forming a protective boundary film to mitigate surface damage. It exhibits enhanced oxidation stability, acting as a free radical scavenger, and improved thermal conductivity due to increased heat transfer efficiency facilitated by nanoparticles. These findings highlight the potential of MoS2-hBN nanolubricant for high-temperature applications, contributing to enhanced engine performance and durability.

Comparison of Rendement, Viscosity, and Degree of Acidity of Bone Gelatin of Bali Cattle Fed with Lamtoro at Different Extraction Temperatures

The increase in Bali cattle bone waste due to increased slaughter has become a severe societal problem because it will pollute the environment. If Bali cattle bone waste is appropriately processed, it will produce products with high nutritional and economic value, including gelatin. This research aimed to compare the yield, viscosity, and degree of acidity (pH) of bone gelatin from Bali cattle fed with lamtoro at different extraction temperatures. The gelatin from Bali cattle bone was produced under the influence of different extraction temperatures of 50; 60; and 70o C and each was repeated 4 times. The research method used was laboratory experimental. Data were analyzed using a Completely Randomized Design (CRD). The parameters observed were yield, pH, and viscosity. The results show that different extraction temperatures (50, 60, 70o C) had a significant effect (P < 0.05) on viscosity while a very significant effect (P < 0.01) on the degree of acidity (pH) and no significant effect (P > 0.05) to the yield. It can be concluded that a higher extraction temperature (70o C) will be accompanied by an increase in gelatin yield, but the extraction temperature of 60o C showed the maximum viscosity and acidity (pH) values

Assessment of the Baking Properties of Rye Flour Based on the Polysaccharide Content and Properties

This study aimed to determine the baking quality of rye flour in terms of the content and properties of its polysaccharides, i.e., starch and pentosans. The study materials were low- and high-extract rye flours produced in industrial mills from the rye grain of two growing seasons (2019 and 2020). The results of the starch content, falling number, amylograph properties, DSC test, content of pentosans, swelling curve test, and laboratory baking test were determined. It was found that the type of flour had a greater impact on the baking quality of rye flour than the year of its production. Research has shown that the most frequently used parameters, such as the falling number and the maximum viscosity of starch paste, are not good indicators for assessing the baking value of currently produced rye flours. From the parameters used for evaluating the properties of the starch–amylolytic complex, the initial and onset temperatures for starch gelatinization were the best indicators for evaluating the baking quality of rye flour. This study revealed a significant correlation between the pentosan content (total, water soluble, and insoluble), swelling curve parameters and quality parameters of rye bread, such as the specific bread volume, bread crumb moisture, and bread crumb hardness. Assessment of the baking value of rye flour based only on the evaluated properties of the starch–amylolytic complex is currently not sufficient to determine the baking quality of rye flour and predict the quality of rye bread. This study on the baking quality of rye flour should be extended to include the assessment of the dough properties related to the pentosan content and the enzymes that degrade these components. It was shown that the properties of rye dough related to the content of pentosan can be characterized based on the swelling curve test as a method that, together with the initial and onset starch gelatinization temperatures, allows better assessment of the baking quality of the commercial rye flour and its suitability for the good-quality rye bread production.

Improving the Thermo-Physical Properties of Plam Oil with Zeolite Nanoparticles

This research aimed to improve the thermo-physical properties of plam oil with NaA zeolite. Palm oil was selected for heating oil due to its high flash point and environmental friendliness compared to synthetic or mineral oil. The effect of NaA zeolite concentration suspended in palm oil was investigated in terms of the specific heat capacity (Cp), viscosity (μ), viscosity index (VI), thermal analysis (TGA) and density (ρ) of palm oil. The NaA zeolite was synthesized by crystallization technique, and X-ray diffraction analysis was performed to determine NaA zeolite crystallinity. The size of NaA zeolite was measured using a particle size analyzer. The average size of the synthesized NaA zeolite was 4767 nm. After grinding process for 180 min, the average size of zeolite decreased to 632 nm. An average 632 nm NaA zeolite particle size was added to palm oil at 0.25, 0.5, 0.75 and 1 wt%. The results showed that when the NaA zeolite concentration increased, the nanofluid’s viscosity at 40 °C and 100 °C was increased. The addition of 1 wt% NaA zeolite resulted in the nanofluid having a maximum viscosity of 41.31 and 8.47 cSt at 40 °C and 100 °C, respectively. The highest viscosity index was 195 cSt when added with 0.5 wt% NaA zeolite. The density of palm oil slightly increased with increasing NaA zeolite concentrations. The specific heat capacity of palm oil increased when NaA zeolite was added. The results showed that NaA zeolite allowed palm oil to store heat energy better than palm oil, enabling it to release and absorb more heat during heat transfer. Thermogravimetric analysis, palm oil initiated to degrade at 263 °C, while the addition NaA zeolite in palm oil indicated that palm oil initiated to degrade at 350 °C. The shift in the degradation curve demonstrated that the nanofluid could withstand high temperatures. Adding NaA zeolite to palm oil showed that palm oil could endure more heat and has a long service life.

Experimental and Simulation Studies of Imidazolium Chloride Ionic Liquids with Different Alkyl Chain Lengths for Viscosity Reductions in Heavy Crude Oil: The Effect on Asphaltene Dispersion.

Heavy crude oil poses challenges in terms of extraction and transportation due to its high viscosity. In the pursuit of effective methods to reduce viscosity in heavy crude oil, this study investigates the potential of imidazolium chloride ionic liquids with varying alkyl chain lengths as viscosity reducers. The experimental results demonstrate that the addition of 1-dodecyl-3-methylimidazole chloride ([C12-MIM]Cl) leads to a maximum viscosity reduction of 49.87%. Solubility parameters were calculated based on characterization of the average molecular structure of the asphaltenes. The viscosity reduction effect is enhanced when the solubility parameter of the ionic liquid closely matches that of the asphaltene. The initial asphaltene deposition point of heavy crude oil is increased from 63% to 68% with the addition of 150 mg/L [C12-MIM]Cl. Furthermore, the average particle size of asphaltene deposits decreases from 79.35 μm to 48.54 μm. The viscosity of heavy crude oil is influenced by the aggregation of asphaltenes. The ability of ionic liquids, especially those with longer alkyl chains, to disperse asphaltene molecules and reduce viscosity has been confirmed through molecular dynamics and quantum mechanical simulations.

Interfacial chemical mechanisms of brine salinity affecting the CO2 foam stability and its effect on the sequestration capacity of CO2 in deep saline aquifer

CO2 foam flooding is an important method to expand the sweep scope of CO2 and significantly improve the ability of sequestrate CO2 in saline aquifer. Salinity is an important factor affecting the CO2 foam stability. In this study, it was found that the stability of CO2 foam prepared by alkyl polyglycoside APG-0810 was effectively improved by increasing the salinity. Molecular dynamics studies showed that increasing salinity promoted the adsorption of APG-0810 molecules at the CO2-water interface and enhanced the degree of inter-entanglement between alkyl chain segments, which dramatically increasing the CO2-water interfacial activity and liquid film strength. The enrichment degree of metal ions around the APG-0810 hydrophilic group also enhanced with the increase of salinity, which improves the disjoining pressure of the bubble liquid film. The binding ability of the hydrophobic groups of APG-0810 on CO2 molecules was enhanced, which inhibited the diffusion process of CO2 molecules inside the bubble. Subsequently, the influence rules of salinity on the CO2 foam rheology in the core were studied, and finds that increasing salinity increase the transition foam quality and the corresponding maximum viscosity. The improvement of liquid film strength reduces the probability of bubble aggregation inside the core, allowing a sufficient number of small-sized bubbles to be trapped by the pores, strengthening the superposition of Jamin effect and expanding the CO2 sweep scope in saline aquifer. In addition, we found that the zero-shear viscosity and yield stress of CO2 foam are positively correlated with salinity, which means that CO2 foam has a higher blocking ability for preferential channel for high-salinity saline aquifer, and the bubble cluster trapped by the capillary force will have a higher starting-pressure, improving the safety of CO2 sequestration in saline aquifer.

Enhancing functional properties of rice starches through hydroxypropylation for development of reduced-fat white sauces

Present study investigated the preparation of commonly used white sauce with 50 % less added fat by using 10 % hydroypropylated Irri and Basmati rice starches in the formulation. The sauces incorporated with hydroxypropylated starches exhibited significantly lower gelatinization temperature and time, while the change in maximum viscosity was insignificant. Significantly improved stability at ambient, refrigeration, and freezing temperatures of reduced-fat white sauces was observed whereas change in the taste was insignificant. Basmati hydroxypropylated starch containing white sauce significantly mimicked the sensory properties of full-fat sauces. The hydroxypropyl groups were found to be 1.06 % and 1.16 % for Basmati and Irri hydroxypropylated starches, respectively. These values fall below the specified limit set by the Food and Drug Administration for the food grade hydroxypropylated starches. Significant improvements in peak viscosity, swelling power, solubility, percent transmittance, and water retention capacity were observed after the chemical modification of both rice varieties.

Investigating Friction and Antiwear Characteristics of Organic and Synthetic Oils Using h-BN Nanoparticle Additives: A Tribological Study

Friction and wear are two major elements that influence the life of a variety of equipment. According to estimates, as much as 30% of the energy used is dissipated as friction. However, this figure can be reduced by developing materials that enhance surfaces and apply lubricants appropriately. This study aims to analyze the impact of hexagonal boron nitride (h-BN) nanoparticles on the rheological and antiwear characteristics of four distinct oil varieties, namely Society of Automotive Engineers SAE-20W50, soybean, Polyalphaolefin PAO-4, and olive oils. The results of the tribological tests demonstrated a noteworthy enhancement in antiwear characteristics with the addition of 0.2 wt.% of h-BN nanolubricant. Among all nanolubricants, the maximum reduction in coefficient of friction (COF) and wear scar diameter was observed at 0.2 wt.% of h-BN in SAE-20W50 oil. Compared to the base oils, the wear scar diameter decreased by 17.93%, 8.80%, 22.65%, and 24.04% for (soybean oil and 0.2 wt.% of h-BN), (SAE20W50 and 0.2 wt.% of h-BN), (PAO4 and 0.2 wt.% of h-BN), and (olive oil and 0.2 wt.% of h-BN), respectively. Rheological test results indicated that with the addition of h-BN nanoparticles, the viscosity of the base oils significantly increased. The maximum viscosity was observed at 40 °C for SAE20W50 base nanolubricants, according to the rheological measurements.

Ion effects on co-existing pseudo-phases in aqueous surfactant solutions: cryo-TEM, rheometry, and quantification

HypothesisSpecific alkaline cation effects control the area per headgroup of alkylester sulphates, which modifies the spontaneous packing of the surfactants. The resulting effective packing minimizes the total bending energy frustration and results in a Boltzmann distribution of coexisting pseudo-phases. These pseudo-phases constitute of micelles and other structures of complex morphology: cylindrical sections, end-caps, branching points, and bilayers, all in dynamic equilibrium. According to our model, excess of end-caps or excess of branching points lead to low viscosity, whereas comparable amounts of both structures lead to viscosity maxima. Relative occurrence of branching points and end-caps is the molecular mechanism at the origin of the salt-sensitive viscosity peak in the “salt-curve” (viscosity against salt concentration at fixed surfactant concentration). Up to now, and as indicated in former papers, this has been a pure model without microscopic verification. ExperimentsIn this work, we introduce explicit counting of the number of coexisting pseudo-phases as observed by state-of-the-art cryogenic transmission electron microscopy (cryo-TEM). The model system used, i.e., sodium laurylethersulfate (SLES)/salt/water, is very common as part of cosmetic formulations. As added salts, we used Li+, Na+, K+, and Cs+ chlorides. In parallel to imaging, we measured the macroscopic viscosities of the different solutions. FindingsWith cryogenic transmission electron microscopy (cryo-TEM), we imaged a variety of morphologies (pseudo-phases) in the different aqueous surfactant/salt solutions: cylindrical micelles with end-caps, discs surrounded by “rims”, entangled thread-like micelles with branching points, networks with gliding branching points, and bilayers. The relative chemical potentials of these morphologies could be approximated simply by counting the relative proportion of their occurrence. This simple multi-scale approach avoids any ad-hoc “specificity” assumption of ions, and is based on the bending energy model in an extended version of the Benedek “ladder model”. It is capable of explaining and even quantifying the location of all viscosity peaks in the “salt-curves” for the different cations investigated, thus confirming the previously proposed model experimentally, and – thanks to cryo-TEM – for the first time on a microscopic scale. Moreover, this approach can also be applied when the added cations lead to newly observed pseudo-phases, such as discs and vesicles. To the best of our knowledge, this is the first time that cryo-TEM is used, together with a mesoscopic model, to describe a macroscopic property such as viscosity and specific ion effects on it, without any a priori assumption about these effects. So, in total, we could a) confirm the predictions of the previously developed model, b) use cryo-TEM imaging and viscosity measurements to predict and find unusual morphologies when varying the cations of the added salt, and c) count the pseudo-phases in cryo-TEM micrographs to quantitatively explain the different nanostructures.