Viscous Flow Properties Research Articles

Viscous flow and structural properties in water-ethanol-urea systems

The structural features of water-ethanol, water-urea and water-ethanol-urea systems were studied on the basis of experimental estimates of kinematic viscosity at different temperatures and concentra-tions. For this purpose, the concentration dependences of the Gibbs energy of activation of the viscous flow, the enthalpy of activation of the viscous flow and the entropy of activation of the viscous flow of the studied systems were analyzed. The results show that ethanol has a structuring and then de-structive effect on water up to a concentration of 0.15 molar, and urea has a destructive effect on the structure of water, starting from such small concentrations. The addition of urea to the ethanol-water system does not affect the inversion point.

Cyclic oxidation resistance and self-healing properties of HfB2-doped glass composite coatings at 900 °C

HfB2-doped glass coating exhibits superior cyclic antioxidative performance compared to pure glass coating. The HfB2 particles inhibit the precipitation of crystals with low thermal expansion coefficient, mitigating the risk of fish-scaling failure. In addition, the HfB2-doped glass composite coating, with high contents of amorphous phases, maintains its viscous flow properties even after multiple high temperature cyclic oxidations, which enables it to self-heal. Moreover, the oxidation product (B2O3) of HfB2 enhances network connectivity of the glass system, providing more unsaturated sites for the chemical bonding of the self-healing process.

Synthesis of 1‐Methyl‐4‐methoxyethyl‐1,2,4‐triazolium Dicyanamide and Its Plasticizing Behavior on HTPB/TDI Curing System**

AbstractIn this paper, a novel ionic liquid plasticizer, 1‐methyl‐4‐methoxyethyl‐1,2,4‐triazole dicyanamide ([MMET][DCA]), was synthesized and characterized. The effect of [MMET][DCA] on the viscous flow properties of HTPB was studied, and then the effect of [MMET][DCA] on the mechanical and thermal properties of the HTPB/TDI curing system was further explored. The results show that the hydrogen bond between [MMET][DCA] and HTPB has a significant effect on the viscosity of HTPB. In the HTPB/TDI curing system, when the di(2‐ethylhexyl)adipate (DEHA) was replaced by an equal amount of [MMET][DCA], the glass transition temperature did not change significantly; the tensile strength of the curing system increased from 0.436 MPa to 0.474 Mpa; the elongation at break increased from 506.2 % to 700.4 %, and the decomposition temperature at 5 % and 10 % mass loss increased by 32 °C and 70 °C, respectively.

Разработка математической модели акустического источника, сопровождающего распад кавитационной каверны на схлопывающиеся пузырьки

Object and purpose of research. This paper is intended to develop a mathematical model of cavitation void fragmentation into separate collapsing bubbles as an acoustic source for further implementation in Logos software package. The study was performed on propeller models in cavitating environment. Subject matter and methods. Volume and quantity of bubbles appearing after fragmentation of a cavitation void on propellers, as well as amplitude and frequency properties of a single bubble collapse are studied as per CFD methods. Viscous flow properties are found from finite-volume (FVM) solution to unsteady Reynolds equations (RANS) closed by a biparametric semi-empirical turbulence model. The coefficients in the mathematical model of acoustic source thus obtained were calibrated through validation that included noise measurements at KSRC Cavitation Tunnel. Main results. This work included numerical simulation of collapse dynamics for a single cavitation bubble at different initial conditions, with approximation of the pressure impact created by bubble collapse in the infinite fluid and near a solid wall. The study estimated volume and quantity of the bubbles created by the fragmentation of cavitation void on propellers (3 propellers of different shape operating at different advance ratios and cavitation numbers). The mathematical model representing above-mentioned process could be further implemented in Logos software as a finite-volume algorithm with k-ω SST turbulence model. The study also created a validation base for further testing and calibration of the mathematical model thus developed. Conclusion. The study was performed as part of project Mathematical simulation on exa- and zetaflops class supercomputers launched by National Centre for Physics and Mathematics (Russia). The analysis of obtained results has shown that the mathematical model suggested in this paper does have practical potential, but it needs additional empirical data for greater flexibility and more accurate estimates. Without this model, these practical tasks still could be handled but at a cost of considerable and, most importantly, unnecessary increase in required hardware resources.

Thermal Properties and Joinability Investigation of BaO–SrO–SiO2–B2O3 Glasses for Oxygen Transport Membrane Application

Three new BaO–SrO–SiO2–B2O3 (BS) glasses with different SrO contents (6–25 mol%) are developed for oxygen transport membrane (OTM) joining application. The content of strontium is investigated first in terms of its effect on the glass‐forming tendency, thermal expansion coefficient, crystallization, shrinkage behavior, and viscous flow properties. Differential scanning calorimetry (DSC) is carried out. Dilatometric tests are performed to obtain coefficients of thermal expansion (CTEs) of BS glasses. The crystallization behavior of the BS glasses is investigated by X‐ray powder diffraction (XRD). Sinking dilatometric measurements simulate the joining procedure and observe the shrinkage behavior of the BS glasses. The viscous flow behavior of the BS glasses is examined via hot stage microscopy. The glass with 15 mol% SrO (BS15) glass shows the best glass‐forming tendency, most matching CTE (11.9 × 10−6 K−1), densest microstructure, highest shrinkage rate (24%), and good viscous behavior at high joining temperatures compared with other BS glasses. BS15 glass is chosen for helium leak test and assembly test joining with Aluchrom and SrTi0.75Fe0.25O3−δ membrane (STF25). The sandwiched sample with two Aluchrom plates sealed by BS15 glass at 1075 °C for 5 min achieves good gas‐tightness with low helium leakage rate <10−9 mbar·l s−1.

Rheology for Modeling of Extrusion of Wood Plastic Composites

AbstractExtensive rheological studies on the wood plastic composites (WPC) of various wood flour content based on the polypropylene (PP) matrix are presented. Viscous flow properties as well as the slip and yield stress phenomena are discussed. Rheological models of Klein and Ostwald de Waele are used for flow modeling, Navier model is applied for slip description and Bingham model is used for yield stress. Process simulations are performed, using recently developed the global computer model of WPC extrusion, to predict the process parameters (flow rate, pressure, and temperature development, melting rate, etc.), and to study the influence of the WPC material characteristics on the process flow. Simulations are validated experimentally, and are discussed with respect to both rheological and modeling aspects. It is concluded that the location of the extrusion operating point which defines the thermo‐mechanical process conditions is fundamentally dependent on the rheological material characteristics, including yield stress and wall slipping.

Ageing Effects on a Softened Bitumen by the Addition of DSA (Dodecenyl Succinic Anhydride).

The softening of aged bitumen is necessary for a successful asphalt rejuvenation in road recycling operations. Thus, this study proposes a novel and successful approach by using Dodecenyl Succinic Anhydride (DSA), a reactive surfactant with a polar head capable of reacting with some polar compounds of bitumen. On this basis, this paper analyses the softening potential and ageing inhibition capability of the addition of 3 wt.% DSA before and after the application of standard laboratory ageing methods (rolling thin film oven, RTFOT and pressure aging vessel (PAV) tests). To that end, different modified bitumens were evaluated by analysing the linear viscoelastic behaviour, viscous flow properties, thin layer chromatography, Fourier transform infrared spectroscopy (FTIR), contact angle measurements and compactibility tests. The results obtained for DSA show its greater potential to soften a model bitumen, when compared to a diluent oil, through physico-chemical processes that bring about a lowering in the polarity along with the alteration of its colloidal stability. Even though ageing processes in bitumen negatively affect its softening capacity, the developed structures still retain the ability to partially compensate for the adverse hardening effects. Furthermore, DSA addition greatly enhances the binder’s wettability on a siliceous-type aggregate and favours asphalt compaction.

Effect of Anions on the Viscous Flow Properties for the Binary Mixtures of Three Kind of Choline - Based Ionic Liquids with Dmso

Effect of Anions on the Viscous Flow Properties for the Binary Mixtures of Three Kind of Choline - Based Ionic Liquids with Dmso

Mediating the slow dynamics of polyacrylates by small molecule-bridged hydrogen bonds.

This report studied the changes in the slow dynamics of polyacrylate by adding a hindered phenol (CA) capable of forming three intermolecular hydrogen bonds (inter-HBs) per molecule with the polymer chain. The CA molecule apparently diminishes the slow modes (with lower peak temperatures and peak heights) of the polyacrylate, although it has a higher glass transition temperature (Tg) than the acrylic matrix, and the rigid CA-bridged HB network significantly amplifies the α-relaxation near Tg (with higher peak temperatures and peak heights). Consequently, the mixtures exhibit a diminishing slow mode that gradually merges with the prominent α-peak with increasing CA loadings. The anomalous dynamics concerning the opposite behaviors of the slow mode and α-relaxation was further rationalized in terms of dissociation of inter-HBs when the temperature is higher than Tg, together with the small molecule-alleviated macromolecular connectivity. This work provides essential insights into the slow dynamics of such HB-driven hybrids, and paves the way for tailoring the viscous flow properties of the hybrid material from a molecular level perspective.

Rheological properties of liquid ebonite compositions filled with shungite

The effect of shungite on the structural and viscous-flow properties of compositions based on oligobutadiene was studied. The strength of coagulation structures of ebonite compositions filled with shungite was determined. The critical filling concentration was established and it is 40 wt.% of shungite per 100 wt.% of oligobutadiene. It was shown that increasing the temperature from 200C to 800C leads to a significant reduction in the shear stress required to destroy the structure of the composition. Temperature and shear rate independently affect the structured composition. Thus, it was shown that shungite powder can be used as a filler in liquid ebonite compositions based on oligobutadiene.

Unusual Growth and Hydration Characteristics of Oil Solubilized Micelles in Aqueous Pluronic Systems.

Lipophile induced modulations of self-assembly characteristics in aqueous Pluronic systems merit attention because of wide-ranging uses of Pluronics as solubilizing agents of lipophilic substances. In this paper, we report unusual evolutions of structural and hydration properties in lavender essential oil (LO) solubilized Pluronic P85 aqueous micellar systems as a function of micellar volume fraction and temperature. Our DLS, SANS, and viscometry studies show that the spherical-to-wormlike micellar structural transition observed in 1% P85 solutions upon solubilization of LO quite unexpectedly gets suppressed with increased P85 concentration to ≥5%. Detailed SANS studies reveal that the core sizes of the oil solubilized micelles cannot attain the threshold value required for the onset of structural transition at higher copolymer concentrations due to their progressive shrinking with an increase in P85 concentration. Oil solubilized P85 solutions show two cloud points and very interestingly exhibit micellar growth upon cooling to their lower cloud points. Steady state fluorescence studies explain this based on increasing dehydration of micellar corona with a decrease in temperature, very much opposite to what is observed in pure aqueous Pluronic systems. The results give new insight into viscous flow properties and low temperature storage possibilities of oil solubilized aqueous Pluronic systems.

Thickening Castor Oil with a Lignin-Enriched Fraction from Sugarcane Bagasse Waste via Epoxidation: A Rheological and Hydrodynamic Approach

Thickening vegetable oils to different extents is of great interest in the design and development of new bio-based lubricant formulations, as achieving a wide range of rheological properties is crucial to the successful replacement of petroleum-based traditional counterparts. With this aim, the influence of epoxidation degree, modified by altering the reaction conditions, on the viscous flow properties of epoxidized castor oil was investigated together with the incorporation of a lignin-enriched fraction from sugarcane bagasse waste to more extensively modify the rheological properties, thereby valorizing this waste fraction. Oil thickening was achieved by promoting the cross-linking between the epoxidized oil and the lignin-enriched fraction that enables the compatibilization of both components. Castor oil epoxidation was assessed by means of standard volumetric titration methods and infrared spectroscopy. In addition, a fully rheological characterization of both epoxidized and lignin-thickened castor oils was carried out. A hydrodynamic approach was also followed, aiming to provide an estimation of the Mark–Houwink–Sakurada parameters and relate the intrinsic viscosity with the average molecular weight of the resulting epoxidized castor oil/lignocellulose macromolecular compounds. The chemical interaction between castor oil and the lignocellulosic material increased as the extent of epoxidation was increased, yielding a variety of rheological responses from Newtonian liquids of increasing viscosities (from around 1 to 500 Pa·s) to viscoelastic liquids.

Impact of alkaline earth oxides on dielectric properties of photoetchable glasses as interposers for integrated circuits packaging

Photoetchable glasses (PEGs) are widely used in integrated circuits as interposers. However, the high dielectric losses intrinsic of PEGs limit their applications in three-dimensional system packaging. Doping with alkaline earth oxides changes the network structure of the PEG, restricting migration of cations, and reducing structural and conduction losses in the glass. After UV exposure and annealing, the dielectric constant and dielectric loss decreases to 4.1 and 0.0025, respectively. Doping with alkaline earth oxides does not significantly decrease the glass transition temperature or viscous flow properties and thus the preferred use of PEGs as interposers. The breakdown filed strength of PEGs can reach 112 kV/cm, which increases their utility and range of applications. Analyses by X-ray diffraction and Raman spectroscopy reveal that alkaline earth oxides form polyhedra resulting in more complex glass networks. A small number of alkaline earth oxides can reduce their dielectric loss. Overall, the introduction of alkaline earth oxides improves their dielectric properties and breakdown filed strength, making PEGs more suitable as VLSI interposers.

Rheological Basics for Modeling of Extrusion Process of Wood Polymer Composites.

Wood polymer composites are materials with pseudoplastic and viscoelastic properties. They have yield stress and exhibit slip during flow. Studies on extrusion and rheology, as well as on process modeling of these highly filled materials are limited. Extensive rheological and extrusion modeling studies on the wood polymer composite based on the polypropylene matrix were performed. Viscous and slip flow properties were determined (with Rabinowitsch, Bagley, and Mooney corrections) at broad (extrusion) range of shear rate and temperature, using a high-pressure capillary rheometer. Rheological models of Klein and power-law were used for flow modeling, and Navier model was applied for slip modeling. A novel global computer model of WPC extrusion with slip effects has been developed, and process simulations were performed to compute the extrusion parameters (throughput, power consumption, pressure, temperature, etc.), and to study the effect of the material rheological characteristics on the process flow. Simulations were validated experimentally, and were discussed with respect to both rheological and process modeling aspects. It was concluded that the location of the operating point of extrusion process, which defines the thermo-mechanical process conditions, is fundamentally dependent on the rheological materials characteristics, including slip effects.

Formulation and processing of novel non-aqueous polyethylene glycol-in-silicone oil (o/o) phase change emulsions

Oil-in-oil phase change emulsions, composed of phase change materials (PCMs) dispersed in a continuous oily medium, have never been reported in the literature. The current study involves the formulation, stabilisation and characterisation of novel anhydrous emulsions of polyethylene glycol (PEG4000) as PCM in silicone oil. Emulsions with different dispersed phase concentrations were evaluated by analysing the viscous flow properties, optical microscopy and modulated differential scanning calorimetry. The results evidence that the emulsions can be pre-stabilised at 80 °C, under high shear conditions, by selecting an adequate silicone surfactant but undergo a severe destabilisation after a cooling and heating cycle. Nevertheless, a post-processing protocol (low shear agitation at 80 °C for 24 h) leads to thermal cycle resistant and storage stable non-aqueous dispersions. This process gives rise to a reduction of the shear-thinning character of the emulsion, shifts the melting and crystallization temperature of the PEG4000 to lower values and reduce its crystallinity. This is attributed to partial compatibility of the crystalline fraction of PEG4000 with other compounds of the emulsion.

Confinement and hydrophilicity effects on geologically relevant fluids in silica nanopores

The confinement effects in brine, water, and oil are explored in hydrophilic silica nanopores. As the nanopores approach a 1.0-nm radius, the confinement effects are very pronounced, changing the interfacial tension behavior, as well as viscous flow properties. Also, a water-brine layer always stays adsorbed in the silica surface, mediating its interaction with the oil, even hindering the oil infiltration in a case.

Viscous flow properties and hydrodynamic diameter of phenothiazine-based redox-active molecules in different supporting salt environments

We report viscous flow properties of a redox-active organic molecule, N-(2-(2-methoxyethoxy)ethyl)phenothiazine (MEEPT), a candidate for non-aqueous redox flow batteries, and two of its radical cation salts. A microfluidic viscometer enabled the use of small sample volumes in determining viscosity as a function of shear rate and concentration in the non-aqueous solvent, acetonitrile, both with and without supporting salts. All solutions tested show Newtonian behavior over shear rates of up to 30 000 s−1, which was rationalized by scaling arguments for the diffusion-based relaxation time of a single MEEPT molecule without aggregation. Neat MEEPT is flowable but with a large viscosity (412 mPa⋅s at room temperature), which is ∼1000 times larger than that of acetonitrile. MEEPT solutions in acetonitrile have low viscosities; at concentrations up to 0.5 M, the viscosity increases by less than a factor of two. From concentration-dependent viscosity measurements, molecular information was inferred from intrinsic viscosity (hydrodynamic diameter) and the Huggins coefficient (interactions). Model fit credibility was assessed using the Bayesian Information Criterion. It is found that the MEEPT and its charged cations are “flowable” and do not flocculate at concentrations up to 0.5 M. MEEPT has a hydrodynamic diameter of around 8.5 Å, which is almost insensitive to supporting salt and state of charge. This size is comparable to molecular dimensions of single molecules obtained from optimized structures using density functional theory calculations. The results suggest that MEEPT is a promising candidate for redox flow batteries in terms of its viscous flow properties.

Analysis of viscous flow properties of styrene–butadiene–styrene-modified asphalt

Three styrene–butadiene–styrene (SBS, a block copolymer) modified asphalt samples with 5% SBS by weight were prepared using three types of common base asphalt to analyze the viscosity and viscous flow properties of SBS-modified asphalts. Rotational viscosity tests were conducted under various temperature and shear rate conditions, and the effects of the test conditions on the viscosity of the base and modified asphalt samples were analyzed. The viscous activation energy (Eη) and non-Newtonian index (n) were calculated using the Arrhenius equation and the power law equation, respectively. The temperature sensitivity and fluid properties were considered relative to Eη and n, respectively, based on which master curves were established to predict viscosity. The results indicate that various types of base asphalt show inconsistent temperature sensitivity and fluid properties after SBS modification. SBS can improve the temperature stability of B# asphalt; however, it has adverse effects on the A# and C# asphalts. Compared with the base asphalt, the n values of the SBS-modified asphalts are all lower than 1, indicating that the asphalt is converted from a Newtonian to non-Newtonian fluid and the non-Newtonian properties of various types of asphalt vary with temperature. Master curves can describe the responses of the SBS-modified asphalt viscosity to test the conditions that adequately predict the viscosity.

The Effect of Zinc Stearate Modification on Aging Characteristics of Asphalt Binder

Different types of modifiers have been investigated to improve aging characteristics of asphalt binders. In this research, the effect of zinc stearate modification has been studied on aging resistance of asphalt binder. For this purpose, viscous flow properties and other rheological characteristics of neat and modified asphalt binders have been evaluated by using conventional experimental tests and superpave protocol test. In order to evaluate rheological behavior of asphalt binder in presence of zinc stearate, a neat asphalt binder sample with three modified samples containing 0.5, 1 and 2 wt% of zinc stearate were aged by means of the Rolling Thin Film Oven Test (RTFOT). The Brookfield rotational viscosity (RV) was implemented at six different temperatures from 100 to 200 degree of centigrade. Furthermore, the dynamic shear rheometer (DSR) was used for evaluating complex modulus (G*) and phase angle (δ) of all neat and modified samples at 10, 20, 30, 40, 50 and 60°C in frequency sweep mode. To evaluate effect of adding zinc stearate by using viscosity results, proportion of asphalt binder’s viscosity after aging to its viscosity before aging was defined as viscosity aging index (VAI). Results showed that adding zinc stearate to neat asphalt binder reduces the viscosity aging index. Results of frequency sweep test indicated that zinc stearate causes the values of complex shear modulus in aging asphalt binder approach to neat state which means the effect of zinc stearate modification is positive for improving aging resistance of asphalt binder.

Rheological and mucoadhesive properties of polysaccharide from Bletilla striata with potential use in pharmaceutics as bio-adhesive excipient

This study described the rheological and mucoadhesive properties of one natural water-soluble polysaccharide from Bletilla striata (BSP). The rheological characteristics of BSP in aqueous solutions and BSP mixed with other polymers were investigated under various conditions, including concentration, temperature, pH, and salt addition. Viscometric studies and ex vivo mucoadhesion tests were also conducted to examine the mucoadhesive properties of BSP. Results indicated that BSP behaved as a shear-thinning fluid at various concentrations, and its viscosity decreased at high temperatures. The viscous flow properties of the BSP mixtures changed at high pH (>5.0). Conversely, the viscosity of the BSP solutions was slightly affected by electrolytes. The viscosities of the BSP mixtures with four other commonly used polymers (sodium alginate, sodium carboxymethyl cellulose, hypromellose, and chitosan) were enhanced. The synergistic viscosity of BSP/mucin mixtures increased as BSP concentrations increased, and the maximum value was observed in the SIF medium without enzymes. The adhesive abilities of 5.0% and 10.0% BSP were almost equivalent to that of 0.5% sodium alginate, suggesting that BSP exhibited a certain mucoadhesive property, although it was weaker than that of the other commonly used mucoadhesive materials. BSP showed potential for pharmaceutical excipient applications in bioadhesive drug delivery systems.