Dynamic Viscosity Measurements Research Articles

Surface properties of ion-inducted whey protein gels deposited on cold plasma treated support

So far no studies have been undertaken on the influence of plasma processing of different solid surfaces on the properties of subsequently formed protein coat. Calcium chloride, magnesium chloride or iron (II) chloride inducing whey protein isolate gels were obtained on glass support previously treated with the plasma at the electric voltage 160 V per 1 min. Dynamic oscillatory and ultrasound viscosity measurements, scanning electron microscopy imaging, surface roughness and contact angles measurements have been performed. Apparent surface free energy was determined using the two approaches: van Oss, Good and Chaudchury (LWAB) and contact angle hysteresis (CAH). Gels surface roughness increased with the increasing of ions concentration. Both approaches used for determination of apparent surface free energy give comparable results. When the air plasma was applied for the support activation, polar groups deposited on the surface had a greater effect on the surface wettability than roughness. Plasma treatment of glass support caused the increase of hydrophobic properties of deposited layers. Wettability properties were affected by the electron donor parameter of energy whose value increased for the samples obtained on the plasma activated supports especially the air treated ones. Plasma treatment of glass plates might have an effect on food processing, production efficiency, microbiological aspects and cleaning process of the gels deposited on their surfaces.

Method and device for measurement of dynamic viscosity

The paper proposes a methodology and ensuing test rig for finding the viscosity of a liquid lubricant. The principle consists in obtaining a contact between two spherical surfaces, one concave and the other one convex. One of the surfaces is kept immobile and to the other, a rotation motion is imposed around the common normal in the contact point and then the law of motion for the mobile lens is found. The law of motion allows for estimation of friction torque, dependent on viscosity at its turn. Applying the method for mineral oils, values comparable to the ones presented by the producer were obtained.

Volumetric and viscometric properties of binary liquid mixtures as potential solvents for flue gas desulfurization processes

Desulphurization processes (FGD) of flue gases from the thermal power and industrial plants, based on organic liquid solvents with mechanism of physical absorption (tetraethylene glycol dimethyl ether) or combination of physical and chemical absorption (N-methyl-2-pyrrolidone), recently gained its significance. The research results presented in this paper include density and dynamic viscosity measurements of following binary systems at atmospheric pressure: polyethylene glycol 200+tetraethylene glycol dimethyl ether, polyethylene glycol 400+tetraethylene glycol dimethyl ether, in temperature range from 288.15 to 333.15K, and binary systems polyethylene glycol 200+N-methyl-2-pyrrolidone and polyethylene glycol 400+N-methyl-2-pyrrolidone, in temperature range from 288.15 to 323.15K. In order to analyze and comment intermolecular interactions, calculated values of excess molar volumes and viscosity deviations were used. Strong, physical interactions of dipole-dipole type or formation of intermolecular hydrogen bonds lead and contribute to negative VE values that occur in these systems. Calculated values of excess and deviation properties were interpolated using the Redlich-Kister polynomial equation. Viscosity modeling has been performed, using predictive, group contribution models (UNIFAC – VISCO and ASOG – VISCO) as well as correlative models (McAlister, Eyring – UNIQUAC and Eyring – NRTL). For simultaneous modeling of excess molar volumes and viscosities, model based on the equation of state was used. For investigated systems, correlative McAllister models gave the best results and can be used for viscosity calculations.

Вязкость магнитных жидкостей при различных концентрациях коллоидных частиц и температурах

In the paper we present experimental results concerning measurements of dynamic viscosity of magnetic colloidal fluids. Magnetic colloidal fluids consist of their carrier fluids and solid magnetite particles with 9-10 nm in size. In the experiment we use two types of magnetic fluids – a kerosene-based magnetic fluid (MF k ) and an undecane-based magnetic fluid (MF u ). They differ by a manufacturer and date of manufacture. Viscosity measurements were carried out by a capillary viscometer equipped with the sensors specially designed for this experiment. Sensors were made on the basis of copper-constantan thermocouples combined with a microvoltmeter and a clock. They allowed measuring the time needed for a control volume of magnetic fluid flows through a capillary of the viscometer. In the experiment we obtained an array of data on viscosity of the fluids MF k and MF u with magnetite particle volume fractions of 0, 6, 10, 13, 16 % at temperatures of 20, 30, 40, 50 °C. Plots of dynamic viscosity versus temperature were built. Viscosities of the magnetic fluids MF k and MF u were compared. It was found that a ratio of viscosity coefficients for these fluids does not depend on temperature in the temperature range considered. Viscosity coefficients of the fluids MF k and MF u also increase in a similar way as particle volume fractions goes up to 10%. If a particle volume fraction is more than 10%, viscosity of the fluid MF k significantly exceeds viscosity of the fluid MF u .

Comparison of selected vegetable oils rheologic properties

The article is focused on measuring and comparison of rheologic parameters of selected vegetable oils. Determined were these properties: density, dynamic, kinematic viscosity and fluidity. Measurements were performed in approximate temperature range (5 - 32) °C on two samples of vegetable oils: sunflower oil and olive oil. Density of vegetable oils was determined by oscillation method using digital densimeter Anton Paar DMA 4500 M at different temperatures. For dynamic viscosity measurement was used rotational viscometer Anton Paar DV-3P, which principle is based on dependency of sample resistance against the probe rotation. Other rheologic parameters as kinematic viscosity and fluidity were determined according to the definitions. Results of measurements are shown as graphical dependencies of rheologic parameters to the temperature. Temperature dependencies of vegetable oils dynamic and kinematic viscosity had decreasing exponential shape which is in accordance with Arrhenius equation and temperature dependencies of fluidity had an increasing exponential shape for both samples. Dependencies of samples density on temperature were characterized by decreasing linear function in measured temperature range. Similar results were obtained by other authors. From measured values can be seen that dynamic viscosity of olive oil is higher than viscosity of sunflower oil. This proportion is caused by different composition of oils.

Nano-reinforced polymeric healing agents for vascular self-repairing composites

In this study, the nano-reinforcement of an epoxy healing agent for vascular self-repairing fiber reinforced composites, is explored for the first time. Multi Wall Carbon Nanotubes (MWCNTs) have been selected, as the nanoscaled reinforcing phase of a low-viscosity epoxy healing agent, in three different weight contents. The rheological behavior of the nanomodified epoxies was evaluated via apparent dynamic viscosity measurements and adjusted accordingly. The resulted nanocomposites were infused via a vascular network, to Double Cantilever Beam (DCB) fractured Glass Fiber Reinforced Composites (GFRPs) specimens in order to assess the effect of the MWCNTs on the healing efficiency (η), in terms of maximum bearing load and interlaminar fracture toughness (GIc) recovery. The employment of the nanoenhanced healing agent increased the calculated healing efficiency (nGIc) up to circa 190%, through the introduction of additional energy consumption mechanisms that were confirmed via a comparative Scanning Electron Microscopy (SEM) study.

Multispectroscopic studies on the interaction of a copper(ii) complex of ibuprofen drug with calf thymus DNA

ABSTRACTThe interaction of copper(II)–ibuprofenato complex with calf thymus DNA (ct-DNA) has been explored following, UV-visible spectrophotometry, fluorescence measurement, dynamic viscosity measurements, and circular dichroism spectroscopy. In spectrophotometric studies of ct-DNA it was found that [Cu(ibp)2]2 can form a complex with double-helical DNA. The association constant of [Cu(ibp)2]2 with DNA from UV-Vis study was found to be 6.19 × 104 L mol−1. The values of Kf from fluorescence measurement clearly underscore the high affinity of [Cu(ibp)2]2 to DNA. The experimental results showed that the conformational changes in DNA helix induced by [Cu(ibp)2]2 are the reason for the fluorescence quenching of the DNA-Hoechst system. In addition, the fluorescence emission spectra of intercalated methylene blue (MB) with increasing concentrations of [Cu(ibp)2]2 represented a significant increase of MB intensity as to release MB from MB-DNA system. The results of circular dichroism (CD) suggested that copper(II)–ibuprofenato complex can change the conformation of DNA. In addition, the results of viscosity measurements suggest that copper(II)–ibuprofenato complex may bind with non-classical intercalative mode. From spectroscopic and hydrodynamic studies, it has been found that [Cu(ibp)2]2 interacts with DNA by partial intercalation mode which contains intercalation and groove properties.

A Lytic Polysaccharide Monooxygenase with Broad Xyloglucan Specificity from the Brown-Rot Fungus Gloeophyllum trabeum and Its Action on Cellulose-Xyloglucan Complexes

ABSTRACTFungi secrete a set of glycoside hydrolases and lytic polysaccharide monooxygenases (LPMOs) to degrade plant polysaccharides. Brown-rot fungi, such as Gloeophyllum trabeum, tend to have few LPMOs, and information on these enzymes is scarce. The genome of G. trabeum encodes four auxiliary activity 9 (AA9) LPMOs (GtLPMO9s), whose coding sequences were amplified from cDNA. Due to alternative splicing, two variants of GtLPMO9A seem to be produced, a single-domain variant, GtLPMO9A-1, and a longer variant, GtLPMO9A-2, which contains a C-terminal domain comprising approximately 55 residues without a predicted function. We have overexpressed the phylogenetically distinct GtLPMO9A-2 in Pichia pastoris and investigated its properties. Standard analyses using high-performance anion-exchange chromatography–pulsed amperometric detection (HPAEC-PAD) and mass spectrometry (MS) showed that GtLPMO9A-2 is active on cellulose, carboxymethyl cellulose, and xyloglucan. Importantly, compared to other known xyloglucan-active LPMOs, GtLPMO9A-2 has broad specificity, cleaving at any position along the β-glucan backbone of xyloglucan, regardless of substitutions. Using dynamic viscosity measurements to compare the hemicellulolytic action of GtLPMO9A-2 to that of a well-characterized hemicellulolytic LPMO, NcLPMO9C from Neurospora crassa revealed that GtLPMO9A-2 is more efficient in depolymerizing xyloglucan. These measurements also revealed minor activity on glucomannan that could not be detected by the analysis of soluble products by HPAEC-PAD and MS and that was lower than the activity of NcLPMO9C. Experiments with copolymeric substrates showed an inhibitory effect of hemicellulose coating on cellulolytic LPMO activity and did not reveal additional activities of GtLPMO9A-2. These results provide insight into the LPMO potential of G. trabeum and provide a novel sensitive method, a measurement of dynamic viscosity, for monitoring LPMO activity.IMPORTANCE Currently, there are only a few methods available to analyze end products of lytic polysaccharide monooxygenase (LPMO) activity, the most common ones being liquid chromatography and mass spectrometry. Here, we present an alternative and sensitive method based on measurement of dynamic viscosity for real-time continuous monitoring of LPMO activity in the presence of water-soluble hemicelluloses, such as xyloglucan. We have used both these novel and existing analytical methods to characterize a xyloglucan-active LPMO from a brown-rot fungus. This enzyme, GtLPMO9A-2, differs from previously characterized LPMOs in having broad substrate specificity, enabling almost random cleavage of the xyloglucan backbone. GtLPMO9A-2 acts preferentially on free xyloglucan, suggesting a preference for xyloglucan chains that tether cellulose fibers together. The xyloglucan-degrading potential of GtLPMO9A-2 suggests a role in decreasing wood strength at the initial stage of brown rot through degradation of the primary cell wall.

Application of eco-friendly nanofluids during grinding of Inconel 718 through small quantity lubrication

The present work explores the application of nanofluids (NFs) in small quantity lubrication (SQL) mode by suspending eco-friendly Silver and Zinc oxide nanoparticles in deionized water. These nanoparticles have already been established as eco-friendly by several researchers. Hence these NFs may be termed as environmentally sustainable, and the present work is the first attempt to use such NFs in environment-friendly grinding of Inconel 718 (IN718) superalloy. The NFs have been supplied into the grinding zone using an in-house developed SQL setup. The results of the grinding process using NFs have been compared with the outcomes of grinding experiments under dry, wet and SQL with soluble oil. Ground surface integrity, wheel topography, and chip morphology have been investigated with the help of Scanning electron microscopy, Energy-dispersive X-ray spectroscopy, Atomic force microscopy and Stereo Zoom microscopy micrographs. The NFs have been characterized through measurements of zeta potential, hydrodynamic diameter, thermal conductivity, dynamic viscosity, and contact angles in relation to IN718 surface. From the present study, it can be concluded that application of NFs resulted in minimization of grinding forces, coefficient of friction, and improvement in the ground surface integrity. Zinc oxide based NFs have shown better grinding responses mainly because of improved lubrication behavior. It is primarily due to better spreadability that has induced stable lubricious film at the contacting surfaces even at a higher temperature. The findings of this work can be regarded as a first step towards the green and sustainable grinding of high strength superalloys.

Measurement and Correlation of Densities and Dynamic Viscosities of Perfluoropolyether Oils

The densities and dynamic viscosities of five different polydisperse perfluoropolyethers (PFPE) were measured at atmospheric pressure over the combined temperature range 263.15–373.15 K. For one PFPE being considered as a high-temperature high-pressure viscosity standard reference material, measurements were made on two separate samples to examine the lot-to-lot variability in density and viscosity; significant variability was observed only for the viscosity data. Experimental data were correlated as a function of temperature. A simple quadratic equation was used for density, while three equations (DIPPR, VFT, and Waterman) were applied to the viscosity data. The DIPPR equation represented the viscosity data with deviations approximately an order of magnitude lower than the other two equations.

Synthesis, spectroscopic studies, aggregation and surface behavior of hexamethylene-1,6-bis(N,N-dimethyl-N-dodecylammonium bromide)

Gemini surfactant, hexamethylene-1,6-bis(N,N-dimethyl-N-dodecylammonium bromide) (12-6-12), was synthesized without solvent, in a short time and with a very good yield. The chemical structure and purity of synthesized dimeric quaternary ammonium salt were confirmed by FT-IR and NMR spectroscopies. The interfacial properties (area occupied by one molecule, adsorption and surface excess concentration of 12-6-12 at the water-air interface), and the aggregation behavior were examined. The critical micelle concentration (cmc) was determined by the surface tension, density, dynamic viscosity and specific conductivity measurements. Standard Gibbs free energy of micellization and apparent and partial molar volumes of surfactant we have also studied. The surface and biological activity against fungi (Aspergillus niger, Penicillium chrysogenum, Candida albicans) show that hexamethylene-1,6-bis(N,N-dimethyl-N-dodecylammonium bromide) has much higher activity than its monomeric analog, i.e. dodecyl trimethyl ammonium bromide. Simple, fast end efficient synthesis without solvent is in good agreement with rules of green chemistry. Unique properties and aggregation behavior of this cationic gemini surfactant, which were examined in details and described in this work, have proved that this compound can be used in many various applications, among the others in smart materials.

Influence of Temperature and Storing Time on Selected Red Wine Physical Properties

Presented article is focused on red wine rheological and thermal properties. Effects of temperature and short term storage on density, rheological parameters and thermal parameters were investigated. First measurement was done at the beginning of storage and then the same sample was measured again after one week of storing. Density was measured by densimeter Mettler Toledo DM 40 at different temperatures. For dynamic viscosity measurement was used rotational viscometer Anton Paar DV-3P. The kinematic viscosity and fluidity were determined according to the definitions. Thermal parameters were measured by instrument Isomet 2104. Temperature dependencies of wine dynamic and kinematic viscosity had decreasing exponential shape and temperature dependencies of fluidity had an increasing exponential shape. Temperature dependencies of red wine thermal conductivity and diffusivity had increasing linear character. Decreasing polynomial functions were obtained for temperature dependencies of red wine density. The values of dynamic and kinematic viscosity, thermal conductivity and diffusivity, and density of red wine were a little bit higher after short term storing, which can be expressed by changed amount of water caused by evaporation. Due to the same reasons were values of fluidity little bit lower after storage.

Dynamic Viscosity and Activation Energy of Wort During Fermentation and Storing

This paper presents the results of wort dynamic viscosity and activation energy during fermentation. The effect of temperature and storing time on both parameters was investigated. Measurements were performed on two wort samples. The first sample was taken at the beginning of fermentation, and the second sample after three hours of fermentation. Both samples were also measured after three weeks of storing. Dynamic viscosity measurements were performed with a digital rotational viscometer Anton Paar DV-3P, the principle of which is based on the dependency of sample resistance to probe rotation. Results of measurements are shown as graphical dependencies of both analysed parameters on temperature. The temperature dependence of dynamic viscosity can be characterised by a decreasing exponential function, while in case of activation energy linear increasing characters were obtained. Longer fermentation and storing period caused a decrease in both analysed parameters, due to the structural changes in wort samples during fermentation and storing.

Fabrication and characterization of isolated lignin as adhesive for three‐ply plywood

In order to reduce the emission of formaldehyde of plywood and improve the utilization of lignin, isolated lignin was successfully prepared from wood chips with polyethylene glycol (PEG) 400 at the various weight ratios. The characterization was determined with thermogravimetry, Fourier transform infrared spectroscopy, 13C‐nuclear magnetic resonance analysis, and dynamic viscosity measurement. The results showed that more PEG moiety were grafted at alpha carbon position of lignin structure on increasing the weight ratio, resulting in the poorer thermostability and more formation of hydrogen bonding. Isolated lignin prepared with weight ratio of 1:4 exhibited the best dynamic viscosity property among all, and the lignin‐based three‐ply plywood which meets the shear strength requirement for type II plywood according to GB/T17657‐2013 were fabricated. Accordingly, isolated lignin with PEG‐400 could be considered as a promising adhesive for preparation of formaldehyde‐free plywood. POLYM. COMPOS., 39:484–490, 2018. © 2016 Society of Plastics Engineers

Molecular consideration on the lyotropic liquid crystalline behavior of poly(2-cyano-p-phenylene terephthalamide) solutions in N-methyl-2-pyrrolidone/calcium chloride

The lyotropic liquid crystalline behavior of poly(2-cyano-p-phenylene terephthalamide) (CY-PPTA) solution in the mixture of N-methyl-2-pyrrolidone and calcium chloride was investigated in terms of concentration and temperature. The intrinsic viscosity was decreased with increasing temperature, indicating the contraction of CY-PPTA chain at higher temperature. In dynamic viscosity measurement, the critical concentration (C*) where phase transition to the liquid crystalline phase takes place was decreased with increasing temperature. Above the C*, the dynamic viscosity was decreased and Bingham behavior got more noticeable with increasing concentration due to the development of the liquid crystalline structures. However, Bingham behavior was more notable at higher temperature at a given concentration. The viscosity curves showed the three distinct flow regions suggested by Asada and Onogi and negative first normal stress difference was observed in the range of intermediate shear rates. Open image in new window

Measurement of temperature-dependent viscosity and thermal conductivity of alumina and titania thermal oil nanofluids

Abstract In this study the results of simultaneous measurements of dynamic viscosity, thermal conductivity, electrical conductivity and pH of two nanofluids, i.e., thermal oil/Al2O3 and thermal oil/TiO2 are presented. Thermal oil is selected as a base liquid because of possible application in ORC systems as an intermediate heating agent. Nanoparticles were tested at the concentration of 0.1%, 1%, and 5% by weight within temperature range from 20 °C to 60 °C. Measurement devices were carefully calibrated by comparison obtained results for pure base liquid (thermal oil) with manufacturer’s data. The results obtained for tested nanofluids were compared with predictions made by use of existing models for liquid/solid particles mixtures.

Isobaric heat capacity at high pressure, density, and viscosity of (diphenyl ether + biphenyl) mixtures

In order to choose an adequate heat transfer fluid (HTF) for particular applications, it is necessary to know accurately the thermophysical properties, such as isobaric heat capacity, density, or viscosity. In this work, we have performed density and dynamic viscosity measurements of pure diphenyl ether and three different binary mixtures of diphenyl ether and biphenyl, including the eutectic composition, over a broad temperature range, i.e., from (288.15 to 373.15)K. A rotational Anton Paar Stabinger SVM 3000 device was used to obtain these experimental values. Moreover, isobaric heat capacities have been measured for these samples in the liquid phase at temperatures from (293.15 to 353.15)K and pressures up to 25MPa using a high-pressure flow calorimeter. From these measurements we have analysed how they depend on temperature and/or pressure. We have also determined the Prandtl, reference Grashof, and reference Rayleigh numbers. In addition, several equations were used to describe the temperature behaviour of viscosity and density, as well as the temperature and pressure dependences of the experimental isobaric heat capacities.

Viscosity measurements of hydrocarbon fuel at temperatures from (303.2 to 513.2) K and pressures up to 5.1 MPa using a two-capillary viscometer

A two-capillary method based on the Hagen–Poiseuille theory was proposed for on-line measurements of dynamic viscosity of hydrocarbons at high temperatures and high pressures. A two-capillary viscometer was designed and proved to be applicable to the viscosity measurements in a mini-tube. The standard uncertainty of dynamic viscosity measurements is identified as (2.22–5.28)% (coverage factor k=2). N-heptane, n-octane and their binary mixture were tested respectively in the calibration experiments of the viscometer. Results showed that the measured maximum relative deviations of all substances were all within 2% and the average absolute deviations were within 0.72%. Finally viscosities of a kerosene kind hydrocarbon fuel were measured using the two-capillary viscometer at temperature from (303.2 to 513.2)K and supercritical pressures of (3.00 and 4.00)MPa.

Behavior of hexadecyltrimethylammonium bromide and Triton X-100 mixture in the bulk phase of aqueous solution in the presence of methanol and propanol

Measurements of density, dynamic viscosity and specific conductivity of the aqueous solutions of p-(1,1,3,3-tetramethylbutyl)phenoxypoly(ethylene glycol) (Triton X-100 or TX-100) and hexadecyltrimethylammonium bromide (CTAB) with methanol or propanol were made. The surfactant mixture concentration ranged from 1×10−6 to 3×10−2M and the mole fraction of alcohol changed from 0 to 1. From the obtained results the critical aggregation concentration (CAC) of alcohol and the critical micelle concentration (CMC) of surfactant mixture were determined. It proved that the short-chain alcohols considerably affect the CMC of surfactants, but surfactants only slightly affect the CAC of alcohols. Moreover, surfactants form micelles only in the range of alcohol concentration below its CAC. Methanol can be treated only as a cosolvent while propanol depending on its concentration range acts as both a cosurfactant and cosolvent. The apparent and partial molar volumes of alcohol, water and surfactant mixture were determined from the commonly known equations. It appeared that these volumes can be also predicted on the basis of the bond lengths and angles between atoms in the molecules as well as the average distance between molecules by approximating the volume of certain functional groups by cages. The composition of mixed TX-100+CTAB micelles was determined from the Rosen's theory of regular solutions. The standard Gibbs free energy of micellization and aggregation was also evaluated. The specific conductivity changes for the studied solutions with methanol or propanol were compared.

Experimental evaluation of thermal conductivity, viscosity and breakdown voltage AC of nanofluids of carbon nanotubes and diamond in transformer oil

The present work reports new experimental results concerning the thermal conductivity, viscosity and breakdown voltage of solutions of diamond nanoparticles and multiwalled carbon nanotubes dispersed in mineral insulating oil for electrical transformers. The thermal conductivity of the solutions (also named nanofluids) was measured using the transient hot wire method. A controlled stress rheometer operating with coaxial cylinders was used for obtaining the shear stress versus shear rate curves and dynamic viscosity measurements. The dielectric strengths of the nanofluids were evaluated through the measurements of the insulation breakdown voltage AC using a dielectric strength analyzer with brass electrodes. From the experimental results, it was found that thermal conductivity and dynamic viscosity increase with increasing the particle concentration. On the other hand, and similarly to what is observed in the literature, the addition of these nanoparticles to the oil decreases its breakdown voltage.