Dynamic Viscosity Measurements Research Articles

Effect of concentration on PVA solutions and its usage in recycling carbon fiber/polyamide 12 prepregs

Abstract Polyvinyl alcohol (PVA) is a biodegradable synthetic polymer with high chemical resistance and excellent mechanical and oxygen barrier properties. Besides these superior properties, it is water-soluble, which provides its wide usage. However, its solubility depends on some factors. Although the temperature is one of these factors and increasing temperature could promote solubility, there is a solubility limit according to hydrolysis degree. In this study, PVA solutions at various concentrations were obtained by mixing fully hydrolyzed PVA1500 and water. Solutions were characterized by density, surface contact angle and dynamic viscosity measurements. Then, solvent casting was used to obtain films, and physical and mechanical properties were determined. Tensile test results showed optimum values at 10–12.5 wt.% PVA concentration. Also, vacuum drying changed the mechanical behavior of films significantly at all concentrations. While ultimate tensile stress values almost doubled and modulus values increased approximately three times, elongations critically decreased. Solutions were also subjected to waste carbon fiber (CF)/polyamide 12 (PA12) prepregs for recycling purposes. Lay-up and compression molding processes were applied to produce CF/PA12 composites. It was seen that mechanical results were significantly increased with increasing PVA concentration.

Dynamic Viscosity Measurement Method Based on the Stokes Drag of Prolate Ellipsoidal Mass

Viscometer plays an important role in the field of tribology. One way to measure viscosity is to use the Stokes drag principle in the underdamped harmonic oscillation phenomenon. This paper proposes a dynamic viscosity measurement method based on the related physical laws. Our experimental model involves a prolate ellipsoidal mass that experiences underdamped harmonic oscillation within viscous liquid samples. We observed the oscillations of the prolate ellipsoid to obtain the viscous damping coefficient of each sample and substituted it to the theoretical formula of dynamic viscosity. Experimental data suggest that the mathematical model has failed to predict the viscosity values of the samples. In addition, the regression curve of the reference viscosity and the measured viscous damping coefficient shows that the two quantities have an exponential relation instead of linear relation as explained in the theoretical model. We considered the regression formula as the empirical measurement transfer function and used it to measure the viscosity of an ISO VG 150 industrial oil sample. This measurement resulted in a 2.40 % of relative error percentage. Lastly, this measurement method is only valid for measuring samples with viscosities ranging from 0.0400 Pa s to 0.256 Pa s.

Biodiesel production performance estimation from simple viscosity measurements

In a biodiesel production industry a quick monitorization of the reaction extent achieved in the process it is important. The usual way to determine the reaction yield is to analyze the FAME content in the biodiesel reaction product. Analytic methods used, mainly gas chromatography, require previous sample treatment or tedious calibrations. Recently, less complicated analytic methods (nuclear magnetic resonance, infrared spectrophotometry) have been developed but they require costly equipment and analysis. The aim of this paper is to develop a cheap and fast method in order to quantify the FAME content in the reaction mixture from simple dynamic viscosity measurements and then the transesterification reaction yield. Therefore, experimentally obtained correlations from biodiesel proceeding of several oil feedstocks are presented in order to estimate the biodiesel FAME content from its dynamic viscosity, a fast determination parameter.

Enhancing Process Stability and Quality Management: A Comprehensive Analysis of Process Capability Indices

Process Capability Indices such as Process Capability Index (Cp) and Corrected Process Capability Index (Cpk), along with Process Performance Index (Pp) and Process Performance Corrected Index (Ppk), are most commonly used tools in quality management within manufacturing processes. They determine whether a process is capable of producing products within established tolerance limits, addressing both short-term and long-term variability. Despite widespread use, the analysis of Process Capability Indices often overlooks special variability within processes, which may lead to misleading interpretations of a process's capability, especially when the determination of tolerance limits is inadequately conducted. This article aims to verify the hypothesis that current analyses of Process Capability Indices fail to consider special variability, which could mislead the interpretation of a process's ability to meet its specifications. Statistical analyses were conducted using the Minitab software, based on dynamic viscosity measurements from the production process of solvent-based paint, to explore the implications of special variability on the interpretation of Process Capability Indices. The study revealed that while Process Capability Indices are useful for identifying quality management opportunities, their effectiveness is limited when special variability is present, often resulting in misinterpretations of a process's true capabilities. The findings highlight the need for methodologies that incorporate considerations of all forms of variability to ensure accurate process capability assessments. This gap in traditional analyses can affect the strategic decision-making in quality management, suggesting a critical area for further research and methodological development. The research confirms the need for a revised approach in analyzing Process Capability Indices, advocating for advanced methods that accurately reflect all forms of variability to improve quality management practices. Future research should focus on developing these methodologies to ensure more reliable and effective use of Process Capability Indices in quality management.

Effect of temperature on the hysteresis phenomenon and dispersion regimes for alumina/water based nanofluids

The present paper deals with a comprehensive experimental study of the hysteresis phenomenon of alumina-water based nanofluids taking place during heating-cooling cycles. The emphasis was particularly put on the relationship between this phenomenon and the dispersion state of alumina nanoparticles. Thus, by carrying out simultaneous thermal conductivity and dynamic viscosity measurements, five dispersion regimes were highlighted. The influence of the temperature on these two properties as well as the pH of the solution was then investigated for six characteristic conditions in the well-dispersed and chain-like agglomerated regimes and for temperatures between 20 and 80 °C. The results evidenced that as long as the temperature, and as a consequence the pH, does not exceed a critical value, no hysteresis phenomenon occurs during the heating and cooling processes. Eventually, it was found out that this critical temperature is strongly dependent on the dispersion regime and the initial pH of the nanofluid.

Shear-induced phase transition in the aqueous solution of an imidazolium-based ionic liquid.

An ionic liquid (IL) is a salt in the liquid state that consists of a cation and an anion, one of which possesses an organic component. Because of their non-volatile property, these solvents have a high recovery rate, and, hence, they are considered as environment-friendly green solvents. It is necessary to study the detailed physicochemical properties of these liquids for designing and processing techniques and find suitable operating conditions for IL-based systems. In the present work, the flow behavior of aqueous solutions of an imidazolium-based IL, 1-methyl-3-octylimidazolium chloride, is investigated, where the dynamic viscosity measurements indicate non-Newtonian shear thickening behavior in the solutions. Polarizing optical microscopy shows that the pristine samples are isotropic and transform into anisotropic after shear. These shear thickened liquid crystalline samples change into an isotropic phase upon heating, which is quantified by the differential scanning calorimetry. The small angle x-ray scattering study revealed that the pristine isotropic cubic phase of spherical micelles distort into non-spherical micelles. This has provided the detailed structural evolution of mesoscopic aggregates of the IL in an aqueous solution and the corresponding viscoelastic property of the solution.

Accelerated Thermo-Catalytic Degradation of Perfluoropolyether (PFPE) Lubricants for Space Applications

Perfluoropolyethers (PFPE) are a class of frequently used lubricants in space applications due to their high stability under demanding conditions. However, they are susceptible to aging, with the aging mechanism being dependent on the specific material combination and storage condition. A Lewis-acid-induced thermo-catalytic degradation mechanism is of concern, for example, under steel-on-steel sliding contact, and can be relevant for long-term storage (LTS). Accelerated aging experiments were performed on Fomblin® Z25 and Krytox™ 143AC to investigate thermal stability under the influence of iron(III) fluoride (FeF3) at elevated temperatures (180 °C, 200 °C, and 220 °C) up to a total duration of 2000 h. The degradation effects were monitored via selected analysis techniques: mass loss of the samples due to degradation and subsequent evaporation during aging, FTIR spectroscopy to investigate changes to the chemical structure, dynamic viscosity measurements for the investigation of a potential impact due to changes in molecular mass, and a ball-on-disc tribological test setup to obtain friction behavior of the aged lubricants. Distinct differences between the two types of PFPE lubricants regarding stability to thermo-catalytic degradation were found. Fomblin® Z25 was highly affected by the presence of FeF3 within the selected aging conditions, exhibiting high mass loss, a significant drop in dynamic viscosity, and an increased coefficient of friction due to degradation reactions.

The density and dynamic viscosity for dilute solutions of [Emim][NTf2] [Bmim][NTf2], and [Bmmim][NTf2] in ethylene glycol

In this paper, three dilute solutions were prepared and studied for density and dynamic viscosity measurement at different temperature ranges and molality ranges. The three dilute solutions are imidazolium cation ionic liquids (ILs) and ethylene glycol (EG). The measured temperature ranges are (293.15–328.15) K for density and (298.15–328.15) K for dynamic viscosity, respectively. The molality ranges of IL in EG are (0.0100–0.5001) mol∙kg−1. The ILs cations are 1-ethyl-3-methylimidazolium, 1-buty-3-methylimidazolium, and 1-butyl-2,3-dimethylimidazolium and anion is bis[(trifluoromethyl)sulfonyl]imide. The molality concentration dependence on apparent molar volume was fitted according to the Redlich-Rosenfeld-Meyer (RRM) equation. The obtained fitted values of apparent molar volumes of infinite dilution (VΦ0/m3∙mol-1), Sv/m3∙mol-3/2∙kg1/2, and Bv/m3∙mol-2∙kg were used for analysis of ion-solvent interaction and ion-ion interaction in solution. The relative viscosities have also been calculated from the dynamic viscosities at different temperatures and substance concentrations. The relationship between the relative viscosity and substance concentration of diluted solution has been characterized by the Jones–Dole equation. The fitted parameters of D and F from the Jones-Dole equation were used for the analysis of interaction changing of solute-solute and solute-solvent. The group introduction of –CH2- (methylene) on position 1 and –CH3 (methyl) on position 2 of imidazolium cation have also been discussed for interaction changing in IL and EG solvent solution. Through the analysis of IL microstructure change, the interaction forces were also described and discussed for the studied solutions.

Error quantification of the Arrhenius blending rule for viscosity of hydrocarbon mixtures

Six hundred and seventy-five measurements of dynamic viscosity and density have been used to assess the prediction error of the Arrhenius blending rule for kinematic viscosity of hydrocarbon mixtures. Major trends within the data show that mixture complexity–binary to hundreds of components—and temperature are more important determinants of prediction error than differences in molecular size or hydrogen saturation between the components of the mixtures. Over the range evaluated, no correlation between prediction error and mole fractions was observed, suggesting the log of viscosity truly is linear in mole fraction, as indicated by the Arrhenius blending rule. Mixture complexity and temperature also impact molar volume and its prediction. However, a linear regression between the two model errors explains less than 20% of the observed variation, indicating that mixture viscosity and/or molar volume are not linear with respect to temperature and/or mixture complexity. Extensive discussion of the intermolecular forces and the geometric arrangement of molecules and vacancies in liquids, which ultimately determines its viscosity, is brought into context with the implicit approximations behind the Arrhenius blending rule. The complexity of this physics is not compatible with a simple algebraic correction to the model. However, sufficient data is now available to determine confidence intervals around the prediction of fuel viscosity based on its component mole fractions and viscosities. At −40°C, when all identified components are pure molecules the modeling error is 13.2% of the predicted (nominal) viscosity times the root mean square of the component mole fractions.

Simultaneous Viscosity and Density Measurements and Modeling on Liquid Undecane, Dodecane, Tridecane, and Tetradecane up to 50 MPa

In this study, simultaneous experimental measurements of dynamic viscosity and density of four Newtonian liquids (undecane, dodecane, tridecane, and tetradecane) were performed in the pressure range from 1.99 to 50.01 MPa, along five isotherms between 298.15 and 353.16 K. The dynamic viscosity and density were determined using the capillary flow technique and a vibrating tube densimeter, respectively. The viability of the methods used was verified through the experimental measurements of the viscosity and density of ethanol and its comparison with data published in the international literature, resulting a maximum deviation of 1.25% for viscosity and 0.58% for density. The relative combined expanded uncertainty (k = 2) for the experimental measurements was estimated to be 1.4% and 0.2% for dynamic viscosity and density data, respectively, considering the impurities of the chemical compounds. Also, two empirical models were used to represent the experimental data reported in this work; for the dynamic viscosity, a maximum deviation of 0.5% was found, while, for density, a maximum deviation of 0.11% was obtained. From density data and using the empirical model, the isothermal compressibility and isobaric thermal expansivity were evaluated under the reported conditions.

Selection of Conditions in PVB Polymer Dissolution Process for Laminated Glass Recycling Applications.

Polyvinyl(butyral) (PVB) post-production waste collected from the windshields of end-of-life vehicles and post-consumer building laminated glass are valuable polymeric materials that can be reused. Every year, large amounts of PVB waste are still being buried in landfills owing to a lack of appropriate recycling techniques. Before reuse, PVB should be thoroughly cleaned of solid contaminants such as glass dust, fused heating wires, and other waste polymers, metals, and ceramics. This can be done by polymer dissolution and filtration. In this study, we propose the purification of PVB from contamination by dissolving the post-consumer polymeric materials into single and binary organic solvents. As part of the experimental work, measurements and optimization of the dissolution time of PVB were performed. PVB dissolves faster when a binary solvent (2-propanol + ethyl acetate) than pure 2-propanol is used. From the point of view of the practical application of PVB solutions, measurements of density and dynamic viscosity as a function of PVB concentration and temperature were performed. The PVB solutions obtained in this work can be widely used as glues for glass, ceramics, metal, impregnating, and insulating materials or as paint additives that are entirely transparent for visible light and to block UV rays.

Formulation, Characterization and Evaluation of Innovative O/W Emulsions Containing Curcumin Derivatives with Enhanced Antioxidant Properties.

In the present study, a series of semisolid Oil in Water (O/W) emulsions containing different Curcumin (Cur) derivatives (Cur powder, Cur extract and Cur complexed with β-cyclodextrin) in varying concentrations, were prepared. Initially, Dynamic Light Scattering (DLS), microscopy, pH and viscosity measurements were performed to evaluate their stability over time. Moreover, the effect of the active cosmetic substances on the Sun Protection Factor (SPF), antimicrobial and antioxidant properties of the prepared emulsions was investigated. It was observed that emulsions containing Cur extract and Cur β-cyclodextrin complex presented great viscosity and pH stability for up to 90 days of storage contrary to the emulsions containing Cur powder which showed unstable behavior due to the formation of agglomerates. All samples presented SPF values between 2.6 and 3.2. The emulsions with Cur in all forms exhibited high antioxidant activity, whereas the emulsion containing Cur β-cyclodextrin complex presented the highest value. Despite their improved stability and antioxidant activity, the emulsions containing Cur extract and Cur-β-cyclodextrin exhibited a low percentage of antimicrobial activity against E. coli and Staphylococcus bacteria. Instead, the emulsions containing Cur powder presented a reduction rate over 90 % against E. coli and Staphylococcus colonies.

In-line measurements of the physical and thermodynamic properties of single and multicomponent liquids.

Microfluidic devices are becoming increasingly important in various fields of pharmacy, flow chemistry and healthcare. In the embedded microchannel, the flow rates, the dynamic viscosity of the transported liquids and the fluid dynamic properties play an important role. Various functional auxiliary components of microfluidic devices such as flow restrictors, valves and flow meters need to be characterised with liquids used in several microfluidic applications. However, calibration with water does not always reflect the behaviour of the liquids used inthe different applications. Therefore, several National Metrology Institutes (NMI) have developed micro-pipe viscometers for traceable inline measurement of the dynamic viscosity of liquids used in flow applications aspart of the EMPIR 18HLT08 MeDDII project. These micro-pipe viscometers allow the calibration of any flow device at different flow rates and the calibration of the dynamic viscosity of the liquid or liquid mixture used under actual flow conditions. The validation of the micro-pipe viscometers has been performed either with traceable reference oils or with different liquids typically administered in hospitals, such as saline and/or glucose solutions or even glycerol-water mixtures for higher dynamic viscosities. Furthermore, measurement results ofa commercially available device and a technology demonstrator for the inline measurement of dynamic viscosity and density are presented in this paper.

Experimental measurement of thermophysical properties of some commercial phase change materials (PCM) for air conditioning applications

This paper presents the measurement of liquid phase density, thermal diffusivity, thermal conductivity, and dynamic viscosity of five commercial PCM (RT2HC, RT5HC, OM05-P, OM08, CrodaTherm9.5) in the temperature range 2 − 30 °C. The density of RT2HC, RT5HC, OM05-P is 23-24% lower than water, that of OM08 is 6% higher than water and that of CrodaTherm9.5 is 14% lower than water. The thermal diffusivity of RT2HC, RT5HC, OM05-P is 22-24% lower than water, that of OM08 is around a half of water and that of CrodaTherm9.5 is 38-40% lower than water. The thermal conductivity of the five PCM is 72-74% lower than water. The dynamic viscosity of RT2HC, RT5HC, OM05-P and OM08 is 2 − 3 times higher than water, and that of CrodaTherm9.5 is from 7.4 to 8.3 times higher than water. The five PCM are expected to provide convective heat transfer performance significantly lower than water .

Enhanced oil recovery with nanofluids based on aluminum oxide and 1-dodecyl-3-methylimidazolium chloride ionic liquid

Surface-active ionic liquids (SAILs) have multiplied the possibilities of surfactant enhanced oil recovery (EOR) methods. Among their multiple promising features, the possibility of functionalization and their stability at harsh conditions should be highlighted for the application. They have been successfully applied to increase oil recovery by improving crucial parameters such as: formulation stability, reduction of water–oil interfacial tension, and wettability. Recently, nanoparticles have attracted attention for EOR applications due to their capacity to modify the properties of rock surfaces. However, to date no research has been conducted on the combination of SAILs with nanoparticles for EOR. In this work, the combination of the SAIL 1-dodecyl-3-methylimidazolium chloride, [C12mim]Cl, with Al2O3 nanoparticles is proposed for EOR. Stable dispersions in brine were achieved, using the polymer polyvinylpyrrolidone (PVP) as a stabilizing agent, and characterized through density and dynamic viscosity measurements. According to stability and interfacial tension studies, a nanofluid consisting of 0.05 wt% [C12mim]Cl, 0.05 wt% Al2O3 and 1.0 wt% PVP, in brine (5.0 wt% NaCl) was proposed for EOR in carbonate reservoirs. The presence of nanoparticles reduced the adsorption of the surfactant-polymer formulation on carbonate rocks and changed the aged rock wettability from oil-wet to water-wet. An additional oil recovery of 10.4 %OOIP was achieved with the surfactant-polymer formulation, in comparison with 14.8 %OOIP obtained with the nanofluid.

Simultaneous compressed liquid viscosity and density measurements of n-alkanes at temperatures between (291 and 353) K and pressures up to 50 MPa

Compressed liquid density (ρ) and dynamic viscosity (η) were simultaneously measured for pure liquid n-alkanes (n-hexane, n-heptane, n-octane, n-nonane, and n-decane) in the temperature range from (291 to 353) K and pressure up to 50 MPa by an experimental system using a coil capillary tube viscometer (CCTV) coupled with a vibrating tube densimeter (VTD). The reliability and validation of this measuring system were verified by determining and comparing both dynamic viscosity and density data of ethanol published in the international literature. The maximum viscosity deviation was 8 μPa ∙ s for viscosity and 0.87 kg ∙ m−3 for density. The measurements were carried out with a relative expanded uncertainty (k=2) of 1.00 % for the measurements of dynamic viscosity and 0.20 % for the measurements of density considering the impurities of the chemical compounds). Both dynamic viscosity and density data were represented using two empirical models, obtaining a maximum deviation of 2.49 % for the dynamic viscosity and 0.12 % for the density with the experimental data. Finally, the isothermal compressibility and isobaric thermal expansivity were calculated from the empirical models at the reported conditions.

Monitoring the Process of Anaerobic Digestion of Native and Microwave Pre-Treated Sludge by Dielectric and Rheological Measurements

The anaerobic digestion (AD) of wastewater sludge presents a promising and efficient method of wastewater and sludge treatment, as it can lower the organic content of sludge while producing a renewable source of energy—biogas—at the same time. However, using native, non-treated industrial wastewater sludge as a substrate for AD may present difficulties, hence we focused our research primarily on the applicability of measuring techniques—viscosity and dielectric measurement. One of our research goals was to investigate the presence of any connection between the aforementioned properties and the overall biogas production, in order to prove whether these measurement techniques were capable of monitoring the process of AD. Our other aim was to investigate how microwave (MW) pre-treatment affected the anaerobic fermentation. Our results revealed that in terms of total biogas yield, microwave irradiation could enhance fermentation by 14%, and also reduced the viscosity of the fermentation media by 13%. However, microwave irradiation did not change the overall tendencies of the AD process regarding these aspects. Moreover, it was discovered that dielectric and absolute viscosity measurements were effective methods for monitoring the fermentation. Additionally, a correlation was found between the accumulating biogas yield, the dielectric constant and loss factor, and the absolute viscosity of the digested media—each of these share a similarity in tendency and can indicate the occurrence of different phases during batch anaerobic fermentation.

Poly-L-Arginine Molecule Properties in Simple Electrolytes: Molecular Dynamic Modeling and Experiments.

Physicochemical properties of poly-L-arginine (P-Arg) molecules in NaCl solutions were determined by molecular dynamics (MD) modeling and various experimental techniques. Primarily, the molecule conformations, the monomer length and the chain diameter were theoretically calculated. These results were used to interpret experimental data, which comprised the molecule secondary structure, the diffusion coefficient, the hydrodynamic diameter and the electrophoretic mobility determined at various ionic strengths and pHs. Using these data, the electrokinetic charge and the effective ionization degree of P-Arg molecules were determined. In addition, the dynamic viscosity measurements for dilute P-Arg solutions enabledto determine the molecule intrinsic viscosity, which was equal to 500 and 90 for ionic strength of 10−5 and 0.15 M, respectively. This confirmed that P-Arg molecules assumed extended conformations and approached the slender body limit at the low range of ionic strength. The experimental data were also used to determine the molecule length and the chain diameter, which agreed with theoretical predictions. Exploiting these results, a robust method for determining the molar mass of P-Arg samples, the hydrodynamic diameter, the radius of gyration and the sedimentation coefficient was proposed.

A High Thermal Conductivity of MgO-H2O Nanofluid Prepared by Two-Step Technique

In this paper, the main goal is to study the impact of nanopowder volume concentration and ultrasonication treatment time on the stability and thermophysical properties of MgO-DW nanofluid at room temperature. The co-precipitation method was utilized to prepare pure MgO nanoparticles with an average particle size of 33 nm. The prepared MgO nanopowder was characterized by using XRD, SEM, and EDX analyses. Then, MgO-DW nanofluid was obtained with different volume concentrations (i.e., 0.05, 0.1, 0.15, 0.2, and 0.25 vol.%) and different ultrasonication time periods (i.e., 45, 90, 135, and 180 min) by using a novel two-step technique. With volume concentration and ultrasonication time of 0.15 vol.% and 180 min, respectively, good stability was achieved, according to the zeta potential analysis. With increasing volume concentration and ultrasonication time period of the nanofluid samples, the thermal conductivity measurements showed significant increases. As a result, the maximum enhancement was found to be 25.08% at a concentration ratio of 0.25 vol.% and agitation time of 180 min. Dynamic viscosity measurements revealed two contrasting trends with volume concentration and ultrasonication time. The lowest value of relative viscosity was gained by 0.05 vol.% MgO-DW nanofluid. The chemical and physical interactions between MgO nanoparticles and DW molecules play an important function in determining the thermal conductivity and dynamic viscosity of MgO-DW nanofluid. These findings exhibit that MgO-DW nanofluid has the potential to be used as an advanced heat transfer fluid in cooling systems and heat exchangers.

In vitro anticancer activities, multi-spectroscopic and in silico DNA binding studies of propranolol drug and its new Zn(II) complex

A new Zn(II) complex of propranolol (PPN), [Zn2(PPN)2(μ-Cl)2] (ZnPPN), was synthesized and characterized using 1H NMR and FT-IR spectroscopies, CHN elemental analysis, cyclic voltammetry (CV) and conductance measurements. Then the interaction of both the drug and its Zn(II) complex with calf thymus DNA (ct-DNA) was studied using differential pulse voltammetry (DPV), multi-spectroscopic, and dynamic viscosity measurements, and also in silico simulations. The cytotoxicity studies against MCF-7 and HEK-293 cell lines were also evaluated and compared. DNA binding studies determined a higher affinity of ZnPPN for ct-DNA compared to the drug alone. Furthermore, the new ZnPPN complex was found as an intercalation binder of ct-DNA by competitive fluorescence and viscosity studies, while PPN binds to ct-DNA via a groove mechanism. Finally, experimental DNA binding and molecular docking studies are all well agreed with each other. The cytotoxicity studies showed that PPN, ZnPPN and cisplatin (CIS) have an IC50 value are 46.43 ± 7.23, 34.23 ± 8.52, 19.96 ± 6.89 µg/ml on MCF-7 cell line, respectively, and no cytotoxicity on the normal cell of HEK-293.