Molecular Viscosity Research Articles

Evaluation and molecular interaction of asphalt modified by rubber particles and used engine oil

This study investigates the molecular mechanism of used oil on improving the compatibility and viscosity reduction of rubberized asphalt (RA) using molecular simulations and lab tests. This validates the feasibility of producing waste oil modified RA while enhancing the sustainable use of resources and pavement performance. The model of RA with used oil was first built by Materials Studio software. Several molecular dynamics parameters were used to explore the molecular behavior, stability and viscosity of asphalt. Furthermore, the relevant experiments were employed to validate the results of molecular simulation. The results show that used oil molecules can promote the dispersion of macromolecules, including asphaltenes, resins and rubbers, making the system more in accord with the asphalt colloid theory. It supplements the light components in the system to provide a stable dispersion medium. FTIR spectra confirm the rubber activation with used oil and microwave radiation. The softening point difference of RA was reduced from 1.9 to 0.35 °C. Viscosity was even reduced by approximately 67.1%.

Effect of rice flour ultrafine particle size on β-glucanase inactivation by microwave treatments and pasting properties in treated flours

The main problem in developing gluten-free products enriched with β-glucans (BG) is the hydrolysis they suffer due to the endogenous β-glucanase content of raw materials. The depolymerization causes a decrease in the molecular weight and viscosity, which is the most important parameter related to the health claims of BG. Hence, it is necessary to inactivate the β-glucanase. Therefore, this study aimed to inactivate the β-glucanase activity present in rice flour (Indica variety) with fine particle size using the microwave (MW) hydrothermal treatment method. The rice flour was conditioned at three different humidities 13, 16, 19 and 25%. Samples of 50 g were subjected to different microwave treatments 1, 2, 4 and 8 min, at 900 W power at 20 seconds intervals of treatment and 1-minute rest. The effect of particle size on inactivating the β-glucanase activity and the effect of MW treatment on the flour pasting property were also studied. The inactivation process followed a first-order kinetic response, and the apparent rate constant of thermal inactivation increased exponentially with the moisture content (M) of the flour, according to the equation -0.02t·exp (0.19·M) (R2 = 0.987). Among the treatments employed 4 min treatment at 25% initial M was found effective for complete β-glucanase inactivation. The effect of flour particle size did not show a significant (p> 0.05) difference on the efficiency of β-glucanase inactivation. Keywords: particle size, β-glucans, rice flour, microwave treatment, β-glucanase activity.

Mechanisms for Zonal Mean Wind Responses in the Thermosphere to Doubled CO2 Concentration

AbstractWe explored mechanisms for the thermospheric zonal mean wind responses to doubled CO2 concentration through investigating the zonal mean momentum balance in the thermosphere using GAIA model simulations in June. The analysis shows that ion drag, molecular viscosity, and meridional pressure gradient force vary 3–20 times more than the other forces due to the doubled CO2 concentration. The three forces strongly attenuate each other; consequently, the increase in zonal mean zonal ion drag dominantly strengthens the southward wind (∼15 ms−1 at maximum) in the northern (summer) hemisphere and latitudes north of 35S. This strengthened ion drag was attributed to increased ion density/relative velocity between ions and neutral particles in the northern/southern hemisphere. Southward of 35, the zonal pressure gradient force and the meridional advection of zonal wind strengthen the southward wind by 4–12 ms−1 in total. On the other hand, the zonal wind is mainly altered by increased meridional pressure gradient force (∼15 ms−1 at maximum) caused by a latitudinally asymmetric response of the thermosphere density to increasing CO2 concentration. Our results suggest that the increased ion density in the northern hemisphere is the underlying trigger for the wind responses to increasing CO2 concentration. Furthermore, we show that the meridional advection was mainly (∼70%) due to that of the DW1 tidal component.

Physically Cross-Linked Biopolymer Systems Based on Chitosan and Hydroxycinnamic Acids and Their Food Preservation Application Studies

Production of physically cross-linked biopolymer systems (PCBS) is attracting scientific and industrial attention due to its proven potential for applications in, for example, food, food packaging, food preservation, pharmaceuticals, and cosmetic industries. Its production versatility allows obtaining products in the form of films, powders, lyophilized products, edible coatings, and gel beads, among others. This review presents different methods for obtaining, characterizing, and applying these PCBS designed and produced using chitosan (CH) and hydroxycinnamic acids (HAs), resulting exclusively from noncovalent interactions. Each variable characterizing each component of the PCBS is evaluated, gaining a better understanding of their roles. The influence of different molecular weights, viscosities, and degree of deacetylation among other variables belonging to the biopolymer is presented, while the role of the type, amount, and position of the substituent groups on the HAs is shown using caffeic, ferulic, coumaric, chlorogenic, and rosmarinic acids as physical cross-linkers. The molar ratio between HAs and CH is a key factor when forming PCBS and in determining their final properties. Thus, we provide a comprehensive study of these PCBS obtained using CH and HAs, highlighting their environmental and sustainable aspects. Benefits from a materials standpoint regarding their competitive barrier effects and mechanical and thermal properties are also emphasized, especially toward their food packaging and food preservation applications.

Antioxidant Activity of Gracilaria lemaneiformis Polysaccharide Degradation Based on Nrf-2/Keap-1 Signaling Pathway in HepG2 Cells with Oxidative Stress Induced by H2O2.

The objective of this research was to investigate the antioxidant activity of Gracilaria lemaneiformis polysaccharide degradation and its underlying mechanism involved in the Nrf-2/Keap-1 signaling pathway in HepG2 cells with oxidative stress induced by H2O2. The result of the scavenging ability of free radicals showed that GLP-HV (polysaccharide degraded by H2O2–vitamin C (Vc)) performed a better scavenging ability than GLP (G. lemaneiformis polysaccharide). Moreover, the scavenging ability of polysaccharide to these free radicals from strong to weak was as follows: superoxide radical, ferric ion, ABTS+, and DPPH radical, and their IC50 values were 3.56 ± 0.0028, 4.97 ± 0.18, 9.62 ± 0.35, and 23.85 ± 1.78 mg/mL, respectively. Furthermore, GLP-HV obviously relieved oxidative stress in HepG2 cells, which strengthened the activity of T-AOC, CAT, GSH-PX, and SOD, and diminished the intensity of MDA, intracellular ROS, and calcium ion based on the Nrf-2/Keap-1 signaling pathway. The PCR result revealed that polysaccharide upregulated the expression of the genes Nrf-2, HO-1, NQO-1, and ZO-1 and downregulated Keap-1. The correlation between chemical properties and antioxidant mechanism of GLP-HV was evaluated via a heat map. The results illustrated that reducing sugar and active groups presented a positive correlation, and molecular weight and viscosity exhibited a negative relation with antioxidant activity.

Developing Water-Quality Model for Jingpo Lake Based on EFDC

Water-quality model simulation is the key to understanding hydrological processes and water-quality dynamic(s). In this study, Jingpo Lake, which is the most typical lake in the northern cold region of China, was selected as the research object. A numerical simulation model for transporting and diffusing the chemical oxygen demand (CODMn) and ammonia nitrogen (NH3N) with ice-covered and open-water periods was constructed and calibrated using the Environmental Fluid Dynamics Code (EFDC). Parameters such as the bottom roughness, ice roughness, diffusion coefficient, horizontal momentum diffusivity, molecular eddy viscosity, molecular diffusivity, buoyancy influence coefficient, CODMn decay rate and NH3N decay rate were validated. The research findings show that there were differences in the hydrodynamic water-quality changing process during the ice-covered and open-water periods, as well as for the seasonal ice-covered waterbody. The key parameter decay rates of the CODMn and NH3N in the ice-covered periods were lower than those in the open-water periods due to the water-temperature decline. The R2 of the CODMn and NH3N reached 90.71% and 79.79%, respectively. Thus, it may be concluded that the EFDC model could well reflect changes in the water level of Jingpo Lake, as well as the transport and diffusion of the CODMn and NH3N in Jingpo Lake.

Angular Momentum Transport by Keplerian Turbulence in Liquid Metals.

We report a laboratory study of the transport of angular momentum by a turbulent flow of an electrically conducting fluid confined in a thin disk. When the electromagnetic force applied to the liquid metal is large enough, the corresponding volume injection of angular momentum produces a turbulent flow characterized by a time-averaged Keplerian rotation rate Ω[over ¯]∼r^{-3/2}. Two contributions to the local angular momentum transport are identified: one from the poloidal recirculation induced by the presence of boundaries and the other from turbulent fluctuations in the bulk. The latter produces efficient angular momentum transport independent of the molecular viscosity of the fluid and leads to Kraichnan's prediction Nu_{Ω}∝sqrt[Ta]. In this so-called ultimate regime, the experiment, therefore, provides a configuration analogous to accretion disks, allowing the prediction of accretion rates induced by Keplerian turbulence.

Preparation and characterization of a low viscosity epoxy resin derived from m-divinylbenzene

To explore thermal and mechanical properties of epoxy material, difunctional aromatic epoxy--divinylbenzene dioxide (DVBDO) had been synthesized by epoxidizing divinylbenzene, using the metal acetylacetone compound grafted Fe3O4 particles as the catalyst. The catalyet had high conversion and epoxy selectivity and could be recyclable. Then the polymerization of DVBDO with different diamine curing agents were reported. The structure and viscosity of DVBDO were firstly characterized. Because it had low molecular weight and viscosity, DVBDO had excellent liquidity and formability. Subsequently to clarify the properties of epoxy thermosets, experiments to determine thermal and mechanical performances were carried out, such as differential scanning calorimetry (DSC), thermal gravimetric (TGA), dynamic mechanical analysis (DMA) and tensile test. It could be observed that the thermoset polymers using DVBDO as epoxy matrix had excellent thermal (Tg was about 201°C) and mechanical properties (tensile strength was 131.99Mpa). Possibly considering that this kind of thermoset polymers had higher rigidity and crosslink density. In conclusion, a new type of one-component liquid epoxy encapsulant material with low viscosity, good filling fluidity, strong heat resistance and excellent storage performance had been developed.

A Review: Current Status and Emerging Developments on Natural Polymer-Based Electrospun Fibers.

In recent years, natural polymer-based electrospun fibers (EFs) with huge specific surface area, good biocompatibility, and biological activity obtained from electrospinning process exhibit tremendous vitality in the field of biomedical areas. Herein, the parameters of electrospinning from two perspectives, polymer solution such as solvent, polymeric relative molecular mass, concentration, viscosity, and conductivity of the solution, and electrospinning process such as spinning voltage, spinning flow rate, needle tip to collector distance, temperature, and humidity are first detailed. Next, the raw materials consisting of polysaccharides such as cellulose, hyaluronic acid, alginate, and chitosan as well as proteins such as collagen, gelatin, silk fibroin, and keratin are summarized. The preparation method and related characteristics of EFs with multistage structures such as porous, core-shell, Janus, bamboo-like and other structures are introduced. The biomedical applications of these natural polymer-based EFs mainly including tissue engineering, drug sustained release, wound dressings, and biomedical sensors are systematically recapitulated. Finally, the outlook on natural EFs is further proposed.

Fluid properties impact on energy separation in Ranque–Hilsch vortex tube

This paper examines the energy separation in vortex tubes which is a passive device that can split a pressurized room temperature gas stream to hot and cold streams. The paper employs numerical simulations to investigate the impact of various working fluids such as helium, air, oxygen, nitrogen, and carbon dioxide on the energy separation in the vortex tube, using the SST k{-}omega turbulence model with viscous heating. A three-dimensional numerical investigation is sued to examine the effect of a single fluid property on vortex tube performance, while keeping the rest of the fluid properties unchanged, which is impossible to achieve via experimental study. The numerical investigation examines the influence of molecular weight, heat capacity, thermal conductivity, and dynamic viscosity on energy separation. The results show that energy separation performance improves with lower molecular weight and heat capacity, and higher dynamic viscosity of the working fluids, while no impact of the thermal conductivity is observed. Out of five gases tested in this study, helium has yielded the maximum temperature separation, while carbon dioxide has yielded the lowest performance. Results show that viscous dissipation contributes to the temperature separation in vortex tube.

Open-cell bio-polyurethane foams based on bio-polyols from used cooking oil

Used cooking oil is a widely available and inexpensive waste with a high application potential as a feedstock for the bio-based polyurethane production. Usually, bio-polyols from vegetable oils have higher viscosity and lower hydroxyl values compared to commercial petrochemical polyols, which limits their usefulness. This article reports on the development of open-cell polyurethane foam systems wherein 100% of the polyol components were bio-polyols obtained from used cooking oil. What is particularly considered is the effect of bio-polyol properties (molecular weight, viscosity and hydroxyl value) on the properties of the final open-cell polyurethane systems - apparent density, thermal conductivity coefficient, content of closed cells, mechanical strength, brittleness and short-term water absorption. It was found that the key step in the synthesis of bio-polyols designed for open-cell polyurethane foams is the epoxidation reaction. The epoxy value has a significant effect on the occurrence of side reactions (mainly oligomerization) during the oxirane ring-opening process determining the properties of bio-polyols. The resulting open-cell foams were characterized by apparent densities from 12.4 to 13.3 kg/m3, thermal conductivity coefficients from 36.6 to 38.2 mW/m∙K, and closed cell contents below 10%, which makes them comparable to commercial products. The results demonstrate that used cooking oil-based polyols can provide an alternative starting material for open-cell polyurethane foam production.

Chondroitin sulfate: are the purity and the structural features well assessed? A review on the analytical challenges

Animal origin chondroitin sulfate is employed as anti-inflammatory drug and food supplement against anti-osteoarthritis, but also as antioxidant, antitumor, anticoagulant, and immune-regulatory agent or as biomaterial in tissue engineering scaffolds and in drug-delivery systems. As its biological properties depend on the structural characteristics, multi-analytical approaches are necessary to correlate specific features of its heterogenic composition to the different bioactivities. This is of paramount importance to assess the efficacy of pharmaceuticals and food supplements, beyond safety quality control. This review would address the issue of chondroitin sulfate characterization according to the Pharmacopeia testing monograph point of view giving an update of the analytical novelties reported in the last ten years that might be employed for the product testing and releasing on the market. Not-instrumental (e.g. colorimetric assays) and instrumental techniques, most of them coupling diverse chromatographic separation methods with spectroscopic and spectrometry detection techniques, mono and bi-dimensional NMR approaches, are compared as tools to evaluate identity, titer, purity grade, monosaccharide and disaccharide composition, averaged molecular weight and viscosity, charge and sulfate content, impurities and related substances including the presence of other glycosaminoglycans.

Gravity Waves in Titan's Atmosphere: A Comparison Between Linearized Wave Model Calculations and HASI Observations

AbstractThe Huygens Atmospheric Structure Instrument (HASI) detected wavelike temperature fluctuations from 500 to 1,000 km on Titan. However, these fluctuation structures have not been satisfactorily reproduced by any theoretical model to date. In this study, we construct a full‐wave model to simulate the observed gravity wave structure. The model includes dissipation processes due to molecular viscosity, which increases exponentially with altitude, and eddy viscosity, which dominates the lower atmosphere. Using our model, we reproduced the observed temperature perturbations with the superposition of two gravity wave modes, one with λz = 600 km and λx = 1,600 km while the other with λz = 140 km and λx = 8,000 km. We estimate the thermal effects introduced by gravity waves and find that gravity waves below 900 km may significantly modify temperature structure of the upper atmosphere by tens of Kelvins. The wave‐induced thermal effect is sensitive to the eddy viscosity, which controls the dissipation and thermal conductivity below 900 km. When the eddy viscosity is increased by a factor of five, the thermal effect of gravity waves changes from −89 K cooling to nearly zero. This heating mechanism may contribute to the large temperature variability of 60 K in Titan's upper atmosphere.

Theoretical Approach for the Fast Estimation of the Turbulent Kinematic Viscosity for Internal Flows

Abstract An analytical expression for turbulent kinematic viscosity (νt), based solely on the hydraulic Reynolds number (Re), was derived and evaluated. The analytical expression is valid for the fast estimation of νt for internal, isotropic, fully developed flows. The expression was compared with experimental and simulation data for air, water, and liquid sodium, and was shown to provide reasonable values for 2100 ≤ Re ≤ 3.6 × 106 and Prandtl number (Pr) range of 0.0107 ≤ Pr ≤ 5.65. In addition, new expressions suitable for the central portion of internal flows, away from the wall, were derived for the turbulent Reynolds number (ReT), showing its relationship to Re, as well as to the ratio of νt and the molecular kinematic viscosity (ν).

Conflicting Effects of Extreme Nanoconfinement on the Translational and Segmental Motion of Entangled Polymers

Physically confining polymers into nanoscale pores induces significant changes in their dynamics. Although different results on the effect of confinement on the dynamics of polymers have been reported, changes in the segmental mobility of polymers typically are correlated with changes in their chain mobility due to increased monomeric relaxation times. In this study, we show that translational and segmental dynamics of polymers confined in disordered packings of nanoparticles can exhibit completely opposite behavior. We monitor the capillary rise dynamics of entangled polystyrene (PS) in disordered packings of silica nanoparticles (NPs) of 7 and 27 nm diameter. The effective viscosity of PS in 27 nm $SiO_2$ NP packings, inferred based on the Lucas-Washburn equation, is significantly smaller than the bulk viscosity, and the extent of reduction in the translational motion due to confinement increases with the molecular weight of PS, reaching 4 orders of magnitude reduction for PS with a molecular weight of 4M g/mol. The glass transition temperature of entangled PS in the packings of 27 nm $SiO_2$ NPs, however, increases by 45 K, indicating significant slowdown of segmental motion. Interestingly, confinement of the polymers into packings made of 7 nm $SiO_2$ NPs results in molecular weight-independent effective viscosity. The segmental dynamics of PS in 7 nm $SiO_2$ NP packings are slowed down even further as evidenced by 65 K increase in glass transition temperature. These seemingly disparate effects are explained by the microscopic reptation-like transport controlling the translational motion and the physical confinement affecting the segmental dynamics under extreme nanoconfinement.

Correlation between the Molecular Structure and Viscosity Index of CTL Base Oils Based on Ridge Regression.

In China, coal-to-liquid (CTL) lube base oils with ultrahigh viscosity index (VI) are very popular. Since it consists of chain alkanes only and can be precisely characterized by molecular structures alone, quantitative 13C nuclear magnetic resonance (NMR) data are used to generate the average structural parameters (ASPs) of CTL base oil. In this work, the ASPs and bulk properties of CTL base oils were tested and compared with those of mineral base oils. Based on the test results, the correlation between the unique property of CTL base oil VI and ASPs was analyzed. To eliminate the effect of significant multicollinearity among the input variables, statistical methods such as ordinary least-squares (OLS), stepwise regression, and ridge regression methods were used to build the VI prediction model. The main findings are as follows: according to the 13C NMR spectrum, CTL base oils had a significantly higher content of isomeric chain alkanes (including several branching structures) than mineral base oil, while the content of cycloalkanes was zero; among several branched structures, the one with the largest difference in content is structure S67, which has the highest percentage in the iso-paraffin structures, all above 25.5% in CTL base oils and below 21.39% in mineral oils; according to the distillation curve of the simulated distillation (SimDist) analysis, CTL base oils with similar carbon number distribution showed lower boiling points, narrower distillation ranges, and higher distillation efficiencies than mineral base oil; correlation analysis showed that the average chain length (ACL), normal paraffins (NPs), and structure S67 caused the CTL base oil to exhibit a higher VI; and from 13C NMR data, the ridge regression model was used to obtain regression coefficients consistent with reality, and the expected VI could be well predicted with a correlation coefficient of 0.935.

A novel highly-efficient bio-based fire retardant for poly (lactic acid): Synthesis, preparation, property and mechanism

In this work, the highly-efficient multifunctional bio-based fire retardant phenylphosphonic difurfurylamine (PPDF) was prepared successfully for poly(lactic acid) using furfurylamine and phenylphosphonic dichloride. Moreover, the structure of PPDF was analyzed by NMR, FTIR and MS. The fire safety, thermal, crystallization, rheological and mechanical properties of PLA/PPDF compounds were systematically tested by LOI, UL94, cone calorimeter test, TGA, DSC, polarizing optical microscope, rheometer, DMA and tensile properties. Surprisingly, only a very small loading of 0.8 wt% loading of bio-fire retardant PPDF could increase the LOI value of PLA from 19.0 % to 30.0 % and achieve V-0 rating in UL-94 vertical burning test. Moreover, PPDF not only reduced the molecular entanglement and viscosity of PLA, but also acted as a nucleating agent to increase crystallinity and crystallization rate of PLA matrix. More importantly, in the gas phase phosphorus, the PLA/PPDF compounds based on highly reactive benzene, phosphorus, phosphooxygen and phosphooxygen benzene radicals from the pyrolysis of PPDF had a highly-efficient fire safety. In the condensed phase, a relative stable residual char layer played a secondary role in the barrier. Thus, the total heat release and ignition time of PLA/PPDF compounds were evidently declined by 8.3 % and 10 s with only 0.8 wt% of PPDF loading.

A Novel Method of Endotoxins Removal from Chitosan Hydrogel as a Potential Bioink Component Obtained by CO2 Saturation.

The article presents a new approach in the purification of chitosan (CS) hydrogel in order to remove a significant amount of endotoxins without changing its molecular weight and viscosity. Two variants of the method used to purify CS hydrogels from endotoxins were investigated using the PyroGene rFC Enzymatic Cascade assay kit. The effect of the CS purification method was assessed in terms of changes in the dynamic viscosity of its hydrogels, the molecular weight of the polymer, microbiological purity after refrigerated storage and cytotoxicity against L929 cells based on the ISO 10993-5:2009(E) standard. The proposed purification method 1 (M1) allows for the removal of significant amounts of endotoxins: 87.9–97.6% in relation to their initial concentration in the CS hydrogel without affecting the solution viscosity. Moreover, the final solutions were sterile and microbiologically stable during storage. The M1 purification method did not change the morphology of the L929 cells.

Study on the chemical structure characterization and emulsification-stripping of heavy oil

The viscosity of heavy oil is of great importance on crude oil recovery, and the intrinsic relationship between the molecular structure of heavy oil and its viscosity is still unclear. To this end, the chemical structure of heavy oil is characterized by Scanning Electron Microscopy (SEM) and Diffusion-ordered Spectroscopy (DOSY). The relationship between the molecular structure and viscosity of heavy oil is revealed. The morphology of molecular aggregates is dominated by spherical particles, vesicles and films, and the corresponding viscosity increases sequentially. DOSY show that the heavy oil molecules rapidly gathered into aggregates with increasing concentrations. If the saturated aggregation concentration (maximum degree of aggregation) is exceeded, the volume of the single aggregate remains generally fixed but its quantity begins to increase. In addition, the structure-activity relationship between chemical agents and emulsification-stripping, including their mechanism of effect are systematically studied by interfacial tension (IFT), emulsification and micromodel experiments. The results show that the hydrophilic-lipophilic balance (HLB) values of surfactants that stabilize the emulsions are between 13.7 and 14.5. There is no obvious consistency between the emulsification effect of the surfactant and its IFT, and the stripping effect depends on its permeation and wetting action on the solid interface. The formation of emulsions in porous media mainly depends on the rotational disturbance and shear fracture of the displacing fluid, and the wettability of the solid surface determines the peeling rate of the oil film. Comparing with the blockage of large-sized emulsions, the migration of small-sized droplets in the channels as a continuous phase contributes more to the enhanced oil recovery.

Biodegradation of Polymers Used in Oil and Gas Operations: Towards Enzyme Biotechnology Development and Field Application.

Linear and crosslinked polymers are commonly used in the oil and gas industry. Guar-derived polymers have been extensively utilized in hydraulic fracturing processes, and recently polyacrylamide and cellulose-based polymers have also found utility. As these polymers are used during various phases of the hydraulic fracturing process, they can accumulate at formation fracture faces, resulting in undesired filter cakes that impede oil and gas recovery. Although acids and chemical oxidizers are often added in the fracturing fluids to degrade or ‘break’ polymer filter cakes, the constant use of these chemicals can be hazardous and can result in formation damage and corrosion of infrastructure. Alternately, the use of enzymes is an attractive and environmentally friendly technology that can be used to treat polymer accumulations. While guar-linkage-specific enzyme breakers isolated from bacteria have been shown to successfully cleave guar-based polymers and decrease their molecular weight and viscosity at reservoir conditions, new enzymes that target a broader range of polymers currently used in hydraulic fracturing operations still require research and development for effective application. This review article describes the current state-of-knowledge on the mechanisms and enzymes involved in biodegradation of guar gum, polyacrylamide (and hydrolyzed polyacrylamide), and carboxymethyl cellulose polymers. In addition, advantages and challenges in the development and application of enzyme breaker technologies are discussed.