Total Surface Tension Research Articles

Modeling of multicomponent three-dimensional vesicles

In many interfacial flow systems, variations of surface properties lead to novel and interesting behaviors. In this work a three-dimensional model of flow dynamics for multicomponent vesicles is presented. The surface composition is modeled using a two-phase surface Cahn–Hilliard system, while the interface is captured using a level set jet scheme. The interface is coupled to the surrounding fluid via a variation of energy approach. Sample energies considered include the total bending, surface tension, and phase segregation energy. The fully coupled system for surface inhomogeneities, and thus varying interface material properties is presented, as are the associated numerical methods. Numerical convergence and sample results demonstrate the validity of the model.

A data-driven approach for the study of coagulation phenomena in waste lubricant oils and its relevance in alkaline regeneration treatments

Coagulation phenomena can occur in certain types of waste lubricant oils (WLO) during regeneration processes involving alkaline treatments, causing plant shutdowns. In this context, this study addresses the nature of the compounds responsible for the coagulation phenomena after the alkaline treatment. For such, an empirical test was developed to assess the coagulation behaviour of WLO, consisting in the addition of KOH to the WLO followed by heating under stirring conditions. This test was performed on 133 samples and four coagulation classes were identified: A; B1; B2 and C. Moreover, a physicochemical characterization of WLO was carried out regarding viscosity at 40°C, saponification number (SN), total acid number (TAN), surface tension, water content, elemental analysis and functional groups (FTIR). 56 samples of fresh lubricant oils for different applications were also characterized and their properties assessed and compared. Multivariate methods were applied to WLO to discriminate among coagulation classes based on FTIR spectra. It was found that coagulation classes A and B1 exhibit statistically similar patterns for all properties determined. Spectral discriminating analysis did not reveal discriminant peaks for class B1 samples, and the presence of specific additives was pointed as the possible factor underlying the increase in viscosity in this oils. Class B2 presents the absence of additives and oxidation products as differentiating features. In addition, B2 samples showed lower TAN SN, and lower concentration of some elements. Lubricants from gear or hydraulic applications can give rise to this class of WLO. Oils of Class C are mainly composed by synthetic ester type base oils, which hamper regeneration processes using alkaline pretreatments. In future studies, WLO type A and B1 can be classified as a single class. The coagulation phenomena classification becomes A – negative, B – precipitate formation and C – positive.

Importance of the tail corrections on surface tension of curved liquid-vapor interfaces

We report molecular simulations of the liquid-vapor cylindrical interface of methane. We apply the truncated Lennard-Jones potential and specific long-range corrections for the surface tension developed especially for cylindrical interfaces. We investigate the impact of the cutoff on the radial density profile, the intrinsic and long-range correction parts to the surface tension, and Tolman length. We also study the curvature dependence of the surface tension as a function of the cutoff used. In this work we shed light that both density and Tolman length are cutoff-dependent whereas the total surface tension is slightly curvature and cutoff dependent.

Surface tension of highly magnetized degenerate quark matter

We study the surface tension of highly magnetized three flavor quark matter within the formalism of multiple reflection expansion (MRE). Quark matter is described as a mixture of free Fermi gases composed by quarks $u$, $d$, $s$ and electrons, in chemical equilibrium under weak interactions. Due to the presence of strong magnetic fields the particles' transverse motion is quantized into Landau levels, and the surface tension has a different value in the parallel and transverse directions with respect to the magnetic field. We calculate the transverse and longitudinal surface tension for different values of the magnetic field and for quark matter drops with different sizes, from a few fm to the bulk limit. For baryon number densities between $2-10$ times the nuclear saturation density, the surface tension falls in the range $2 - 20$ MeV /fm$^{2}$. The largest contribution comes from strange quarks which have a surface tension an order of magnitude larger than the one for $u$ or $d$ quarks and more than two orders of magnitude larger than for electrons. Our results show that the total surface tension is quite insensitive to the size of the drop. We also find that the surface tensions in the transverse and parallel directions are almost unaffected by the magnetic field if $eB$ is below $\sim 5 \times 10^{-3} $ GeV$^2$. Nevertheless, for higher values of $eB$, there is a significant increase in the parallel surface tension and a significant decrease in the transverse one with respect to the unmagnetized case.

Electric-Assisted Capillary Rise Adsorption of Polar and Nonpolar Solvents by Cellulose and Chitosan.

Electric-assisted capillary rise adsorption of polar and nonpolar solvents by cellulose and chitosan was studied by employing an electrostatic generator to assist a common capillary rise wetting by taking the anode and cathode electrodes respectively linked to a metal tube charged with samples and the probe solvent. To vary the voltage at 0, 100, 200, and 300 V, respectively, the recorded dynamic adsorption results showed that the cellulose and chitosan both kept a stable adsorption of the nonpolar hexane and diiodomethane, obviously ignoring the voltage increase. Moreover, the hexane amount adsorbed by cellulose and chitosan is similar, while the diiodomethane amount was adsorbed to a greater amount by cellulose as compared with the chitosan corresponding to these two biomaterials-based nonpolar components, for example, greater for cellulose and smaller for chitosan. Results also showed that the adsorption of polar water and formamide was gradually increased with the voltage increase, especially for chitosan, to correspond to the polar component of these materials, for example, greater for chitosan and smaller for cellulose. These adsorption behaviors suggested that the application of an extra electric field can only enhance the adsorption of polar solvent, and the molecular structure, for exmaple, the β-(1-4)-linked d-glucosamine units of chitosan, has sensitive electric field responses in polar solvent adsorption as compared with those of the β(1-4)-linked d-glucose units of cellulose. The reason for the electric adsorption behaviors was known due to the presence of an extra electric-field-induced reduction of the total surface tension of solvent and mainly the polar component.

Towards a better hydraulic cleaning strategy for ultrafiltration membrane fouling by humic acid: Effect of backwash water composition

As a routine measurement to alleviate membrane fouling, hydraulic cleaning is of great significance for the steady operation of ultrafiltration (UF) systems in water treatment processes. In this work, a comparative study was performed to investigate the effects of the composition of backwash water on the hydraulic cleaning performance of UF membranes fouled by humic acid (HA). Various types of backwash water, including UF permeate, Milli-Q water, NaCl solution, CaCl2 solution and HA solution, were compared in terms of hydraulically irreversible fouling index, total surface tension and residual HA. The results indicated that Milli-Q water backwash was superior to UF permeate backwash in cleaning HA-fouled membranes, and the backwash water containing Na+ or HA outperformed Milli-Q water in alleviating HA fouling. On the contrary, the presence of Ca2+ in backwash water significantly decreased the backwash efficiency. Moreover, Ca2+ played an important role in foulant removal, and the residual HA content closely related to the residual Ca2+ content. Mechanism analysis suggested that the backwash process may involve fouling layer swelling, ion exchange, electric double layer release and competitive complexation. Ion exchange and competitive complexation played significant roles in the efficient hydraulic cleaning associated with Na+ and HA, respectively.

New studies on basil (Ocimum bacilicum L.) seed gum: Part I – Fractionation, physicochemical and surface activity characterization

Basil seed gum (BSG) was fractionated by non-solvent fractionation method (ethanol precipitation). Two fractions were obtained and called PER-BSG and SUPER-BSG which had the highest and lowest molecular weight (MW), respectively. Another fraction was obtained by protease treatment which protein moieties of BSG removed without making different in molecular weight. The molecular weight, moisture, ash, protein content, intrinsic viscosity, total sugar, total uronic acid, monosaccharide units, functional groups (FTIR) and surface tension were investigated for total BSG and all fractions. BSG was composed of 92.44% (w/w) sugar and 6.51% (w/w) uronic acid; while PER-BSG and SUPER-BSG comprised of 83.02% and 88.39% (w/w) sugar, and 3.84% and 13.39% uronic acid, respectively. FTIR results confirmed the presence of uronic acid as it had absorptions at wavenumber 1400 and 1600 cm−1. Significant difference was determined between monosaccharide compositions of fractions; especially in xylose content which substantial value existed for SUPER-BSG (10%). The BSG exhibited higher intrinsic viscosity (39.27 dl g−1) in comparison to its fractions. BSG and all fractions had the same molecular conformation which random coil conformation was recognized in dilute regimes and SUPER-BSG had the highest chain flexibility. The SUPER-BSG imparted the best surface activity as it had the highest protein content and lowest MW. Decreasing protein content by enzyme hydrolysis led to surface activity of BSG reduced considerably by changing its hydrophobic character. This attribute confirmed that protein and molecular weight plays an important role in surface activity of BSG.

A non-foaming proteosurfactant engineered from Ranaspumin-2

Advances in biological surfactant proteins have already yielded a diverse range of benefits from dramatically improved survival rates for premature births to artificial photosynthesis. Presented here is the design, development, and analysis of a novel biosurfactant protein we call Surfactant Resisting Foam formatioN (SRFN). Starting with the Tungara frog's foam forming protein Ranaspumin-2, we have engineered a new surfactant protein with a destabilized hinge region to alter the kinetics and equilibrium of the protein structural transition from aqueous globular form to an extended surfactant structure at the air/water interface. SRFN is capable of approximately the same total surface tension reduction, but with the unique property of forming quickly collapsible foams. The difference in foam formation is attributed to the destabilizing glycine substitutions engineered into the hinge region. Surfactants used specifically to increase wettability, such as those used in agricultural applications would benefit from this new proteosurfactant since foamed liquid has greater wind resistance and decreased dispersal. Indeed, given growing concern of organsilicone surfactant effects on declining bee populations, biological surfactant proteins have several unique advantages over more common amphiphiles in that they can be renewably sourced, are environmentally friendly, degrade readily into non-toxic byproducts, and reduce surface tension without deleterious effects on cell membranes.

Superhydrophobic surfaces of electrospun block copolymer fibers with low content of fluorosilicones

Abstract A series of well-defined poly[methyl(3,3,3-trifluoropropyl)siloxane]- b -poly(methyl methacrylate) (PMTFPS- b -PMMA) diblock copolymers with low content of PMTFPS were synthesized by atom transfer radical polymerization (ATRP) of MMA from PMTFPS macroinitiators (PMTFPS-Br). The polymerization result reveals that the ATRP of MMA from PMTFPS-Br is fist-order with respect to MMA under different polymerization conditions, demonstrating a typical characteristic of living polymerization. The results also show that PMTFPS- b -PMMA diblock copolymers can exhibit a total surface tension ( γ S ) varying from 25.28 mN/m to 21.87 mN/m with the change of PMTFPS contents from 2.6 wt% to 22.2 wt%. Moreover, the water contact angles of electrospun PMTFPS- b -PMMA surfaces could be higher than 150° with water roll-off angles less than 10°, which denotes a superhydrophobic property. However, the electronspinning conditions, especially the concentration of spinning solution, would have important effect on the surface morphology, surface composition and wetting behavior of electrospun films. It was found that bead-free fibers with uniform diameter as well as good superhydrophobic property could be prepared on condition that the polymer concentration of spinning solution was as high as 32 wt% in the mixed solvent of DMF and THF.

Correlations between Crude Oil Composition and Produced Water Quality: A Multivariate Analysis Approach

A matrix of 18 synthetic produced water samples was analyzed by partial least-squares (PLS) regression modeling. This has been done to investigate the correlation between crude oil properties and water solubility and affinity of the dissolved hydrocarbons for air/water interface which is referred to as produced water quality. The synthetic produced water samples were prepared with nine crude oils and two aqueous phases in the presence and absence of divalent cations (Ca2+, Mg2+). The total organic carbon content and dynamic surface tension was determined for the samples. The findings of the PLS modeling are summarized as follows: produced water quality was not correlated to the amount (wt %) of aromatics, resins, and asphaltenes in the crude oils but with the amount (wt %) of heteroatoms present in the different fractions. The water solubility and affinity for air/water interfaces of the crude oil hydrocarbons was promoted by oxygen-containing compounds and reduced by nitrogen- and sulfur-containing compo...

Dynamic Adsorption of Organic Compounds Dissolved in Synthetic Produced Water at Air Bubbles: The Influence of the Ionic Composition of Aqueous Solutions

A detailed analysis of the dynamic adsorption of crude oil components dissolved in produced water onto air bubble surfaces is presented. Synthetic produced water was prepared using three crude oils and aqueous solutions with varying ionic composition. The total organic carbon content, molecular mass, and dynamic surface tension was determined for the samples. A modified version of the Ward–Tordai model was used to evaluate the experimental data. This allowed for determination of the characteristic diffusion coefficients and investigation of the adsorption mechanisms. The adsorption process was diffusion-controlled on short time scales, while adsorption barriers occurred on longer time scales. The presence of salts in the aqueous solutions had a strong influence on the time at which deviations from diffusion-controlled kinetics took place. This was explained in terms of salting-out of larger hydrocarbons. The presence of divalent cations did not have a major influence on the salting-out effect nor the time...

Dynamic adsorption of water soluble crude oil components at air bubbles

A detailed analysis of the dynamic adsorption of crude oil components dissolved in produced water onto air bubble surfaces is presented. Nine different crude oils were used to prepare synthetic produced water samples. The total organic carbon content, molecular mass and dynamic surface tension was determined for the samples. The experimental data were applied in a modified version of the Ward–Tordai model, in order to evaluate the adsorption mechanism. This allowed for determination of characteristic diffusion coefficients and investigation of adsorption mechanisms. All the crude oils contained water soluble components within a relatively narrow range of molecular size, but different polarity. The adsorption mechanism was purely diffusion controlled at short time scales regardless of the chemical composition of the crude oil. Further analyses were performed on two of the crude oils by selectively extracting interfacially active components (acids and bases) from the crude oils. Both acidic and basic compounds were present in the produced water samples, but their affinity for the air/water interface varied. There were no correlation between the amount of acids and bases in the crude oils and the solubility and surface activity of the respective water soluble fractions.

Interplay between long‐ and short‐range interactions drives neuritogenesis on stiff surfaces

Substrate factors such as surface energy distribution can affect cell functions, such as neuronal differentiation of PC12 cells. However, the surface effects that trigger such cell responses need to be clarified and analyzed. Here we show that the total surface tension is not a critical parameter. Self-assembled monolayers of alkylsiloxanes on glass were used as culture substrates. By changing the nanoscale structure and ordering of the monolayer, we designed surfaces with a range of dispersive (γ(d) ) and nondispersive (γ(nd) ) potentials, but with a similar value for total free-energy (50 ≤ γ(d) + γ(nd) ≤ 55 mN m⁻¹). When seeded on surfaces displaying γ(d) /γ(nd) ≤ 3.7, PC12 cells underwent low level of neuritogenesis. On surfaces exhibiting γ(d) /γ(nd) ≥ 5.4, neurite outgrowth was greatly enhanced and apparent by only 24 h of culture in absence of nerve growth-factor treatment. These data indicate how the spatial distribution of surface potentials may control neuritogenesis, thus providing a new criterion to address nerve regeneration issues on rigid biocompatible surfaces.

Relationship Between Total Surface Tension of Monomer and Its Homopolymer

The surface and interfacial properties of polymers are important for their applications. In one of our previous articles, we discussed the relationship between the dispersive surface tension component and the density and molecular weight of solvents and polymers to seek a simple and easy method to estimate the rationality of surface tension results of polymers. We found that for 30 organic solvents and 12 polymers, there was a good relationship between the dispersive surface tension and the experiential parameter 1/ρ2 M 0.2 w . In this article, the existence of the squared density term is simply deduced from the general molecular interaction energy equation and is proved with four pairs of polymer/monomer; these are polystyrene/styrene, polyisoprene/isoprene, polymethyl methacrylate/methyl methacrylate, and polyvinyl acetate/vinyl acetate.

Comprehensive analysis of surface free energy of asphalts and aggregates and the effects of changes in pH

Moisture damage is a major factor in the deterioration of asphalt pavements. In order to combat this problem, it is essential to understand the effects of moisture on the adhesive and cohesive bonds in asphalt concrete mixtures. These effects can be quantified through the use of surface free energy, which is a thermodynamic material property that has been successfully used to select asphalt binders and aggregates that have the necessary compatibility to firm strong bonds and resist moisture damage. This study aimed at understanding the effects of material characteristics and additives on surface energy and the resulting bond between asphalt binders and aggregates. As such, the study involved measuring the surface free energy of 37 neat and polymer modified asphalt binders and 11 aggregates were measured. In addition, the surface free energy was measured for three asphalt binders after two anti-strip agents were added separately (six binder-anti-strip agent combinations) and for nine asphalt binders that were both short and long-term aged. The study also examined the effect of water pH on surface energy and water-aggregate adhesive bond. It was found that anti-strip agents, in general, reduced the cohesive bond energy of asphalt binder, allowing better wetting and adhesion to aggregates and increase in resistance to moisture damage. Aging of the asphalt either increased or decreased the cohesive bond depending upon the chemical composition of the unaged asphalt binder. Statistical analysis was conducted to rank the moisture resistance of asphalt binders and asphalt–aggregate combinations, respectively. The results showed that the pH of the water increased slightly due to contact with the aggregates, but did not significantly alter the total surface tension of the water or surface free energy components of the asphalt binder.

Surface and mechanical properties of some new biopolyurethane composites

Surface tension parameters and morphology of biopolyurethane composite surfaces based on natural polymers, before and after applying high frequency cold plasma treatment, have been evaluated. These surface tension parameters were calculated having on their basis the geometrical mean approach [Owens and Wendt, J Appl Polym Sci,13, 1741 (1969); Rabel Physicalische Blatter, 33, 151 (1977); and Kalble J. Adhesion, 1, 102 (1969)], acid/base method [Lifshitz-van der Waals, van Oss et al., Langmuir,4, 884 (1988)], and on the theoretical methods involving quantitative structure–properties relationships (Bicerano). For all the investigated films, the polar terms contribute significantly to the total surface tension as due to the large electron donor interactions. High frequency cold plasma alters the surface energy of composites by changing their surface polarity and hydrophilicity. Hydrophile/hydrophobe balance was studied by means of the free energy of hydration and interfacial tension between biomaterials and water. Mechanical properties of the polyurethane biocomposites were investigated in comparison with those of the porcine carotid arteries. POLYM. COMPOS., 31:1956–1964, 2010. © 2010 Society of Plastics Engineers.

One-loop results for kink and domain wall profiles at zero and finite temperature

Using dimensional regularization, we compute the one-loop quantum and thermal corrections to the profile of the bosonic ($1+1$)-dimensional ${\ensuremath{\varphi}}^{4}$ kink, the sine-Gordon kink, and the $C{P}^{1}$ kink, and higher-dimensional ${\ensuremath{\varphi}}^{4}$ kink domain walls. Starting from the Heisenberg field equation in the presence of the nontrivial kink background we derive analytically results for the temperature-dependent mean field which display the onset of the melting of kinks as the system is heated towards a symmetry-restoring phase transition. The result is shown to simplify significantly when expressed in terms of a self-consistently defined thermal screening mass. In the case of domain walls, we find infrared singularities in the kink profile, which corresponds to interface roughening depending on the system size. Finally we calculate the energy density profile of ${\ensuremath{\varphi}}^{4}$ kink domain walls and find that in contrast to the total surface tension the local distribution requires composite operator renormalization in $3+1$ dimensions.

Adsorption and fouling characterization of Klebsiella oxytoca to microfiltration membranes

The Klebsiella oxytoca, a dominating strain in the membrane biofouling layer of treating wastewater membrane bioreactor (MBR), was taken as a model in this manuscript. Its surface properties and interfacial energy were first explored. Then its adsorption and fouling properties on polyvinylidenefluoride (PVDF) and polypropylene (PP) membranes were characterized, respectively. With the higher total surface tension ( r T O T ) and van der waals force ( r L W ) , the K. oxytoca cell and the PVDF membrane were more hydrophilic than the PP membrane. Both membranes and K. oxytoca were proved to be typically strong electron donors. The negative total interfacial energy occurred in both K. oxytoca-membrane systems. K. oxytoca showed stronger attraction to PP membrane than to PVDF membrane within a short range. More K. oxytoca tended to be adsorbed on PP membrane than on PVDF membrane. The permeation flux decreased with increasing the pressure, and K. oxytoca showed a greater fouling potential to PP membrane.

On The Properties Of Surfactant Monolayers At Low Surface Tensions

The properties of surfactant monolayers at the air/water interface depend strongly on the monolayer surface density. As the density increases, the monolayers undergo transitions from gas to liquid and condensed phases, and transform from 2D to 3D geometry as their stability limit is reached. For a given surfactant, the higher the surface density, the smaller is the monolayer area, and lower is the resulting surface tension at the interface. We found that for selected lipid mixtures and lung surfactant extracts, the monolayer surface tension - area isotherms deviate from the expected dependence. For these mixtures, the captive bubble surfactometer measurements show that at low surface tensions (< 20 mN/m) the reduction of surface tension is accompanied by an increase rather than a decrease of monolayer area. We used a combination of experimental techniques, theoretical models and computer simulations to investigate the properties of monolayers of varying composition at low surface tensions. We hypothesize that the observed effect originates from monolayer 2D-3D transformations. Monolayer wrinkling in particular leads to a decrease of monolayer apparent area and lowers the total surface tension.

Effects of chemical structure and plasma treatment on the surface properties of polysulfones

AbstractThe correlation between surface tension parameters and the chemical composition of polysulfone, chloromethylated polysulfone and quaternized polysulfone membranes, before and after plasma treatment, was investigated. Calculations are based on the geometric mean approach of Owens, Wendt, Rabel and Kälble, as well as on the theoretical methods involving quantitative structureproperty relationships on the basis of the group contribution techniques. The chemical modifications of polysulfone membranes and the low pressure plasma treatment affect the contact angle corresponding to different liquids. Consequently, the total surface tension and the polar component increase with the substitution degree of chloromethylated polysulfone and with the quaternization degree of the ammonium groups, in quaternized polysulfone samples. The plasma treatment modifies the surface energy of the samples, increasing their surface polarity and wettability. Surface wettability trends were also studied by means of the free energy of hydration between compounds and water.