Polar Component Of Surface Tension Research Articles

Statistical evaluation of the changes in cellulose properties caused by the stepwise solvent exchange and esterification

The objective of the research was to empirically confirm the changes in cellulose reactivity caused by the pre-treatment with solvents of different polarity. Therefore, 5 solvents varying in their polar component of surface tension from 0 to 4.6 mN/m were chosen. Their impact on the biopolymer properties was carefully analysed concerning chemical structure, crystallinity and surface characteristics. It was revealed that the length of 6OH⋯O3′ intermolecular H-bonds increased upon each solvent-exchange from (0.2748 ± 0.0001) nm to approx. 0.2760 nm for non-polar solvents, hence, potentially affecting cellulose structure and availability of active centres capable of reaction. As a consequence of structural variations, dioxane- and toluene-exchanged cellulose exhibited, respectively, the lowest (around 0.6 mJ/m2) and the highest (approx. 3.1 mJ/m2) polar component of surface free energy. Therefore, these samples were esterified. Further investigation successfully confirmed expected differences. Toluene-exchanged sample exhibited degree of substitution oscillating around 20%, while dioxane-exchanged specimen – approx. 7%.

Langmuir-Blodgett deposition and physicochemical surface characterization of two-dimensional perovskite nanosheets on ITO-PET substrates

We successfully obtained Ca2NaNb4O13− single perovskite nanosheets by delaminating x = 4 Dion-Jacobson type KCa2NaNb4O13 layered materials. These nanosheets were then deposited onto conductive, transparent, and flexible indium tin oxide-polyethylene terephthalate (ITO-PET) substrates using the Langmuir-Blodgett (LB) technique. The polar and apolar (dispersive) surface tension components of LB nanofilms composed of Ca2NaNb4O13− perovskite nanosheets and the work of adhesion between the nanofilms and silicon and ITO-PET substrates were determined through contact angle measurements combined with mathematical modeling based on surface thermodynamics. The results showed that the apolar surface tension components had similar values for all surfaces studied, while the polar surface tension components of the nanofilms deposited on the substrates had higher values than those of the bare substrates. The higher polar interaction observed between the nanofilm and ITO-PET resulted in higher total work of adhesion of the nanofilm to the ITO-PET surface in water, while the total work of adhesion computed between the nanofilm and Si was higher in air.

Liquid partial surface tensions obtained by an adapted Good-Girifalco approach from interfacial tensions and DiPEVa solubility parameters

This publication highlights the achievement of partial surface tension properties of liquids using an adapted Good-Girifalco approach from interfacial tensions and DiPEVa solubility parameters. The proposed method is simple to apply, and different databases of interfacial tension of water and one of squalene were compared. The water interfacial tension data was appropriate for estimating the dispersive component of the surface tension. In contrast, the squalene interfacial tension is more accurate for calculating the polar component of surface tension because of the miscibility behavior of the liquids. The approach strengthens the relationship between solubility parameters and the surface tension parameter. Due to the enormous importance of 3DSP, especially HSP, for the current technological field, the extension of its physicochemical background to the surface tension parameter is of paramount importance for the area of ​​Materials Science. Thus, the data presented here are especially relevant for applications dependent on surface and interfacial phenomena or dielectric constant related to 3DSP.

Surface modification of sized vegetal fibers through direct fluorination for eco-composites

Natural fibers are frequently used as alternatives of glass fibers as polymer matrix reinforcement to form composite materials. However, their natural hydrophilicity prevents them from being easily compatible with hydrophobic polymers, which represent the majority of matrices. To solve this, direct fluorination of sized natural fibers (flax fibers sized with DGEBA) was performed. EDX, FTIR and 19F NMR analysis evidenced the chemical grafting of fluorine on DGEBA structure and the ablation of the oxiranes rings on this molecule. Chemical modifications of DGEBA have induced a hydrophobic character of this layer, by reducing at 0 the polar component of surface tension. Thereby, treated fibers are supposed to be perfectly chemically compatible with the hydrophobic polymer matrices (e.g. polypropylene). Additionally, the fluorination time also allows the dispersive component of surface tension and the rugosity of fibers to be tailored in order to perfectly adjust these characteristics and fit with the polymer. Moreover, this chemical modification was achieved without altering the mechanical properties of fibers for short fluorination times.

Stochastic transient Liquid-Solid Phase Separation reveals multi-level Dispersion States of Particles in Suspension

Abstract Wall slip or, more usually, liquid-solid phase separation at the boundary wall when measuring the rheological properties of particulate suspensions is normally considered an undesirable source of error. However, exclusion of a structure consisting of multiple particulates at a planar boundary can, in turn, reveal the nature of that structure and the way it interacts with other elements in the dispersion. Using a system of surface-treated ground calcite particles, designed to control lyophilicity, dispersed, respectively, in two comparative liquids, hexadecane (dispersive surface tension component only) and linseed oil (both dispersive and polar surface tension components), the relative wettability of the particulate surface can be studied. The static state is viscoelastic, with the elastic component reflecting the network of interacting forces acting to structure the particles together and/or to trap liquid within the long-range particle-particle matrix. As strain is applied under plate-plate geometry, selected aggregate structures become size-excluded at the wall, leading to a loss of shear coupling with the bulk polydisperse suspension. At high strain, given optimal solids content, this results in a stochastic transition between two discrete stress data sets, i.e. that with full shear coupling and that with only partial coupling. Stress recovery is subsequently monitored as strain is step-wise reduced, and the progress toward loss of the stochastic transient phenomenon, together with its parallel change in magnitude, is used to describe the re-formation of primary agglomerates. Cessation of the phase separation indicates re-build of the close-to-static structure. Under certain conditions it is observed that the cessation may be accompanied by a secondary relaxation of state, indicating the build of a secondary but weaker structure, likened to the well-known dual-level flocculation in aqueous colloidal suspension. Rheo-optical observations using small angle light scattering illumination (SALS) are used to confirm a structure model switching from static (uncoupled with shear) to rotating (fully coupled to the boundary-defined shear) and finally uniformly sheared.

Surface tension determination in glyoxal-silica dispersed system

Preliminary studies have shown the possibility of using glyoxal-silica dispersed system for soil stabilization in groundwork base and utility systems. However, the problem associated with optimizing the composition can be solved by measuring energy characteristics. Since the interaction in glyoxal-silica system takes place at the interphase the surface tension was chosen as an energy parameter. The aim of research was to compare calculated by Zisman’s and Owens-Wendt-Rabel-Kaelble (OWRK) methods surface tension values of glyoxal-silica composition. Polymineral sand was used as the silica model. The surface tension value calculated by Zisman's method is σc=27.47 mN/m. According to the OWRK method, the polar component of surface tension for test material is σSP=12.61 mN/m, dispersion component is σSD=13.50 mN/m, and the total value of surface tension is σS=26.11 mN/m. Comparison of surface tension values calculated by different methods has shown good repeatability. However, the OWRK method provides a more detailed overview of interaction in the glyoxal-silica system and makes it possible to estimate the contribution of polar and dispersion components to the total value of a surface energy characteristic. Therefore, the OWRK method can be recommended for characterizing the structure formation process when optimizing the organomineral compound composition.

Flexible, Durable, and Unconditioned Superoleophobic/Superhydrophilic Surfaces for Controllable Transport and Oil–Water Separation

AbstractSuperoleophobic/superhydrophilic surfaces have incomparable advantages for oil–water separation and oil droplet manipulation; however, such surfaces are difficult to obtain on the basis of surface tension theory, and existing attempts are either not fully functional or are nondurable. Here, a solution to achieve the combination of superoleophobicity and superhydrophilicity by emphasizing the polar component of surface tension is proposed. The developed surfaces can be flexibly applied to almost any solid substrate and exhibit superoleophobic and instantaneous superhydrophilic property. The surfaces applied to certain substrates can be used for controllable oil transport, oil–water separation, and emulsion demulsification. Furthermore, a novel ferroconcrete‐like structure to substantially increase the durability of the developed surfaces without affecting the superwettability is developed. The coated steel meshes preserve the ability of the material to separate oil–water mixtures even after over 400 m abrasion, which can be a significant step toward its widespread application.

Plasma effect on polyhydrosilane/metal interfacial adhesion/cohesion interactions

Interactions between a polyhydrosilane film and some metals – gold, silver, aluminum – were theoretically estimated from the work of spreading. This parameter was calculated from disperse and polar components of surface tension corresponding to the polymer and metal. The polyhydrosilane surface properties were experimentally determined from contact angle measurements introduced in the Fowkes relation. To enhance the polymer/metal compatibility, nitrogen plasma exposure was applied, revealing that after this treatment the cohesion interactions are lower than the adhesion ones. An increase in surface polarity was reflected in a higher work of adhesion between metal and polymer substrates, particularly with gold. To confirm the theoretical results regarding the adhesion properties, an atomic force microscopy experimental method was applied in order to determine the adhesion between a gold covered tip and a polyhydrosilane film surface. These results are essential for optimizing polymer surface features for designing reliable electronic components.

Tensiometric method to reliably assess wetting properties of single fibers with resins: Validation on cellulosic reinforcements for composites

Wetting properties and capillary parameters are of first interest for composite and especially bio-composite manufacturing, interface compatibility between reinforcement and matrix, and durability. Few studies have been dedicated in literature to continuous textile fibers and uncured liquid resins wetting properties, and particularly the methods used may be ambiguous, revealing a wide dispersion in results. In this work a reliable method is proposed to determine properly the wetting properties of fibers and some resins commonly used for composite applications. Firstly, a procedure to characterize dispersive and polar components of surface tension for an epoxy and a partially bio-based resin with a tensiometer is proposed. Then a new method was applied on single fibers of semi-synthetic cellulose (viscose), which allows deriving representative values of contact angles from a series of measurements, minimizing the measurement scatter even when using a conventional tensiometer. Resin components and contact angles between cellulose fibers and test liquids, including resins, led to characterize dispersive and polar components of fiber surface energy.

Mechanism analysis of membrane fouling behavior by humic acid using atomic force microscopy: Effect of solution pH and hydrophilicity of PVDF ultrafiltration membrane interface

The adhesion forces of membrane–humic acid (membrane–HA) and HA–HA were measured by atomic force microscopy (AFM) in conjunction with self-made modified membrane-coated and HA-coated probes, respectively. Normalized flux decline rate and the irreversible fouling index of fouling experiments with HA kept good linear correlations with the AFM force measurements. The extended Derjaguin–Landau–Verwey–Overbeek (XDLVO) theory was used to explain the influence and regularity of HA solution pH and hydrophilicity of polyvinylidene fluoride (PVDF) ultrafiltration (UF) membrane interface on membrane fouling behavior. The results of AFM force measurements illustrated that the adhesion force in acidic environment was much stronger than that in alkaline or neutral environment and the adhesion force of PVDF/polyvinylalcohol membrane–HA (PA–HA) was weaker than that of PVDF/polyvinylpyrrolidone membrane–HA (PP–HA). XDLVO theoretical calculated results demonstrated that the polar component of surface tension (γAB) of membrane–foulant could be effectively increased by improving the hydrophilicity of the PVDF UF membrane interface and reducing the solution acidity, which resulted in the decrease of absolute values of the membrane–HA interfacial free energy of adhesion (ΔGmlfAD), the mitigation of the membrane fouling rate and the irreversible fouling degree. The results preliminarily proved that the measurements of microscopic interfacial forces with modified AFM colloidal probes had potential application values in UF membrane fouling behavior.

Biocidal activity of cellulose materials for medical implants

ABSTRACTSurface wettability trends, and blood component adhesion of some cellulose acetate phthalate/hydroxypropyl cellulose blend films are analyzed in view of adapting the system to biomedical applications. The results show that intermediate blend compositions of the corresponding films influence the surface tension parameters—controlled by the interactions occurring in the system. Increasing hydrophobicity and, implicitly, decreasing the polar surface tension components, are correlated with the adhesion/cohesion of blood components and plasma proteins. Thus, the work of spreading proteins on the hydrophobic blend surfaces indicated that albumin is not absorbed preferentially, while fibrinogen is characterized by a higher degree of adhesion on the surfaces, and also that selective adsorption of plasma proteins modifies blood compatibility. In addition, the obtained results and the ascertained antimicrobial activity of the studied blends contribute to the development of new applications in the biomedical field. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41932

O2플라즈마 처리에 따른 필름기질의 친수 및 소수화 상반효과

We studied the effects of <TEX>$O_2$</TEX> plasma on the hydrophilic/hydrophobic contrast of film substrates. PET (polyethylene terephthalate) and FEP (fluorinated ethylene propylene) films were treated by <TEX>$O_2$</TEX> plasma, and the surface of the films was investigated using atomic force microscopy(AFM), X-ray photoelectron spectroscopy (XPS), and contact-angle and surface energy measurements. Surface energies were calculated from the measured contact angles between several solutions and the films based on the geometric mean and Lewis acid-base method. The contact angle of PET films treated by <TEX>$O_2$</TEX> plasma decreased with increasing treatment time in water and surfactant solution, and surface energy increased with increasing polar component of surface tension of the film. In contrast, the contact angle of the <TEX>$O_2$</TEX> plasma-treated FEP film decreased, and surface energy decreased with decreasing nonpolar component of surface tension of the film.

The effect of oxidation treatment by KClO3/H2SO4 system on intersurface performance of carbon fibers

The polyacrylonitrile-based (PAN-based) carbon fibers with progressive amounts of the oxidation treatment have been investigated using a number of surface analytical methods. The chemical content and structure of oxidated fibers have been interrogated by X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM), then compared to the untreated ones. The value of oxygen content increased from 4.71% to 18.84%, meanwhile, the grooves on the surfaces of the carbon fibers were deepened gradually after treatments. The results of dynamic contact angle (DCA) measurements suggest that the increase in carbon fiber surface tension is mainly because of the polar component of surface tension. After treated with increasing amounts of oxidants, the monofilament tensile strength decreased less than 3.1%.

Effect of surface tension and coefficient of thermal expansion in 30 nm scale nanoimprinting with two flexible polymer molds

We report on nanoimprinting of polymer thin films at 30 nm scale resolution using two types of ultraviolet (UV)-curable, flexible polymer molds: perfluoropolyether (PFPE) and polyurethane acrylate (PUA). It was found that the quality of nanopatterning at the 30 nm scale is largely determined by the combined effects of surface tension and the coefficient of thermal expansion of the polymer mold. In particular, the polar component of surface tension may play a critical role in clean release of the mold, as evidenced by much reduced delamination or broken structures for the less polarized PFPE mold when patterning a relatively hydrophilic PMMA film. In contrast, such problems were not notably observed with a relatively hydrophobic PS film for both polymer molds. In addition, the demolding characteristic was also influenced by the coefficient of thermal expansion so that no delamination or uniformity problems were observed when patterning a UV-curable polymer film at room temperature. These results suggest that a proper polymeric mold material needs to be chosen for patterning polymer films under different surface properties and processing conditions, providing insights into how a clean demolding characteristic can be obtained at 30 nm scale nanopatterning.

Plasma polymerized thiophene: molecular structure and electrical properties

Polythiophene (PTh) is of interest for transistors, light emitting diodes and sensors. Plasma polymerization is a solvent-free, room temperature process that can be used to rapidly deposit thin polymer films onto a wide variety of substrates. This paper describes the synthesis of plasma polymerized thiophene (PPTh) and the dependence of molecular structure and properties on the polymerization conditions. Transparent plasma polymerized thiophene films, deposited at about 50 nm min −1, had a density of about 1.75 g cc −1, depending on the carrier gas used (if any) and on the plasma power. The molecular structure consisted of opened thiophene rings and included significant amounts of unsaturation, oxygen and nitrogen. When nitrogen was used as a carrier gas at a low power or when a high power was used (with no carrier gas), there was significantly more oxygen, nitrogen, and sulfur–oxygen bonds. When a high power was used, the films exhibited a higher polar component of surface tension and a higher internal stress. The undoped films exhibited non-linear current–voltage (IV) behavior typical of Schottky metal-semiconductor barriers with breakdown at reverse bias. Iodine doping yielded ohmic IV behavior, perhaps reflecting the formation of a conducting iodine percolation network.

Baseline Studies of the Clay Minerals Society Source Clays: Colloid and Surface Phenomena

The interface between the surfaces of clay minerals and other materials (aqueous solution, organic moieties, biomolecules, etc.) is of great importance to many geological, technological and biological processes. The examination of the structure and composition of mineral surfaces is advancing rapidly. However, the crystal structure of a mineral is only part of the information needed to understand the activity of the surface; we still do not fully understand the chemical and physical interactions at the surface or interface. One very powerful methodology for the study of surfaces and interfacial interactions is the determination of the thermodynamic properties of the surface. It became possible in the late 1980s to determine quantitatively the apolar and polar surface-tension components and parameters of liquids and solids (van Oss et al., 1988; van Oss, 1994), and the experimental techniques necessary for obtaining surface free-energy components of minerals, and particularly of colloid-sized minerals, are also a recent development (Costanzo eta!., 1990; van Oss et al., 1990, 1992; Giese et al., 1991).

Surface Free Energy, Adsorption and Zeta Potential in Leacril/Tannic Acid System

Surface free energy components, apolar Lifshitz−van der Waals, γsLW, and polar electron acceptor, γs+, and electron donor, γs-, were determined for leacril (a copolymer of 90% acrylonitryle and 9% vinyl acetate) fibers with preadsorbed tannic acid solutions (10-5−10-2 M). A thin layer wicking method was applied for this purpose. The components were calculated considering van Oss et al.'s (J. Chem. Rev. 1988, 88, 927) polar components of surface tension of probe liquids (formamide and water, γw- = γw+ = 25.5 mJ/m2 for water) as well as those suggested very recently by Lee (Langmuir 1996, 12, 1681), who considered for water γw- = 19 mJ/m2 and γw+ = 34.2 mJ/m2. The trend of changes of the calculated components is the same, except for the surface treated with 10-2 M tannic acid. However, the electron donor components of the leacril calculated with Lee's data are somewhat lower. From the calculated work of spreading of water, results indicate that the bare leacril surface is slightly hydrophobic, the surface treated with 10-5 M tannic acid becomes low hydrophilic, and in the range of concentrations 10-4−10-3 M becomes increasingly hydrophobic. When equilibrated with 10-2 M it is again hydrophilic. The changes can be explained by reorientation of the tannic acid molecules on the leacril surface and micelle formation above cmc, which was determined to be at ca. 3 × 10-4 M. Adsorption measurements show that the process is very fast and physical in nature. The rate constants and empirical diffusion coefficients were evaluated at 275, 283, 293, and 303 K. Also thermodynamic functions for the adsorption process were calculated from the adsorption isotherms. It was concluded that hydrogen bonding and Lifshitz−van der Waals interactions are responsible for the adsorption, while electrostatic interactions play a rather second-order role. The leacril shows small negative zeta potentials which drop almost to zero at concentrations higher than 10-4 M.

Adhesion of edible oils to food contact surfaces

AbstractAdhesion of oils and fatty food products to packages is an important storage problem, because it increases product‐package interactions that alter quality. Reducing such adhesion would also allow savings in recycling and cleaning processes. The aim of our work was to test if some thermodynamical adhesion models were correlated to edible oils’ bulk adhesion as measured experimentally. Food‐contact surfaces were low‐density polyethylene, polyethylene teraphthalate, stainless steel, and glass. The Young‐Dupré equation and five models of adhesion from the literature were used to calculate solids’ surface tension and the thermodynamical work of adhesion (Wa). The dispersive, polar, acid‐base, and hydrogen surface tension components of oils and solids were calculated. The experimental adhesion, or amount of edible oils remaining on solid surfaces after contact, was found to be correlated to Young‐Dupré Wa, involving contact angle measured by specially designed image analysis technique. Two models, involving, respectively, surface tension’s hydrogen component and a linear dependence of Wap on the liquid polar surface tension component, fitted best with oil bulk adhesion as measured experimentally. Our theoretical approach to fatty food material adhesion seems, so far, consistent to predict global residues of edible oils on solid surfaces.

Organic-inorganic character of plasma-polymerized hexamethyldisiloxane

Plasma polymerization is a useful method for depositing thin films on substrates. The films formed are cross-linked, and their character depends on the plasma polymerization process conditions. The influence of power and monomer flow rate on the character of plasma-polymerized hexamethyldisiloxane (PPHMDSO) was investigated. The deposition rate increased strongly with HMDSO flow rate at low powers, indicating that the plasma is mono-mer-deficient. Increasing the power yielded a rapid drop in deposition rate, which reached a relatively flow rate-independent plateau at high power. At high flow rates and low powers, the similarity between the plasma polymer with its high hydrocarbon concentration and the monomer was greatest. At high powers, the monomer was more intensively fragmented yielding a more inorganic structure rich in silicon and oxygen. Generally, the plasma polymer seems to be a silicon-oxygen network with short hydrocarbon chains that may include hydroxyl and/or carbonyl groups attached to the silicon in the backbone. The inorganic nature of the plasma polymer at high powers and low flow rates is reflected in its relatively high polar component of surface tension. © 1996 John Wiley & Sons, Inc.

Plasma copolymerization: Hexafluoropropylene and a nonpolymerizable gas

Plasma polymerized (PP) fluoropolymer films have been synthesized by the plasma copolymerization of hexafluoropropylene (HFP) and a nonpolymerizable gas. Plasma etching was inhibited by fluorine scavenging and HF formation on the addition of hydrogen and was accelerated on the addition of oxygen. Nitrogen, oxygen, and hydrogen were incorporated into the deposited polymer molecules when added to the HFP plasma. The polar component of surface tension increased on nitrogen addition and the dispersive component on hydrogen addition. The higher surface tension drove the deposition and coalescence of smaller particles from the gas phase polymerization yielding smooth surfaces. The significant drop in breakdown voltage on the addition of nitrogen was attributed to a different conduction mechanism in the relatively polar PP fluoropolymer film. © 1996 John Wiley & Sons, Inc.