Wettability and surface free energy of bovine serum albumin films

Measurements of the contact angle for water, glycerol, formamide, ethylene glycol, and diiodomethane on polymethyl methacrylate covered by adsorptive bovine serum albumin (BSA) films were made. Adsorption was performed from solutions in the concentration range 0–100 g/L. From the obtained contact angles the Lifshitz-van der Waals components and the values of the electron-acceptor and electrondonor parameters of the acid-based components of the films were calculated for six triplets of liquids. The biggest changes in the BSA film structure occurred under a monolayer coverage (i.e., at BSA concentrations of <2.5 g/L). On the basis of the contact angles of glycerol, ethylene glycol, and formamide it was concluded that the density of BSA polar groups was almost constant. The surface density of the hydrophobic part of the BSA film also seemed constant regardless of the concentration of the solution from which the BSA adsorptive film was created. This conclusion could be drawn from the almost constant contact angle of diiodomethane.     

温度对杨木木粉表面自由能和表面极性的影响

通过毛细管上升法测定了经过不同温度处理的杨木木粉的表面接触角,依据Washburn方程和Owens-wendt-Kaelble法,求解了经过不同温度处理的杨木木粉的表面自由能及其极性分量和非极性分量。结果表明,杨木木粉的表面自由能为23.43 mN/m,体现分子色散力的非极性分量为4.64 mN/m,在处理时间为2 h的条件下,随着处理温度的上升,杨木木粉的总表面自由能略有下降,体现其分子色散力的非极性表面自由能上升,体现其表面极性值的极性表面自由能下降,并分析了上述结果的原因。     

Solid surface free energy components determination by the thin-layer wicking technique

A thin-layer wicking technique [1] and van Oss et al.'s [2] approach to interfacial free energy interactions were tested to determine the solid surface free energy components: apolar Lifshitz-van der Waals, y^l,w _y; and polar, electron donor, γ^- _y, and electron acceptor, γ⁺ _y. For this purpose, the penetration rates of n-alkanes, diiodomethane, water, formamide, toluene and chloroform were measured. For these studies, silica, used for thin-layer chromatography, and α-Al₂O₃ were used as the model solids. It was found that both are strongly polar, electron donor solids with weak electron acceptor interactions. It is concluded that van Oss, Good et al.'S [2] approach to the interfacial free energy interactions and the thin-layer wicking technique are very useful for cxplaining many interfacial phenomena taking place in the dispersed systems. However, more experimental work using different systems is needed.     

Effect of woody biomass surface free energy on the mechanical properties and interface of wood/polypropylene composites

The aim of this study is to investigate the effect of surface free energy of wood flour (WF) and silanized WF on the mechanical properties and interface of wood/polypropylene (PP) composites. The contact angles of three probe liquids against unmodified and modified spruce WF were tested by capillary rise method based on the Washburn equation. Then the surface free energy and its corresponding dispersion and polar components were calculated according to the method developed by Owens–Wendt–Kaelble. The tensile strength and flexural strength of the wood/PP composite samples made with unmodified and modified WF were tested and the flexural fracture surfaces were analyzed by scanning electron microscopy (SEM). The results showed that the surface free energy of WF increased from 26.0 to 36.1?mJ/m², which was higher than that of PP (29.4?mJ/m²), and its corresponding polar component decreased from 13.1 to 4.4?mJ/m², and the dispersion component increased from 12.9 to 31.7?mJ/m² after the modification with 4 wt.% vinyltriethoxy silane, which makes it possible for spreading of PP on the surface of WF, the tensile strength and flexural strength of wood/PP composites made with modified WF were obviously improved. In addition, the improved compatibility between WF and PP was well confirmed by SEM.     

Morphology and failure in nanocomposites. Part II: surface investigation

Polymer composites filled with calcium carbonate (CaCO₃) nanofillers (<100 nm), and kaolin filler of layered structure, both well suited to create nanocomposites, were analysed. The aim of this study was to investigate the influence of surface properties of the filler and matrix on the adhesion parameters at the interface in composites. The inverse gas chromatography, contact angle and capillary measurements were used for the surface characterization of filler and matrix. Although these methods are based on different assumptions, we found the same trends in the effects of filler surface treatment and/or matrix chemical structure on the changes in the dispersive and polar components of the surface energy. The energetics of the filler and matrix was varied in order to investigate the work of adhesion, interfacial energy and coefficient of spreading, and their influence on the composite properties. We found that the surface treatment of calcium carbonate filler lowered the filler surface energy and the work of adhesion in the composite with poly (vinyl acetate) matrix. The mechanical, thermal and morphological properties of the composite with treated CaCO₃, measured in the first part of this paper, indicated a weak and thin interphase. In the composite with kaolin filler the higher interaction with the polyacrylate copolymer matrix based on styrene as compared to the one based on methyl methacrylate, was confirmed by the higher work of adhesion in the interphase, resulting in a stronger reinforcing of the composite.     

反相气相色谱技术表征丁苯橡胶表面性质

采用反相气相色谱技术,以丁苯橡胶（SBR）作为固定相,分别测定分子探针在不同温度下通过SBR表面的保留时间,并计算出SBR表面色散自由能在303K、313K、323K、333K、343K下分别为47.50,46.58,46.03,45.49和45.23 mJ/m2,其表面色散自由能随温度的升高呈线性降低。SBR Lewis酸常数Ka为0.35,碱常数Kb为1.55,为两性弱碱性材料。     

Plasma treatment effect on the surface energy of carbon and carbon fibers

The surface energy dispersive (γ^D_S) and polar (γ^P_S) components of carbon model surfaces (bal planes, prismatic surfaces, vitreous carbon) and of carbon fibers (high strength and high modulus, respectively) were determined systematically before and after plasma treatment. The method used is essentially based on the wetting contact angle measurements within two liquids. In all cases (γ^P_S) is markedly increased by the plasma treatment. For carbon fibers, with increasing plasma treatment duration (γ^P_S) is increasing toward a limiting value (-30 mJ/m²) while (γ^D_S) is depressed toward low values (-10 mJ/m²). The parallel evolution of surface topography is followed by SEM observations. The changes in surface energy of carbon model surfaces is also discussed.     

用反气相色谱测定碳纤维表面能

详细阐述和分析了反气相色谱法的原理、仪器和测试方法。根据国内外碳纤维生产厂商应用该方法对其碳纤维表面能测试事例表明,该方法测定碳纤维表面能以及建立起来的软件处理系统,使得测定精度显著提高。指出该新测定方法值得推广应用。     

超细HMX的表面能研究

用DCAT21型表面/界面张力仪测量了原料HMX（奥克托今,45μm～62μm）、超细HMX（0.2μm～1.7μm）和黏结剂FPM2602的接触角,并计算出它们的表面能。分析了HMX随粒径变化时其表面能的变化规律和黏结剂包覆超细HMX表面能的基本要求。结果表明,细化HMX表面能随粒径的减小有增加的趋势;黏结剂的表面能低于超细HMX的表面能,理论和实验均证明黏结剂FPM2602能包覆于超细HMX的表面。     

反相气相色谱法表征稀土顺丁橡胶的表面性质

采用反相气相色谱技术分别在30℃、40℃、50℃、60℃、70℃温度下,对顺丁橡胶的表面色散自由能与表面Lewis酸碱性质进行测试。分别测得2种顺丁橡胶在给定温度下的表面色散自由能分别为47.18、46.61、46.16、45.99和45.60 mJ/m2;47.12、46.25、45.81、45.65和44.83 mJ/m2。结果表明,该聚丁二烯橡胶为Lewis弱碱性两性聚合物材料,其Lewis酸碱常数为ka=0.35;碱常数kb=1.8。     

The role of the surface free energy in the selection of a suitable excipient in the course of a wet-granulation method

Pellets containing metronidazole were produced in a centrifugal granulator, with hydroxypropylcellulose (Klucel LF®) as binding agent, and corn starch, microcrystalline cellulose (Vivapur 101®) and lactose as excipients. The wettability of the pharmaceutical powders was assessed by means of contact angle measurements, and the dispersive and polar surface energies were determined. The spreading coefficients, the work of adhesion and the work of cohesion were calculated and correlated with the pellet properties (friability, bulk and tapped density, and porosity). The aim was to investigate the role of the surface free energy of one- and two-component powder compositions in pellet production. The interactions between the particles were found to be connected with the measured pellet parameters. It was concluded that, in the course of the growth of the pellets, the particle sizes of the pharmaceutical powders and the interactions between them are important. If the work of cohesion of the binder is lower than the work of cohesion of the substrate and the work of adhesion, then the optimal amount of the binding agent is that which coats the particles uniformly in minimal quantity and in continuous layer.     

Effect of crosslinking on the surface free energy and surface reorganization of waterborne fluorinated polyurethane

To endow waterborne fluorinated polyurethanes (WFPUs), films with stable lower surface free energy and lower surface reorganization after the films contacted with water, a series of crosslinked WFPUs (CWFPUs) emulsions were prepared by adjusting the content of aziridine (AZ). The effect of crosslinking on the surface free energy, glass-transition temperature (T _g), water absorption, and surface composition of dry/hydrated WFPUs and CWFPUs films were studied by CAs test, dynamic mechanical analysis, water absorption measurements, and X-ray photoelectron spectroscopy. When the fluorine content was 0.5%, the surface free energy of the CWFPUs films modified by 0.4% AZ content (CWFPU-6-0.5-CK0.4) reached to the lowest value of 15.76 mN m⁻¹ which almost equaled to the surface free energy (15.45 mN m⁻¹) of the dry uncrosslinked films (WFPU-6-0.5). With the increasing of AZ content, the T _{g, hard} of hard segments of the CWFPUs films increased and the water absorption of the CWFPUs films decreased, which suggested the formation of the crosslinked network structures. The studies of the surface elements and groups composition of dry/hydrated WFPUs and CWFPUs both confirmed that the surface reorganization and the migration of fluorinated side chains were restricted by the crosslinked network structures. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47167.     

Performance of sea water dilution on the surface free energies of the crude oils in water-flooded carbonate rock

Although several investigations have studied the low-salinity water injection (LSWI) performance during the past decades, the effect of crude oil type on the interfacial tension (IFT) and wettability alteration is still in dark. In this regard, this study is aimed to obtain the thermodynamic energies including adhesion, cohesion and spreading coefficient during LSWI. To achieve this goal, IFT and static contact angle values of three different crude oils (i.e. light, medium and heavy) are measured as a function of sea water salinity. The obtained results revealed that the dilution of sea water can change the wettability of reservoir rock from oil wet state towards water wet state, while crude oil type implies no significant effect on the wettability alteration. Besides, the results illustrated that although the dilution of sea water unfavorably changed the IFT of light and heavy crude oils, it could favorably change the spreading coefficient.     

反相气相色谱法表征HDPE的表面性质

采用反相气相色谱技术,分别测定不同分子探针在不同温度下通过高密度聚乙烯(H DPE)的保留时间,计算HDPE表面色散自由能与表面Lewis酸碱常数.HDPE表面色散自由能随温度的升高呈线性降低,且为弱碱性的Lewis两性聚合物材料.     

Studies on the surface free energy and surface structure of PTFE film treated with low temperature plasma

The surface free energy and surface structure of poly(tetrafluoroethylene) (PTFE) film treated with low temperature plasma in O₂, Ar, He, H₂, NH₃, and CH₄ gases are studied. The contact angles of the samples were measured, and the critical surface tension γ_c (Zisman) and γ_c (max) were determined on the basis of the Zisman's plots. Furthermore, the values of nonpolar dispersion force γ^a_s, dipole force γ^b_s, and hydrogen bonding force γ^c_s to the surface tensions for the plasma-treated samples were evaluated by the extended Fowkes equation. Mainly because of the contribution of polar force, the surface free energy and surface wettability of PTFE film which was treated with H₂, He, NH₃, Ar, and CH₄ for a short time increased greatly. Electron spectroscopy for chemical analysis (ESCA) shows that the reason was the decrease of fluorine and the increase of oxygen or nitrogen polar functional group on the surface of PTFE. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1733–1739, 1997     

Effect of pigmentation on the surface chemistry and surface free energy of paper coating binders

The effect of the addition of clay and TiO₂ pigments on the surface energy and surface chemistry of films made from polymers used in paper coating formulations was evaluated. The polymers were carboxymethyl cellulose, polyvinyl alcohol and a protein-based polymer - all water-soluble - and two styrene-butadiene latexes of different carboxylation levels. The morphology of the surfaces was characterized by SEM examination, gloss measurement and stylus profilometry. Chemical composition was determined by EDS and XPS techniques. Surface energy and its Lifshitz-van der Waals and acid-base components were obtained from contact angle measurements using the van Oss et al. approach. Even though the addition of pigment increasingly upset the planar surface of the films, their surface chemistry and surface energy were only slightly affected over the pigmentation range studied (up to 40% by volume) and were dominated by the characteristics of the binder polymer.     

Surface Tension of Molten Glass from Drop Profile. Application to the Characterization of the Interface in Glass/Polymer Blends

A modified drop shape method has been developed to allow the simple determination of the surface free energy of a mineral glass. Our approach is based on the study of the profile of a large sessile drop of glass. The drop is formed by heating a glass cylinder settled on a horizontal solid plane.

The experimental parameters, in particular the size of the glass drop, leading to the accurate characterization of the surface free energy, have been determined by using mercury as a model of a high surface free energy liquid. It has been shown that the ratio between the diameter of the drop and the capillary length, (γ/ρμ)^1/2, must be of the order of 10.

In this paper, practical details and results of measurements are presented for a series of four different glasses. A clear relationship between glass composition and surface free energy is observed. In particular, tin oxide reduces significantly the surface free energy of zinc phosphate glass. The coalescence of glass particles is probably related to glass surface and glass/polymer interfacial free energies. A discussion on how this may impact glass/polymer blend processability is presented.     

Surface energy mapping of Kevlar® fibers by inverse gas chromatography

The surface energy characteristics of three Kevlar® fibers have been systematically studied using two inverse gas chromatography (IGC) techniques, i.e., at an infinite probe dilution and at a finite probe concentration, with the latter allowing a unique mapping of the surface energy levels, which complements greatly the more traditional characterization of the highest energy sites. The standard thermodynamic parameters, such as the free energy −Δ , and the adsorption enthalpy and entropy (Δ and −Δ ), as well as the dispersive and the specific component ( and ΔG^sp/I^sp) of the fiber surface energy, were determined from the retention behavior at zero coverage of selected molecules of various polarity. The values are between 49–58 mJ m⁻² for the three fibers at 50°C. The polar components, ΔG^sp or I^sp, calculated by three different methods, reveal the polar feature of the fiber surface. It is interesting to note that the adsorption enthalpies Δ for the short chain alkane probes are nearly the same as their liquefaction energies. Using the second IGC approach, i.e., at finite concentration, the isotherms for the adsorption of n-octane and n-hexylamine on the three selected Kevlar® fibers were constructed by the one-peak method. These are shown to be instrumental to establish the corresponding energy distribution functions. The results may indicate that, unlike the alkane probes, the polar molecules interact strongly with the Kevlar® fiber surfaces, which appear, in this case, energetically heterogeneous. The resulting energy distribution mapping opens new avenues towards the surface characterization of the global surface without the restriction of the averaging imposed by other bulk analysis techniques. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 487–500, 1998     

Effect of electron beam irradiation and vinyl acetate content on the physicochemical properties of LDPE/EVA blends

The radiation‐induced crosslinking, compatibility, and surface modification of low density polyethylene/ethylene vinyl acetate blends (LDPE/EVA) were investigated. The structural and physical properties were characterized in terms of gel content, hot set, mechanical properties, contact angle, and surface free energy. The highest crosslink density was obtained at 20 wt % of EVA. Gel content of LDPE/EVA blends was increased with increasing irradiation dose, vinyl acetate (VA), and EVA contents. The hot set results are consistent with the gel content data. Mechanical testing showed that the tensile strength of samples increased with increasing irradiation dose up to 180 kGy, whereas the elongation at break was decreased with increasing irradiation dose. Contact angle measurements showed that the surface hydrophillicity of LDPE blend was increased with increasing irradiation dose and contents of both VA and EVA. The surface free energy was greatly dependent on irradiation dose and content of both VA and EVA. The total surface free energies of different LDPE formulations were in the range 17.25–32.51 mN/m, in which the polar (^pσ) and disperse (^dσ_s) values were within the range 16.52–26.6 and 0.9–5.91 mN/m, respectively. In conclusion, electron beam irradiation and blending LDPE with EVA improved the wettability or adhesion properties of LDPE/EVA blends. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Adhesion interaction in water/n-alcohol mixtures between silanized silica and polymer particles

The adhesion of polyethylene and nylon particles to silanized silica plates was investigated in water/n-alcohol (methanol, ethanol, 1-propanol, and 1-butanol) mixtures. Silica plates were treated with γ-aminopropyltriethoxysilane, methyltriethoxysilane, and perfluoroethyltrimethoxysilane. The number of particles adhering to the plate at 60 min as an apparent equilibrium adhesion value increased as a result of the silanization of silica and decreased with increasing volume ratio of n-alcohol in the water/n-alcohol mixtures. The acid-base components of the surface free energies of the substrates and liquids were decreased by the silanization of silica and by the addition of cthanol to water. The apparent equilibrium particle adhesion is discussed in terms of the total potential energies of interaction which were calculated as the sum of the electrical double layer, Lifshitz-van der Waals, and acid-base interactions, using the electrokinetic potentials and the surface free energy components. In addition, the relationship between the extent of particle adhesion and the work of adhesion was investigated. The particle adhesion in the present systems was found to be dominated by the acid-base interaction between the particle and the substrate.