羟基和酯基型Gemini双季铵盐表面活性剂在煤沥青表面的润湿特性

以自制的羟基和酯基型Gemini双季铵盐表面活性剂为研究对象,在考察其表面活性的基础上,进一步研究了表面活性剂在煤沥青表面的润湿性。研究表明,羟基型Gemini表面活性剂在煤沥青表面的接触角随疏水链长度的增长呈先减小后增大趋势,其中C₁₂-OH在煤沥青表面的润湿效果最好;对于m-n-m酯基型Gemini表面活性剂而言,接触角随疏水链长度的增长而降低。当疏水链长度一定时,m-6-m在煤沥青表面的润湿效果比m-2-m好。在一定浓度范围内,C₁₀-OH、C₁₂-OH和12-2-123种Gemini表面活性剂的表面张力与其在煤沥青表面黏附张力呈线性关系。煤沥青表面的Zeta电位随Gemini表面活性剂浓度的增大呈先增大后趋于平稳的趋势。     

ADSORPTION AND WETTING PROPERTIES OF PLURONIC BLOCK COPOLYMERS ON HYDROPHOBIC SURFACES STUDIED BY OPTICAL WAVEGUIDE LIGHTMODE SPECTROSCOPY AND DYNAMIC TENSIOMETRIC METHOD

Adsorption of four different poly(ethylene oxide)/poly(propylene oxide)/poly(ethylene oxide) triblock copolymers (Pluronics®) onto the hydrophobized surface of the sensor was measured by the optical waveguide lightmode spectroscopy (OWLS). Adsorbed amounts of Pluronic PE10300, PE10500, PE6400, and PE6800 determined in the concentration range of 10^?2?10?gdm^?3 were found to follow the order of the hydrophobicity of the Pluronic compounds characterized by their hydrophil–lipophil balance (HLB) values. Wettability of two hydrophobic surfaces, the poly(lactide-co-glycolide), PLGA70/30 copolymer (used as drug carrier in pharmaceutical applications) and silylated glass, in aqueous solutions of the above Pluronics were studied by a dynamic tensiometric method. The significant increase in the wetting tension observed after the adsorption of the surfactants, and hence the decrease of the apparent contact angle as the indication of the wetting effect on both the biopolymer and the hydrophobic glass, was correlated to the poly(ethylene oxide) (PEO) content of the adsorbed layer obtained on the hydrophobized sensor surface by the OWLS method.     

THE EFFECT OF SUBSTRATE GEOMETRY ON DYNAMIC CONTACT ANGLES IN SURFACE WETTING

Dynamic contact angles play a central role in the problem of wetting of surfaces. A solid surface is moving steadily through the free surface of a liquid. The angle between the plunging solid surface and the liquid free surface at the line of solid-liquid contact is the dynamic contact angle. This work compares experimentally measured dynamic contact angles of horizontally rotating rolls of different diameters with those of circular fibers, and tapes. The comparison also includes dry and pre-wet surfaces. Dynamic contact angles depend on the geometry of the wetted substrate. Specifically the geometry through its curvatures affects the surface tension forces at the contact line. Smaller diameter rolls generate smaller angles. In wetting of circular fibers the angles are the smallest compared to tapes and rolls. Flat dry tapes form the largest angles when they are wetted. This implies that the curvatures of the circular rolls and fibers contribute to the balance of surface energies at the contact line. Pre-wet surfaces generate considerably smaller angles at the same wetting speeds. In contrast with that, the diameter of rolls does not affect the critical speed of air entrainment.     

Contact angle of surfactant solutions on precipitated surfactant surfaces. III. Effects of subsaturated anionic and nonionic surfactants and NaCl

The contact angles of saturated calcium dodecanoate (CaC₁₂) solutions containing a second subsaturated surfactant on a precipitated CaC₁₂ surface were measured by using the drop shape analysis technique. The subsaturated surfactants used were anionic sodium dodecylsulfate (NaDS), anionic sodium octanoate (NaC₈), and nonionic nonylphenol polyethoxylate (NPE). Comparing at the critical micelle concentration (CMC) for each surfactant, NaC₈ was the best wetting agent, followed by NaDS, with NPE as the poorest wetter (contact angles of 32⁰, 42⁰, and 62⁰, respectively). Surface tension at the CMC increased in the order NaC₈<NPE<NaDS, and subsaturated surfactant adsorption increased in the order NPE≪NaDS (1.4 vs. 84 μmole/g); adsorption of the NaC₈ was not measurable. Interfacial tension (IFT) reduction at the solid-liquid interface due to subsaturated surfactant adsorption is an important contribution to contact angle reduction, in addition to surface tension reduction at the air-water interface. Surfactant adsorption onto the soap scum solid is crucial to solid-liquid IFT reduction and to good wetting. The fatty acid was the best wetting agent of the three surfactants studied, probably because calcium bridging with the carboxylate group synergizes surfactant adsorption onto the solid of the higher molecular weight soap. NaCl added to NaDS surfactant results in depressed CMC, lower surface tension at the CMC, decreased NaDS adsorption onto the solid, and decreased reduction in solid-liquid IFT. The contact angle is not dependent on the NaCl concentration for NaDS. The NaCl causes an increased tendency to form monolayers, which decrease air-water surface tension, but a decreased tendency to form adsorbed aggregates on the solid; the two trends offset each other, so wettability is not affected by added salt. The Zisman equation does not describe the wetting data for these systems well except for NaDS, further emphasizing the danger of ignoring solid-liquid IFT reduction in interpreting wetting data in these systems.     

固体表面温度对冻结液滴的相变过程与表面润湿特性的影响

通过液滴可视化实验,发现并归纳了冻结液滴在不同基底温度下于铝板表面融化过程的动态表面润湿特性,结合力学分析,总结了液滴润湿面积、体积、接触角等润湿参数与相变时间之间的变化规律。实验结果表明：液滴的润湿性主要受重力、表面张力、热毛细力的影响,重力对液滴的横向扩散促进作用、表面张力与热毛细力受底板温度影响具有抑制液滴润湿过程的作用;两种不同条件下,冻结液滴高度变化规律相同,随着融化的进行,液滴高度骤降,然后缓慢降低;不同冻结条件下,冻结液滴的润湿过程主要发生在融化初始阶段,重力促进液滴的润湿过程,液滴接触角处于65°～85°之间,而在润湿后阶段,接触角减小,重力的作用减弱,表面张力的作用增强,液滴的扩散进程受阻,体积下降的趋势也变缓;不同升温条件下,冻结液滴的润湿过程几乎没有发生,热毛细力与表面张力在润湿过程中占据主导性,随着基底温度的升高,液滴内部与三相线温差逐渐增大,Ma数呈增加的趋势,数值由1802增至22876,热毛细力始终抑制液滴的运动。     

Wettability of polytetrafluoroethylene and polymethyl methacrylate by aqueous solutions of TX-100 and TX-165 mixture with propanol

The measurements of the contact angle of the aqueous solutions of TX-100 and TX-165 mixture with propanol on polytetrafluoroethylene (PTFE) and polymethyl methacrylate (PMMA) were carried out. On the basis of the obtained results, the dependence between the cosine of contact angle and surface tension as well as between the adhesion and surface tension of the solutions in the light of the work of adhesion of the solutions to the PTFE and PMMA surface was discussed. The dependence between the adhesion and surface tension for PMMA was correlated to the surface concentration of propanol as well as TX-100 and TX-165 mixture concentration determined from the Frumkin equation at the PMMA-air, PMMA-solution and solution–air interfaces. For this purpose, the surface tension of PMMA covered by a surface active agent film was determined using the Neumann et al. equation and next the PMMA–solution interface tension was evaluated from the Young equation. The values of the surface tension of PMMA covered by propanol and surfactants mixture layer were applied to describe the changes of the adhesion work of solutions to PMMA surface as a function of propanol and surfactants mixture concentration. The adhesion work of the aqueous solutions of TX-100 and TX-165 mixture with propanol to the PTFE and PMMA surfaces was discussed in the light of the adhesion work of particular components of the solutions. On the basis of the results obtained from the contact angle measurements, the standard Gibbs free energy of adsorption of particular components of solution was also considered.     

ADSORPTION AND WETTING PROPERTIES OF PLURONIC BLOCK COPOLYMERS ON HYDROPHOBIC SURFACES STUDIED BY OPTICAL WAVEGUIDE LIGHTMODE SPECTROSCOPY AND DYNAMIC TENSIOMETRIC METHOD

Adsorption of four different poly(ethylene oxide)/poly(propylene oxide)/poly(ethylene oxide) triblock copolymers (Pluronics®) onto the hydrophobized surface of the sensor was measured by the optical waveguide lightmode spectroscopy (OWLS). Adsorbed amounts of Pluronic PE10300, PE10500, PE6400, and PE6800 determined in the concentration range of 10^-2-10 gdm^-3 were found to follow the order of the hydrophobicity of the Pluronic compounds characterized by their hydrophil-lipophil balance (HLB) values. Wettability of two hydrophobic surfaces, the poly(lactide-co-glycolide), PLGA70/30 copolymer (used as drug carrier in pharmaceutical applications) and silylated glass, in aqueous solutions of the above Pluronics were studied by a dynamic tensiometric method. The significant increase in the wetting tension observed after the adsorption of the surfactants, and hence the decrease of the apparent contact angle as the indication of the wetting effect on both the biopolymer and the hydrophobic glass, was correlated to the poly(ethylene oxide) (PEO) content of the adsorbed layer obtained on the hydrophobized sensor surface by the OWLS method.     

Effect of surfactant compounding on the wettability of talcum powder

Talcum powder is one of the leading causes of pneumoconiosis, adding compound surfactants to the dust removal process can significantly increase the effectiveness of the dust removal. Therefore, it is of great significance to study the effect of compound surfactants on the wettability of talcum powder. This paper focuses on the ability of compound surfactants to increase the wettability of talcum powder surface by using Materials Studio 8.0. The simulation results were analyzed from the water adsorbed amount, interaction energy, and water molecule concentration profile. Combined with the experimental data of contact angle, the optimal surfactant compounding method was obtained. The simulation results revealed that stable adsorption structures can be formed by the compound of anionic and nonionic surfactants, which can reduce the electrostatic repulsion between anionic surfactants effectively and promote the directional arrangement of nonionic surfactants on the talcum powder surface. When the molar ratio of sodium dodecyl sulfate (SDS) and Polysorbate 80 was 0.4:0.6, the amount of absorbed water reached 113, which is better than monomers and other compound surfactants. The contact angle experiment results indicated a consistent variation law with the simulation results. The contact angle decreased from 68.48° to 19.84° using the compounding method mentioned above, which has the optimum wetting effect among the four compounding methods. The research results will provide a reference for the application of compound surfactants in talcum powder dustproof work.     

Surface tension and contact angle of herbicide solutions affected by surfactants

Contact angle and surface tension were measured for distilled and hard water solutions of adjuvants, Ortho X-77, Span-20, Sterox-NJ. Surfactant-WK, Triton B-1956, Triton X-114, Tween-20, and Sun Oil 11E. The same parameters were measured for suspensions of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] and ametryne [2-(ethylamino)-4-(isopropylamino)-6-(methylthio)-s-triazine] with and without each adjuvant. All adjuvants reduced surface tension and contact angle of distilled water; Surfactant-WK was most effective and Tween-20 was least effective. Increasing concentration of surfactants from 0 to 0.1% (v/v) gave progressive reduction in surface tension and contact angle while higher concentrations, 0.1 to 2.0% (v/v), had no further effect. Surfactant-WK at 0.1% (v/v) in distilled water reduced the surfact tension from 72.8 dynes/cm to 27 dynes/cm and contact angle from 110° to 41°. An additional increase in Surfactant-WK concentration from 0.1% (v/v) to 2% (v/v) did not further reduce surface tension and contact angle. Sun Oil 11E was identical in behavior except that it was less effective than the surfactants. Water hardness up to 1,000 ppm as Ca ions did not affect surface tension and contact angle in surfactant solutions. An aqueous solution of atrazine had a higher surface tension and contact angle than ametryne in the absence of surfactants. However, these differences were not observed when surfactants were added to either herbicide.     

Numerical simulations of drop impact and spreading on horizontal and inclined surfaces

The phenomenon of drop spreading is important to several process engineering applications. In the present work, numerical simulations of the dynamics of drop impact and spreading on horizontal and inclined surfaces were carried out using the volume of fluid (VOF) method. For the horizontal surfaces, the dynamics of impact and spreading of glycerin drops on wax and glass surfaces was investigated for which the experimental measurements were available [Šikalo, Š., Tropea, C., Ganic, E.N., 2005a. Dynamic wetting angle of a spreading droplet. Experimental Thermal and Fluid Science 29, 795-802; Šikalo, Š., Tropea, C., Ganic, E.N., 2005b. Impact of droplets onto inclined surfaces. Journal of Colloid and Interface Science 286, 661-669]. The influence of surface wetting characteristics was investigated by using static contact angle (SCA) and dynamic contact angle (DCA) models. The dynamics of drop impact and spreading on inclined surfaces and the different regimes of drop impact and spreading process were also investigated. In particular, the effects of surface inclination, surface wetting characteristics, liquid properties and impact velocity on the dynamics of drop impact and spreading were investigated numerically and the results were verified experimentally. It was found that the SCA model can predict the drop impact and spreading behavior in quantitative agreement with the experiments for less wettable surfaces (SCA>90^°). However, for more wettable surfaces (SCA<90^°), the DCA observed at initial contact times were order of magnitude higher than SCA values and therefore the DCA model is needed for the accurate prediction of the spreading behavior.     

Preparation and surface activity of modified soy protein

A series of novel surfactants have been prepared by the reaction of hydrolyzed soy protein with alkyl succinic anhydride. These novel surfactants exhibit excellent surface active properties including surface tension, foaming, emulsifying, wetting power, and buffer ability. The hydrophobic modified protein exhibit more surface activity than original protein because of the enhanced hydrophobicity in structure. The increase in hydrophobic chain length leads to an increase in the surface activity. The surface tension reduction is correlated to the hydrophobicity of the modified molecule, which was determined by a fluorescent probe. In application on cotton bleaching procedures, these surfactants increase the whiteness of fabrics. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3498–3503, 2006     

粗糙表面上的移动接触线和动态接触角

提出一个粗糙表面上移动接触线和动态接触角的数理模型：毛细数较低时表观接触线前缘存在极薄的前驱膜,表观接触线在“湿”固体表面上移动,不同于传统模型中认为表观接触线在“干”固体表面上移动.在Moffatt角区内部流动解的基础上,通过引入接触线特征参数表征表观接触线在前驱膜上的滑移程度,导出动态接触角的速度关系.与不同研究者实验数据对比发现量纲1特征参数反映固体材料特性和表面特性对动态湿润过程的影响,与液相的性质无关.结合前期提出的滞后张力模型,对动态法和静态法测量静接触角产生的差异给出合理解释.     

Capillary wetting rates in nylon fibrous assemblies

The capillary wetting rates in nylon fibrous assemblies were evaluated from the change in electrical conductivity due to wetting. The wetting liquids used were aqueous potassium chloride solutions of various pHs, in both the absence and the presence of ionic surfactants. Sodium dodecyl sulfate and dodecyltrimethylammonium chloride were chosen as surfactants. The contact angles of the wetting liquids on the nylon fiber were measured by the Wilhelmy method and the isoelectric point of the fiber was determined from electrokinetic data. The minimum wetting rate and the maximum contact angle were observed near pH 4, which coincided with the isoelectric point of the nylon fiber. In the presence of surfactant ions, the minimum wetting rate was also obtained at the concentration where the surface charge of nylon was neutralized. These experimental findings indicate that the capillary wetting rates in nylon fibrous assemblies are influenced by the electrical phenomena at the nylon/ solution interfaces via the contact angle and the structure of the adsorbed surfactant layers.     

Adsorption of Binary Mixtures of Anionic Surfactants at Water–Air and Poly(Tetrafluoroethylene)–Water Interfaces

Measurements of the surface tension (γ _LV ) and the advancing contact angle (θ) on poly(tetrafluoroethylene) (PTFE) were carried out for aqueous solutions of sodium decyl sulfate (SDS) and sodium dodecyl sulfate (SDDS) and their mixtures. The results obtained indicate that the values of the surface tension and the contact angle of solutions of surfactants on PTFE surface depend on the concentration and composition of the surfactants mixture. On the curves presenting the relationship between the surface tension, contact angle and monomer mole fraction of SDDS (α) in the mixture of SDDS and SDS, there is a minimum at α equal to 0.8 which together with the negative values of the interaction parameters indicate that synergism occurs in surface tension and contact angle reduction almost in the range of concentration corresponding to the saturated monolayer of surfactants at the water–air interface. The results and calculations obtained also indicate that for single surfactants and their mixtures at a given concentration in the bulk phase, the values of surface excess concentration of the surfactants at water–air and PTFE–water interfaces are nearly the same, which suggests that the orientation of SDDS and SDS molecules at both interfaces in saturated monolayer should be vertical to the interfaces. Taking into account the values of the monomer mole fractions of the surfactants in a mixed monolayer at the water–air interface and values of the contact angle of a single surfactant on the PTFE surface, it is possible in a simple way to predict the values of the contact angle of a mixture at a given concentration and composition.     

Urine Advancing Contact Angle on Several Surfaces

Urine wetting properties may influence the design and performance of catheters, urinalysis instruments, and lab-on-a-chip technologies. In this study the advancing contact angle _adv of urine on several materials is characterized. Material type and surface tension have a significant effect on _adv, while pretreatment and aging do not. Mean urine _adv are between ≈78° and ≈89° on hydrophilic surfaces, and up to over ≈105° on hydrophobic surfaces. Expected urine contact angles will decrease from the DI water contact angles by on average 10°, and up to 20°, while urine surface tension will be lower than DI water by 12.12 mN/m and 18.53 mN/m. A unit change (mN/m) in surface tension results in a 0.75° change in _adv. These results indicate that systems attempting to exploit urine wetting must account for highly variable conditions.     

Effect of Activated Gas Plasma on Surface Characteristics and Bondability of RTV Silicone and Polyethylene

An RTV silicone and high density polyethylene are exposed in an activated gas plasma for varying times and varying conditions. Both oxygen and argon are used. Changes in critical surface tension of wetting as determined by contact angle measurements are reported. Bondability of the treated surfaces is evaluated with both the aged bonds and aged surfaces prior to bonding being evaluated. In contradiction to some of the recent work reported in the literature on the effect of activated inert gas on surface characteristics, contact angles always decreased on the materials studied indicating an increase in surface energy. The significance of the results on present adhesion theories is discussed.     

Theoretical study of wetting behavior of nanoparticles at fluid interfaces

In this work, a theoretical model was developed to describe the wetting behavior of nanoparticles at liquid‐vapor interface by the integration of the renormalization group transformation, the cell theory, and the modified fundamental measurement theory with the first‐order mean spherical approximation method. The results show that the new model can be used to investigate the global behavior and surface tensions of nanoparticle/fluid systems. Particularly, the nanoparticle's wetting behavior inside critical region was discussed systematically. More important, this work proposed a methodology for calculating line tension and contact angle, showing that line tension has considerable influence on wetting properties for small nanoparticles, whereas it is negligible for large nanoparticles. Therefore, this work provides a general method for studying the wetting behavior of nanoparticles that may find wide applications in the field of chemical engineering. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

Wetting and adsorption properties of cetyltrimethylammonium bromide and Triton X-100 mixture with short-chain alcohol in polymer–solution–air system

Measurements of the contact angle of the aqueous solutions of Triton X-100 (TX-100) and cetyltrimethylammonium bromide (CTAB) mixture with methanol or propanol on the polytetrafluoroethylene (PTFE) and nylon-6 surfaces were made. On the basis of the obtained results, the Gibbs surface excess concentration of alcohol and TX-100 + CTAB mixture at the polymer–solution and polymer–air interfaces was calculated and compared to that at the solution–air one. The standard Gibbs free energy of alcohol adsorption was determined by different methods. For TX-100 and CTAB mixture, this energy was calculated using the values of critical micelle concentration (CMC) of that mixture, the surface tension and contact angle of aqueous solution of alcohol as well as the surface tension and contact angle of the aqueous solution of TX-100 and CTAB mixture with alcohol at CMC. The polymer–solution interfacial tension, the adhesion tension, and the adhesion work of the studied solutions to the polymer surface were also determined. From the obtained data, it results that the studied solutions can wet completely only the nylon-6 surface and that below alcohol critical aggregation concentration the adsorption of surfactants and alcohols at the polymer–water and water–air interfaces is similar for PTFE and different for nylon-6.