Critical Surface Tension Of Wetting Research Articles

Plasma-induced Polymerization and Grafting of Acrylic Acid on the Polypropylene Nonwoven Fabric Using Pulsed Underwater Diaphragm Electrical Discharge

Polypropylene (PP) nonwovens are used in many hygiene, healthcare and medical products due to their low cost, high chemical resistance and inertness. From an economic point of view, PP textiles would be used as an excellent support material in regenerative medicine or tissue engineering, but here surface functionalization is necessary to ensure cell adhesion and proliferation. Acrylic acid (AAc) is an excellent source of carboxylic-rich (-COOH) coatings suitable for this purpose, but their multistep preparation is time-consuming. Plasma polymerization provides an excellent solution to this demanding procedure since the process of polymerization and grafting to the substrate takes place simultaneously. Here, we propose a relatively fast and effective method for AAc plasma polymerization by using a pulsed underwater diaphragm electrical discharge operated in an aqueous solution consisting of AAc. AAc layers are successfully grafted onto PP nonwovens, which are continuously rewound through the slit where the plasma is generated. The presence of plasma polymerized AAc layer in the fibrous structure of PP nonwoven was monitored by SEM, FTIR and XPS measurements. Additionally, the improved wettability and adhesion characteristics were investigated by the critical wetting surface tension (CWST) method, the standard method of strike-through time (STT) and „tape-peel“ test. Resulting AAc modified PP nonwoven possesses hydrophilic character, enhanced adhesion and a considerable amount of -COOH groups on the surface. Although after the washing test the FTIR and XPS results indicated a lower concentration of the carboxylic groups, the CWST and STT measurements confirmed the stable hydrophilic character of the PP nonwovens surface.

Determination of critical surface tension of wetting of textured water-repellent surfaces

The object of study is aluminum textured with a femtosecond laser and modified with silanes to reduce surface energy. The presence of a special texture on the surface, such as protrusions or hairs, and the inherently low surface energy of the material allow maximizing the water repellency properties. The determination of the critical wetting surface tension by the Zisman method has a pronounced wetting transition point, but the coordinates of this point cannot be accurately predicted. In this work, the Zisman method is considered as a tool for comparing the effectiveness of modifiers for femtosecond laser-textured surfaces. In this work, periodic structures were created by laser ablation on the surface of aluminum, the surface was modified to achieve the Cassie state when wetted with water, and the critical surface tension of wetting was determined by the Zisman method. As a result, it is shown that the Zisman method in combination with the data on the water contact angle values is an effective tool for characterizing the quality of surface modification of textured samples. It is shown that for textured aluminum surfaces, the most effective modifier is silane, which maintains the Cassie wetting state, with a contact angle increased from 155 to 160°. Paraffin has been shown to be a less effective modifier with an implicit wetting plateau and a transition in the range of 30 to 40 mN/m. It is shown that the textures that have acquired water repellency in the course of spontaneous hydrophobization are very unstable to the action of liquids with reduced polarity, although they have high values of the water contact angle. In practice, the creation of water-repellent coatings on aluminum is a promising substrate due to their widespread use in the aviation, automotive, and energy industries due to their high mechanical strength, lightness, and stability of properties.

An explicit correlation between surface functionality, wettability, and leukocyte removal by electrospun filter media

The major motive of this investigation was to derive a correlation between surface functionality, wettability, and leukodepletion efficiency of electrospun filter media. Towards this, different extents of hydrophilicity and various functionalities were introduced to the electrospun poly (ethylene-co-vinyl alcohol) (EVAL) filter media via photografting of 2-hydroxyethyl acrylate (HEA) branches, photografting of N-(3-sulfopropyl)-N-methacroyloxyethyl-N,N- dimethylammonium betaine (SMDB) branches, and integration of glycine. All the filter media were designed to asymmetric filters with fiber sizes varying from 1.7 ± 0.2 μm to 2.4 ± 0.2 μm, pore sizes from 7.8 ± 1.5 μm to 23.3 ± 5.0 μm, water contact angles from 69 ± 10° to 134 ± 3 critical wetting surface tension (CWST) from 61.8 mN/m to > 88 mN/m and their performance was ascertained by carrying out whole blood filtration studies. It was observed that hydrophilic filter media resulted in a decreased adhesion of white blood cells (WBCs) than the unmodified EVAL filter media due the formation of a hydration layer. However, the hydrophilic SMDB grafted EVAL (PSMBD-g- EVAL) showed a high WBC adhesion than expected because of the net negative polarity of the PSMDB branches by which they could grasp the WBC even in presence of hydration layer. The efficacy of WBC adhesion by hydrophobic glycinated EVAL (EVAL-GLY) filter media was nearly as that of unmodified EVAL while the red blood cell (RBC) recovery was less pronounced (67 % lower than unmodified EVAL) due to the pore occlusion. However, there was no significant change in platelet adhesion for all filter media except PHEA-g-EVAL. Hemolysis induced by all the modified filter media was notably lesser than that of unmodified EVAL and was nearly zero. Thus, it is concluded that WBC and platelet adhesion are interdependent under dynamic conditions and it is difficult to achieve a selective adhesion of one in presence of the other.

Glycine integrated zwitterionic hemocompatible electrospun poly(ethylene-co-vinyl alcohol) membranes for leukodepletion

This paper describes a novel strategy for the hemocompatibility improvement of poly(ethylene-co-vinyl alcohol) (EVAL) membranes by incorporation of a naturally occurring zwitterion, glycine. Crystalline glycine was directly integrated to the EVAL fibers via electrospinning. The membranes were characterized by Attenuated Total Reflection—Fourier Transform Infrared spectroscopy (ATR-FTIR), Scanning Electron Microscopy (SEM), Water Contact Angle measurements (WCA) and measurement of Critical Wetting Surface Tension (CWST). The impact of glycine integration on the membrane parameters was assessed by variations in fiber diameter, pore size and percentage porosity. The release of glycine from the membranes was also quantitatively evaluated by ninhydrin assay. The interplay of zwitterion structural features on the blood compatibility was studied by in vitro hemocompatibility evaluation and blood filtration studies. The outcomes of these investigations highlight that glycine incorporated membranes offer greater hemocompatibility than virgin EVAL membranes in terms of reduced hemolysis, increased RBC retention, decreased adhesion and activation of platelets. The type of membrane modification can be considered in future for the development of leukodepletion filter membranes.

Critical Surface Tension of Sulfide Minerals

The Zisman plot was prepared based on the contact angles of sulfide minerals determined using the sessile drop method. The estimated critical surface tension of wetting (ϓcw) was slightly smaller than that of floating (ϓcf), estimated based on natural floatability. However, the order of the ϓcf values, i.e. pyrite > sphalerite > galena > chalcopyrite, estimated from natural floatability, corresponded to that of the ϓcw values obtained from the Zisman plot using the contact angles . Thus, research on critical surface tension using the above-mentioned results should provide meaningful material for the flotation separation of complex sulfide minerals.

Separators for alkaline water electrolysis prepared by plasma-initiated grafting of acrylic acid on microporous polypropylene membranes

Highly hydrophilic separators for alkaline water electrolysis were prepared by plasma-initiated grafting of acrylic acid on porous polypropylene (PP) membranes. The membranes were activated in a low-pressure radio-frequency discharge in oxygen and subsequently graft polymerization of acrylic acid was performed in aqueous solution. The membranes were characterized by gravimetric grafting degree (GD), SEM, FTIR, critical wetting surface tension (CWST) test, mechanical strength, and electrolytic conductivity. Moreover, the membranes were applied as separators in alkaline electrolysis cell, and content of hydrogen in the produced oxygen was measured to determine membrane permeability to hydrogen dissolved in the electrolyte. It was observed that increasing GD improves performance of membranes as separators in alkaline electrolysis, although the particular effects on the electrolytic conductivity and hydrogen permeability strongly depend on structure the of initial PP substrate. Ageing test conducted in 30 wt% KOH at 60 °C revealed that although considerable degrafting took place at beginning of the test, the remaining polyacrylic acid provided highly hydrophilic character to membrane for 7000 h of the test.

Wetting and adhesion properties of rhamnolipid and surfactin

The measurements of the contact angle of the aqueous solution of rhamnolipid (RL) and surfactin (SF) on polytetrafluoroethylene (PTFE), polyethylene (PE), polymethyl methacrylate (PMMA), nylon 6 and quartz were performed. The obtained values of the contact angle were analyzed by applying the components and parameters of the surface tension of aqueous solution of surfactants, PTFE, PE, PMMA, nylon 6 and quartz. This analysis showed that the contact angle of the solution on the hydrophobic solids can be predicted theoretically knowing the Lifshitz-van der Waals component of the water surface tension, the surface tension of the solids and that of the solution. Based on the contact angle values the critical surface tension of studied solids wetting, the adsorption of surfactants at the solid-water interface, the standard Gibbs free energy of adsorption as well as the work of adhesion of solutions to PTFE, PE, PMMA, nylon 6 and quartz surfaces were determined. It proved that the critical surface tension of wetting of the studied solids is different from their surface tension and that the work of adhesion of the aqueous solutions of RL and SF to PTFE, PE, PMMA, nylon 6 and quartz surfaces can be predicted from the components and parameters as well as the total surface tension of solids and solutions.

Gamma processes of shear flocculation, oil agglomeration and liquid–liquid extraction

Gamma flotation process is characterized by emphasis on the control of solution surface tension and the separation of minerals in suspension with this technique is based on the differences in wettability of minerals. The wettability properties of mineral surfaces can be defined in terms of their values of critical surface tension of wetting (γc) as a quantifying parameter, which is an essential property to achieve selectivity in surface chemistry-based separation processes. That is, the gamma flotation technique utilizes the differences in the critical surface tension of wetting (γc) of minerals. Similar to the flotation method, shear flocculation, oil agglomeration and liquid–liquid extraction processes also utilize differences in wettability of minerals. Therefore, the separations of minerals by the control of surface tension in the shear flocculation, oil agglomeration and liquid–liquid extraction methods can be provided. In this study, the separations of some minerals with these processes have been investigated by using the control of the solution surface tension and the successful results could be reached. Consequently, these new separation processes have been defined as ‘gamma shear flocculation’, ‘gamma oil agglomeration’ and ‘gamma liquid–liquid extraction’.

Effect of contact angle, surface tension and zeta potential on oil agglomeration of celestite

The influences of contact angle, surface tension and zeta potential on oil agglomeration recovery of celestite mineral have been investigated in the present work. Therefore, celestite mineral in methanol–water suspension was agglomerated by the use of oil (kerosene) in the presence of sodium oleate as a surfactant. The zeta potential values of celestite surfaces were measured depending on pH and sodium oleate concentration. The zeta potential values of celestite surfaces became negative even more owing to the sodium oleate adsorption. However, this phenomenon did not affect the oil agglomeration recovery at all. It was found that both increasing contact angle and surface tension raised the oil agglomeration recovery of celestite mineral. Eventually, the agglomeration degree of celestite mineral in the suspension was not lower than a particular surface tension value corresponding to the critical solution surface tension for oil agglomeration (γc-a). The γc-a values were slightly greater than the critical surface tension of wetting (γc) values.

Surface flotation of particles on liquids. Principles and applications

Surface flotation was modeled by a spherical particle residing at the liquid/gas interface and forces operating in the system. Basing on this model and known expressions for the forces, different equations were presented, which relate (1) attachment contact angle with particle central angle as a function of particle size and density as well as liquid density and surface tension, (2) detachment contact angle as a function of particle size and density as well as liquid density and surface tension for the case when the particle starts to sink in the liquid, and (3) recalculated rest contact angle for the case when the mass of particle is neglected. The presented formulas can be useful for determination of attachment, detachment, and rest contact angles, and for selection of reference liquids for Washburn-type techniques of contact angle determination as well as for finding the critical surface tension of wetting.

Correlation of Flocculation and Agglomeration of Dolomite with its Wettability

Wettability is an important parameter which affects the shear flocculation and oil agglomeration behaviors of minerals. The critical surface tension of wetting (γc) as a wettability parameter describes wetting characteristics of any mineral. In this study, the correlation of shear flocculation and oil agglomeration processes of dolomite with its wettability parameter is investigated. The experimental studies have indicated that these processes improved with decreasing wettability depending on the increase of oleate adsorption despite a simultaneous increase in the zeta potential of dolomite. On the other hand, the flocculation and agglomeration of dolomite decreased with decreasing surface tension and did not occur below a particular value of surface tension, corresponding to the critical surface tension of wetting (γc) and the critical solution surface tension (γc-a) values, respectively. Also, the γc-a values are slightly higher than the γc values, indicating that the agglomeration of the particles requires a lower wettability.

Zwitterionic sulfobetaine‐modified non‐woven fabric for blood filtration

AbstractBlood filtration requires a high removal ratio of leukocytes and with simultaneous high recovery ratio of platelets and other beneficial components. Problems are often encountered with blood filter materials in terms of high platelet loss. Zwitterions such as phosphorylcholine, sulfobetaine and carboxybetaine show effective resistance against protein adsorption and platelet adhesion. The study reported was aimed at achieving surface modification of poly(butylene terephthalate) non‐woven fabric (PBTNF) using UV radiation‐induced graft copolymerization of a zwitterionic sulfobetaine, N‐(3‐sulfopropyl)‐N‐methacroyloxyethyl‐N,N‐dimethylammonium betaine (SMDB), in order to improve the wettability and platelet recovery ratio of the PBTNF. Attenuated total reflection Fourier transform infrared and X‐ray photoelectron spectroscopy results showed that SMDB was successfully grafted onto the PBTNF. Photoinitiator concentration, monomer concentration and UV irradiation time affected markedly the degree of grafting. Critical wetting surface tension, water wetting time and hemolysis tests showed an improvement in wettability and blood compatibility as a result of graft copolymerization of SMDB. A blood filter material composed of SMDB‐modified PBTNF reduced platelet adhesion and had higher platelet recovery compared to poly(acrylic acid)‐modified PBTNF. It was found that SMDB monomer was successfully grafted onto PBTNF using UV radiation. The degree of grafting of SMDB could be controlled by varying the photoinitiator concentration, monomer concentration and UV irradiation time. SMDB‐modified PBTNF showed significant improvement in wettability and blood compatibility. The zwitterionic structure of SMDB is resistant to platelet adhesion. The SMDB‐modified PBTNF could be a candidate for a blood filter material and in other medical applications. Copyright © 2010 Society of Chemical Industry

Wettability of quartz by aqueous solution of cationic surfactants and short chain alcohols mixtures

Advancing contact angle measurements for aqueous solution mixtures of cetyltrimethylammonium bromide (CTAB) and cetylpyridinium bromide (CPyB) with methanol, ethanol and propanol on quartz surface were carried out. From the obtained results it appeared that quartz wettability by these mixtures depends on the kind of alcohol and cationic surfactant and that there is linear dependence between the adhesion and surface tension of aqueous solution of the mixtures of CTAB and CPyB with alcohols at constant CTAB or CPyB concentration. This dependence can be described by linear equations which constants depend on CTAB and CPyB concentration and the kind of alcohol. The slope of all linear dependences between the adhesion and surface tension is positive. The critical surface tension of quartz wetting determined from these dependences by extrapolating the adhesion tension to the value corresponding to the surface tension of solution at which should be observed the contact angle strictly equal zero depends on the kind of alcohol and constant CTAB or CPyB concentration and is lying in the range from 25.9 to 33.3 mN m −1. The minimal value of the critical surface tension of wetting is somewhat lower, and the maximal is higher than the apolar component of the surface tension of quartz covered with monomolecular film of water. The dependence between the adhesion and surface tension at constant alcohol concentration is not linear, and it is difficult to determine the critical surface tension of quartz surface wetting from this dependence. A positive slope of the adhesion tension against the surface tension curves at constant CTAB or CPyB concentration indicates that alcohol molecules probably do not penetrate to the “bare” quartz surface and are adsorbed rather at quartz/monomolecular CTAB or CPyB film–solution interface because CTAB and CPyB molecules interact more strongly with quartz surface than those of water. In the presence of alcohol rather a monolayer of CTAB or CPyB is formed at quartz–water interface. However, in the absence of CTAB or CPyB alcohol molecules are probably adsorbed at quartz/monomolecular water film–solution interface. This conclusion is confirmed by the calculations of the adhesion work of aqueous solution of alcohols to the quartz surface. For the calculations of the adhesion work the surface tension of the quartz covered with a water film and alcohol surface tension components was taken into consideration.

The wettability of polytetrafluoroethylene and polymethylmethacrylate with regard to interface behaviour of Triton X-165 and short chain alcohol mixtures: I. Critical surface tension of wetting and adhesion work

Wetting of polymers (PTFE, PMMA) by aqueous solutions of Triton X-165 mixtures with methanol, ethanol and propanol was studied in a wide range of alcohol and Triton X-165 concentration. The Triton X-165 concentration range corresponded to its unsaturated and saturated monolayer in the absence of alcohol. The wetting properties of Triton X-165 and alcohol mixtures were determined on the basis of advancing contact angles measurements by the sessile drop method. From the obtained contact angle values the relationships between cos θ, the adhesion tension and surface tension of the solutions, cos θ and the reciprocal of the surface tension were determined. On the basis of these relationships the correlation between the critical surface tension of PTFE and PMMA wetting and the surface tension of these polymers and work of adhesion of aqueous solution of TX-165 and alcohols mixtures to PTFE and PMMA surface was discussed. The critical surface tension of PTFE wetting was found to be close to its surface tension determined from the contact angles for polar liquids, but the critical surface tension of PMMA wetting considerably lower than its surface tension and even the Lifshitz–van der Waals components of this surface tension.

Role of hydrophobicity and surface tension on shear flocculation and oil agglomeration of magnesite

This paper describes the role of hydrophobicity and surface tension on the shear flocculation and oil agglomeration of magnesite mineral. The experimental results have demonstrated that these processes were closely correlated with the particle hydrophobicity; however, they were not lowered by increasing the surface charge due to sodium oleate adsorption. Also, higher degrees of hydrophobicity were required to achieve the maximum aggregation in the oil agglomeration of magnesite fines in comparison to its shear flocculation. On the other hand, these aggregation processes decreased depending on the decrease in the contact angle with decreasing surface tension. Eventually the shear flocculation and oil agglomeration of fine particles in the suspension did not take place below a particular value of surface tension, corresponding the critical surface tension of wetting ( γ c) and the critical solution surface tension ( γ c-a) values, respectively.

The wettability of polytetrafluoroethylene and polymethylmethacrylate by aqueous solutions of Triton X-100 and propanol mixtures

Measurements of advancing contact angles (θ) were carried out for aqueous solutions of Triton X-100 (TX-100) and propanol mixtures at constant TX-100 concentration equal to 1×10−7, 1×10−6, 1×10−5, 1×10−4, 6×10−4 and 1×10−3M, respectively, on polytetrafluoroethylene (PTFE) and polymethyhmethacrylate (PMMA). Using obtained results the changes of cosθ and adhesional tension against surface tension of all series of aqueous solutions of TX-100 and propanol mixtures (γLV) for PTFE and PMMA surfaces were shown. On the basis of these changes it was deduced that adsorption of TX-100 and propanol mixtures at PTFE-solution and solution-air interfaces is the same but the adsorption of TX-100 and propanol mixtures at solution-air interface is considerably higher than at PMMA-solution one. In the case of PTFE this conclusion was confirmed by relationship between cosθ and the reciprocal of the surface tension of solution. Extrapolation of the relationships between cosθ and/or adhesional tension and the surface tension of solutions to the points corresponding to the cosθ=1 and adhsional tension equal to the surface tension of solution, the critical surface tension of PTFE and PMMA wetting was determined. The average values of critical surface tension of wetting determined from these relationships for PTFE are lying in the range of its surface tension values determined from contact angles of different kinds of liquids, which can be find in the literature, but for PMMA are considerably lower than the surface tension. The double value of the critical surface tension of PTFE wetting is equal to adhesion work of the solution to its surface and for PMMA there is not any correlation between these magnitudes.Using the measured values of the contact angles and Young equation the PTFE(PMMA)-aqueous solution interfacial tension was determined. The interfacial tension values of PTFE-aqueous solution were also calculated from the Fainerman and Miller equation in which the correcting parameter of nonideality of the surface monolayer was introduced and compared to those obtained from Young equation. From this comparison it results that the changes of PTFE-solution interface tension as a function of propanol concentration can be described by the Fainerman and Miller equation.

Correlation of shear flocculation of some salt-type minerals with their wettability parameter

This paper considers the importance of surface hydrophobicity in the shear flocculation process and presents a correlation between the shear flocculation and the wettability parameter for barite, celestite and calcite as salt-type minerals. The critical surface tension of wetting ( γ c) as a wettability parameter describes wetting characteristics of any mineral. The variation of the shear flocculation behaviours of barite, celestite and calcite with sodium oleate concentration in various methanol solutions was investigated. The shear flocculation of these minerals in the methanol solutions increased rapidly towards the optimum surfactant concentration, and thereafter remained relatively constant or increased slightly. On the other hand, the shear flocculation of the minerals decreased with increasing methanol concentration, depends on decreasing surface tension. The γ c values of these minerals as a function of surfactant concentration were determined using a shear flocculation approach. It was found that the γ c values did not change much at surfactant concentrations above the optimum. This result provides a reason for the observed lack of significant increase in the shear flocculation of the mineral suspensions when surfactant concentrations higher than the optimum are used. Furthermore, a strong correlation between the effective shear flocculation and the critical surface tension of wetting ( γ c) value was established. As the effective shear flocculation of these salt-type minerals increased sharply below a particular γ c value, it was not much improved after reaching the γ c value obtained at the optimum concentration of sodium oleate.

The Influence of Surfactant on the Surface Characterization of Celestite in Spherical Oil Agglomeration

This study investigates the relationship between the critical surface tension of wetting of celestite and agglomeration recovery as well as the zeta potential in dependence of pH and amount of collector (Na‐Oleate). For this purpose, effects of pH and collector amount on the agglomeration recovery are investigated and zeta potential measurements and Fourier Transform Infrared Spectrophotometer (FTIR) analyses are carried out to determine the adsorption type of Na‐Oleate on celestite surface. The sessile drop technique is used for the measurement of contact angle and determination of the critical surface tension of wetting (YC) of celestite. The maximum agglomeration recovery is obtained at pH 7. The critical surface tension of wetting of celestite is very close to the surface tension of kerosene, which is 25.95 mN/m. Furthermore, at the optimum Na‐Oleate amount of 10 kg/ton, the critical surface tension of wetting of celestite is approximately equal to the surface tension of kerosene.

Effect of plasticizing sugars on water vapor permeability, surface energy and microstructure properties of zein films

Sugars are natural plasticizers for food biopolymers and zein is the most important protein of corn. In this research, sugars (fructose, galactose and glucose) were used as plasticizers and the water vapor permeability (WVP), contact angle and microstructure of the zein films were studied. The pure zein film had high WVP and adding of sugars to 0.7 g/g zein caused to decrease of WVP. Films containing galactose had the lowest WVP. All samples had the lowest contact angle with ethanol and the highest contact angle with water. The zein films containing galactose had the highest water contact angle within the plasticized films. The pure zein films and the films containing fructose had higher critical surface tension of wetting ( γ c) than the films containing glucose and galactose. Adding sugar plasticizer to zein films increased the surface tension of zein films. In the unplasticized zein films, loose structures with a lot of cavities and voids were observed. The films plasticized by fructose had smooth surface and plasticizer particles distributed throughout of the films.

Spreading of liquid drops over solid substrates: 'like wets like'

The classic hydrodynamic wetting theory leads to a linear relationship between spreading speed and the capillary force, being determined only by the surface tension of the liquid and its viscosity. Both equilibrium and dynamic processes of wetting are important in adhesion phenomena. The theory appears to be in good agreement with the results generated from experiments conducted on the spreading of poly(dimethylsiloxane) (PDMS) on soda-lime glass substrate and fails to account for the behavior of other liquids. In this study, the spreading kinetics of four different liquids (hexadecane, undecane, glycerol and water) was determined on three different solids, namely, soda-lime glass, poly(methyl methacrylate) (PMMA) and polystyrene (PS). Droplets from the same liquid allowed to spread under identical conditions on three different substrates produce distinctly different behaviors. The results show that the equilibrium contact angles are qualitatively ranked in accordance with the critical surface tension of wetting (γ c) of the respective solid, i.e., high-γ c solids caused the low surface tension liquids to assume the least equilibrium spreading (largest contact angle). On the other end, low-γ c solids with the lowest surface tension liquid produce the most wetting (smallest contact angle). The results suggest that equilibrium spreading could be explained on the basis of the axiom 'like wets like'; in other words, polar surfaces tend to be wetted by polar liquids and vice versa.