Some Effects of Corona Discharge Treatment of Biaxially-Oriented Polypropylene Film

The effects of the unit corona-treatment energy on the contact angle of various liquids, on the surface free energy, on the extent of oxidation of a surface layer, and on the adhesion of acrylic adhesive were studied using a biaxially-oriented polypropylene (BOPP) film. The surface free energy was determined with the van Oss-Chaudhury-Good (VCG) approach as well as with the wettability method. The extent of oxidation of the surface layer of the corona-treated BOPP film was evaluated with X-ray photoelectron spectroscopy. The adhesion strength of joints between the BOPP film and the acrylic adhesive was measured using the 180°-peel test.

In the range of the unit corona-treatment energy up to 1.2 kJ/m², a rapid increase in the surface free energy with the treatment energy is observed. In the range above that value, the surface free energy rises relatively slowly. The extent of oxidation of the surface layer and the adhesion strength of joints between the BOPP film and the acrylic adhesive are approximately in direct proportion to the unit energy of the corona treatment. A five-fold growth of the adhesion strength of the studied joints within the examined range of the treatment energy was found.     

Some Effects of Corona Discharge Treatment of Biaxially-Oriented Polypropylene Film

The effects of the unit corona-treatment energy on the contact angle of various liquids, on the surface free energy, on the extent of oxidation of a surface layer, and on the adhesion of acrylic adhesive were studied using a biaxially-oriented polypropylene (BOPP) film. The surface free energy was determined with the van Oss-Chaudhury-Good (VCG) approach as well as with the wettability method. The extent of oxidation of the surface layer of the corona-treated BOPP film was evaluated with X-ray photoelectron spectroscopy. The adhesion strength of joints between the BOPP film and the acrylic adhesive was measured using the 180°-peel test.

In the range of the unit corona-treatment energy up to 1.2 kJ/m², a rapid increase in the surface free energy with the treatment energy is observed. In the range above that value, the surface free energy rises relatively slowly. The extent of oxidation of the surface layer and the adhesion strength of joints between the BOPP film and the acrylic adhesive are approximately in direct proportion to the unit energy of the corona treatment. A five-fold growth of the adhesion strength of the studied joints within the examined range of the treatment energy was found.     

On the interpretation of contact angle hysteresis

The determination of solid surface free energy is still an open problem. The method proposed by van Oss and coworkers gives scattered values for apolar Lifshitz-van der Waals and polar (Lewis acid-base) electron-donor and electron-acceptor components for the investigated solid. The values of the components depend on the kind of three probe liquids used for their determination. In this paper a new alternative approach employing contact angle hysteresis is offered. It is based on three measurable parameters: advancing and receding contact angles (hysteresis of the contact angle) and the liquid surface tension. The equation obtained allows calculation of total surface free energy for the investigated solid. The equation is tested using some literature values, as well as advancing and receding contact angles measured for six probe liquids on microscope glass slides and poly(methyl methacrylate) PMMA, plates. It was found that for the tested solids thus calculated total surface free energy depended, to some extent, on the liquid used. Also, the surface free energy components of these solids determined by van Oss and coworkers' method and then the total surface free energy calculated from them varied depending on for which liquid-set the advancing contact angles were used for the calculations. However, the average values of the surface free energy, both for glass and PMMA, determined from these two approaches were in an excellent agreement. Therefore, it was concluded that using other condensed phase (liquid), thus determined value of solid surface free energy is an apparent one, because it seemingly depends not only on the kind but also on the strength of interactions operating across the solid/liquid interface, which are different for different liquids.     

Comparison of the Lifshitz–van der Waals/acid–base and contact angle hysteresis approaches for determination of solid surface free energy

Total surface free energy, γ_S ^TOT, for several solids (glass, PMMA, duralumin, steel and cadmium) was calculated from the surface free energy components: apolar Lifshitz–van der Waals, γ_S ^LW, and acid–base electron–donor, γ_S ^-, and electron–acceptor, γ_S ⁺. Using van Oss and coworkers' approach (Lifshitz–van der Waals/acid–base (LWAB) approach), the components were determined from advancing contact angles of the following probe liquids: water, glycerol, formamide, diiodomethane, ethylene glycol, 1-bromonaphthalene and dimethyl sulfoxide. Moreover, receding contact angles were also measured for the probe liquids, and then applying the contact angle hysteresis (CAH) approach very recently proposed by Chibowski, the total surface free energy for these solids was calculated. Although the thus determined total surface free energy for a particular solid was expected to depend on the combination of three probe liquids used (LWAB approach), as well as on the kind of the liquid used (CAH approach), surprisingly the average values of the surface free energy from the two approaches agreed very well. The results obtained indicate that both approaches can deliver some useful information about the surface free energy of a solid.     

On the use of Washburn's equation for contact angle determination

A systematic study on the possibility of Young's contact angle determination from Washburn's equation was performed using the so-called thin-layer wicking technique in which the rate of penetration of a liquid into the porous layer of a solid is measured. Commercial (Merck) SiO₂ deposited on the glass plate for thin-layer chromatography was used as a model solid and n-alkanes (from pentane to hexadecane), diiodomethane, and α-bromonaphthalene were employed as the probe liquids. It was shown that the contact angle calculated from Washburn's equation was not equal to Young's contact angle of a drop of the same liquid, placed on a flat surface of the solid. Consequently, the solid surface free energy components calculated using contact angles from Washburn's equation are not the true values. However, the approach previously suggested by us has been verified again, as it gives consistent values of the surface free energy components determined from all the liquids used.     

Analysis and surface energy estimation of various model polymeric surfaces using contact angle hysteresis

Wetting of hydrophobic polymer surfaces commonly employed in electronic coatings and their interaction with surfactant-laden liquids and aqueous polymer solutions are analyzed using a contact angle hysteresis (CAH) approach developed by Chibowski and co-workers. In addition, a number of low surface tension acrylic monomer liquids, as well as common probe liquids are used to estimate solid surface energy of the coatings in order to facilitate a thorough analysis of surfactant effects in adhesion. Extensive literature data on contact angle hysteresis of surfactant-laden liquids on polymeric surfaces are available and are used here to estimate solid surface energy for further understanding and comparisons with the present experimental data. In certain cases, adhesion tension plots are utilized to interpret wetting of surfaces by surfactant and polymer solutions. Wetting of an ultra-hydrophobic surface with surfactant-laden liquids is also analyzed using the contact angle hysteresis method. Finally, a detailed analysis of the effect of probe liquid molecular structure on contact angle hysteresis is given using the detailed experiments of Timmons and Zisman on a hydrophobic self-assembled monolayer (SAM) surface. Hydrophobic surfaces used in the present experiments include an acetal resin [poly(oxymethylene), POM] surface, and silane, siloxane and fluoro-acrylic coatings. Model surfaces relevant to the literature data include paraffin wax, poly(methyl methacrylate) and a nano-textured surface. Based on the results, it is suggested that for practical coating applications in which surfactant-laden and acrylic formulations are considered, a preliminary evaluation and analysis of solid surface energy can be made using surfactant-laden probe liquids to tailor and ascertain the quality of the final coating.     

Tissue adhesive using synthetic model adhesive proteins inspired by the marine mussel

The surface free energy and its dispersion and polar components of pigskin were determined by wettability measurements. The contact angles and work of adhesion of solutions of the synthetic model adhesive sequence poly(Gly-Tyr-Lys) inspired by marine adhesive proteins were measured on the epidermis and the dermis of pigskin. Also the surface free energy of pigskin was determined using contact angles of certain probe liquids. When a poly(Gly-Tyr-Lys) buffer solution containing tyrosinase as a bioadhesion formulation was used to close an incision of a living pig, a good incision adhesion and reduced immunological response after 1 week were observed from photographs using an optical microscope and the amount of macrophages by image analysis.     

Properties of compression-densified wood,Part II: surface energy

Surface energy of yellow-poplar wood from three wood treatment groups was studied using sessile-drop contact-angle measurements and the Chang acid–base model for surface energy calculation. Water, glycerol, formamide, ethylene glycol and α-bromonaphthalene were used as probe liquids. Wood treatments were control, hygro-thermal treatment and densification. Contact angle trends for densified and hygro-thermally treated wood were found to be the same. Total surface energy decreased with both hygro-thermal treatment and densification.     

Synthesis,characterization, and UV‐curing properties of silicon‐containing (Meth)acrylate monomers

Eight different silicon‐containing (meth)acrylate monomers are synthesized by the substitution reaction of chlorosiloxanes with 2‐hydroxyethyl methacrylate or 2‐hydroxyethyl acrylate. Their molecular structures are confirmed by IR, ¹H‐NMR, and ¹³C‐NMR spectroscopic analyses. The effects of silicon content on the UV‐curing behavior, physical, surface, and thermal properties are investigated. The UV‐curing behavior is analyzed by photo differential scanning calorimetry. The surface free energy of the UV‐cured film is calculated from contact angles measured using the Lewis acid‐base three liquids method. The silicon‐containing (meth)acrylate monomers perform much better than traditional (meth)acrylate monomers on UV‐curing. The silicon‐containing monomers have higher final conversions and fast UV‐curing rates in photopolymerization. The surface free energy decreases with increasing silicon content, because silicon in the soft segment is transferred to the surface, producing a UV‐cured film; this is confirmed by X‐ray photoelectron spectroscopy measurements. All these advantageous properties enable these synthetic silicon‐containing monomers to perform better in applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

功能表面材料与流体界面相互作用对垂直降液膜流动特性的影响

通过调节水温度、添加表面活性剂以及铝合金壁面表面改性处理来改变降膜流体与固体表面之间的表面自由能差值,运用JDC-2000型精密测微仪测定垂直降液膜的厚度,研究固体表面和液体间相互作用对流体垂直降膜流动特性的影响;考察了液膜雷诺数、流体温度、添加表面活性剂、固体表面材料物理化学性质等因素对垂直壁面降液膜流动特性的影响规律。实验结果表明:改变固体表面与降液膜流体的物理化学特性,即改变固液界面的相互作用能够改变流体的降膜流动特性。降液膜平均厚度随液固表面自由能差的增大而减小。     

聚碳硅烷／聚硅烷共混体系的表面自由能

制备了几种聚碳硅烷/聚硅烷共混物,通过两种已知表面张力的小分子液体在共混物表面接触角的测定,采用调和平均法求得了共混物的表面自由能,研究了共混物相容性和聚硅烷的含量及其分子量对共混体系表面自由能的影响。     

毛细上升法研究水处理滤料的表面热力学特性

基于Washburn方程用亲油亲水比(LHR)比较了0.9～1.2 mm无烟煤、锰砂和石英砂滤料的润湿性; 同时以正己烷、1-溴萘、甲酰胺和去离子水为探针液, 用Washburn方程和van Oss-Chaudhurry-Good(vCG)理论对滤料表面自由能成分进行了估算。实验测得无烟煤、锰砂和石英砂的LHR值依次为1.93、0.75和0.69, 说明无烟煤的亲油性较好而锰砂和石英砂表现出了亲水性; 估得无烟煤、锰砂和石英砂滤料的表面自由能非极性成分和极性成分依次为38.8、38.0、37.7 mJ·m-2和0.73、6.8、8.7 mJ·m-2,初步说明水处理滤料的表面润湿性与其表面自由能极性成分γABs之间有一定的相关性; 而后者归因于滤料的表面化学组成。     

Wettability Modification of Nanomaterials by Low-Energy Electron Flux

Controllable modification of surface free energy and related properties (wettability, hygroscopicity, agglomeration, etc.) of powders allows both understanding of fine physical mechanism acting on nanoparticle surfaces and improvement of their key characteristics in a number of nanotechnology applications. In this work, we report on the method we developed for electron-induced surface energy and modification of basic, related properties of powders of quite different physical origins such as diamond and ZnO. The applied technique has afforded gradual tuning of the surface free energy, resulting in a wide range of wettability modulation. In ZnO nanomaterial, the wettability has been strongly modified, while for the diamond particles identical electron treatment leads to a weak variation of the same property. Detailed investigation into electron-modified wettability properties has been performed by the use of capillary rise method using a few probing liquids. Basic thermodynamic approaches have been applied to calculations of components of solid–liquid interaction energy. We show that defect-free, low-energy electron treatment technique strongly varies elementary interface interactions and may be used for the development of new technology in the field of nanomaterials.     

Surface energy of untreated and surface-modified cellulose fibers

Average advancing and receding contact angles made against cotton and glass fibers by a set of probe liquids are determined using the Wilhelmy technique. The dispersive and polar components of the surface energy are calculated from the measured contact angles using both the geometric and the harmonic mean methods. It is found that these components are similar for untreated cellulose and glass fibers, and that they both have a high polar component, corresponding to a hydrophilic surface. Changes in surface energy caused by treatment of the cellulose fiber surfaces with melamine, polyethyleneimine (PEI), and a silane coupling agent are reported. It is found in particular that polyethyleneimine treatment of cellulose significantly reduces the polar component of its surface energy. While treatment of glass fibers with a silane coupling agent reduces the polar component and increases the dispersive component of the surface energy it shows little effect on the surface energy of cellulose.     

A comparison of nitrogen adsorption and thermogravimetric methods in the assessment of the pore size distribution of mesoporous silica gels

The pore dimensions are determined by using adsorption and thermogravimetry methods for unmodified silica gel Si-100 and silanized silica gel Lichrosorb RP-18. Thermal desorption measurements for various liquids were performed under quasi-isothermal conditions. Methanol, acetone, benzene and n-hexane were used as a wetting liquids. Pore size distributions and total pore volumes derived from thermal desorption compare reasonably well with results obtained from the analysis of adsorption isotherms of nitrogen. For different types of adsorbates the effects connected with the presence of the surface liquid film are discussed. The presence of long alkyl chains on the silica surface strongly influences the pore diameter calculated from thermogravimetric data.     

Comparative study of surface properties determination of colored pearl-oyster-shell-derived filler using inverse gas chromatography method and contact angle measurements

Mollusk shells, such as clam, mussel, oyster and pearl oyster shells, are potential candidates for commercial calcium carbonate-based fillers. In this work, the surface properties of colored pearl-oyster-shell-derived filler (CMF) were investigated with comparison to those of pearl oyster shell powder (MSP), using an inverse gas chromatography (IGC) method and contact angle measurements. A developed computational model for the interpretation of surface free energy heterogeneity distributions was applied to both samples. The contact angle measurements revealed an amphiphilic nature. The dispersion component of surface free energy for both samples calculated using the Owens–Wendt–Kaelble (OWK), van Oss–Chaudhury–Good (vOCG) and Wu methods were consistent with those determined using the IGC method. The deconvolution of surface energetic sites confirmed their energetic heterogeneity. The CMF displayed lower work of cohesion, which could be beneficial to the fabrication of polymer composites, as typically reduced filler particle-particle interactions would result.     

Surface properties of EPDM,silicone rubber,and their blend during aging

Surface energy of EPDM, silicone rubber, and their 50 : 50 (by weight) blend during aging was determined by contact angle measurement using water and formamide as the probe liquids. The surface energy increases initially with aging time. The results are explained on the basis of the polar component of the surface energy. Blending offers a good degree of protection toward aging of EPDM rubber. The generation of polar groups during aging is confirmed by IR and ESCA investigations. © 1995 John Wiley & Sons, Inc.     

Liquid film effect on dynamics of optical oxygen probe. Comparison with polarographic oxygen probes. Diffusion coefficients measuring technique

The dynamic behaviour of the optical oxygen probe at the presence of the liquid film is well described by unsteady one-directional oxygen diffusion into the probe membrane through liquid film. It is shown that the asymmetry caused by hyperbolic form of the Stern-Volmer relation between the probe signal and oxygen concentration is strongly suppressed in the presence of liquid film for the optical probes used in this work. In such case, the response calculated with respect to the mean oxygen concentration in the membrane describes well the optical oxygen probe dynamics.Liquid film effects on the signal of the optical and the polarographic oxygen probes are compared. Special attention is paid to find properties of membranes minimizing the liquid film effect on the rate of its response. From this point of view, the most suitable material for the optical probe membrane is one with high diffusivity but low solubility. Thus, silicone (used by optical probe manufacturers in these days) is the least suitable material. When both probes are covered with the same membrane, the response of polarographic probe is faster and less influenced by the liquid film compared with optical one. From this point of view, the polarographic probe is more suitable for monitoring of fast changing oxygen concentration in bulk liquid as it occurs, e.g. measurement of k_La in gas-liquid dispersions, usually with the need to know the L_L parameter characterizing the liquid film diffusion resistance. In addition, only the polarographic probe allows determination of a local value of the parameter L_L (under the given hydrodynamic conditions where the probe is situated) which is not possible with an optical probe. The optical probe is more suitable for measurements under steady-state conditions and for slower oxygen changes, even under the conditions, when the liquid film resistance is high in comparison with the membrane resistance as it occurs for diffusivity measurements in liquids. A modified method for evaluation of the oxygen diffusion coefficient in liquids from the dynamic probe response is presented.     

Effect of graphene film on laser textured alumina surface characteristics

Laser gas assisted texturing of alumina surface is considered and the effects of graphene film on the properties of the textured surface are examined. Since laser texturing under the high pressure nitrogen gas jet environments results in formation of aluminum nitride compounds, free energy of the textured surface reduces considerably. The mismatch between the surface free energies of the graphene film and the laser textured surface makes it difficult to transfer the graphene film on the textured surface without rippling and edge defects. A graphene oxide film is formed at the textured surface prior to transferring of the graphene film. The characteristics of the laser textured and the graphene transferred surfaces are assessed using the analytical tools including electron and atomic force microscopes, Raman spectroscopy, X-ray diffraction, and UV visible absorbance spectroscopy. Surface hydrophobicity of the graphene transferred and laser textured surfaces is determined incorporating the water droplet contact angle measurement technique. Friction coefficient of the graphene transferred and laser textured surfaces are measured using the scratch tester. It is found that laser texturing results in hydrophobic characteristics because of the micro/nano size pillars formed at the surface and reduced surface energy due to aluminum nitride compounds. Transferring of the graphene film on to the laser textured surface reduces both the water droplet contact angle and the contact angle hysteresis. The presence of the graphene film reduces the friction coefficient and it does not alter notably the absorption characteristics of the laser textured surface.     

Wettability of Surface Oxyfluorinated Polypropylene Fibres and Its Effect on Interfacial Bonding with Cementitious Matrix

The surface of high molecular weight polypropylene monofilament fibre was modified using a oxyfluorination method. The oxyfluorination treatment level was varied and a hydrolysis post-treatment was also applied. Contact angles of oxyfluorinated, hydro-lyzed oxyfluorinated and unmodified polypropylene fibres were obtained by dynamic contact angle (DCA) measurement using three liquids of known dispersion, acid and base surface free energy components. The surface free energies were then calculated according to the acid-base theory developed by Good, van Oss and Chaudhury. Surface oxyfluorination largely increased the acid and base components of the fibres' surface free energy compared with unmodified polypropylene fibres. The oxyfluorinated and unmodified polypropylene fibre surfaces were observed by Scanning Electronic Microscopy and Photoacoustic Infrared Spectroscopy. It was found that the surface oxyfluorination largely increases the roughness of the polypropylene surfaces and the carbonyl group content increases as the treatment level increases. The interfacial shear bond strengths between the cementitious matrix and the polypropylene fibres treated under various conditions were determined by embedded fibre pull-out tests. Results showed that the fibre surface oxyfluorination treatments increase the interfacial bond strengths. The correlations between the shear bond strengths and surface free energy components were established. Results showed that fibre/concrete interfacial bonding was best correlated with the acid component of surface free energy of polypropylene fibres.