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Wetting Properties (wetting + property)
Selected AbstractsContact Angle Analysis During the Electro-oxidation of Self-Assembled Monolayers Formed by n -OctadecyltrichlorosilaneADVANCED FUNCTIONAL MATERIALS, Issue 19 2010Nicole Herzer Abstract The electrochemical oxidation process of self-assembled monolayers formed by n -octadecyltrichlorosilane (OTS) molecules on silicon wafers has been studied in a droplet of water by means of in situ water contact angle measurements. The application of different bias voltages between the substrate and a counter electrode placed into the droplet resulted in changes of the chemical nature of the monolayer, which yielded a significant alteration of the surfaces properties. Due to the changes of the wetting properties of the monolayer during the electro-oxidation process a change in the contact angles of the water droplet is concomitantly observed. This allows the in situ monitoring of the electro-oxidation process for large modified areas of several millimeters in diameter. The chosen approach represents an easy way to screen the major parameters that influence the oxidation process. Afterwards, the oxidized regions are characterized by Fourier-transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS) measurements, and atomic force microscopy (AFM) investigations to obtain more information about the electro-oxidation process. The observations are correlated to experimental results obtained for oxidations performed on a smaller dimension range in the water meniscus of a conductive, biased AFM tip. A good correlation of the results in the different dimension ranges could be found. [source] A Simple, One-Step Approach to Durable and Robust Superhydrophobic Textiles,ADVANCED FUNCTIONAL MATERIALS, Issue 22 2008Jan Zimmermann Abstract Superhydrophobic textile fabrics are prepared by a simple, one-step gas phase coating procedure by which a layer of polymethylsilsesquioxane nanofilaments is grown onto the individual textile fibers. A total of 11 textile fabrics made from natural and man made fibers are successfully coated and their superhydrophobic properties evaluated by the water shedding angle technique. A thorough investigation of the commercially relevant poly(ethylene terephthalate) fabric reveals an unparalleled long-term water resistance and stability of the superhydrophobic effect. Because of the special surface geometry generated by the nanoscopic, fibrous coating on the microscopic, fibrous textiles, the coated fabric remains completely dry even after two months of full immersion in water and stays superhydrophobic even after continuous rubbing with a skin simulating friction partner under significant load. Furthermore, important textile parameters such as tensile strength, color, and haptics are unaffected by the silicone nanofilament coating. For the first time, an in-depth characterization of the wetting properties, beyond simple contact angle measurements, as well as a thorough evaluation of the most important textile parameters is performed on a superhydrophobic fabric, which reveals a true potential for application. [source] Fabrics with Tunable OleophobicityADVANCED MATERIALS, Issue 21 2009Wonjae Choi A simple "dip-coating" process that imbues oleophobicity to various surfaces that inherently possess re-entrant texture, such as commercially available fabrics, is reported. These dip-coated fabric surfaces exhibit reversible, deformation-dependent, tunable wettability, including the capacity to switch their surface wetting properties (between super-repellent and super-wetting) against a wide range of polar and nonpolar liquids. [source] Wettability investigations on the cellulosic surface of alfa fibersJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008N. Bohli Abstract A wettability study was performed on samples of alfa fibers with the Wilhelmy plate technique. The set of test liquids employed in the measurement of the contact angles was composed of water, heptane, diiodomethane, ,-bromonaphthalene, and formamide. During their first immersion in high-surface-energy test liquids, the alfa fibers showed anisotropic behavior: they had an advancing contact angle of 67 ± 6° in one orientation of immersion and an angle of 112 ± 9.5° in the opposite one. Optical microscopy revealed the existence of fibrils on the alfa-fiber surface. They kept almost the same orientation and were responsible for the interesting hydrophobic/hydrophilic behavior of the fibers. Contact angle measurements and investigations of the hysteresis were also performed. The various results were examined according to the heterogeneities of the fibers. The surface energy of the alfa fibers was determined with three theoretical models: the geometric model, the Good,Van Oss,Chaudhury model, and the Chang model. A comparative study of these models was undertaken. The study of the wetting properties of alfa fibers will provide essential information for optimized composites and so will help us in choosing the right chemical treatment necessary to enhance adhesion in alfa-fiber-based composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Theoretical study of wetting behavior of nanoparticles at fluid interfacesAICHE JOURNAL, Issue 3 2009Jianguo Mi Abstract 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 [source] Differences in Wetting Characteristics of Bi2O3 Polymorphs in ZnO Varistor MaterialsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2000Mattias Elfwing Detailed analysis of the microstructure of grain boundaries, especially triple-grain and multiple-grain junctions, in ZnO varistor materials has been performed using transmission electron microscopy. Different polymorphs of Bi2O3 are shown to exhibit different wetting properties on ZnO interfaces. Recent investigations suggest that the equilibrium configuration consists of crystalline Bi2O3 in the triple-grain and multiple-grain junctions and an amorphous bismuth-rich film in the ZnO/ZnO grain boundaries. The present investigation supports this suggestion for ,-Bi2O3 and also adds to the microstructural image and wetting properties of ,-Bi2O3. [source] Topographical and Wettability Effects of Post-Discharge Plasma Treatments on Macroporous Polystyrene-Divinylbenzene Solid FoamsPLASMA PROCESSES AND POLYMERS, Issue 10 2009Cristina Canal Abstract The aim of this study was to evaluate the morphological characteristics and wetting properties of polystyrene-divinylbenzene (PS-DVB) solid foams and their modification through post-discharge plasmas. The low-density solid foams are mainly macroporous, but show a small fraction of mesopores; their characterization revealed differences in topography between the smoother surface and the rougher bulk, while from the chemical point of view both regions of the PS-DVB solid foams are hydrophobic. The macroporous structure of these materials with high pore volume makes them interesting for the design of new drug delivery systems, but some active principles and the physiological media are hydrophilic; therefore, it would be of interest to modify the wettability of the materials via post-discharge plasma treatments. [source] Copolymerizations of butyl methacrylate and fluorinated methacrylates via RAFT miniemulsion polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2007Tian-Ying Guo Abstract Copolymerizations of n -butyl methacrylate (BMA) and fluoro-methacrylates (including 2,2,3,4,4,4-hexafluorobutyl methacrylate, HFBMA and 2,2,2-trifluoroethyl methacrylate, TFEMA) were carried out via reversible addition-fragmentation chain transfer miniemulsion polymerization, using cumyl dithiobenzoate as a chain transfer agent. The experimental results show that the copolymerizations exhibit "living" fashion, with controlled molecular weights and narrow polydispersities. The reactivity ratios of BMA and fluoromethacrylate in this kind of polymerization system were investigated by size exclusion chromatography and nuclear magnetic resonance, from which the Q - and e -values of HFBMA and TFEMA were calculated. Compared with its corresponding non-fluoric methacrylate, fluorinated methacrylate exhibits higher resonance stability of the radical adducts. The Q -value of fluorinated methacrylate is higher (QBMA = 0.82 to QHFBMA = 1.70 and QEMA = 0.76 to QTFEMA = 1.01), and e -value is much larger (eBMA = 0.28 to eHFBMA = 1.24 to and eEMA = 0.17 to eTFEMA = 1.29) for its rather unique high electron-withdrawing inductive effect of the fluoroalkyl ester group. The thermal property and the wetting property of copolymers were also discussed. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5067,5075, 2007 [source] | |||||||||||||||||||