Contact Angle (contact + angle)

Distribution by Scientific Domains
Distribution within Polymers and Materials Science

Kinds of Contact Angle

  • advancing contact angle
  • dynamic contact angle
  • receding contact angle
  • water contact angle

  • Terms modified by Contact Angle

  • contact angle analysis
  • contact angle measurement

  • Selected Abstracts


    Contact Angle, WAXS, and SAXS Analysis of Poly(,-hydroxybutyrate) and Poly(ethylene glycol) Block Copolymers Obtained via Azotobacter vinelandii UWD

    BIOTECHNOLOGY PROGRESS, Issue 3 2005
    Kerry J. Townsend
    This study investigated and correlated physical properties and cell interactions of copolymers obtained by a poly(ethylene glycol) (PEG)-modulated fermentation of Azotobacter vinelandii UWD. PEGs with molecular weights of 400 and 3400 Da and di(ethylene glycol) (DEG) were used to modulate the bacterial synthesis of poly(,-hydroxybutyrate) (PHB). The PHB crystallinity was determined by wide-angle X-ray scattering (WAXS). Small-angle X-ray scattering (SAXS) showed that lamellar distances decreased between the PHB and the PHB modulated with PEG or DEG. Furthermore, the contact angle of water on the PHB/PEG polymer surfaces decreased when compared to that of PHB. The significant decrease of the contact angle and corresponding increase in surface tension, as well as significant decrease in cell adhesion, suggest the presence of hydrophilic PEG and DEG within the hydrophobic surface. [source]


    Investigation of a New Approach to Measuring Contact Angles for Hydrophilic Impression Materials

    JOURNAL OF PROSTHODONTICS, Issue 2 2007
    Gerard Kugel DMD
    Purpose: The purpose of this investigation was to examine the initial water contact angles of seven unset impression materials using commercially available equipment, in an effort to determine whether polyether impression materials (Impregum) have lower contact angles and are, therefore, more hydrophilic than VPS impression materials. Materials and Methods: The hydrophilic properties of unset polyether and VPS impression materials were analyzed with respect to their water contact angle measurements using the commercially available Drop Shape Analysis System DSA 10. Twenty-five data points per second were collected via video analysis. There was no delay from start of measurement and data collection. Data was collected for approximately 12 s. Droplet size was determined on the thickness of canula. If the droplets became too small in volume, the water that evaporated during the measurement was large in comparison to the volume of the droplet. Therefore, 5 ,l was chosen as the lowest volume. Five trials were conducted per series for each featured material. Contact angles were calculated using the circle fitting method. Three tests using this technique were designed to control the variables of contact angle measurement with regard to time, the varying amount of fluid in contact with impression material during clinical use, and material thickness. Sample thickness of impression material was controlled by stripping the paste flat on a glass plate using a marking template to ensure a constant film thickness. Tests were conducted in a climatized room at 24C 1C. Deionized water was used as the fluid. The device was calibrated according to manufacturer's instruction for Young,Laplace fitting prior to the measurements. Results were analyzed using One-Way ANOVA, Tukey test, and t -test, as appropriate. Results: Comparing the fast setting impression materials by One-Way ANOVA and Tukey tests (p < .05) revealed the initial contact angles to range from 66.2 1.5 to 127.5 4.4, of which the polyether material was the lowest after 45 s (66.2 1.5), 120 s (70.3 2.8), and 24 h (80.3 1.0) after start of the mix. The selected times represent the different stages of unset material, ranging from 45 s as the earliest practical data collection time to 24 h, at which a stone model would be poured. The polyether materials tested exhibited lower contact angles and, thus, significantly higher initial hydrophilicity than all measured VPS materials. Additionally, Impregum impression materials are more hydrophilic in the unset stage than in the set stage. VPS may show a stepwise development of hydrophilicity in the set stage that was not observed in the unset stage. Conclusions: The polyether impression materials tested were significantly more hydrophilic before, during, and after setting than that of VPS impression materials. Regardless of the amount of water in contact with the impression material, the polyether impression materials showed a significantly higher hydrophilicity in the unset stage than the VPS materials. The initial contact angle was not dependent on the thickness of the material. All parameters, including variation of time, volume of water droplet, and thickness of material, resulted in different absolute contact angles, but did not lead to a dramatic change in the ranking of the materials with regard to their hydrophilic behavior. [source]


    Determining Contact Angles of Powders by Liquid Penetration

    PARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 4 2004
    Ulrich Teipel
    Abstract The wettability of a powder is important, especially in chemical and pharmaceutical technologies when considering the manufacturing process and the properties of the final product. However, contact angle methods for powders are problematic. The common measurement techniques are the sessile drop method and the liquid penetration method. In this work the determination of contact angles of powders by liquid penetration is considered. In particular, we investigated the influence of the sample preparation and sampling device on the wetting process. A bulk with constant properties during the measurement must be guaranteed. We postulate a packing procedure to obtain reproducible measurements by ensuring constant powder properties. [source]


    Influence of whey peptides on the surface activity of ,-casein and ,-lactoglobulin A

    INTERNATIONAL JOURNAL OF DAIRY TECHNOLOGY, Issue 2 2010
    ZAHUR U HAQUE
    Whey protein hydrolysate (WPH) was fractionated by reverse-phase chromatography to obtain fractions of varying surface-hydrophobicities. A model oil,water interface (MI) was pre-coated with the WPH or fractions thereof. Contact angle (,) of sessile drops of ,-casein (,-CN) or ,-lactoglobulin A (,-LGA) were measured on the MI. Pre-coating of MI with un-fractionated WPH decreased ,, that is, increased surface activity, of both ,-CN (35,8.3) and ,-LGA (38,21.3). Conversely, pre-coating of MI with the fractions significantly increased , of both proteins as a function of hydrophobicity. Data provide insight into variability of whey protein functionality in food applications. [source]


    Surface modification of quarry stone by hexamethyldisiloxane plasma treatment

    APPLIED ORGANOMETALLIC CHEMISTRY, Issue 10 2007
    Jose A. Lpez-Barrera
    Abstract The surface of quarry stone was modified by continuous plasma polymerization of hexamethyldisiloxane. The hydrophilic surface of the quarry stone was made hydrophobic and impermeable to water. Three different reaction times were analyzed. All of them resulted in the formation of a homogenous layer on the quarry stone surface. Contact angle and FT-IR analyses show that the hydrophobic character of the surface is due to methyl groups on the surface. The change in the contact angle with temperature and the wetting temperature (Tw) are also discussed. Copyright 2007 John Wiley & Sons, Ltd. [source]


    Evidence for surfactant contributing to the gastric mucosal barrier of the horse

    EQUINE VETERINARY JOURNAL, Issue 6 2000
    M. T. ETHELL
    Summary This study was undertaken to determine the hydrophobicity of the luminal surface of the equine stomach and to elucidate the ultrastructure of the lining imparting that property. Gastric and duodenal mucosal samples from 5 horses were collected immediately after euthanasia and subjected to surface contact angle measurement using a goniometer. Gastric mucosal samples from 4 horses and a foal were examined by electron microscopy following a fixation procedure known to preserve phospholipids and oligolamellar structures. Contact angles for the equine gastric glandular mucosal surface (mean s.e. 78.0 11.0) were greater than for the duodenum (33.4 8.7), (P = 0.003). The contact angles for gastric squamous tissue (50.4 4.5) tended to be greater than for duodenum (P = 0.15). Electron microscopy revealed the existence of surfactant as abundant osmiophilic phospholipid material within both squamous and glandular gastric mucosae. These results indicate the hydrophobic nature of the equine gastric mucosae. We propose that the water-repellent nature of the stomach contributes to the ,gastric mucosal barrier' and is imparted by surface-active phospholipid adsorbed to the surface. Phospholipids may also be utilised as a physical barrier to back-diffusion of acid by lining intracellular canaliculi and oxyntic ducts where other defence mechanisms are absent. [source]


    Investigation of a New Approach to Measuring Contact Angles for Hydrophilic Impression Materials

    JOURNAL OF PROSTHODONTICS, Issue 2 2007
    Gerard Kugel DMD
    Purpose: The purpose of this investigation was to examine the initial water contact angles of seven unset impression materials using commercially available equipment, in an effort to determine whether polyether impression materials (Impregum) have lower contact angles and are, therefore, more hydrophilic than VPS impression materials. Materials and Methods: The hydrophilic properties of unset polyether and VPS impression materials were analyzed with respect to their water contact angle measurements using the commercially available Drop Shape Analysis System DSA 10. Twenty-five data points per second were collected via video analysis. There was no delay from start of measurement and data collection. Data was collected for approximately 12 s. Droplet size was determined on the thickness of canula. If the droplets became too small in volume, the water that evaporated during the measurement was large in comparison to the volume of the droplet. Therefore, 5 ,l was chosen as the lowest volume. Five trials were conducted per series for each featured material. Contact angles were calculated using the circle fitting method. Three tests using this technique were designed to control the variables of contact angle measurement with regard to time, the varying amount of fluid in contact with impression material during clinical use, and material thickness. Sample thickness of impression material was controlled by stripping the paste flat on a glass plate using a marking template to ensure a constant film thickness. Tests were conducted in a climatized room at 24C 1C. Deionized water was used as the fluid. The device was calibrated according to manufacturer's instruction for Young,Laplace fitting prior to the measurements. Results were analyzed using One-Way ANOVA, Tukey test, and t -test, as appropriate. Results: Comparing the fast setting impression materials by One-Way ANOVA and Tukey tests (p < .05) revealed the initial contact angles to range from 66.2 1.5 to 127.5 4.4, of which the polyether material was the lowest after 45 s (66.2 1.5), 120 s (70.3 2.8), and 24 h (80.3 1.0) after start of the mix. The selected times represent the different stages of unset material, ranging from 45 s as the earliest practical data collection time to 24 h, at which a stone model would be poured. The polyether materials tested exhibited lower contact angles and, thus, significantly higher initial hydrophilicity than all measured VPS materials. Additionally, Impregum impression materials are more hydrophilic in the unset stage than in the set stage. VPS may show a stepwise development of hydrophilicity in the set stage that was not observed in the unset stage. Conclusions: The polyether impression materials tested were significantly more hydrophilic before, during, and after setting than that of VPS impression materials. Regardless of the amount of water in contact with the impression material, the polyether impression materials showed a significantly higher hydrophilicity in the unset stage than the VPS materials. The initial contact angle was not dependent on the thickness of the material. All parameters, including variation of time, volume of water droplet, and thickness of material, resulted in different absolute contact angles, but did not lead to a dramatic change in the ranking of the materials with regard to their hydrophilic behavior. [source]


    Glass bead grafting with poly(carboxylic acid) polymers and maleic anhydride copolymers

    POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 2 2008
    H. Zengin
    Abstract Glass beads were etched with acids and bases to increase the surface porosity and the number of silanol groups that could be used for grafting materials to the surfaces. The pretreated glass beads were functionalized using 3-aminopropyltriethoxysilane (APS) coupling agent and then further chemically modified by reacting the carboxyl groups of carboxylic acid polymers with the amino groups of the pregrafted APS. Several carboxylic acid polymers and poly(maleic anhydride) copolymers, such as poly(acrylic acid) (PAA), poly(methacrylic acid) (PMA), poly(styrene-alt-maleic anhydride) (PSMA), and poly(ethylene-alt-maleic anhydride) (PEMA) were grafted onto the bead surface. The chemical modifications were investigated and characterized by FT-IR spectroscopy, particle size analysis, and tensiometry for contact angle and porosity changes. The amount of APS and the different polymer grafted on the surface was determined from thermal gravimetric analysis and elemental analysis data. Spectroscopic studies and elemental analysis data showed that carboxylic acid polymers and maleic anhydride copolymers were chemically attached to the glass bead surface. The improved surface properties of surface modified glass beads were determined by measuring water and hexane penetration rates and contact angle. Contact angles increased and porosity decreased as the molecular weights of the polymer increased. The contact angles increased with the hydrophobicity of the attached polymer. The surface morphology was examined by scanning electron microscopy (SEM) and showed an increase in roughness for etched glass beads. Copyright 2007 John Wiley & Sons, Ltd. [source]


    Surface Structures and Osteoblast Activity on Biomedical Polytetrafluoroethylene Treated by Long-Pulse, High-Frequency Oxygen Plasma Immersion Ion Implantation

    ADVANCED ENGINEERING MATERIALS, Issue 5 2010
    Liping Tong
    Abstract Polytetrafluoroethylene (PTFE) is a biologically safe polymer used widely in clinical medicine including oral and orthopedic surgery. However, the high bio-inertness of PTFE has hampered wider applications in the biomedical fields. In this work, we extend the treatment time in long-pulse, high-frequency oxygen plasma immersion ion implantation of PTFE and a more superhydrophobic surface with a water contact angle of 160 is created. X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) reveal that the optimized long-pulse, high-frequency oxygen plasma immersion ion implantation process induces a rougher surface and to a lesser extent alters the surface oxygen concentration on the PTFE. Our data, especially long-term contact angles, suggest that the superhydrophobility stems from surface roughness alteration. Furthermore, the activity of MC3T3-E1 osteoblasts cultured on the treated surfaces is promoted in terms of quantities and morphology. [source]


    Organic Electronics: High Tg Cyclic Olefin Copolymer Gate Dielectrics for N,N,-Ditridecyl Perylene Diimide Based Field-Effect Transistors: Improving Performance and Stability with Thermal Treatment (Adv. Funct.

    ADVANCED FUNCTIONAL MATERIALS, Issue 16 2010
    Mater.
    Abstract A novel application of ethylene-norbornene cyclic olefin copolymers (COC) as gate dielectric layers in organic field-effect transistors (OFETs) that require thermal annealing as a strategy for improving the OFET performance and stability is reported. The thermally-treated N,N, -ditridecyl perylene diimide (PTCDI-C13)-based n-type FETs using a COC/SiO2 gate dielectric show remarkably enhanced atmospheric performance and stability. The COC gate dielectric layer displays a hydrophobic surface (water contact angle = 95 1) and high thermal stability (glass transition temperature = 181 C) without producing crosslinking. After thermal annealing, the crystallinity improves and the grain size of PTCDI-C13 domains grown on the COC/SiO2 gate dielectric increases significantly. The resulting n-type FETs exhibit high atmospheric field-effect mobilities, up to 0.90 cm2 V,1 s,1 in the 20 V saturation regime and long-term stability with respect to H2O/O2 degradation, hysteresis, or sweep-stress over 110 days. By integrating the n-type FETs with p-type pentacene-based FETs in a single device, high performance organic complementary inverters that exhibit high gain (exceeding 45 in ambient air) are realized. [source]


    High Tg Cyclic Olefin Copolymer Gate Dielectrics for N,N,-Ditridecyl Perylene Diimide Based Field-Effect Transistors: Improving Performance and Stability with Thermal Treatment

    ADVANCED FUNCTIONAL MATERIALS, Issue 16 2010
    Jaeyoung Jang
    Abstract A novel application of ethylene-norbornene cyclic olefin copolymers (COC) as gate dielectric layers in organic field-effect transistors (OFETs) that require thermal annealing as a strategy for improving the OFET performance and stability is reported. The thermally-treated N,N, -ditridecyl perylene diimide (PTCDI-C13)-based n-type FETs using a COC/SiO2 gate dielectric show remarkably enhanced atmospheric performance and stability. The COC gate dielectric layer displays a hydrophobic surface (water contact angle = 95 1) and high thermal stability (glass transition temperature = 181 C) without producing crosslinking. After thermal annealing, the crystallinity improves and the grain size of PTCDI-C13 domains grown on the COC/SiO2 gate dielectric increases significantly. The resulting n-type FETs exhibit high atmospheric field-effect mobilities, up to 0.90 cm2 V,1 s,1 in the 20 V saturation regime and long-term stability with respect to H2O/O2 degradation, hysteresis, or sweep-stress over 110 days. By integrating the n-type FETs with p-type pentacene-based FETs in a single device, high performance organic complementary inverters that exhibit high gain (exceeding 45 in ambient air) are realized. [source]


    Poly(2-(dimethylamino)ethyl methacrylate) Brushes with Incorporated Nanoparticles as a SERS Active Sensing Layer

    ADVANCED FUNCTIONAL MATERIALS, Issue 11 2010
    Smrati Gupta
    Abstract A simple, fast, and versatile approach to the fabrication of outstanding surface enhanced Raman spectroscopy (SERS) substrates by exploiting the optical properties of the Ag nanoparticles and functional as well as organizational characteristics of the polymer brushes is reported. First, poly(2-(dimethylamino)ethyl methacrylate) brushes are synthesized directly on glassy carbon by self-initiated photografting and photopolymerization and thoroughly characterized in terms of their thickness, wettability, morphology, and chemical structure by means of ellipsometry, contact angle, AFM, and XPS, respectively. Second, Ag nanoparticles are homogeneously immobilized into the brush layer, resulting in a sensor platform for the detection of organic molecules by SERS. The surface enhancement factor (SEF) as determined by the detection of Rhodamine 6G is calculated as 6,,106. [source]


    Fabrication of a Superhydrophobic Surface from a Smectic Liquid-Crystal Defect Array

    ADVANCED FUNCTIONAL MATERIALS, Issue 18 2009
    Yun Ho Kim
    Abstract A novel fabrication method is developed for the preparation of superhydrophobic surfaces. The procedure uses focal conic structures of semi-fluorinated smectic liquid crystals (LCs) whose periodic toric focal conic domains (TFCDs) are prepared on a surface modified substrate. Reactive ion etching (RIE) on the periodic TFCD surface leads to a superhydrophobic surface with a water contact angle of ,160 and a sliding angle of ,2 for a 10,L water droplet. The results show that this phenomenon is due to the development of a dual-scale surface roughness arising from the nanoscale protuberance caused by applying the RIE process to the top of the microscale TFCD arrays. The unique surface behavior is further verified by demonstrating that RIE on a flat lamellar liquid crystal film, in which the director is aligned parallel with surface, results in a relatively low hydrophobicity as compared to when periodic TFCDs are subjected to REI. The observations made in this publication suggest that a new approach exists for selecting potential candidates of superhydrophic surface formation based on spontaneous self-assembly in smectic liquid-crystalline materials. [source]


    Addressable Protein Patterning via Switchable Superhydrophobic Microarrays,

    ADVANCED FUNCTIONAL MATERIALS, Issue 15 2007
    J.-Y. Shiu
    Abstract We report on a simple process to create a switchable superhydrophobic surface where the water contact angle can be switched from a superhydrophobic state (ca.,167) to a completely wetted state (<,10). In the superhydrophobic state, the switchable superhydrophobic surface was resistant to the adsorption of proteins. However, once converted to a wetted state, the same surface promoted protein adsorption. We have developed a novel multicomponent protein-patterning technique based on this unique property of the switchable superhydrophobic surface. It is demonstrated that up to 100,,100 protein spots can be created within one second. Each element on the switchable superhydrophobic microarray can be addressed individually and different types of biomolecules can be selectively deposited on the microarray without losing their activity. When integrated with microfluidic channels, the switchable superhydrophobic surface allows the parallel patterning of protein molecules to be carried out without cross contamination. [source]


    Volume of a liquid drop detaching from a sphere

    HEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 6 2010
    Kenji Katoh
    Abstract A theoretical and experimental study is conducted to investigate the detached volume from a pendant drop on the surface of a sphere. Observation of drop detachment by high-speed video camera reveals that the movement of the upper part of the neck of the drop is quite slow compared to that of the detaching lower part. The surface profile of the upper part was calculated approximately as a static problem using the axisymmetric Laplace equation. Using the drop profile, the system energy, including the work done by the solid,liquid wetting behavior, was calculated. Based on the condition of minimum energy, the volume of the detached part V was calculated. The volume V increases with the sphere diameter and approaches the value for the pendant drop attached to a plate. In addition, V is strongly dependent on the wettability between the sphere and the liquid and decreases with the receding contact angle. The detached volume of the water drop was measured for spheres of porous brick of various diameters. The experimental and theoretical results were found to be in good agreement. 2010 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/htj.20305 [source]


    Frost formation on a bionic super-hydrophobic surface under natural convection conditions

    HEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 7 2008
    Yunjun Gou
    Abstract A bionic super-hydrophobic surface has a multiple micro-nano-binary structure (MNBS) similar to the lotus leaf surface microstructure. This kind of surface has a contact angle of water greater than 150 and a roll angle smaller than 5. In this paper, the frost deposition phenomena on a bionic super-hydrophobic surface were observed. The surface has many micro bumps and its contact angle is 162. The formation of water droplets, the droplet freezing process, the formation of initial frost crystals and the frost layer structure on a cold bionic super-hydrophobic surface under natural convection conditions were closely observed. The frost layer structure formed on the super-hydrophobic surface shows remarkable differences to that on a plain copper surface: the structure is weaker, looser, thin, and easily removed and most importantly, it is of a very special pattern, a pattern similar to a chrysanthemum, a frost layer structure that has not been reported before to the best of the present authors knowledge. The experimental results also show that a super-hydrophobic surface has a strong ability to restrain frost growth. The frost deposition on this bionic surface was delayed 55 minutes when compared with a plain copper surface under the conditions of a cold plate temperature of ,10.1C, air temperature of 18.4C, and relative humidity of 40%. A theoretical analysis was also presented to explain the observed phenomena. 2008 Wiley Periodicals, Inc. Heat Trans Asian Res, 37(7): 412,420, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20216 [source]


    Superhydrophobic to Superhydrophilic Wetting Control in Graphene Films

    ADVANCED MATERIALS, Issue 19 2010
    Javad Rafiee
    The wetting of graphene films from superhydrophobic (contact angle of ,160) to superhydrophilic (,0) is controlled using surface chemistry/roughness effects. Graphene sheets dispersed in water/acetone solvents are deposited on various substrates, where the contact angle of the graphene films could be tuned from superhydrophobic to superhydrophilic by simply controlling the relative proportion of acetone and water in the solvent. [source]


    Implications of ideas on super-hydrophobicity for water repellent soil

    HYDROLOGICAL PROCESSES, Issue 17 2007
    G. McHale
    Abstract Water repellence is an important factor in soil erosion due to its role in inhibiting the re-establishment of vegetation after fire and due to its enhancement of run-off. Water repellence is studied across a range of diverse disciplines, such as chemistry, materials, textiles and soil and reclamation science. In recent years many basic studies of water repellence of materials have focused on the role of the sub-mm surface topography of a material in modifying the intrinsic hydrophobicity imparted by the surface chemistry to create super-hydrophobicity. In this report, we first illustrate the types of hydrophobic effects created by a suitable coupling of small scale surface topography with surface chemistry using three materials: an etched metal, a foam and a micro-fabricated pillar structure. These experiments demonstrate the general applicability of the ideas and suggest that they could apply to a granular material such as, a fine sandy soil, particularly when the grains have become coated with a hydrophobic layer. This applicability is confirmed by contact angle measurements of droplets of water on hydrophobic sand. A theoretical model describing the application of these ideas in a loose-packed, but regular, array of uniform spherical grains is then presented and discussed. When the grains are in a dry state initially, the effect of the surface is to increase the apparent water repellence as observed through the contact angle. However, when the spaces between the grains are filled with water, the effect is to provide greater wetting. To qualitatively confirm the enhancement of contact angle caused by the granular structure, model surfaces using 600 and 250 m hydrophobic glass beads were created. On these surfaces, the contact angle of droplets of water was increased from 108 to 126 and 140 , respectively. Copyright 2007 John Wiley & Sons, Ltd. [source]


    Nanostructured ZnO-Based Surface with Reversible Electrochemically Adjustable Wettability

    ADVANCED MATERIALS, Issue 6 2009
    Chantal Badre
    A ZnO-based smart surface functionalized by a surface-confined sub-monolayer layer of a purpose-built redox molecule is realized. The hybrid ferrocene/ZnO assembly exhibits a controllable wetting behavior with a contact angle that can be rapidly and reversibly adjusted to a defined value ranging from 110, to less than 10, (see figure). [source]


    Height functions for applying contact angles to 3D VOF simulations

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 8 2009
    S. Afkhami
    Abstract A rigorous methodology is presented for applying a contact angle as a contact line boundary condition within a 3D volume-of-fluid-based flow algorithm, based on the recently developed height function methodology that yields accurate interface normals and curvatures from volume fractions. We demonstrate that the approach yields accurate estimates of curvature and surface tension at a contact line, values that converge with spatial refinement. We then study the efficacy of this approach via examples of both static and dynamic contact line phenomena. Copyright 2008 John Wiley & Sons, Ltd. [source]


    Complex Droplets on Chemically Modified Silicon Nanograss,

    ADVANCED MATERIALS, Issue 18 2008
    Ville Jokinen
    Dropping in. Chemically modified silicon nanograss combines nanoscale topography with lithographically defined chemical patterns. The material exhibits a high wettability gradient that allows tailoring of complex droplet shapes. The oxidized nanograss is completely wetting, while the polymer-coated nanograss has a contact angle of ca. 170 and is ultrahydrophobic. Novel droplet behavior on these surfaces is studied experimentally. [source]


    One-Step Solution-Immersion Process for the Fabrication of Stable Bionic Superhydrophobic Surfaces,

    ADVANCED MATERIALS, Issue 6 2006
    S. Wang
    A simple morphogenesis technique for fabricating stable bionic superhydrophobic surfaces at ambient temperature using copper as a model system is presented. The resulting flowerlike cluster coating of copper fatty acid carboxylates (see figure) has a high contact angle of about 162. This study opens up new avenues for the industrial fabrication of superhydrophobic surfaces that may be useful in a wide variety of applications. [source]


    Pool boiling on a superhydrophilic surface

    INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 2 2003
    Y. Takata
    Abstract Titanium Dioxide, TiO2, is a photocatalyst with a unique characteristic. A surface coated with TiO2 exhibits an extremely high affinity for water when exposed to UV light and the contact angle decreases nearly to zero. Inversely, the contact angle increases when the surface is shielded from UV. This superhydrophilic nature gives a self-cleaning effect to the coated surface and has already been applied to some construction materials, car coatings and so on. We applied this property to the enhancement of boiling heat transfer. An experiment involving the pool boiling of pure water has been performed to make clear the effect of high wettability on heat transfer characteristics. The heat transfer surface is a vertical copper cylinder of 17 mm in diameter and the measurement has been done at saturated temperature and in a steady state. Both TiO2 -coated and non-coated surfaces were used for comparison. In the case of the TiO2 -coated surface, it is exposed to UV light for a few hours before experiment and it is found that the maximum heat flux (CHF) is about two times larger than that of the uncoated surface. The temperature at minimum heat flux (MHF) for the superhydrophilic surface is higher by 100 K than that for the normal one. The superhydrophilic surface can be an ideal heat transfer surface. Copyright 2002 John Wiley & Sons, Ltd. [source]


    Characterization of acrylic acid grafted poly(ethylene terephthalate) fabric

    JOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010
    Navdeep Grover
    Abstract The preirradiation grafting of acrylic acid (AA) onto poly(ethylene terephthalate) (PET) had been found to affect the thermal and physical characteristics of fabric. The grafted fabrics with various graft levels were characterized by thermal gravimetric analysis (TGA), ATR-FTIR spectroscopy, contact angle, differential scanning calorimetry (DSC), X-ray diffraction (XRD), atomic force microscopy (AFM), and scanning electron microscopy (SEM). The initial decomposition temperature and T50 were increased with the increase in degree of grafting. The percentage crystallinity was decreased as the degree of grafting increases. The detailed elemental analysis was done by X-ray photoelectron spectroscopy (XPS). The atomic ratio (O1s/C1s) was found to increase significantly with increasing the degree of grafting and reached 0.64 at 14.5% grafting from 0.38 for virgin PET. The surface topography and morphology was strongly influenced as the degree of grafting was increased. 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]


    Synthesis and characterization of novel polyimide/SiO2 nanocomposite materials containing phenylphosphine oxide via sol-gel technique

    JOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010
    Canan Kizilkaya
    Abstract In this article, a series of novel polyimide/silica (PI/SiO2) nanocomposite coating materials were prepared from tetraethoxysilane (TEOS), ,-glycidyloxypropyltrimethoxysilane (GOTMS), and polyamic acid (PAA) via sol-gel technique. PAA was prepared by the reaction of 3,3,,4,4,-benzophenone tetracarboxylic dianhydride (BTDA) and bis (3-aminophenyl) phenyphosphine oxide (BAPPO) in N -methyl-2- pyrrolidone (NMP). BAPPO was synthesized hydrogenation of bis (3-nitrophenyl) phenyphosphine oxide (BNPPO) in the presence of Pd/C. The silica content in the hybrid coating materials was varied from 0 to 20 wt %. The molecular structures of the composite materials were analyzed by means of FT-IR and 29Si-NMR spectroscopy techniques. The physical and mechanical properties of the nanocomposites were evaluated by various techniques such as, hardness, contact angle, and optical transmission and tensile tests. These measurements revealed that all the properties of the nanocomposite coatings were improved noticeable, by the addition of sol-gel precursor into the coating formulation. Thermogravimetric analysis showed that the incorporation of sol-gel precursor into the polyimide matrix leads to an enhancement in the thermal stability and also flame resistance properties of the coating material. The surface morphology of the hybrid coating was characterized by scanning electron microscopy (SEM). SEM studies indicated that nanometer-scaled inorganic particles were homogenously dispersed throughout the polyimide matrix 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]


    Effects of soft segments on the surface properties of polydimethylsiloxane waterborne polyurethane prepolymer blends and treated nylon fabrics

    JOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010
    Meng-Shung Yen
    Abstract This study of waterborne polyurethane prepolymer blends was done to investigate the effects of different types of soft segments on the dispersion properties and other properties of treated nylon fabrics. The particle size of the dispersion increased, the surface tension of the dispersion decreased, and the contact angle of the nylon fabric with the dispersion decreased when the blending amount of the polydimethylsiloxane polyurethane prepolymer increased. The add-on of ether-type polyurethane increased rapidly when the ether-type polyurethane was blended with a small amount of the polydimethylsiloxane polyurethane prepolymer, whereas the add-on of the ether-type polyurethane reached a maximum at a blending content of 10%. The add-on of the ester-type polyurethane prepolymer constantly decreased with increasing blending amount of the polydimethylsiloxane polyurethane prepolymer. The vertical wicking height of the treated nylon fabrics decreased slightly when the treating agent contained a small amount of the polydimethylsiloxane polyurethane prepolymer. For the treated nylon fabrics with blended prepolymers, the drying time was faster than for the untreated fabric, and the moisture ratio reached about 10% in 15 min 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]


    Wettability investigations on the cellulosic surface of alfa fibers

    JOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008
    N. 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]


    Photostability of isotactic polypropylene containing monoazo pigment

    JOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008
    Zahra Ahmadi
    Abstract The photodegradation of isotactic polypropylene (PP) films containing a monoazo pigment and hindered amine light stabilizers (HALS) has been undertaken. PP films were exposed to medium pressure mercury lamp radiation in the laboratory for periods of up to 8 weeks and the degree of degradation (oxidation/deterioration) was examined using FTIR spectroscopy and differential scanning calorimetry (DSC) as well as by measuring changes in the mechanical properties, contact angle, and density. The results of these measurements indicate that unstabilized PP films degraded after only 240-h irradiation. By adding an organic pigment to PP films along with antioxidant and HALS, the photostability of PP films increased to the 1500-h level. 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]


    Laser scanning confocal microscope characterization of dye diffusion in nylon 6 fibers treated with atmospheric pressure plasmas

    JOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2008
    Chunxia Wang
    Abstract The effect of atmospheric pressure plasma treatment on wettability and dyeability of nylon 6 fibers is investigated. The plasma treatments resulted in an average of 10,20 decrease in the advancing contact angle and 20,30 decrease in the receding contact angle. An increased dye diffusion rate of nylon 6 fibers was observed using laser scanning confocal microscope (LSCM). Scanning electron microscope confirmed that the fiber surfaces were roughened, and X-ray photoelectron spectroscopy showed that the polar groups on the fiber surfaces increased after the plasma treatments. As the plasma treatment time increased, a greater degree of etching was achieved and more polar groups such as hydroxyl and carboxyl groups produced on the surfaces of the nylon 6 fibers, leading to a better wettability and thus a better dyeability of the fiber. This study proved that LSCM may be effectively used in detecting the change of dye diffusion rate in nylon fibers treated with plasmas and the mounting medium should have a close refractive index as the fiber to avoid distortion of the fiber cross section image. 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]


    Water-repellent finishing of cotton fabrics by ultraviolet curing

    JOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2008
    F. Ferrero
    Abstract Cotton fabrics were water-repellent-finished by radical ultraviolet curing of silicone and urethane acrylates with different formulations. The fabrics were impregnated with undiluted resins and with toluene solutions or water emulsions. Moreover, cationic ultraviolet-curable systems were also investigated, such as an epoxy-functional polysiloxane and mixtures of an epoxy resin with hydroxyl-containing silicone additives. The gel content and polymerization yield were considered for the ultraviolet-curing process evaluation. Water-resistance properties were determined in terms of the contact angle, wettability, moisture adsorption, and water vapor permeability measurements, whereas the morphology and surface composition of treated fabrics were examined with scanning electron microscopy and energy-dispersive X-ray analysis. 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]