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Receding Contact Angle (receding + contact_angle)
Selected AbstractsVolume of a liquid drop detaching from a sphereHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 6 2010Kenji 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] Laser scanning confocal microscope characterization of dye diffusion in nylon 6 fibers treated with atmospheric pressure plasmasJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2008Chunxia 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] Characterization of crosslinking effects on the physicochemical and drug diffusional properties of cationic hydrogels designed as bioactive urological biomaterialsJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 10 2005David S. Jones This study examined the effects of concentration and type of crosslinker (tetraethyleneglycol diacrylate, TEGDA; diethyleneglycol dimethacrylate, DEGDMA; and polyethyleneglycol dimethacrylate, PEGDMA) on the mechanical and drug diffusional properties of hydrogels that had been selected as candidate coatings for bioactive medical devices. Hydrogels (dimethylaminoethylmethacrylate-covinylpyrrolidone; 1:1) were prepared by free radical polymerization and characterized using tensile analysis, dynamic contact angle analysis and analysis of swelling at pH 6.0. The release of fusidic acid and chlorhexidine was evaluated using buffered medium at pH 6.0 and, in addition, using dissolution medium that had been buffered to pH 9 in the presence and absence of elevated concentrations of calcium, representative of urinary encrustation. Crosslinker concentration, but not type, affected the advancing and receding contact angles. Conversely, both crosslinker type and concentration affected the mechanical and swelling properties of the hydrogels. Maximum swelling and elongation at break were associated with the PEGDMA-crosslinked hydrogels whereas TEGDA-crosslinked hydrogels exhibited the maximum ultimate tensile strength and Young's modulus. Drug release from all systems occurred by diffusion. The mass of chlorhexidine and fusidic acid released was dependent on crosslinker type and concentration, with hydrogels crosslinked with PEGDMA offering the greatest mass of drug released at each sampling period. The mass of fusidic acid but not chlorhexidine released at pH 9.0 in a calcium augmented medium was lower than that released in the same medium devoid of elevated calcium, due to the formation of the poorly soluble calcium salt. In conclusion, this study has uniquely examined the effects of crosslinker type and concentration on physicochemical and drug release properties essential to the clinical and non-clinical performance of bioactive hydrogels for medical device application. [source] Grafting CVD of Poly(vinyl pyrrolidone) for Durable Scleral Lens Coatings,CHEMICAL VAPOR DEPOSITION, Issue 1-3 2010Kyra L. Sedransk Abstract Grafting (g)CVD from the monomer 1-vinyl-2-pyrrolidone (VP) and the Type II initiator benzophenone (BP) under 254,nm UV irradiation yields durable hydrophilic coatings on substrates of poly(methacrylic acid) (PMA) derivatives, desirable for scleral lens applications. The gCVD polymerization of the VP monomer is essentially complete, and little excess BP remains in the film. Process optimization, through single variable and two fractional factorial experiments, result in retention of >90% of the as-deposited film thickness after rinsing. Increasing the initiator dosing time beyond 10,min, or the UV exposure time beyond 5,min, has little effect on the as-deposited thickness, or percentage of film retained after rinsing. This suggests that UV irradiation rapidly transforms most of the BP absorbed on the surface to initiating radicals. Once sufficient initiator dosage and UV exposure have been achieved, the initial deposition thickness is controlled primarily by the total flux of monomer to the surface, which is consistent with previous studies. For all samples, thickness loss occurs primarily during the first 30 days of saline soak-testing with no statistically significant loss (p,>,0.25) during the next 90 days of soak testing. While the additional UV exposure time has a limited effect on initial film thickness, it does increase long term thickness retention, most likely by forming crosslinked and branched structures within the film. All samples tested retain sufficient gCVD coating thickness to impart improved hydrophilicity at the surface throughout the entire 120 day saline soak-testing period. The fractional factorial experiments correlate improved hydrophilicity with an interaction between initiator dosage time and UV exposure time. Indeed, decreasing these two process variables in tandem provides the greatest reduction in contact angle. While the uncoated PMA displayed 92.3°,±,2.1° advancing and 86.7°,±,3.0° receding contact angles with water, the most hydrophilic gCVD coating lowers the advancing and receding contact angles to 39.5°,±,2.6° and 36.2°,±,1.6°, respectively. [source] | ||||||||||