Capillarity Tests Research Articles

On-line Atmospheric Pressure Plasma (APP) treatment of polypropylene fabrics

Modification of the intrinsically low surface energy of Polypropylene (PP) fabrics is important to achieve improvements in surface properties, such as wettability, and to introduce new kinds of treatments on the market, such as printability and dye uptake. The aim of this work is to show results of characterization of PP fabrics chemically and physically modified by Low Temperature Atmospheric Pressure Plasma (APP). The first technological advantage of a two meters wide APP system is the possibility to treat large area samples directly on-line, thanks to the combination with a roll-to-roll system. The possibility of employing dry processes allows to implement a new technological approach to low-environmental impact surface functionalization, which turns into considerable reduction of energy use and dramatic savings in water consumption. Two different plasma conditions, mixA and mixB, involving respectively O-and N-functionalizing gas mixtures, were performed on PP fabrics. Capillarity tests allow us to macroscopically detect wettability improvements of PP fabrics.

DBD modification of polyethylene powder hydrophobicity

Problems of the powder particles plasma modification are practically the same as in the case of solid films. Troubles of the powder treatment are related with its three-dimensional character, small size of particles, treated large area and problems with powder manipulation, that also must not be neglected. For modification of polymer powder surface properties like wettability and adhesion without changing powder bulk properties there have been mostly applied methods employing low temperature (cold) plasma treatment at low pressures. Presented contribution describes design and investigation of a novel plasma reactor exploiting the dielectric barrier discharge burning in air at atmospheric pressure by ambient temperature and its usability tests. For tests HDPE powder Borealis CB 9155-01 was used. This plasma reactor is of a very simple construction in comparison with other in literature described apparatuses used for this purpose and needs no vacuum equipment. Powder capillarity tests had proved significant powder capillarity changes induced by DBD plasma modification. Modification effect reduction (aging) is remarkably small (max. reduction about 20% in one year after the modification date), hence modification effect is very time stable.

Model for Capillary-Induced Radial Flow in Cohesionless Soils

Abstract Capillary phenomena in cohesionless soils play an important role in the migration of liquids through the unsaturated zone above and close to groundwater sources. The purpose of this paper is to present the results of a theoretical and experimental study of capillary flow in the radial direction. A closed-form solution for the time-dependent advance of wetting front radius is derived as a function of porosity, degree of saturation, hydraulic conductivity, and capillary head. A laboratory test called the “radial horizontal capillarity test” was developed to measure the radial movement of the wetting front as a function of time and experiments were conducted. Values of capillary-induced hydraulic conductivity and capillary head from the theory and experiments on sands and silt are close to those obtained from linear horizontal capillarity tests.

Siliconic and Acrylic Resins Dispersed in Water as Protectives for Stone Surface

The aim of the present work is to compare the protective effect of solvent and water dispersed products on marble, Lecce and Istria stones. This choice is justified by the need of products effective also from the ecological and toxicological point of view. To obtain these informations two tests have been chosen: contact angle and water absorption. The contact angle may, in theory, be considered a measure of the water repellency, since complete wetting implies a contact angle of 0° and absolutely no wetting an angle of 180°. This does not apply to the water absorption by capillarity test because the absorption variation may be caused by either the water repellency action of the treatments or by the pore filling. However this test may give practical information about the general effect of the treatments. Moreover, the effect of treatments on permeability was investigated by vapour permeability test. Protective effect was studied after application of the products and at various stages of artificial weathering.

New Techniques for Studying Seepage Problems Using Models

Synopsis A technique for overcoming the effects of capillary rise in model seepage studies where there is a free surface is described: the porous medium (sand) is pre-treated with a water-repellent silicone. The method of pre-treatment is given, and the effect this has on capillarity and permeability is considered. The use of an electrical probe to locate water surfaces and any associated zones of partial saturation in capillarity and model seepage tests is described. A second electricaltechnique to determine hydraulic potential by electrical analogy applied direct to the model using the percolating water as an electrolyte is also described. Two-dimensional seepage tests employing these various techniques have been performed on four types of model: an earth dam; an idealized dam with a parabolic upstream face; a vertical wall; and a uniform open channel. The accuracy with which the free surfaces (and in one case, seepage surface) are simulated by the models is assessed. The hydraulic potentials found by direct observation, by electrical analogy applied to the model, and by calculation, are compared. Comparison is also made between calculated and measured rates of flow. A three-dimensional seepage test has been performed without taking measurements; viewsof the free surface in three dimensions are shown. The extension of these techniques to the study of unsteady three-dimensional flow witha free boundary through anisotropic soil of composite section is discussed. Appendices outline the chemistry of the sand treatment and compare the mechanisms of capillary rise in the treated and untreated sand. On décrit une méthode pour surmonter les effets de la montée capillaire dans des études de la filtration sur maquette oů une surface libre existe: le milieu poreux (sable) est trait´ au préalable au moyen d'un silicone hydrophobant. On décrit la méthode de traitement préalable, et l'on considere les effets qu'elle a sur la capillarité et la perméabilité. Une méthode pour localiser les surfaces d'eau et les zones de saturation partielle qui leur sont associées, dans des essais de capillarité et de filtration sur maquette en utilisant une sonde électrique, fait l'objet d'une description. Une seconde technique Clectrique pour Ctablir le potentiel hydraulique paranalogie électrique appliquée directement à la maquette en utilisantl'eau filtrante en qualité d'électrolyte est aussi dérite. Des essais de filtration à deux dimensions utilisantces différentes techniques ont été effectués sur quatre types de maquettes: un barrage en terre, un barrage idéalisé à paroi en amont parabolique, unmur vertical, et un canal ouvert uniforme. La précision avec laquelle les surfaces libres (et dans un cas, la surface de filtration) sont simulées par les maquettes est évaluée Les potentiels hydrauliques trouvés par observation directe, par analogie électrique appliquee à la maquette, et par le calcul, sont comparés. Une comparaison est aussi faite des taux d'écoulement calculés et mesures. Un essai de filtration à trois dimensions a été effectué sans prendre de mesures; des vues de la surface libre en trois dimensions sont présentées. Une application plus étendue de ces techniques à l'étude d'un écoulement instable à trois dimensions avec une limite libre à travers un sol anisotropique de coupe composite fait l'objet d'une discussion. Des annexes donnent un apercu de la chimie relative au traitement du sable, et comparent les mécanismes de la montée capillaire dans le sable traité et non traité.