Porosity, paper surface

Fluidyibsorbamy. Fluids like ink penetrate into paper during the printing process. The further the ink penetrates, the less glossy the print. The degree of penetration in paper is generally a function of the paper porosity and wettabiUty by the fluid. It can be controlled by the particle size, shape, and chemical nature of the filler or filler surface. In particular, plate-like fillers, such as clays, tend to produce the best fluid holdout because they tend to overlap and reduce the porosity at the paper surface (see Inks). 

The quality of a printed image is greatly enhanced when a coating is applied to the paper surface. Coating the paper lowers the roughness of the surface, generates gloss, provides an ink receptive surface with controlled porosity and improves... 

The gloss of the printed paper is determined by the smoothness of the paper surface and the ink holdout. In turn, the ink holdout is mainly determined by the porosity and the chemical and physical structure of the coated surface. Coatings need to be porous on a microscopic scale so that the soluble component of printing inks is able to penetrate the paper and dry more quickly. The intensity and brilliance of the printed image and the ink consumption depend on the pigments staying on the surface. The hydrophobicity of the coated surface and the surface tension both influence the ink uptake. 

Blistering in web offset process (due to high temperatures in the drying section of the printing machine, the humidity of the paper web will evaporate instantaneously. Unless the coating has a high porosity, this will lead to blisters on the printed paper surface)... 

Surface Sizing. Surface sizing is generally used for modification of other properties of paper or paperboard such as printabiHty, smoothness, porosity, coefficient of friction, opacity, surface strength, anti-linting or coating holdout. Anionic starch is perhaps the most common additive or co-additive used for surface sizing. 

Figure 13.5 Plug-type dezincification on the internal surface of a brass condenser tube. Note the extreme porosity of the copper plugs. Tube wall thickness was 0.040 in. (0.10 cm). Compare to Fig. 13.13. (Courtesy of National Association of Corrosion Engineers, Corrosion 89 Paper No. 197 by H. M. Herro.)...

If measurements are made in thin oxide films (of thickness less than 5 nm), at highly polished Al, within a small acceptance angle (a < 5°), well-defined additional maxima and minima in excitation (PL) and emission (PL and EL) spectra appear.322 This structure has been explained as a result of interference between monochromatic electromagnetic waves passing directly through the oxide film and EM waves reflected from the Al surface. In a series of papers,318-320 this effect has been explored as a means for precise determination of anodic oxide film thickness (or growth rate), refractive index, porosity, mean range of electron avalanches, transport numbers, etc. 

Multilayer deposition of halloysite is possible not only on large solid surfaces but also on soft biological surfaces such as wood or cotton cellulose microfibers (Figure 14.18). This coating allows a drastic increase in the porosity of the fibers and materials made from them (paper and textile). 

Acidic micro- and mesoporous materials, and in particular USY type zeolites, are widely used in petroleum refinery and petrochemical industry. Dealumination treatment of Y type zeolites referred to as ultrastabilisation is carried out to tune acidity, porosity and stability of these materials [1]. Dealumination by high temperature treatment in presence of steam creates a secondary mesoporous network inside individual zeolite crystals. In view of catalytic applications, it is essential to characterize those mesopores and to distinguish mesopores connected to the external surface of the zeolite crystal from mesopores present as cavities accessible via micropores only [2]. Externally accessible mesopores increase catalytic effectiveness by lifting diffusion limitation and facilitating desorption of reaction products [3], The aim of this paper is to characterize those mesopores by means of catalytic test reaction and liquid phase breakthrough experiments. 

All symbols are defined at the end of the paper. Equation 10 defines the pure water permeability constant A for the membrane which is a measure of its overall porosity eq 12 defines the solute transport parameter D /K6 for the membrane, which is also a measure of the average pore size on the membrane surface on a relative scale. The Important feature of the above set of equations is that neither any one equation in the set of equations 10 to 13, nor any part of this set of equations is adequate representation of reverse osmosis transport the latter is governed simultaneously by the entire set of eq 10 to 13. Further, under steady state operating conditions, a single set of experimental data on (PWP), (PR), and f enables one to calculate the quantities A, Xy 2> point... 

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