Paper surface penetration

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). 

When a surfactant is injected into the liquid beneath an insoluble monolayer, surfactant molecules may adsorb at the surface, penetrating between the monolayer molecules. However it is difficult to determine the extent of this penetration. In principle, equilibrium penetration is described by the Gibbs equation, but the practical application of this equation is complicated by the need to evaluate the dependence of the activity of monolayer substance on surface pressure. There have been several approaches to this problem. In this paper, previously published surface pressure-area Isotherms for cholesterol monolayers on solutions of hexadecy1-trimethyl-ammonium bromide have been analysed by three different methods and the results compared. For this system there is no significant difference between the adsorption calculated by the equation of Pethica and that from the procedure of Alexander and Barnes, but analysis by the method of Motomura, et al. gives results which differ considerably. These differences indicate that an independent experimental measurement of the adsorption should be capable of discriminating between the Motomura method and the other two. 

Depositing pigment particles on the paper surface creates many problems related to the penetration, adhesion and cohesion of these particles, and sometimes results in poor highligter smear resistance, gloss inconsistency of photo prints and the like. 

We start by discussing the surface penetration phenomenon. This can, for instance, be investigated by using what in paper science is known as the Bristow wheel, where absorption in a paper strip mounted on a rotating wheel is studied. The absorption time in such a set-up is controlled by simply varying the peripheral speed or the applicator box width. Figure 7.39 (59) shows some early absorption results obtained by using the Bristow wheel absorption technique. All curves show some measurable absorption volume, visible also for... 

Beta particles have a very small mass and move much faster and farther than alpha particles, traveling as much as several meters through air. They can pass through paper and penetrate as far as 4-5 mm into body tissue. External exposure to beta particles can bum the surface of the skin, but they do not travel far enough to reach the internal organs. Heavy clothing such as lab coats and gloves are needed to protect the skin from beta particles. 

The purpose of sizing is to modify the surface of the fibers to control penetration of aqueous liquids into the paper. The penetration usually correlates with the absorbency, repellency (hydrophobic ty), and spreading of the aqueous liquid concerned. Control of these important properties may be required for three purposes ... 

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. 

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