Opacity coated 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. 

The opacity of plastic foams, and polymers with scratched surfaces, is also governed by Fresnel s law. The n value of the gas which occupies the scratch indentation is much lower than that of the polymer. Light may be directed through rods of transparent polymers, such as PMMA. This effect may be enhanced when the rod or filament is coated with a polymer with a different refractive index, such as polytetrafluoroethylene (ptfe). Optical fibers utilize this principle. 

A unique two-coat, topcoat system is used in the automobile industry. A basccoat is applied to a primed surface to provide opacity, color, and a metallic appearance, while the clearcoat provides gloss mid a miiioilike finish (referred to as distinctness of image). 

The final pigment black concentration to produce a good opacity is 2-5%, for base coats up to 10%, calculated on resin solid. Pigment blacks with extremely high-structure and surface area can be used for electro-conductive coatings [4.27, 4.29]. The carbon black content in this case is 30-50% on resin solid. 

For surface coloration, which includes coated tablets, the choice of color is usually restricted to insoluble pigments. The reasons for this include their lack of color migration, greater opacity, and enhanced color stability over water-soluble colors. ... 

Amorphous silica has become increasingly important in paper technology. It cannot be used alone because it affects coating rheology and adhesive demand. But used in combinations with other fillers, it improves the brightness, opacity, and ink receptivity of paper. Similarly, talc is used as a 10 to 40% replacement for other fillers to improve paper surface smoothness and ink receptivity. Talc is also used in place of clay if clay is not locally available. 

Most paint formulations consist of disperse systems (solid in liquid dispersions) [2]. The disperse phase consists of primary pigment particles (organic or inorganic) which provide the opacity, colour and other optical effects these are usually in the submicron range. Other coarse particles (mostly inorganic) are used in primers and undercoats to seal the substrate and enhance adhesion of the top coat The continuous phase consists of a solution of polymer or resin which provides the basis for a continuous film that seals the surface and protects it from the outside environment Most modem paints contain latexes which are used as film formers. These latexes - which typically have a glass transition temperature (Tg) below... 

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