Paint coatings continued pigments

Paints also continue to play a part in space age camouflage. Unlike the coloured coatings of the past, whose concealment value depended on tone, reflectivity and pigment, the vital characteristic of modern protective coatings is their ability to absorb radio frequency energy so that the word concealment is given a whole new meaning. 

Paints or surface coatings are complex multiphase colloidal systems that are appUed as a continuous layer to a surface [1], A paint usually contains pigmented materials to distinguish it from clear hlms that are described as lacquers or varnishes. The main purpose of a paint or surface coating is to provide aesthetic appeal as well as to protect the surface. For example, a motor car paint can enhance the appearance of the car body by providing color and gloss and it also protects the car body from corrosion. 

Safety No year goes by without some widely used chemical being declared suspect on toxicity grounds. The paint industry has responded rapidly to eliminate toxic chemicals from coatings or to show how they can be used safely in an industrial environment. Examples are the elimination of specific ether-alcohol solvents and the introduction of air-fed hoods for spraying isocyanates. Of particular interest in corrosion prevention is the current pressure to eliminate chromate pigments. Currently there are no equally effective alternatives and the emphasis has had to be on safe usage. The search for replacements continues. 

Commercial interest inP.V.5 l, Constitution No. 58055 1,has declined considerably. The pigment continues to be used in industrial paints, especially throughout the USA. Its full shade is a brilliant, deep bluish maroon. In white reductions, the pigment produces clean, reddish violet shades. It lacks tinctorial strength and the coatings are fast to neither acid nor alkali. P.V.5 1 is also not very lightfast, which practically precludes its use in products for exterior application, particularly in reduced shades. 

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... 

Organic coatings are used to block the penetration of carbon dioxide or chloride ions. They form a continuous polymeric film on the surface of the concrete, of a thickness ranging from 100 to 300 pm. The binder can already be present in the liquid paint as a polymer, or the polymer can be formed due to chemical reactions between monomeric components that are mixed just before application. Modem coating systems are usually built up of several layers applied consecutively. They are compatible with the alkalinity of the concrete and are based on various types of polymers (e. g. acrylate, polyurethane, epoxy), pigments and additives, and are made suitable for application by the addition of solvents or diluents. 

Continuous efforts have therefore been made to develop binders for one-pack paints which must be completely compatible with active pigments such as zinc dust. Mixtures of ethyl silicate and zinc can be stored for unlimited periods in the absence of water. If the hydrolysis and condensation reactions caused by atmospheric moisture can be sufficiently accelerated during application of the coating, a one-pack system can be produced. 

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