Constituents of Paints

Paints also contain additives, which are added in small quantities to modify some properties of the pigments and binder constituents. 

The four broad fundamental constituents (1) pigments, (2) binders, (3) solvents, and (4) additives will be discussed in greater detail as follows. 

Pigments are insoluble, fine particle-size materials that confer on a paint its color and opacity. Pigments are used in paint formulation to carry out one or more of the following tasks  

Pigments should be insoluble in the medium in which they are used, chemically inert, free of soluble salts, and unaffected by normal temperatures. They should be easily wetted for proper dispersion, nontoxic, noncorrosive, and have low oil-absorption characteristics. They should be durable and fast to light (as much as possible). 

In general the following properties of pigments are important in selecting a pigment for any particular product  

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Extender an inorganic material in powder form which has a low refractive index and consequently little obliterating power, but is used as a constituent of paints to adjust the properties of the paint, notably its working and film-forming properties and to avoid settlement on storage. 

In the last few years the characterization of the organic constituents of paint media by GC analysis has received increasing attention, due to the fact that organic materials used as binders or varnish are likely to be involved in the degradation process. 

The constituent of paint, 2-nitropropane, exhibiting genotoxicity and hepatocarcinogeni-city was oxidized by liver microsomes forming nitric oxide, which was identified as a ferrous NO complex [61]. Clement et al. [62] concluded that superoxide may participate in the microsomal oxidation of /Y-hydroxyguanidincs, which produced nitric oxide, urea, and the cyanamide derivative. Caro et al. [63] suggested that the oxidation of ketoxime acetoxime to nitric oxide by microsomes enriched with P-450 isoforms might be mediated by hydroxyl or hydroxyl-like radicals. 

Titanium is mined as rutile (Ti02) and ilmenite (FeTiOs). The refined oxide is an important constituent of paints, while the relatively light but highly corrosion-resistant metal is increasingly used structurally and for chemical process equipment despite its high cost. 

Finally, another halogenated solvent that causes toxic effects after acute exposure is dichloromethane or methylene chloride. It is used for degreasing engines and metalwork, and is the main constituent of paint stripper. If it is used in confined, enclosed spaces, such as rooms without adequate ventilation, it can lead to serious, unexpected toxic effects. As the solvent is breathed in by the worker it becomes localized in body fat. Later the... 

Solvents are volatile liquids added to dissolve or disperse the filmforming constituents of paints and allied products. They evaporate during the drying, and therefore, do not become a part of the dried film. In brief they... 

Linseed oil and tung oil, important constituents of paints, are esters (Sec. 33.6) derived from acids that contain two or three double bonds per molecule 9,12-octadecadi-enoic acid, for example. On exposure to air, paint forms a tough protective film oddly enough, after the initial rapid evaporation of solvent, this drying of paint is accompanied by a gain in weight. What kind of process do you think is involved Be as specific as you can be. 

Dichloromethane is used as a noncombustible solvent and extractant for oils, fats, waxes, fish oil, etc. from industrial and animal products, as well as caffeine, hops, castor oil, cocoa butter, and ethereal oils from substances of plant origin. It is used in the deparaffination of petroleum and the azeotropic dewatering of solvents. Dichloromethane is a constituent of paint-removal pastes and baths, but is increasingly being replaced by aqueous systems. It is used as a solvent in the production of cellulose-acetate-based or cellulose-acetobutyrate-based films and is employed industrially in the leather, metal, rubber, adhesives, and plastics industries. 

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