Paints, heat-resisting

Uses Substrate wetting agent and spreading agent for solv. and water-based systems, wood/furniture varnishes, industrial/household appliance paints, heat-resist, coatings, aq. flexographic inks, primers for plastics, overprint varnishes... 

Because the heat distortion temperature of cured epoxy resins (qv) increases with the functionality of the curing agents, pyromellitic dianhydride is used to cross-link epoxy resins for elevated temperature service. The dianhydride may be added as a dispersion of micropulverized powder in liquid epoxy resin or as a glycol adduct (158). Such epoxies may be used as an insulating layer in printed circuit boards to improve heat resistance (159). Other uses include inhibition of corrosion (160,161), hot melt traffic paints (162), azo pigments (163), adhesives (164), and photoresist compounds (165). 

Silicone resins with high phenyl contents may be used with medium or short oil alkyds as blends in air-dried or baked coatings to improve heat or weather resistance the alkyd component contributes to adhesion and flexibiUty. AppHcations include insulation varnishes, heat-resistant paints, and marine coatings. 

In addition to poly(methyl methacrylate) plastics and polyacrylonitrile fibres, acrylic polymers find widespread use. First introduced in 1946, acrylic rubbers have become established as important special purpose rubbers with a useful combination of oil and heat resistance. Acrylic paints have become widely accepted particularly in the car industry whilst very interesting reactive adhesives, including the well-known super-glues are also made from acrylic polymers. 

Although rolling and dipping are sometimes used, power spray painting is the usual method of paint application. Among the coatings used are polyurethane, epoxy, acrylic, alkyd and vinyl based paints. With paints that are oven cured, products must have sufficient heat resistance to survive without distortion, etc. 

The polymer has been stable to hydrolysis and does not alter its properties when heated to 500°C. Polyalumoxanes find use as binders in the preparation of heat-resistant paints and for special treatment of textiles. 

In contrast to most other representatives of its class, P.Y.97 is also much more heat resistant. In a performance test, in which prints formulated at 5% pigment concentration are applied to sheet metal covered with white paint, most monoazo... 

A further important application of these pigments is in paints. The natural red iron oxides are also used in primers for steel structures and cars, for marine coatings and for anti-fouling paints. In the USA, the metallic browns are used for these purposes. The level of soluble salts in the latter pigments is low and this reduces corrosion problems. The metallic browns are also used in heat resistant enamels. 

Vinyltoluene. Vinyltoluene (VT) is a mixture of meta- and para-vinyltoluenes, typically in the ratio of 60 40. This isomer ratio results from the ratio of the corresponding ethyltoluenes in thermodynamic equilibrium. Vinyltoluene is produced for special applications. Its copolymers are more heat-resistant than the corresponding styrene copolymers, and it is used as a specialty monomer for paint, varnish, and polyester applications. 

Oligophenylethoxysiloxanes are used as modifiers for various polymers to improve their weather resistance and other technical characteristics, as well as to increase the heat resistance of coatings. E.g., PES-50 is used to modify polyethers, aciylic and epoxy polymers PES-80 is used to modify alkyd and urea-formaldehyde resins. Besides, PES-80 is used as an additive in paints and enamels (to improve their flow properties, gloss and colour), as well as in concrete mixes (to improve the water resistance and durability of concrete works). 

Polyphenylsilsesquioxane varnishes are used as binding agents for heat-resistant, protective and decorative enamels. To increase low adhesion, which is characteristic of silicone varnishes, enamels are often supplemented with various organic modifiers, pigments and fillers used in the vamish-and-paint industry. 

Some of the paint types belonging to classes such as alkyds, coaltar epoxies, epoxy, heat-resistant, inorganic zinc types, polyurethanes, water-borne coatings as described by Sigma coatings are given in Table 1.29. 

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