Based Coatings

Other forms of carbon-carbon composites have been or are being developed for space shutde leading edges, nuclear fuel containers for sateUites, aircraft engine adjustable exhaust nozzles, and the main stmcture for the proposed National Aerospace plane (34). For reusable appHcations, a siHcon carbide [409-21 -2] based coating is added to retard oxidation (35,36), with a boron [7440-42-8] h Lsed sublayer to seal any cracks that may form in the coating. 

Other. 2-Nitro-1-butanol is an excellent solvent for many polyamide resins, cellulose acetate butyrate, and ethylceUulose. It can be utilized in paint removers for epoxy-based coatings. 2-Hydroxymethyl-2-nitro-l,3-propanediol is usebil for control of odors in chemical toilets. Its slow release of formaldehyde ensures prolonged action to control odor, and there is no reodorant problem which sometimes is associated with the use of free formaldehyde. 2-Hydroxymethyl-2-nitro-l,3-propanediol solutions are effective preservative and embalming fluids. The slow Uberation of formaldehyde permits thorough penetration of the tissues before hardening. 

Sihcone-based coatings are well suited for high temperature and high speed appHcations. They are flexible, tough, and resistant to thermal and oxidative deterioration. They have good surface resistance and are fungus- and flame resistant. However, they possess a high coefficient of thermal expansion and have poor adhesion. 

The manufacture of alkyd resins (qv), which are obtained by the reactions of polybasic acids or anhydrides, polyhydric alcohols, and fatty oils and acids, consumes about 17% of the phthahc anhydride demand. While materials such as maleic anhydride, isophthahc acid, and fumaric acid can also be used, phthahc anhydride is the most important. The resin provides a binder for coatings that are apphed for either protection or decoration. Ak quahty concerns have put alkyd resins under pressure from water-based coatings which do not emit organic vapors upon drying. 

Binders in Ceramics, Powder Metallurgy, and Water-Based Coatings of Fluorescent Lamps. In coatings and ceramics appHcations, the suspension rheology needs to be modified to obtain a uniform dispersion of fine particles in the finished product. When PEO is used as a binder in aqueous suspensions, it is possible to remove PEO completely in less than 5 min by baking at temperatures of 400°C. This property has been successfully commercialized in several ceramic appHcations, in powder metallurgy, and in water-based coatings of fluorescent lamps (164—168). 

Catalysts. The alkanolamines continue to find use as blocked catalysts for textile resins, coatings resins, adhesives, etc. Of particular utifity in curing durable-press textiles is AMP-HCl. Other salts, such as those of the benzoin tosylate or A-toluenesulfonic acid, find utifity in melamine- or urea-based coatings (18) (see Amino resins and plastics). 

Negatwe P/ate Coatings. The bulk of negative plates have a diazo-based coating. This often comprises an A/-aryl- or alkyl aminobenzenedia zonium salt condensed with formaldehyde (66) or a methylol derivative (67) to form a low molecular weight polymer such as the following ... 

Fig. 2. Conventional thermally cured, organic solvent base coating system.

Coal-tar pitch for other uses is similarly subject to a few national specifications but mainly sold to users specifications. Pitch intended for roofing, dampproofing, and waterproofing is the subject of ASTM specification D450 and Federal specification R-P-381 hot-appHed tar-based coatings (pipeline enamels) are the subject of BSS 4164/1987, amended in 1988, and, in the United States, of American Water Works Association (AWWA) specification C203. 

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