Urethane finishes

Topcoats over primer are often applied by airless spray. Trends to higher standards of exterior durability have encouraged the use of methacrylated alkyds and two-component urethane finishes. 

Sherwin-Williams, the largest U.S. coatings supplier overall, is the top U.S. producer of TS coatings. They have been leaders in industrial urethane finishes and are active in PC, WB, RC, and HS coatings. Recent research and development in the cathodic ED field has led to the introduction of several new products for the automotive and appliance industries. 

The durability and solvent resistance of nitrocellulose-urethane finishes have prompted studies of these coatings for metal substrates. Excellent adhesion to steel and aluminum has been demonstrated. Pigmented systems dry rapidly and have high initial gloss and scratch resistance. 

Lumitol . [BASF AG] Hydroxylicpoly-acrylitte resins us in combination widi polyisocyanates to produce poty-urethane finishes with chemicai and solvent resistance. 

Micothane. [Dexter Spec. Coatings] Resistant urethane finishes. 

Polyethylene glycol (PEG) Capillary structure filled with PEG PEG soluble in water, low vapor pressure wet or dry wood is soaked in PEG, replaces water in cell walls and fills capillaries moist feel to bulked wood, hydroscopic urethane finish used ASE about 98 % Art carvings, preservation of old wood... 

A hard-coaf urethane finish designed for use over rigid substrates when abrasion resistance and weatherability properties are a must. It meets or exceeds an automotive quality type of finish. 

Water-Vapor Permeability. Water-vapor permeabiUty depends on the polymer used for the coating layer and its stmcture. Vinyl-coated fabrics have Httie water-vapor permeabiUty due to the coating layer. Although polyurethane polymer is water-vapor permeable, urethane-coated fabrics also have low permeabiUty values due to their soHd layer stmcture. On the other hand, man-made leathers have good permeabiUty values as high as that of leather due to their porous layer stmcture. The permeabiUty of grain-type is lower than that of suede-type, influenced by finishing method. 

The rate of stripping or the stripabiUty on cataly2ed urethane and epoxy resin finishes can be increased by adding formic acid, acetic acid, and phenol. Sodium hydroxide, potassium hydroxide, and trisodium phosphate [10101-89-0] may be added to the formula to increase the stripabiUty on enamel and latex paints. Other activators include oleic acid [112-80-17, trichloroacetic acid [76-85-9], ammonia, triethanolamine [102-71-6], and monoethyl amine. Methylene chloride-type removers are unique in their abiUty to accept cosolvents and activators that allow the solution to be neutral, alkaline, or acidic. This abihty gready expands the number of coatings that can be removed with methylene chloride removers. 

The paint is sensitive to moisture during storage and application but then becomes exceptionally water-resistant. Its best use is for exterior exposure in an aggressive environment but where the maximum gloss and color retention is required. It is preferable to apply the urethane as a finishing coat over epoxy undercoating and priming. 

It is claimed that the cured film has similar properties and durability to the two-pack urethane. It also is used as an anti-graffiti finish. 

Charge the OH functional urethane water dispersion prepared in Example 8 (200 g, 0.1603 eq. OH) to a suitable container. Vigorously stir the dispersion with a mechanical stirrer and slowly add the 18.8% NCO water-dispersible polyisocyanate described above (40.0 g, 0.1791 eq.). This will give an NCO-OH equivalent ratio (index) of 1.12. To this mixture, add Silwet L-77 (a flow aid from OSi Specialties) and thoroughly mix. Use a draw-down bar to make 6-mil (0.006-in.) wet-thickness films on glass plates and 5-mil (0.005-in.) films on Bonderite-treated steel panels (Bonderite is from Henkel). Condition the resultant films at 72°F and 50% RH for 2-3 weeks before evaluating. For the finished... 

Various finishes can be achieved — gloss, satin (or egg-shell) or matt. This is accomplished by the addition of particles of size 1-5 pm of, for example, silica, china clay or the white pigment, TiCK The degree of mattness depends on various factors, such as particle size, surface treatment of the particles, rate of film formation, and the polymer composition, e.g., urethane/acrylate compared with epoxy/acrylate. The former requires smaller particles larger particles cannot be used as they create a rough surface. 

Urethane c Automotive coatings, wood sealer and finish, concrete sealer... 

It would seem that such broadened use of flexible plastics and rubbers in exterior-body structural members will compel the conclusion that high performance materials are needed. They must not only be relatively light, flexible, serviceable at temperature extremes, and easily fabricated and finished, but they must be as strong and as tough as possible. The public will demand this. One type of flexible synthetic polymer which meets these requirements very well indeed is the thermoplastic urethane elastomers which have already proved themselves in flexible front ends, sight shields, and fascia in production model automobiles. 

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