Coating, powder

Nickel-coated powder products are used as conductive pigments for appHcation in surface coatings (qv), adhesives (qv), injection mol ding powders. 

Low viscosity cellulose propionate butyrate esters containing 3—5% butyryl, 40—50% propionyl, and 2—3% hydroxyl groups have excellent compatibihty with oil-modified alkyd resins (qv) and are used in wood furniture coatings (155). Acetate butyrate esters have been used in such varied apphcations as hot-melt adhesive formulations (156), electrostatically spray-coated powders for fusible, non-cratering coatings on metal surfaces (157—159), contact lenses (qv) with improved oxygen permeabiUty and excellent wear characteristics (160—162), and as reverse-osmosis membranes for desalination of water (163). 

Table 2. Melt-Mixed PVC Coating Powder Formulation ...

Polyamides. Coating powders based on polyamide resins have been used in fusion-coating processes for along time (1). Nylon-11 [25587-80-8] h.2LS been used almost exclusively however, more recently, coating powders also have been sold based on nylon-12 [24937-16-4]. The properties of these two resins are quite similar. Nylon-6 [25038-54-4] and nylon-6,6 [32131 -17-2] are not used because the melt viscosities are too high. 

Nylon coating powders are available for electrostatic spray and fluidized-bed appHcation. Nylon coatings are very tough, resistant to scratching and... 

Thermoplastic polyesters achieved some commercial success during the mid-1980s however, these were eventually replaced by nylon coating powders in functional coatings and thermosetting polyester powders in decorative appHcations because of lack of any unique characteristics or price advantages (see Polyesters, thermoplastic). 

Unsaturated polyester resin powders can provide a colored and finished exterior molded surface or a finish ready for painting. Normally, a primer/sealer must be appHed to molded articles prior to painting. In addition to the unsaturated polyester resin, multifimctional unsaturated monomers such as triaHyl cyanurate (TAC) [101-37-1] or diaHyl phthalate (DAP) [131-17-9] suitable peroxide initiators (qv) or mixtures thereof, and mold release agents (qv) are used to formulate the coating powder (46). 

Acryflc coating powders have achieved some success in Japan utilizing resins having gflcydyl methylacrylate functionality cured with C q—0 2 dicarboxyflc acids (49). Hybrid polyester—acryflc coating powders have also been reported in which an acid functional polyester resin coreacts with a glycidyl-containing acryflc polymer (50). Hydroxyl functional acryflc resins cured with blocked isocyanates have also been available for many years in the United States and achieved some commercial success as appliance finishes. 

The worldwide market for coating powders increased at an aimualized growth rate of 12—13% in the 1980s. Moreover, worldwide coating powder usage for thermosetting decorative powders is expected to increase to 332,000 t by 1992, a 264% increase over the quantity sold in 1984 (75). A significant factor... 

The only components in a coating powder which might cause the waste to be classified as hazardous are certain heavy-metal pigments sometimes used as colorants. Lead- (qv) and cadmium-based pigments (qv) are seldom used, however, and other potentially hazardous elements such as barium, nickel, and chromium are usually in the form of highly insoluble materials that seldom cause of the spent powder to be characterized as a hazardous waste (86). 

Table 7. Lower Explosive Limits Range for Coating Powders...

D. Richart, Update on Health and Safety Mspects of Powder Coatings, Powder Coating 90 Conference Papers, Gardner PubHcations, Cincinnati, Ohio, Oct. 1990. 

---