Powder coatings additives

There were over 3000 electrostatic powder spray lines and about 800 other powder coating installations operating in the United States as of 1991. Eor additional general information on the safety aspects of powder coatings, see References 90, 93, and 94. 

Powder coating is a solventless coating system that is not dependent upon a sacrificial medium such as a solvent, but is based on the performance constituents of solid TP or TS plastics. It can be a homogeneous blend of the plastic with fillers and additives in the form of a dry, fine-particle-size compound similar to flour. The three basic methods are the fluidized bed, electrostatic spray, and electrostatic fluidized bed processes (9). 

Brauer, Stansbury Flowers (1986) modified these cements in several ways. The addition of various adds - acetic, propionic, benzoic etc. -accelerated the set. The use of zinc oxide powders coated with propionic add improved mixing, accelerated set, reduced brittleness and increased compressive strength from 63 to a maximum of 72 MPa. The addition of plasticizing agents such as zinc undecenylate yielded flexible materials. Incorporation of metal powders had a deleterious effect and greatly increased the brittleness of these cements. The addition of fluorides was not very successful, for fluoride release was not sustained. 

A powder coating is the result of the application of a powder binder system, which generally consists of a resin, a crosslinker, flow additives, degassing agents, pigments or dyes, charge control agents, etc. Such a binder system is ap-pHed to the substrate as a fine, extruded powder (Fig. 20, step A), then melted at... 

Because the binder systems are solid at room temperature, they can be produced by the existing methods used for powder coatings.32 Solid resins, pigments, photoinitiators and other additives are premixed, then melted and dispersed in an extruder... 

Among the emerging pollutants of industrial origin, Bisphenol A [2,2 bis(4-hydroxydiphenyl)pro-pane] (BPA) has special relevance since it was one of the first chemicals discovered to mimic estrogens as endocrine disrupters.147 This compound was first reported by Dianin in 1891.1411 BPA is produced in large quantities worldwide, mainly for the preparation of polycarbonates, epoxy resins, and unsaturated polyester-styrene resins.149 The final products are used in many ways, such as coatings on cans, powder paints, additives in thermal paper, in dental composite fillings, and even as antioxidants in plasticizers or polymerization inhibitors in polyvinyl chloride (PVC). To a minor extent, BPA is also used as precursor for flame retardants such as tetrabromobisphenol A or tetrabromobisphenol-S-bis(2,3-dibromopropyl) ether.150 This substance can enter the environment... 

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