Thermoplastic coatings spraying

The Hquid monomers are suitable for bulk polymerization processes. The reaction can be conducted in a mold (casting, reaction injection mol ding), continuously on a conveyor (block and panel foam production), or in an extmder (thermoplastic polyurethane elastomers and engineering thermoplastics). Also, spraying of the monomers onto the surface of suitable substrates provides insulation barriers or cross-linked coatings. 

Uses Used in any type of coating (varnish, stain, solv.- or water-based, bake or air dry enamels) food pkg. coatings Features Exc. weather durability, water repellency, improved salt spray and humidity resist., improved slip and mar resist. min. effect on dirt pick-up, gloss, and clarity preserves integrity of thermoplastic coatings Reguiatory FDA 21CFR 175.300... 

Thermoplastic coatings are often fabricated from powders. To coat a metallic object it is either dipped into a fluidized bed from which the powder deposits or one uses a spray gun to project the powder onto the metal surface. In electrostatic powder coating the polymer powder is projected in the presence of an electric field. This permits coating of recesses and hidden faces that are not in line of sight with the spray gun. After application of the powder, the object is annealed, and the powder transforms into a compact polymer coating. 

The diversity of release products and the wide range of release problems make classification difficult. One approach is by product form, with subdivisions such as emulsions, films, powders, reactive or iaert sprays, reactive coatings, and so on. Another approach is by appHcation, eg, metal casting, mbber processiag, thermoplastic iajection mol ding, and food preparation and packagiag. 

The volume of thermosetting powders sold exceeds that of thermoplastics by a wide margin. Thermoplastic resins are almost synonymous with fluidized-bed appHed thick-film functional coatings whereas thermosetting powders are used almost exclusively in electrostatic spray processes and appHed as thin-film decorative coatings. 

Various thermosetting and thermoplastic resins BS 3900 Powder/liquid system in factory. Airless spray/trowel in field Superior chemicai and abrasion resistance compared with enamels. Comparatively expensive. Simultaneous coating internally/externally possible. Various resins available to suit particular requirements. 

Thermoplastic resins, such as vinyl chlorides, vinyl acetates and polyamides are employed, particularly in the water industry, on buried pipes and fittings. To provide both internal and external coating, application may be by one of these principle techniques dipping in a plastisol, fluidised beds or electrostatic spray. 

When the solubility of the thermoplastic is poor at room temperature it may be possible to produce a dispersion in a mixture of diluents and latent solvents. This dispersion may be applied by conventional paint spray equipment. The coated item is placed in an oven where the diluents evaporate off. The latent solvents then dissolve the thermoplastic and evaporate from this solution at a controlled rate, thus producing a continuous him. P.V.F., and p.v.d.f. and p.t.f.c.e. coatings are produced from dispersions of this type. 

Spray 0.1 ohm per square foot hard, dense coating. mechanical bonding to plastic special applications equipment required requires special applicator safety procedures for dust and fumes warps thermoplastics not suitable for thin-walled designs not field repairable. 

Some specialized uses of PETN are summarized below. Expendable cartridges for small arms are made by coating unglazed grains or single base smokeless powder with PETN, spraying with plasticized thermoplastic binder and compression molding to the desired shape (Ref 99). Tucker et al (Ref 85) describe a spark detonator without primary expls. Secondary... 

A very promising new field of application for ASA and ASA-PC blends is automotive body panels. Until now, these have been made almost exclusively from painted metal. Since painting is costly, automotive companies are attempting to save costs by developing technologies that dispense with this operation. As in the case of the smart car, bulk coloured thermoplastics (e.g. PBT -PC blends) may be used to make body panels. However, such parts must still be sprayed with a top coat in order to achieve the desired scratch resistance and UV stability. 

When the thermosetting overprint lacquer No. 1 (Table VII) was applied to aluminum foil and cured at 275 °F (135 °C) for 10 s, heat resistance of the coating was in excess of 500 F (260 C). The thermoplastic overprint lacquer No. 2, when dissolved in an alcohol-water blend, may be applied directly to the wet lithographic ink in order to improve gloss and permit the use of less expensive inks, eliminate starch sprays ordinarily used to prevent setoff, improve scuff resistance, and eliminate hydrocarbon effluents by replacing heat-set inks with oxidizing inks. 

---