Clear coating

Cleai-coat applications Clear coating Cleai-liquor advance Cleaion... 

Polymerization. Thermal polymerization or curing of an ink film at elevated temperatures can foUow many different chemical paths. Condensation and cross-linking reactions may be accompHshed with or without the use of catalysts. However, this method of drying generally has not been widely used for printing inks, except those used for metal and glass decoration, and some clear coatings. 

A major use for 2,4-di-/ f2 -amylphenol is in the production of uv stabilizers the principal one is a benzotriazole-based uv absorber, 2-(2 -hydroxy-3, 5 -di-/ f2 -amylphenyl)-5-chlorobenzotriazole [25973-55-17, which is widely used in polyolefin films, outdoor furniture, and clear coat automotive finishes (56). Another significant use for 2,4-di-/ f2 -amylphenol is in the photographic iadustry. A number of phenoxyacetic acid derivatives of... 

The growth rate for 2,4-di-/ f2 -amylphenol is predicted to be above GNP growth rate, mainly driven by the use of the benzotriazole derivative as a uv stabilizer for clear-coat appHcations in auto finishes (see Table 3). 

Using present ideas of glass structure, frits can be formulated to have maximum durability. Zirconia enamels have a lower than optimum acid resistance, but titania enamels have superior durability at low pH values. Encouraging crystallisation in the enamel enhances mechanical strength and therefore chemical resistance by reducing the incidence of damage sites which act as foci for attack. The addition of an extra (clear) coat on to the top most coat of enamel gives superior chemical resistance". 

Some substituted hydroxy compounds give with poly (vinyl alcohol) firm, white gels which form clear coatings when dried in layer form. A few typical compounds are ... 

Microgels with an acrylic core for waterborne base coats have been reported to resist the attack of subsequent clear coats, exhibit mechanical toughness and flexibility and have a good durability and chemical resistance [347]. 

Figure 5.2 Micrographs of metal-coated lipid tubules. Top panel shows scanning electron micrograph of copper-plated microtubules (bar = 2.0 (Jim), while bottom panel shows optical micrograph of iron-coated microtubules embedded in acrylic-urethane clear coating (bar = 25 p,m). Reprinted from Ref. 135 with permission of Wiley-VCH.

The paint industry uses P.R.175 primarily to color industrial paints and also automobile repair finishes. High transparency makes the pigment an important product for transparent and metallic effect finishes. The pigment is suited to twocoat metallic automobile (O.E.M.) finishes, also referred to as base coat/clear coat finishes, especially if the clear coat contains UV absorbants. Its lightfastness and weatherfastness are excellent. P.R.175 does not bloom, is completely fast to overpainting, and is heat stable up to 200°C. 

Etherification to produce cyanoethyolated, benzylated or allylated wood surfaces does not result in an improvement in UV resistance, but the latter two treatments have been found to improve the performance of clear coatings on the modified substrate (Kiguchi, 1990b). Kalnins (1984) methylated wood by pre-treating with concentrated aqueous... 

Williams, R.S. (1983). Effect of grafted UV stabilizers on wood surface erosion and clear coating performance. Journal of Applied Polymer Science, 28(6), 2093-2103. 

Innovation process Water-based low-solvent dipping coatings have been state-of-the-art for some time as primers. In the mid 1980s the development of water-based fillers and topcoats was advanced by VW. These have become estabhshed extensively in Germany. Solvent-free powder clear coatings have been used by DaimlerCluysler (as powder slurry suspended in water) and by BMW since 1997. 

Clear coatings containing oligoester diols 1, 2, and 3 crosslinked with a hexakis(methoxymethyl)melamine (HMMM) resin were prepared, baked and tested. 

Enamel Properties. Clear coatings were formed by crosslinking the PHBA-modified oligomers with a standard melamine resin. Baking at 175° was necessary to obtain optimal properties. The cured films were glossy and nearly transparent except for films made from 60/40 PHBA ratio polyol. Adhesion was excellent. 

Standard UV equipment and clear coats cannot ensure curing of coating in the shadowed areas. 

The use of high-intensity, short-wavelength UV lamps, which are known to cure clear coats in seconds, raises concerns about worker safety. 

Many of the clear coats that would be possibly suitable for coating and curing entire vehicle bodies contain free isocyanates and would not be accepted in an assembly line due to health and safety concerns. 

There are great efforts to develop not only clear coats, but also primers and base coats that would be curable by UV or EB. The current approaches to UV/EB technology are ... 

Cationic and photolatent base clear coat formulations curing in shadowed areas... 

Cure by electron beam could apply to primers, base coat, and clear coat... 

Other possible applications are clear coats in automotive interiors (dashboard instrument screen-printed and top coats for gloss control, interior vinyl clear coat with excellent mar resistance and low gloss, wood grain printing and top coats for interior laminates), on alloy wheels and wheel covers and under the hood parts, and UV curable paint over physical vapor deposition (PVD) surfaces of various parts. Other examples are ... 

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