2008年4月15日火曜日

Urushiol-based lacquers
Quick-drying solvent-based lacquers that contain nitrocellulose, a resin obtained from the nitration of cotton and other cellulostic materials, were developed in the early 1920s, and extensively used in the automobile industry for 30 years. Prior to their introduction, mass produced automotive finishes were limited in colour, with Japan Black being the fastest drying and thus most popular. General Motors Oakland automobile brand automobile was the first (1923) to introduce one of the new fast drying nitrocelluous lacquers, a bright blue, produced by DuPont under their Duco tradename.
These lacquers are also used on wooden products, furniture primarily, and on musical instruments and other objects. The nitrocellulose and other resins and plasticizers are dissolved in the solvent, and each coat of lacquer dissolves some of the previous coat. These lacquers were a huge improvement over earlier automobile and furniture finishes, both in ease of application, and in colour retention. The preferred method of applying quick-drying lacquers is by spraying, and the development of nitrocellulose lacquers led to the first extensive use of spray guns. Nitrocellulose lacquers produce a very hard yet flexible, durable finish that can be polished to a high sheen. Drawbacks of these lacquers include the hazardous nature of the solvent, which is flammable, volatile and toxic; and the handling hazards of nitrocellulose in the lacquer manufacturing process. Lacquer grade or soluble nitrocellulose is closely related to the more highly nitrated form which is used to make explosives.

LacquerLacquer Nitrocellulose lacquers
Lacquers using acrylic resin, a synthetic polymer, were developed in the 1950s. Acrylic resin is colourless, transparent thermoplastic, obtained by the polymerization of derivatives of acrylic acid. Acrylic is also used in enamels, which have the advantage of not needing to be buffed to obtain a shine. Enamels, however, are slow drying. The advantage of acrylic lacquers, which was recognized by General Motors, is an exceptionally fast drying time. The use of lacquers in automobile finishes was discontinued when tougher, more durable, weather and chemical resistant two-component polyurethane coatings were developed. The system usually consists of a primer, colour coat and clear topcoat, commonly known as clear coat finishes. It is extensively used for wooden finishing

Acrylic lacquers
Due to health risks and environmental considerations involved in the use of solvent-based lacquers, much work has gone in to the development of water-based lacquers. Such lacquers are considerably less toxic and more environmentally friendly, and in many cases, produce acceptable results. More and more water-based coloured lacquers are replacing solvent-based clear and coloured lacquers in underhood and interior applications in the automobile and other similar industrial applications. Water based lacquers are used extensively in wood furniture finishing as well.

Japanning

Lacquerware

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