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UV-absorbers are added to polyurethane and other varnishes (e.g. spar varnish) to work against UV damage but are decreasingly effective over the course of 2–4 years, depending on the quantity and quality of UV-absorbers added, as well as the severity and duration of sun exposure.
Often, a final coat of wax is applied over the finish to add a degree of protection. French polishing is a finishing method of applying many thin coats of shellac using a rubbing pad, yielding a very fine glossy finish. Ammonia fuming is a traditional process for darkening and enriching the color of white oak.
Polyurethane varnish may also lack the "hand-rubbed" lustre of drying oils such as linseed or tung oil; in contrast, however, it is capable of a much faster and higher "build" of film, accomplishing in two coats what may require many applications of oil. Polyurethane may also be applied over a straight oil finish, but because of the relatively ...
Polyurethane synthesis, wherein the urethane groups −NH−(C=O)−O− link the molecular units A kitchen sponge made of polyurethane foam . Polyurethane (/ ˌ p ɒ l i ˈ jʊər ə ˌ θ eɪ n,-j ʊəˈr ɛ θ eɪ n /; [1] often abbreviated PUR and PU) refers to a class of polymers composed of organic units joined by carbamate (urethane) links.
The technique, which became known as japanning, involves applying several coats of varnish which are each heat-dried and polished. In the 18th century, japanning gained a large popular following. Although traditionally a pottery and wood coating, japanning was the popular (mostly black) coating of the accelerating metalware industry.
Without elasticity, the varnish would soon crack, allowing water to penetrate the wood beneath. Prior to the development of modern polymer chemistry, varnish production was rudimentary. Originally, spar varnish was a "long oil" varnish, composed primarily of drying oil with a small proportion of resin, usually boiled linseed oil and rosin. [1]
Moisture cured polyurethane–urea coatings have been made by reacting 1,2,3-triazole rich polyether polyols with HMDI at NCO/OH eq. ratio of 1.2 to obtain isocyanate-terminated polyurethane prepolymers. The prepolymers were cured under atmospheric moisture to make polyurethane–urea free films. [5]
Heat-sensitive carbon fiber tubes coated with a UV curable powder coating. Powder coating is a type of coating that is applied as a free-flowing, dry powder.Unlike conventional liquid paint, which is delivered via an evaporating solvent, powder coating is typically applied electrostatically and then cured under heat or with ultraviolet light.
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