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Choosing a clear finish for wood involves trade-offs between appearance, protection, durability, safety, requirements for cleaning, and ease of application. The following table compares the characteristics of different clear finishes. 'Rubbing qualities' indicates the ease with which a finish can be manipulated to deliver the finish desired.
A table green wood-stained and varnished with three layers of polyurethane varnish Polyurethane varnishes are typically hard, abrasion-resistant, and durable coatings. They are popular for hardwood floors but are considered by some wood finishers to be difficult or unsuitable for finishing furniture or other detailed pieces.
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.
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 glue (trade names include Gorilla Glue and Excel) is becoming increasingly popular in the US after being used for years in other countries. It bonds to textile fibers, metals, plastics, glass, sand, ceramics and rubber, in addition to wood. Polyurethane wood adhesives are normally prepolymers terminated with isocyanate groups. When ...
#7 Finish. A #7 finish is produced by polishing with a 280–320 grit belt or wheel and sisal buffing with a cut and color compound. This is a semi-bright finish that will still have some polishing lines but they will be very dull. Carbon steel and iron are commonly polished to a #7 finish before chrome plating.
As mass production of cars made the process untenable, paint began to be dried in ovens. Nowadays, two-component (catalyzed) paint is usually applied by robotic arms and cures in just a few hours either at room temperature or in heated booths. Until several decades ago lead, chromium, and other heavy metals were used in automotive paint.
Phenol-formaldehyde resins, as a group, are formed by a step-growth polymerization reaction that can be either acid- or base-catalysed.Since formaldehyde exists predominantly in solution as a dynamic equilibrium of methylene glycol oligomers, the concentration of the reactive form of formaldehyde depends on temperature and pH.