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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.
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.
Polyurethane can be used as an adhesive, especially as a woodworking glue. Its main advantage over more traditional wood glues is its water resistance. It was introduced to the general North American market in the 1990s as Gorilla Glue and Excel, but had been available in Europe much earlier. Polyurethane is the basis for some construction ...
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] This gave flexibility, [ 2 ] even though its weather resistance was still poor, and thus re-coating was required relatively frequently.
In polyurethane chemistry, prepolymers and oligomers are frequently produced and then further formulated into CASE applications - Coatings, Adhesives, Sealants, and Elastomers. An isocyanate (usually a diisocyanate) is reacted with a polyol. All types of polyol may in theory be used to produce polyurethane prepolymers.
Polyurethane dispersion, or PUD, is understood to be a polyurethane polymer resin dispersed in water, rather than a solvent, although some cosolvent may be used.Its manufacture involves the synthesis of polyurethanes having carboxylic acid functionality or nonionic hydrophiles like PEG (polyethylene glycol) incorporated into, or pendant from, the polymer backbone. [1]