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Onions, in particular, produce a sulfur product that acts as a lacrimator, or a substance that causes tearing: “This volatile chemical escapes from the damaged onion into the air, and lands in ...
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. [5]
Castor oil by itself has been used in making a variety of polyurethane products, ranging from coatings to foams, and the use of castor oil derivatives continues to be an area of active development. Castor oil derivatized with propylene oxide [9] makes polyurethane foam for mattresses and yet another new derivative is used in coatings [10]
Oil-based defoamers have an oil carrier. The oil might be mineral oil , vegetable oil or any other oil that is insoluble in the foaming medium, except silicone oil . An oil-based defoamer also contains a wax and/or hydrophobic silica to boost the performance.
Sweating is often a preliminary step to further cooking in liquid; [1] onions, in particular, are often sweated before including in a stew. [ a ] This differs from sautéing in that sweating is done over a much lower heat, [ 2 ] sometimes with salt added to help draw moisture away, and making sure that little or no browning takes place.
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]
Blocked isocyanates are particularly useful in products with a dual cure mechanisms. As an example, Ultraviolet light initiates the polymerization of an acrylate based polymer that contains hydroxy groups on the polymer backbone. The system would also contain an isocyanate blocked with a malonate. This is now a one-component system.