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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.
This is of particular interest in the area of polyurethane coatings, where light stability is a critical factor and is the main reason that aliphatic isocyanates are used in making polyurethane coatings. When PU foam, which is made using aromatic isocyanates, is exposed to visible light, it discolors, turning from off-white to yellow to reddish ...
Most coatings have four basic components. These are the resin, solvent, pigment and additive systems [5] but the resin or binder is the key ingredient. Continuing environmental legislation in many countries along with geopolitics such as oil production are ensuring that chemists are increasingly turning to waterborne technology for paint/coatings and since resins or binders are the most ...
The major application of 4,4′-MDI is the production of rigid polyurethane. [9] These rigid polyurethane foams are good thermal insulators and used in nearly all freezers and refrigerators worldwide, as well as buildings.
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]
Alkyd resins are usually classed as long oil, [11] medium oil and short oil. [12] These terms represent the oil length in the resin. [ 13 ] Alkyds are also modified with phenolic resin , styrene , vinyl toluene , acrylic monomers (to make them dry more quickly) and isocyanates to produce a polyurethane modified alkyd.
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]
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 film build, accomplishing in two coats what may require multiple applications of oil. Polyurethane may also be applied over a straight oil finish, but because of the relatively ...