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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 ...
As with aliphatic polyurethane or acrylic coatings, polyaspartic coatings made with aliphatic isocyanates and derivatives are UV and light stable and have a low yellowing tendency. When coating concrete, polyaspartics can be installed in both clear and pigmented form.
Aliphatic compounds can be saturated, joined by single bonds , or unsaturated, with double bonds or triple bonds . If other elements ( heteroatoms ) are bound to the carbon chain , the most common being oxygen , nitrogen , sulfur , and chlorine , it is no longer a hydrocarbon, and therefore no longer an aliphatic compound.
Thermoplastic polyurethane (TPU) is any of a class of polyurethane plastics with many properties, including elasticity, transparency, and resistance to oil, grease, and abrasion. Technically, they are thermoplastic elastomers consisting of linear segmented block copolymers composed of hard and soft segments.
[16] [17] As an example, polyurethane foam is a big user of polyether polyols. [18] Polyester polyols can be used to produce rigid foam. [19] [20] They are available in both aromatic and aliphatic versions. [21] [22] They are also available in mixed aliphatic-aromatic versions often made from recycled raw materials, typically polyethylene ...
However, aliphatic epoxy resins polymerize very slowly at room temperature, so higher temperatures and suitable accelerators are usually required. Because aliphatic epoxies have a lower electron density than aromatics, cycloaliphatic epoxies react less readily with nucleophiles than bisphenol A-based epoxy resins (which have aromatic ether groups).
The word polyurea is derived from the Greek words πολυ- - poly- meaning "many"; and ουρίας - oûron meaning "to urinate" (referring to the substance urea, found in urine). Urea or carbamide is an organic compound with the chemical formula (NH 2) 2 CO. The molecule has two amine groups (–NH 2) joined by a carbonyl functional group (C=O).
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]