WebDownload scientific diagram Chemical structures of the four isocyanates (HDI, uretdione, biuret, and isocyanurate) present in HDI-based paints and clear coats. from publication: Determination of ... WebWith a further increase in the isocyanate index, the average cell diameter was reduced due to the excess of isocyanate groups in the system . It enhanced crosslinking and strengthened the cellular structure by forming more urea and biuret groups in the reactions of isocyanates with amines and ureas, respectively.

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WebNov 7, 2024 · Generally, HDI is converted into HDI-biuret and HDI-trimer as commercial products. The chemical structure of HDI-biuret and HDI-trimer are shown in Figure 1. HDI-biuret, has an average functionality within the range of 3. ... The nitrogen atoms N in DABCO bind with isocyanate (NCO) to form an activated complex, which then reacts … WebOne such composition is DESMODUR N-3200, a low viscosity biuret of HDI. The isocyanate or isocyanurate equivalent weight of the biuret or trimer crosslinking agent … hideaway fencing

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WebMay 13, 2024 · The presence of a strong electron-withdrawing group on the aryl ring reduces the nucleophilicity of the nitrogen atom of the urea intermediate, therefore, further reaction of 25/26 with another equivalent of isocyanate in cycle 3 fails to afford the biuret product. When o-tolyl isocyanate was employed, urea 27 was formed as the major … Biuret is a chemical compound with the chemical formula HN ... (those with alkyl or aryl groups in place of one or more H atoms) are prepared by trimerization of isocyanates. For example, the trimer of 1,6-hexamethylene diisocyanate is also known as HDI-biuret. Structure of biuret in the solid state (blue = N, red … See more Biuret is a chemical compound with the chemical formula HN(CONH2)2. It is a white solid that is soluble in hot water. A variety of organic derivatives are known. The term "biuret" also describes a family of organic compounds … See more Biuret is also used as a non-protein nitrogen source in ruminant feed, where it is converted into protein by gut microorganisms. It is less favored than urea, due to its … See more Biuret was first prepared and studied by Gustav Heinrich Wiedemann (1826 – 1899) for his doctoral dissertation, which was submitted in 1847. His findings were reported in several articles. See more The parent compound can be prepared by heating urea at 150 °C for ~6 hours until it gets slightly cloudy, then recrystallizing from water. After that, it can be recrystallized … See more The biuret test is a chemical test for proteins and polypeptides. It is based on the biuret reagent, a blue solution that turns violet upon contact with … See more • Cyanuric acid • Allophanic acid, the carboxylic acid derivative of biuret See more Webisocyanates. The short-term absorption rates for HDI monomer, biuret, and isocyanurate were determined and used to estimate the exposure time required to reach a body burden equal to the American Conference of Governmental Industrial Hygienists (ACGIH) inhalation threshold limit value (TLV) or OregonState occupational exposure limit (OEL). howell woltz articles