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Methylene diphenyl diisocyanate (MDI) is an aromatic diisocyanate. Three isomers are common, varying by the positions of the isocyanate groups around the rings: 2,2′-MDI, 2,4′-MDI, and 4,4′-MDI. The 4,4′ isomer is most widely used, and is also known as 4,4′-diphenylmethane diisocyanate. [3] This isomer is also known as Pure MDI.
The isocyanate is commonly referred to in North America as the 'A-side' or just the 'iso'. The blend of polyols and other additives is commonly referred to as the 'B-side' or as the 'poly'. [citation needed] This mixture might also be called a 'resin' or 'resin blend'. In Europe the meanings for 'A-side' and 'B-side' are reversed.
The global market for diisocyanates in the year 2000 was 4.4 million tonnes, of which 61.3% was methylene diphenyl diisocyanate (MDI), 34.1% was toluene diisocyanate (TDI), 3.4% was the total for hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI), and 1.2% was the total for various others. [18]
More specifically, it is an aliphatic diisocyanate. It is a water white liquid at room temperature and is manufactured in relatively small quantities. It is also known as 4,4'-methylenedi(cyclohexyl isocyanate) or methylene bis(4-cyclohexylisocyanate) [2] and has the formula CH 2 [(C 6 H 10)NCO] 2.
In chronic toxicity tests, mice exposed to low levels of PPI developed no side effects. Only those mice exposed to the two highest concentrations developed any lung symptoms. [ 3 ] The two highest doses used in this study were 1.0 and 6.0 mg per cubic meter for 6 hours each day, 5 days each week for 2 years.
1.1 Methylene diphenyl diisocyanate (MDI) 7 comments. 1.2 Sentient nerves. 12 comments. 1.3 Compression ratio vs displacement. 8 comments. 1.4 Flamethrowers.
Other formaldehyde derivatives include methylene diphenyl diisocyanate, an important component in polyurethane paints and foams, and hexamine, which is used in phenol-formaldehyde resins as well as the explosive RDX. Condensation with acetaldehyde affords pentaerythritol, a chemical necessary in synthesizing PETN, a high explosive: [51]
A significant undesired side reaction which occurs during the baking process produces aromatic polyamines. Urethane crosslinkers based on toluene diisocyanate (TDI) can be expected to produce toluene diamine as a side reaction, whereas those based on methylene diphenyl diisocyanate produce diaminodiphenylmethane and higher order aromatic ...