What are the mechanism of polyurethane reaction?
One mechanism includes catalyst forming a complex with isocyanate groups which will then react with an alcohol moiety to produce urethane. This reaction is often assumed to be an intermediate or equilibrium reaction, leading to hyperbolic reaction rate expressions.
How do isocyanates work?
Isocyanates are compounds containing the isocyanate group (-NCO). They react with compounds containing alcohol (hydroxyl) groups to produce polyurethane polymers, which are components of polyurethane foams, thermoplastic elastomers, spandex fibers, and polyurethane paints.
What is a polyol compound?
A polyol is an organic compound containing multiple hydroxyl groups. The term “polyol” can have slightly different meanings depending on whether it is used in food science or polymer chemistry. Polyols containing two, three and four hydroxyl groups are diols, triols, and tetrols, respectively.
What is a polyurethane polyol?
Polyurethanes are formed by reacting a polyol (an alcohol with more than two reactive hydroxyl groups per molecule) with a diisocyanate or a polymeric isocyanate in the presence of suitable catalysts and additives.
What is polyol used for?
Polyols are used in a variety of products including elastomers, fibers, flexible foam, adhesives, sealants, inks, paints, and coatings. When used in engineering plastics, they are often copolymerized with other monomers to produce polyurethane and polyester elastomers.
What is NCO in MDI?
NCO – an isocyanate chemical group. This designation refers to the nitrogen, carbon, and oxygen atom of the isocyanate group. %NCO – a measure of the isocyanate content of a prepolymer or other isocyanate-containing compound measured as the weight percent of unreacted isocyanate groups in the material.
Are isocyanates heavier than air?
flammable liquid that readily evaporates when exposed to air. Gaseous methyl isocyanate is approximately 1.4 times heavier than air.