Synthesis and Applications of Isocyanate Free Polyurethane Materials
The manufacture of conventional polyurethanes include the use of isocyanates, which in turn require using toxic and hazardous phosgene. The safety devices are necessary to prepare these monomers. Therefore, the huge investment is inevitable for this process. Also, these monomers cannot be considered as environmentally friendly chemicals. The increasing global awareness for protection of environment from chemical pollutants has created a necessary demand for environmentally benign products. The reaction of cyclic carbonates (polycarbonates) with amines results in formation of hydroxyurethanes that can be taken into account as a unique reaction. This specific reaction has been investigated over last few years. Most chemists have been strongly attracted by this technique that is due to its potential application to prepare the green, non-toxic, non-sensitive towards moisture isocyanate free polyurethanes. This review is focused on the variety of catalysts used to prepare isocyanate free polyurethanes from five membered cyclic polycarbonates. Also, the reaction mechanism and kinetics for their synthesis have been discussed. In this review, the six-membered cyclic carbonates depicted the higher reactivity rather than five-membered cyclic carbonates for production of non-isocyanate polyurethanes. The various functions of isocyanate free polyurethanes in different fields such as coatings, construction and bio-composites have been summarized.
