Polyurethanes are prepared by reacting polyols (alcohols with more than two reactive hydroxyl groups in each molecule) with diisocyanates or polymeric isocyanates. Suitable catalysts and additives are used wherever necessary. Since a variety of diisocyanates and a wide range of polyols can be used for the production of polyurethane, a wide spectrum of polyurethane materials can be produced to meet the requirements for specific applications. It can also be noted that polyurethanes can exist in a variety of forms including rigid foams, flexible foams, speciality adhesives, chemical-resistant coatings, sealants, and elastomers.