Polyurethanes have been used to make high-quality coatings for over 50 years, and are the preferred polymer for a range of demanding applications. They are formulated with both aliphatic and aromatic isocyanates, along with a variety of hydroxyl functional polyols. The polyols typically make up the majority of the overall coating formulation. The polyol is often the deciding factor in film properties such as modulus, glass-transition temperature and elasticity.
Performance and cost considerations determine the raw materials used for a specific application. The coatings can be solventborne, waterborne or 100% solids, depending on the processing requirements. Due to the breadth of this topic, comments will be limited to the most significant commercial polyisocyanates.