Polyurethane The term polyurethane encompasses a vast family of products with numerous varied characteristics in terms of mechanical, chemical and physical properties. Through the right choice and proportion of polyols and diisocyanates it is possible for products to range from soft and sponge-like, such as flexible foams with extremely low density (pillows, mattresses, etc.) to products with elevated resistance to compression and flexion stress (for applications in sporting goods, such as hiking boots, ski boots, etc.). In order to have a general guide regarding the characteristics of polyurethane, the primary distinctions to consider relate to its chemical nature, or rather, if it has an ester or ether base. In commerce there is also a third family of polyurethane, which derives from the synthesis of caprolactam, which exhibits intermediate characteristics between polyester and polyether.