Polyurethane Biodegradation

Polyurethanes represent a class of polymers that have found a widespread use in the medical, automotive and industrial fields. Polyurethanes can be found in products such as furniture, coatings, adhesives, constructional materials, fibers, paddings, paints, elastomers and synthetic skins. Polyurethane is abbreviated as PUR in compliance with official German and International standards. However, the abbreviation PU is more commonly used in English texts. Advantages of polyurethanes are that they increase the tensile strength and melting points making them more durable (Bayer 1947). Their resistance to degradation by water, oils, and solvents makes them excellent materials for the replacement of plastics (Saunders and Frisch 1964). As coatings, they exhibit excellent adhesion to many substances, abrasion resistance, electrical properties and weather resistance for industrial purposes (Saunders and Frisch 1964; Urbanski et al. 1977; Fried 1995). Depending on the chemical structures of the polyisocyanates and polyols, PU can adopt various forms ranging from flexible to rigid and from low density to solid elastomer. The chemical composition of PU precludes them from being classified as pure plastics and hence called as a mixed polymer. The urethane group, which is the basis of this class of mixed polymer, represents a small part of the macromolecule and some PU products do not contain a urethane group. Despite the lack of this base unit, all PU are based on the composition of polyisocyanates. The polyisocyanate polyaddition is distinct from polymerization and polycondensation for the production of synthetic polymers and this feature explains their versatility.