Urethane

Urethane is a term that can refer to the carbamate ester functional group or to polyurethane materials that contain urethane linkages. In polymers, the defining feature is the urethane or carbamate bond, commonly represented as the linkage -O-CO-NH-, which forms when a diisocyanate or polyisocyanate reacts with a polyol or amine to join chains.

Polyurethanes are produced primarily by the step-growth reaction of isocyanates with polyols, often with chain extenders and catalysts. The resulting urethane bonds link polymer segments into networks or flexible chains. In foam formulations, moisture or blowing agents create gas that expands the material, producing either rigid or flexible foams. Additives such as catalysts, surfactants, and fillers tailor processing and end-use properties.

Applications for polyurethane materials are broad. Rigid foams provide insulation in construction and refrigeration; flexible foams are common in furniture and bedding; coatings and sealants protect and decorate surfaces; elastomeric versions are used in wheels, rollers, and impact-resistant parts; and various polyurethane resins are employed in adhesives and composites. The ability to vary the chemical components allows a wide range of hardness, resilience, chemical resistance, and temperature performance.

Safety and environmental considerations center on the isocyanates used to produce polyurethanes. Isocyanates can be hazardous and sensitizing, requiring proper ventilation, handling procedures, and personal protective equipment. Regulations govern exposure and waste management in manufacturing and application settings.

Historically, the first polyurethane was synthesized in 1937 by Otto Bayer and colleagues, marking the start of a rapidly developed class of materials with versatile applications.