polyuretan

Polyuretan, commonly known as polyurethane, is a class of polymers formed by reacting polyols with di- or polyisocyanates to create urethane linkages. It encompasses a wide range of materials, including rigid plastics and foams, flexible foams, elastomers, coatings, adhesives, and sealants. The properties and uses are highly dependent on the formulation and processing methods.

Chemistry and production: Polyurethane formation is a step-growth polymerization in which hydroxyl groups of polyols react with isocyanate groups to form urethane bonds. Common diisocyanates include methylene diphenyl diisocyanate (MDI) and toluene diisocyanate (TDI); polyols can be based on polyether or polyester. In foam production, water is often used as a blowing agent; it reacts with isocyanate to release carbon dioxide, creating foam structures. Processing also employs catalysts, surfactants, and other additives to tailor reactivity and foam morphology.

Types and applications: Rigid polyurethane foams provide thermal insulation in buildings, refrigeration, and appliances. Flexible foams are used in furniture cushioning, bedding, and automotive seating. Polyurethane elastomers are durable and used in wheels, rollers, seals, and wear parts. Coatings, primers, adhesives, and sealants rely on polyurethane chemistries for adhesion and protective properties. Across industries, polyurethane offers versatility through customizable density, hardness, and resilience.

Processing and safety: Common processing routes include reaction injection molding, spray foaming, slabstock foaming, and coating or casting. The chemistry allows extensive property tuning, but isocyanates can pose health risks; proper ventilation, protective equipment, and handling protocols are required.

Environmental and history: Polyurethanes were developed in the mid-20th century and have since become among the most widely used polymers. Current research focuses on bio-based polyols and recycling to reduce environmental impact.