polyuretaaneja

Polyuretaaneja, or polyurethanes, are a large family of polymers produced by the reaction of polyols with di- or polyisocyanates, forming urethane linkages. The choice of reactants and processing conditions yields materials that range from soft, flexible foams to rigid foams, elastomeric solids, coatings, and adhesives.

Chemistry and processing: The typical synthesis is a step-growth polyaddition in which polyols react with di- or polyisocyanates to form urethane bonds. Catalysts, often amines or metal compounds, speed the reaction. In foam systems, water reacts with isocyanate to release carbon dioxide, creating a cellular structure; blowing agents are also used. The resulting materials can be formulated to balance rigidity, flexibility, thermal stability, and chemical resistance.

Forms and uses: Rigid polyurethane foams provide thermal insulation in buildings and appliances; flexible foams are used in furniture and bedding; polyurethane elastomers serve in wheels, rollers, coatings, and sealants. Coatings and adhesives extend protection and bonding for wood, metal, and composites, while specialty grades find niche applications in footwear, automotive interiors, and packaging.

Environmental and health aspects: Exposure to isocyanates can irritate airways and cause sensitization, so industrial practice emphasizes ventilation, monitoring, and protective equipment. End-of-life handling includes mechanical recycling of foams into fillers and chemical recycling that can depolymerize polyurethanes back toward polyols and isocyanates; research continues into bio-based polyols and more sustainable processing.

History: Polyurethanes were first synthesized in 1937 by Otto Bayer and colleagues, with rapid development in the following decades, enabling a broad range of materials and applications.