聚氨酯Polyurethane

异氰酸酯基（–N=C=O）的碳原子高度亲电，醇羟基加成到 N=C 键上生成氨基甲酸酯，不放出小分子。常用异氰酸酯有 MDI（二苯甲烷二异氰酸酯）和 TDI（甲苯二异氰酸酯），多元醇有聚醚多元醇和聚酯多元醇。异氰酸酯与水反应生成胺并放出 CO₂，这正是软泡发泡的原理。软段（长链多元醇）和硬段（异氰酸酯与扩链剂）的微相分离使聚氨酯弹性体兼具弹性和强度。

The carbon of the isocyanate group (–N=C=O) is strongly electrophilic, and an alcohol OH adds across the N=C bond to give a urethane with no by-product. Common isocyanates are MDI (methylene diphenyl diisocyanate) and TDI (toluene diisocyanate), and polyols are polyether or polyester polyols. Isocyanate reacts with water to give an amine and release CO₂, which is how flexible foams are blown. Microphase separation of soft segments (long-chain polyols) and hard segments (isocyanate plus chain extender) gives polyurethane elastomers both elasticity and strength.

1937 年德国法本公司的奥托·拜耳及其同事发明了二异氰酸酯加聚法，开发出聚氨酯，最初目的是绕开杜邦尼龙专利以制造纤维。二战期间用于涂料和黏合剂，1950 年代软质泡沫和硬质泡沫工业化。1959 年杜邦推出氨纶（Lycra）弹性纤维。

In 1937 Otto Bayer and colleagues at IG Farben invented diisocyanate polyaddition and developed polyurethanes, initially to make fibres without infringing DuPont's nylon patents. They were used for coatings and adhesives during the Second World War, and flexible and rigid foams were commercialised in the 1950s. DuPont launched spandex (Lycra) elastic fibre in 1959.

软泡用于床垫、沙发和汽车座椅；硬泡是冰箱和建筑保温的主要材料；弹性体用于鞋底、滚轮和密封件；还有涂料、合成革、胶黏剂、氨纶和医用导管。异氰酸酯有强烈的呼吸道致敏性，1984 年印度博帕尔事故中泄漏的异氰酸甲酯造成数千人死亡。为此正在发展不使用异氰酸酯的聚氨酯合成路线。

Flexible foams fill mattresses, sofas and car seats; rigid foams are the main insulation for refrigerators and buildings; elastomers make shoe soles, wheels and seals; and there are coatings, synthetic leather, adhesives, spandex and medical tubing. Isocyanates are potent respiratory sensitisers, and methyl isocyanate leaked at Bhopal in India in 1984 killed thousands of people. Isocyanate-free routes to polyurethanes are under development.