What Is Polyurethane? Where Does Polyurethane Come From?
Polyurethane is a general term for macromolecular compounds containing repeating urethane groups on the main chain. Polyurethane can produce different products with various properties by changing the type and chemical structure of raw materials, specifications, and formula ratios.
Regarding the origin of polyurethane, we must start with isocyanates. Organic isocyanate is a compound that does not exist in nature. It was first synthesized by German chemist Wurtz in 1849 by metathesis reaction of alkyl sulfate and potassium cyanate. At that time, no suitable use was found for isocyanates, and no research was carried out on the polyaddition reaction of cyanate esters. It was found that various polyurethane and polyurea compounds could be produced, but they were not practical.
Nearly a century later, in 1937, in the laboratory of I.G. Farben (Farben) in Leverkusen, Germany, the chemist Otto Bayer and his colleagues applied the principle of addition polymerization using liquid isocyanates and liquid polyethers or dimethacrylates. The alcohol polyester produced a new material, which was different from the polyolefins and the plastics produced by polycondensation that had been discovered at that time, which was polyurethane. From 1941 to 1942, the German Bayer company established a 1,200-ton/year polyurethane plant. The initial polyurethane production technology began to be developed, and began to develop in Europe and the United States, and gradually spread to other countries and regions.
China's polyurethane industry started relatively late compared to developed countries, but China has now developed into the world's largest producer and consumer of polyurethane. Entering the 21st century, leading enterprises in mChina's polyurethane industry have sprung up. After breaking through the technical and technological barriers of large-scale synthesis, leading enterprises in China's industry quickly occupy the market by virtue of their scale advantages and leading cost and technology "super bases". Since then, China's polyurethane industry has continued to progress in the fields of production scale, product variety, and technical level, and some products have become the strongest in the world.
Polyurethane adhesives and sealants are one of the application forms of polyurethane materials, which can be widely used in many fields such as electronic appliances, building materials, automobiles and transportation.
Properties of Polyurethane Adhesives
1. Strong adhesive force, large initial adhesive force and wide application range
Since the -NCO in the molecular chain of the polyurethane adhesive can react with various functional groups containing active hydrogen to form interfacial chemical bonds, it has strong adhesion to various materials. It can not only bond porous materials, such as foamed plastics, ceramics, wood, fabrics, etc., but also bond a variety of metals, inorganic materials, plastics, rubber and leather, etc. It is a wide range of adhesives.
2. Outstanding low temperature resistance
At very low temperature, general polymer materials are converted into glass state and become brittle, while polyurethane adhesives can maintain high peel strength even below -250 ℃, and their shear strength decreases with the decrease of temperature. a substantial increase.
China has become the global consumption center of PU adhesives and sealants, and the production of global enterprises has gradually shifted to my country, and the production and sales of products have maintained rapid growth. According to the "China Adhesive Tape and Adhesive Market Report and the "Thirteenth Five-Year" Development Plan" issued by the China Adhesive and Adhesive Tape Industry Association, during the "Thirteenth Five-Year Plan" period, my country's adhesive industry is still in an important period of development opportunities. The average annual growth rate is 8.3%. At the end of 2020, my country's adhesive production reached 10.337 million tons, with sales of 132.8 billion yuan.