Jul 25,2022

Introduction to Polyurethane

Polyurethane (PU) is the abbreviation of polyurethane, which is made of polyisocyanate and polyhydroxy polymer addition, and is a polymer compound containing many repeated carbamate chain segments (-NHCOO-) in the polymer main chain. The research and development of polyurethane in China began after the founding of New China, and domestic polyurethane has been developed rapidly after the reform and opening up: the synthesis of isocyanate, polyol and additives has completed industrial production, and the production and application of series of polyurethane products have been expanded year by year. At present, the annual output of domestic polyurethane products exceeds 6 million tons, accounting for about 1/3 of the world.

The rapid development of polyurethane is attributed to the excellent performance of the material, such as wear resistance, high mechanical strength, high elasticity, aging resistance, corrosion resistance and so on. These excellent properties are closely related to the molecular structure of polyurethane materials: the main chain of polyurethane molecule is made of flexible long-chain polyol and rigid isocyanate block, which can effectively disperse the stress effect, and the coexistence of polar and non-polar chain segments also improves the chemical stability of polyurethane, while the extensive hydrogen bonding within the polymer further improves the mechanical properties of the material. In addition, the -NCO group of isocyanate is very active and can react rapidly with alcohols, water, organic amines, etc. The processing properties of the material are good. Through the control of reaction conditions and catalysts, a variety of polyurethane products with different hardnesses and structures can be obtained, such as elastomers similar to rubber or plastic, sponges with open-hole structures, rigid foams with closed-hole structures, adhesives, coatings, sealants, etc., which are widely used in various fields of national production and life.

Foam materials are the most produced category of polyurethane products, including two types of rigid foams and soft foams. Rigid foam is mainly used in the field of insulation and filling, such as pipe insulation, building exterior wall insulation, refrigerator insulation, etc.; when used as filling material, it can be used for waterproofing and plugging, filling of coal mines and other mining areas, etc. Soft foam is mainly used in automobiles and furniture, such as sofa sponge, car seat padding, etc.

Polyurethane coating has strong adhesion, and the coating film has excellent wear resistance, water resistance and chemical resistance, etc. It is mainly used in furniture, building materials and industrial printing ink, etc. Due to its excellent flexibility, mechanical strength and resistance, polyurethane has the advantages of water resistance, scratch resistance and dry crack resistance as an interior wall coating. Recently, water-based polyurethane interior wall coatings have been widely used, and the construction process is odorless, safe and environmentally friendly, making it a high-grade coating of great interest. In addition, polyurethane made from polyether polyol has outstanding water resistance, and is also widely used for equipment anti-corrosion, such as ship shells, pipe interiors, etc. Polyurethane coated on fabric can improve its permeability and play the role of wind and rain protection, which is mostly used in punching clothes.

Polyurethane materials have strong polarity, which allows them to bond strongly with most materials and can be used as adhesives in bonding applications. By adjusting the ratio of isocyanate and polyol, the performance of the cured material can be adjusted to achieve high adhesion to the base material, excellent water resistance, oil resistance and chemical resistance. Polyurethane adhesives are mainly used in the packaging, construction, wood, automotive, and shoe industries. In the past, solvent-based polyurethane adhesives were commonly used, but in recent years, with the deepening of the concept of green chemistry, water-based polyurethane adhesives have developed significantly and are used in the furniture and footwear industries.

Polyurethane elastomer is a kind of material with both rubber and plastic properties, which has good tensile strength, tear strength, impact resistance, abrasion resistance, weather resistance, hydrolysis resistance, oil resistance and other advantages. It is mainly used as structural materials (such as hoses, gaskets, belts, rollers, gears, pipes, etc.), insulators, shoe soles, and solid tires. For example, as a mining sieve plate, it has lower noise, higher permeability and wear resistance than the traditional metal sieve plate. In addition, polyurethane has excellent biocompatibility and can be used as biomedical materials for cardiac pacemakers, artificial blood vessels, artificial bones, etc.

Due to the excellent performance of polyurethane, its production and varieties are also growing year by year, and it has become the fifth largest polymer material. With the development of science and technology and the growth of social demand, it is believed that more polyurethane products with excellent performance will be shown in front of the world.

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