Classroom on basic knowledge of polyurethane (PU)

The full name of polyurethane is polyurethane Carbamate is a general term for macromolecular compounds containing repeating carbamate groups on the main chain. It is formed by the addition polymerization of organic diisocyanate or polyisocyanate and dihydroxy or polyhydroxy compounds. In addition to urethane, polyurethane macromolecules can also contain ether, ester, urea, biuret, allophanate and other groups. Depending on the raw materials used, products with different properties can be produced, generally divided into two categories: polyester type and polyether type. It can be used to make plastics, rubber, fibers, rigid and flexible foams, adhesives and coatings, etc. Polyurethane is an emerging organic polymer material, known as"the fifth largest plastic". Due to its excellent performance, it is widely used in construction, automobiles, light industry, Textile, petrochemical, metallurgy, electronics, national defense, medical, machinery and many other fields.

1. raw materials

TDI, MDI, AA and other products belong to Polyurethane raw materials, not polyurethane products. Polyurethane raw materials mainly include: isocyanate, polyester polyol (generated by the reaction of polyol and polybasic acid, commonly used polybasic acid is adipic acid, commonly used polyols include 1,2 butanediol, ethylene glycol, etc.), polyether polyol (Commonly used ones include PPG, POP, PTMEG, etc.), solvents (commonly used ones include DMF, TOL, MEK, etc.), chain extenders (commonly used ones include BDO) and various additives.

(Isocyanate is the general name for various esters of isocyanate. If classified by the number of -NCO groups, it includes monoisocyanate R-N=C=O and diisocyanate O=C =N-R-N=C=O and polyisocyanates, etc. At present, the most widely used and produced ones are: TolueneDiisocyanate, referred to as TDI and diphenylmethane diisocyanate, MethylenediphenylDiisocyanate, referred to as MDI)
【TDI]

Toluene diisocyanate, abbreviated as TDI, is mainly used in soft foam, coatings, and elastomers ,adhesive. Among them, soft foam is the largest consumer area, accounting for more than 70%, and coatings account for more than 15%. Flexible polyurethane foam has a wide range of applications in furniture, construction and transportation. In addition, TDI can also be used to produce rigid polyurethane foam materials, adhesives, concrete sealants, nylon-6 cross-linking agents, polyurethane coatings and polyurethane elastomer intermediates.
【MDI]

Diphenylmethane diisocyanate abbreviationMDI, products can be divided into pure MDI, polymerized MDI, liquefied MDI, modified MDI, etc. Pure MDI is mainly used to generate slurry, sole solution, spandex, TPU and polyurea spraying, etc. Polymerized MDI is mainly used in the production of polyurethane rigid foam and CASE fields. Polyurethane rigid foam is widely used in the insulation industry, such as refrigerators and freezers, solar water heaters, insulation pipes, etc. It can also be used to produce imitation wood furniture, PU boards, etc.
【Polymethylene polyphenyl polyisocyanate]

Polymethylene polyphenyl polyisocyanate, Abbreviated as PAPI, or crude MDI. PAPI is actually a mixture of 50% MDI and 50% polyisocyanate with a functionality greater than 2. Polymerization can occur when the temperature rises. Soluble in chlorobenzene, o-dichlorobenzene, toluene, etc. PAPI has low activity,It is a new type of textile material with high added value. There are four main forms of use: bare yarn, core-spun yarn, covered yarn, and twisted yarn, such as stockings, swimsuits, dance suits, silk-cotton covered yarn, clothing, etc. In traditional textiles, only less than 5% of spandex can be added to greatly improve the quality of traditional fabrics, showing a soft, comfortable, beautiful and elegant style.
【Polyurethane paving Packing materials]

Polyurethane paving material There are many types, including floor covering materials, waterproof materials, pouring materials, etc. Floor covering materials are used for laying sports venues and floors, waterproof materials are used for waterproofing and heat insulation on building roofs, and pouring materials are used for construction, Water blocking, waterproofing, reinforcement, reinforcement and anti-corrosion in coal mines, railways, oil exploration, water conservancy, electricity and geological drilling and other departments.

Four. Extension

【Water-based polyurethane]

Water-based polyurethane is a new polyurethane system that uses water instead of organic solvents as the dispersion medium. It is also called water-dispersed polyurethane, water-based polyurethane or water-based polyurethane. Water-based polyurethane uses water as the solvent and has the advantages of no pollution, safety and reliability, excellent mechanical properties, good compatibility, and easy modification. It can be widely used in coatings, adhesives, fabric coatings and finishing agents, leather finishing agents, and paper surface treatment. agents and fiber surface treatment agents.
【Spray polyurethane ]

is composed of isocyanate components (<font face An elastomer material produced by the reaction between component A) and resin component (component R). Isocyanate can be either aromatic or aliphatic. The A component can be said to be a monomer, a polymer, an isocyanate derivative, a prepolymer and a semi-prepolymer; a prepolymer and a semi-prepolymer. It is produced by the reaction of hydroxyl-terminated compounds and isocyanates. The R component must be composed of a hydroxyl-terminated resin (such as diol, triol, multi-strong hydroxyl polymer polyol, etc.) and a hydroxyl-terminated (aromatic or aliphatic) chain extender. In the hydroxyl-terminated resin , must contain a catalyst to increase reaction activity.
【Biodegradation PU material]

Biodegradable plastics are currently a hot topic in global development. There are basically two technical approaches to industrialization: one is to develop high molecular weight biodegradable materials, typical varieties such as polylactic acid ( Biodegradable plastics such as PLA), polybutylene succinate (PBS), polycarbonate lactone (PPS), polyhydroxy fatty acid (PHA), etc. Although these biodegradable plastics have excellent biodegradability, they are generally mechanically Performance, especially shortcomings such as poor toughness and temperature resistance. The other is to develop low molecular weight biodegradable polyols and use isocyanate chain extension to make polyurethane biodegradable plastics with high molecular weight.
【Green life Material polyol]

The upstream raw materials of traditional polyols come from petroleum and Natural gas and other resources, but with the increasingly serious energy shortage and people's increasing awareness of environmental protection, the development and utilization of renewable resources to manufacture biomass polyols has made greenPU materials have become a New highlights. At present, the raw materials for preparing biomass polyols mainly include vegetable oils, plant cellulose, and lignin polyols. Biomass polyols can replace some polyether polyols and are used to manufacture a variety of PU materials, including PU rigid foam, adhesives, coatings, elastomers and plastic tracks, etc., and have been used in fields such as automobile building exterior insulation boxes and refrigerators.

Due to severe energy shortage and people's increasing awareness of environmental protection, the development and utilization of renewable resources to produce biomass polyols has made green PU materials a new bright spot. At present, the raw materials for preparing biomass polyols mainly include vegetable oils, plant cellulose, and lignin polyols. Biomass polyols can replace some polyether polyols and are used to manufacture a variety of PU materials, including PU rigid foam, adhesives, coatings, elastomers and plastic tracks, etc., and have been used in fields such as automobile building exterior insulation boxes and refrigerators.