Types Of Polyurethane
1、 Polyurethane foam is the foam product with the largest output. The relative density is mostly between 0.03 and 0.06. The thermal conductivity of hard foam is only about 40% of that of cork or polystyrene foam. It has sufficient strength, oil resistance and bonding ability. It is an excellent shockproof, heat insulation and sound insulation material. It is widely used for insulation of household appliances (refrigerators, freezers, water heaters, solar water heaters, heat pump water heaters, beer preservation barrels, incubators, etc.) Equipment thermal insulation (heat supply pipeline, crude oil chemical pipeline, tank body, refrigerated transportation, passenger car thermal insulation, etc.), building energy conservation (external wall thermal insulation, roof waterproof thermal insulation, cold storage, building plate, anti-theft door / garage door, rolling shutter door, etc.), as well as packaging and decoration (decorative board, imitation wood furniture, handicrafts, etc.). Polyurethane flexible foam has good elasticity and is also an ideal cushion and mattress material.
2、 Polyurethane rubber can be divided into mixing type, thermoplastic type and casting type according to its processing mode. Mixed raw rubber is saturated or hydroxyl terminated polyurethane with a small amount of double bonds. It can be processed and formed by the processing method of ordinary rubber, and the output is small. Thermoplastic rubber can be divided into full thermoplastic and semi thermoplastic. The former has linear structure and the latter has a small amount of crosslinking. They can be formed by thermoplastic processing methods and equipment. Cast rubber is mostly made of liquid prepolymer and chain extender, which are quickly mixed and then cast into shape or sprayed, with strong adaptability. At present, about two-thirds of polyurethane rubber products are molded by casting method. The reaction injection molding technology appeared in recent years can be directly injected from liquid monomer and rapid reaction molding. It has the advantages of high production efficiency, less equipment investment and good part performance.
③ Polyurethane coatings are divided into two-component and single component: the two-component polyurethane coatings are polyether type, and the two-component solutions of polyisocyanate and polyether are directly mixed; One component polyurethane coating is unsaturated polyester type, including oil modified type, wet curing type and closed type. Polyurethane coating shall be applied by means of spray, electrodeposition and impregnation. The coating is wear-resistant, resistant to gasoline, grease, water and inorganic acid vapor, has high insulation and adhesion, and has bright color for a long time.
④ Polyurethane adhesives are generally composed of two-component systems of polyisocyanates and hydroxyl containing polyester compounds. It can contain curing initiator, powder filler (titanium oxide, zinc oxide, cement), solvent (acetone, ethyl acetate, chlorinated hydrocarbon). The two components are mixed directly before application, and the storage period is 1 ~ 3H. The curing time shall not be less than 24h at room temperature, or 1 ~ 3H at 100 ~ 150 ℃ and pressurized to 0.03 ~ 0.05Mpa. This kind of adhesive has high adhesive force with various materials. After curing, it is stable to water, mineral grease, fuel, aromatics and atmosphere. The working temperature is - 200 ~ 120 ℃, and the price is expensive. It is applied to the connection of metal, plastic, glass and ceramic structures in aviation, space technology, construction and machinery, as well as the copying materials of polymer film, the bonding of sole and upper, etc.
