Full polyurethane called polyurethane, is collectively repeat urethane groups (NHCOO) macromolecular compound containing in the main chain. It is made from an organic diisocyanate or polyisocyanate compound with two or more hydroxyl polyaddition. The following reaction formula: -N = C = O + HO- → -NH-COO-, in addition to the polyurethane macromolecule carbamate, can also contain ether, ester, urea, biuret, allophanate, etc. groups.
(Cyanate
Description: H-O-C≡N (n) cyanate H-N = C = O (isocyanate) has a (positive) cyanate and isocyanate two kinds. The free acid is a mixture of both, not separation opening, but its esters are two forms. Cyanate is volatile and corrosive liquids. There is a strong smell of acetic acid. Density 1.14. Boiling point 23.6 ℃. Show strong acidity in aqueous solution. Unstable, easily polymerization. Ammonia and carbon dioxide generated during hydrolysis. When generating carbamates and alcohols role. (N) isocyanate R-O-C≡N easy polymerization, and susceptible to hydrolysis, was obtained in pure form difficult. Isocyanate R-N = C = O or O = C = N-R-N = C = O, generally unpleasant odor with a liquid. Cyanate cyanuric acid can be prepared by thermal decomposition. )
Polyurethane products form soft, semi-rigid and rigid foams, elastomers, paints, adhesives, sealants, synthetic leather coating resins, elastomeric fibers, widely used in automobile manufacturing, refrigerator manufacturing, transportation, civil engineering construction, footwear, synthetic leather, textile, machinery, petrochemical, mining machinery, aerospace, medical, agriculture and many other fields.
Depending on the different raw materials, can have different types of products, generally two types of polyester and polyether. Polyether polyurethane is mainly polyurethane material preparation defined for polyol, a polyurethane polyol that is prepared entirely from polyether polyol or a majority of possession in the system.
Polyether polyols in the molecular structure, an ether bond cohesive energy is low, and easy to rotate, so it is a good low-temperature polyurethane material prepared by its supple performance, excellent hydrolysis resistance, although not as good as the mechanical properties of polyester polyurethane, but low viscosity materials , easy and isocyanate component miscible additives, excellent processing performance.
Polyester polyols are generally referred to by a dicarboxylic acid with a glycol and other polyester polyol by condensation reaction. Broadly containing ester group (COO) or a carbonate group (OCOO) polyol. Polyurethane foams are widely used. Soft foam is mainly used for furniture and vehicles of various mat materials, insulation materials; rigid foam insulation is mainly used for household appliances, housing wall waterproofing spray foam insulation, pipe insulation materials, building panels, refrigerated trucks and cold storage insulation and other materials; semi-rigid foam used in automotive instrument panels, steering wheel and so on. The market has a variety of specifications for polyurethane foam combination of materials (two-component premix), mainly for the (cold cure) high resilience foams, semi-rigid foams, casting and spraying hard foam plastic.
(Diethyl ether
1. When a mixture of ethanol and concentrated sulfuric acid was heated to 140 ℃ can intermolecular dehydration products with ether. Concentrated sulfuric acid as a dehydrating agent where the catalyst.
2. Equation: 2 CH3-CH2-OH – catalyzed and concentrated H2SO4 → at 140 ℃ CH3-CH2-O-CH2-CH3 + H2O)
Polyurethane elastomer
Polyurethane elastomer is a polyurethane composite material of a variety, because of its structure with soft and hard two segments, can be designed to impart molecular material having a high strength, toughness, wear resistance, oil resistance, excellent performance, both with rubber having high elasticity and rigidity of plastic, called “wear-resistant rubber.”
Polyurethane elastomer can now use the same general rubber mastication, mixing, curing molding process (refer MPU); also be made of liquid rubber, cast molding or spraying, casting, centrifugal molding (refer to CPU); can also be prepared into pellets, and, like ordinary plastic, injection, extrusion, calendering, blow molding and other processes (of CPU). Molding or injection molded parts, within a certain range of hardness, but also can be cut, grinding, drilling and other machining. Processing of diversity, the polyurethane elastomer very wide applicability, applications continue to expand.
Oil resistance, ozone resistance, aging resistance, radiation resistance, low temperature, transparent sound good, strong adhesion, excellent biocompatibility and blood compatibility. These advantages is the polyurethane elastomer widely used in military, aerospace, acoustics, biology and other reasons.
The main advantage of polyurethane elastomer:
1, the performance of the adjustable range. A number of physical and mechanical performance indicators can be adjusted by selection of raw materials and formulations, within a certain range, to meet the different requirements for product performance. Such as hardness, is often an important indicator of the product’s users, both made of polyurethane elastomer Shore A hardness of 20 or so soft printing rollers, but also made more than 70 Shore D hardness of hard rubber roller rolling, this is a general elastomeric material difficult to do. Polyurethane elastomer is a polar polymer material composed of many segments and hard segments composed of flexible chain, with the improvement and increase of the polar group density hard segment proportion of elastomer original strength and hardness will be increased accordingly.
2, superior wear resistance. Particularly where there is water, oil wetting medium existing working conditions, the wear resistance is often several times to several times the ordinary rubber materials. Metallic materials such as steel, although very hard, but not necessarily wear, such as large pump irrigation area of the Yellow River, the overcurrent protection components and metal mouth ring ring after a lot of sediment erosion, does not take hundreds of hours to severe wear leakage , while the use of polyurethane elastomer coated mouth ring and ring protection is continuous operation 1800 into a small yet wear. Others, such as rice milling used rubber roller hulling machine, vibrating screen sieve Coal Preparation and track stadium runway, dynamic oil seals used forklift crane elevator wheel and wheel roller skates, etc. are also polyurethane elastomer It comes in. In this reference point is needed to improve the coefficient of friction of the low-hardness polyurethane elastomer member, to improve wear resistance under load bearing, you can add a small amount of aluminum disulfide, graphite or silicone oil in such a polyurethane elastomer, etc. lubricant.
Post time: Nov-24-2018