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What are the characteristics of polyurethane catalysts?
Edit:Nantong Yutai Chemical Products Co., Ltd.   UpDate:2019-10-11

[English name] Bis (tri-n-butyltin) Oxide


[Molecular formula] C24H54OSn2


[Molecular weight] 596.20


[CA registration number] [56-36-9]


[abbreviation and alias] BTBTO, TBTO, Bistributyl-tinoxide, bis(tri-n-butyltin) oxide, bis-tributyltin oxide


[Structure]


[Physical properties] Colorless liquid, bp 180 ° C / 2.0 mmHg, d 1.170g / cm3. It is soluble in most organic solvents and insoluble in water.


[Preparation and Commodities] Large multinational reagent companies are available for sale. The reaction of anhydrous tin tetrachloride with butyl magnesium bromide to form tetrabutyltin, and then metathesis with tin tetrachloride to form tributyltin chloride, and finally reacted with potassium hydroxide to obtain tributyltin oxide.


[Caution] It is generally used in a dry anhydrous system and operated in a fume hood. Place in a fume hood to avoid direct contact.


In the presence of a bromine reagent, tributyltin oxide promotes oxidation of propenol, benzyl alcohol, secondary alcohols, and sulfides. This method is very practical, and for a compound containing a primary alcohol and a secondary alcohol, the secondary alcohol can be selectively oxidized to a ketone (Formula 1).

In the presence of NBS, tributyltin oxide also oxidizes the secondary alcohol to a ketone with high selectivity, and the reaction occurs on a secondary alcohol having a lower steric hindrance (Formula 2).

Tear strength: Polyurethane elastomers have higher tear strength, especially polyesters, which are more than twice that of natural rubber. Load carrying capacity: Although the compressive strength of the polyurethane elastomer is not high at low hardness, the polyurethane elastomer can increase the hardness while maintaining the rubber elasticity, thereby achieving high load carrying capacity. The hardness of other rubbers is very limited, so the carrying capacity cannot be greatly improved.

Abrasion resistance: Polyurethane elastomers have excellent wear resistance. The test results are usually in the range of 0.03 to 0.20 mm / m, which is about 3 to 5 times that of natural rubber. In actual use, the effect is usually better due to the influence of lubricants and other factors. Wear resistance is related to the tear strength of the material and the surface condition. Polyurethane elastomers have much higher tear strength than other rubbers, but their own friction coefficient is not low, generally 0.5 or more. This requires careful addition of oily lubricants or a small amount of molybdenum disulfide or Graphite, silicone oil, tetrafluoroethylene powder, etc. can reduce the friction coefficient and reduce friction heat. The coefficient of friction is also related to factors such as material hardness and surface temperature. In all cases, the coefficient of friction increased with decreasing hardness, increased with increasing surface temperature, and reached a maximum at about 60 °C.

Polyurethane catalyst water resistance: Polyurethane elastomer has good water resistance at room temperature, and has no obvious hydrolysis in one or two years, especially polybutadiene type, polyether type and polycarbonate type. Heat resistance and oxidation resistance: Polyurethane elastomers have good heat resistance in an inert gas, and are excellent in oxygen resistance and ozone resistance at normal temperature, particularly polyesters. The combination of high temperature and oxygen accelerates the aging process of the polyurethane. Polyurethane elastomers have a maximum temperature limit of 80-90 ° C for continuous use in air and 120 ° C for short-term use. The temperature that significantly affects thermal oxidation is about 130 °C. Depending on the variety, the polyester type has better thermal oxidation resistance than the polyether type. As the temperature is lowered, the hardness, tensile strength, tear strength and torsional rigidity of the polyurethane elastomer are significantly increased, and the rebound and elongation are lowered.


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