Analysis on the application of waterborne polyurethane (WPU) in coatings
Waterborne polyurethane Analysis on the application of waterborne polyurethane (WPU) in coatings Waterborne polyurethane is used in waterborne wood coatings, which is expected to obtain excellent film hardness, heat resistance and dielectric properties, and good film-forming properties. The higher the degree of microphase separation of aqueous polyurethane, the greater the difference of softening temperature, the better the film formation and heat resistance, but for wood coatings, film hardness and resistance to media is also an important measure of the performance of the index. In order to improve the dielectric resistance and the hardness of the coating, it is necessary to increase the crosslinking density and increase the proportion of the rigid segments in the molecular segments, it certainly will reduce the flexibility and relative molecular mass of the waterborne polyurethane molecules. These are not conducive to the micro phase separation, the mixing degree increased, unfavorable to the film. The research route is of high hardness, low molecular weight (less than 1000) polyester polyurethane preparation to obtain a high degree of crosslinking, heat resistance, chemical resistance and film hardness. At the same time, with good flexibility, high molecular weight (more than 2000) linear polyester preparation or low branching polyurethane, to improve the degree of microphase separation, the coating has excellent film-forming properties, reduce film-forming agent dosage, improve the film hardness rise velocity. And through these 2 kinds of polyurethane copolymerization to obtain comprehensive performance. Test method for aqueous polyurethane dispersion Huajinsi The aqueous poly (ethylene glycol) dispersion 4188/4100 (FOD) does not contain any free OH group, but they are still able to react with poly (ethylene glycol) as a hardening agent. This is due to the reaction of the amide backbone of the polyurethane dispersion. Because we can not calculate correctly, we can only recommend the following methods: 2, 4, 6, 8, 10, 12, 16%, a combination of isocyanate curing agent to quickly test. Aqueous ammonia fat dispersion with different curing agent, stirring for 10 minutes and then construction in plastic or wood substrate. After drying at room temperature on the 7 film angels bridge complete placement. 7 days after the test of chemical resistance (water, alcohol, coffee, fruit pulp, etc.) and mechanical properties (pendulum hardness, pencil hardness, scratch resistance, etc.), the results can be seen how much hardener. In this case, the hardener with 10~12% can achieve good film performance. The relationship between hardening agent weight and paint performance of hydroxylamine PUD binder Hardening agent Film state Film properties PUD binder No hardener: bad alcohol resistance Flexible elastic membrane Not very scratch resistant PUD binder Add 2% hardener: bad alcohol resistance Flexi...
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