Polyurethane prepolymer 120 degrees, what is the precondensation temperature of waterborne polyureth

Of course, there will be an impact, if it is a prepolymer of TDI system, to get a relatively stable performance of low free prepolymer, then it is best not to have too high temperature, because TDI volatility is high, the temperature is below 60 for one to half an hour, and then the temperature is controlled at 70-80, and the reaction is 2h. If MDI or other isocyanates are used as prepolymers, the temperature can be 5 or 10 higher without much effect. However, if the temperature is too high, this will be accompanied by the occurrence of side reactions, and as the temperature increases, the reaction speed of the isocyanate group with various active hydrides will also increase.

The self-polymerization reaction rate of isocyanate is also accelerated, when the temperature is 130-150, the rate constants of each reaction are almost the same, the isocyanate group reacts with carbamate or urea bond, resulting in cross-linking, and the urethane, urea or biuret generated above this temperature is not very stable and may decompose. The NCO value of the prepared prepolymer will definitely be on the low side.

The general NCO content is mainly designed according to the formulation you are proparating. It cannot be said how much is the most appropriate. The landlord above [Jinghai Resin Zhang] told you that it is the NCO value of the prepolymer of general polyurea.

The prepolymer isocyanate content is of course low and good, and generally bayer Cojuya 4 10 is very common.

Yes, it should be kept warm at 45 degrees for half an hour, and then slowly warmed up, the maximum temperature is different according to the type of isocyanate you choose, and the temperature should be raised to 65-70 degrees with TDI theory alone. If you use others, for example, the MDI temperature should be high.

Generally, the isocyanate content is about 13%, and some manufacturers are about 22%.

There are by-products, which seriously affect the quality of products.

Hello, we are happy to serve you and give you the following answers: the pre-polycondensation temperature of waterborne polyurethane polymerization is generally between 120-140, and the specific temperature depends on the structure and performance requirements of the polymer. The higher the pre-excited chain polycondensation temperature, the better the structure and properties of the polymer, but it will also lead to an increase in the molecular weight of the polymer, which will affect the brightness and grandchild properties of the polymer.

Therefore, when selecting the pre-polycondensation temperature, the influence of temperature and molecular weight should be considered comprehensively according to the structure and performance requirements of the polymer to determine the optimal pre-polycondensation temperature.