Many people are concerned about the storage of prepolymer, and some people respond to their own storage problems.
1. Moisture problem of polyurethane storage
Polyurethane in storage process usually absorb moisture, and the existence of water will lead to unfavorable results and reaction of NCO in polyurethane, polyurethane and generate carbamido viscosity, then with urea as the branching point can further react with the NCO groups, the formation of shrinkage of two urea branched or cross-linked to the storage stability of polyurethane elastomer to reduce or even gel products.
2, there are two possible sources of water
(1) the humidity in the storage environment is too large;
(two) the storage vessel is not sealed well and contains moisture. The solution should be to reduce the humidity of the place and isolate the air from the polyurethane. It is better to use nitrogen to protect the air.
3, polyurethane storage NCO value changes, polyurethane elastomer products in the room temperature preservation process, often produce the following situations
(1) polyisocyanate in polyurethane continues to react with oligomer polyols to decrease the NCO value;
(two) a small amount of water in the mixture reacted with polyisocyanate to reduce the NCO value.
4, NCO value reduction has some harm
(a) that would make the polyurethane larger viscosity, poor mobility, easy deaeration;
(two) than before the experiment set NCO value is low, leading to fill more isocyanate, increase operation;
(three) a small amount of water reacted with polyisocyanate to form a by-product of biuret two urea and urea, which also affected the properties of the product.