To make the defoamer work well, the method of adding defoamer is very important.Defoamer generally needs to be dispersed under high shear rate, if the effect is better in two additions, that is, the defoamer used is divided into two parts, one in the grinding stage to join, one in the With paint stage to join, so that the role of defoamer play the best, the amount can be reduced to a minimum.
It takes at least 24h after the defoamer is added to give full play to its effect, so we must pay attention to this point when we try it, if we test it in advance, we will often come to the wrong conclusion. The coating production process requires good durability of the defoamer’s action. Sometimes it will be found that the stored paint will often fail to achieve the initial defoaming ability in the construction and film formation process. In a solution with a concentration greater than cmc, the defoamer is likely to be soluble, so that it loses its role in spreading on the surface, and the effectiveness of defoaming is greatly reduced.
The correct use of defoamer, need to master the right amount, and the lowest effective amount is good. This requires the coating formula designer to conduct repeated tests to get the data. The general test method is: prepare samples with different defoamer content wax emulsion formulation according to the above use method, prepare samples with the same conditions, observe the speed of bubble breakage and the amount of bubbles remaining in the dry film to judge the size of defoaming ability. You can observe the shrinkage to determine the gloss to judge which dosage is the most appropriate.
In order to determine the persistence of the defoamer, the sample with defoamer can be sealed tightly in a 50 ℃ oven after 30d, and the initial determination of the defoaming capacity of the sample for each performance comparison. This condition is generally equivalent to 6 months to 1 year of storability at room temperature.
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