Foam has always been a source of headaches for painters. As the coating preparation process will add dispersant, thickener, leveling agent, and other additives, resulting in the formation of elastic film bubbles in the coating system, this type of bubble is more stable, so you need to add defoamer for waterbased coating to eliminate and inhibit the bubble generation.
In the face of coating foam generation, we need to understand whether the system has stable bubble components, and then choose the appropriate water-based coating defoamer. The defoaming effect of silicone defoamer will be better than others, but we should pay attention to the dosage when we use it, if we are not careful, it will affect the appearance of the coating or other performance. It should also be noted that in the face of different systems of coatings, the choice of a defoamer is also different, such as acrylic emulsion, polyurethane dispersions, water-soluble resins and other systems of the applicable defoamer is different, according to the specific experimental data to verify.
Some defoamers have strong foam-breaking ability, but poor foam-inhibiting performance, which is not very effective in the process of paint use, this time you can consider choosing two or more kinds of defoamers for mixed-use and dividing them into two put into the paint, respectively, the grinding process to add the good foam-inhibiting effect of defoamer, in the paint stage to join the strong foam-breaking power of defoamer.
Defoaming and system viscosity have a great relationship, viscosity is small then defoaming is naturally fast, and vice versa, if the viscosity is too large, then in the choice of defoamer, the appropriate less. In addition, defoaming and the volatility of the system are also related, to volatile very fast paint, the surface will dry, and when the bubbles float to the surface too late to break, it is fixed and will accumulate more and more. So how to choose the right defoamer for your system? Nanhui defoamer recommends that we use a high-speed stirring method to test the defoaming ability of the defoamer. Fixed speed, stirring time, dosage, viscosity, and other parameters, and then compare the height of the foam and the elimination of time.
Generally high viscosity emulsion paint, due to the difficulties of defoaming, stable foam factors are also more, add a little more, generally 0.3-1.0%; low viscosity emulsion paint or water-soluble coatings, especially water-soluble coatings, due to a certain amount of co-solvent, you can reduce the dosage, generally 0. 01-0.2% can be. Other water-based paints or resins are about 0.1%. Anyway, the higher the dosage is, the better, and more will cause shrinkage and other problems, silicone defoamer will also affect the recoatability, so the specific amount to be added will be based on their own system foaming situation.
