The bubble problem of waterproof coating has always been a headache for everyone, and the bubble in waterproof coating is often caused by the lower the surface tension, the less free energy required for the system to form foam, and the easier it is to produce foam. However, such foam is not necessarily stable. Only when the system contains surfactant that can form an elastic film, such as dispersant, thickener, leveling agent, etc., can foam be stable.
Defoamers are used to prevent the formation of bubbles in lubricating oil. The principle of action is to change the surface tension of foam to make small bubbles gather into large bubbles, so as to break the bubbles and achieve defoaming.
After understanding the basic principle of foam stabilization, it is easy to remove foam. First, pay attention to whether there are any foam stabilizing components in the system, and then choose a suitable defoamer. Generally, defoamers containing silicon have better effects, but it should be noted that they may affect other properties. It should also be noted that different types of defoamers should be used for different systems, such as acrylic acid lotion, polyurethane dispersion and other systems. The type of defoamer applicable to each system is different, which should be verified through experiments. There are many defoamers with strong defoaming ability, but their defoaming ability is poor and they have little effect on the bubbles generated during use. In this case, it is necessary to consider mixing two or more defoamers and adding them in two batches. When grinding, add a waterproof coating defoamer with good defoaming effect, and when forming a film, add a defoamer with good defoaming effect.
Polyether modified organosilicon is a polyether siloxane copolymer (abbreviated as silicone ether copolymer) made from polyether segments in siloxane molecules. Polysiloxane defoamers have the characteristics of rapid defoaming, long defoaming time, and safety and non toxicity, but they are difficult to dissolve in water, resistant to high temperatures, and have poor resistance to strong alkalinity. Polyether defoamers have good water solubility, high temperature resistance, and strong alkalinity resistance, but their defoaming speed and defoaming time are not ideal. By grafting polyether chains onto polysiloxane chains through condensation technology, they have the advantages of Class II defoamers and become a high-performance defoamer with broad application prospects.
