India What are the Free of silicone defoamers for paints(1)
India Selection of antifoaming agents for different applications:
A substance that can reduce the surface tension of water, solution, suspension, etc., prevent the formation of foam, or reduce or eliminate the original foam. [1]
Defoaming agents should have the following properties: ① strong defoaming power and low dosage; ② Adding to the foaming system does not affect the basic properties of the system, i.e. does not react with the defoaming system; ③ Low surface tension; ④ Good balance with the surface; ⑤ Good heat resistance; ⑥ Good diffusion and permeability, high positive spreading coefficient; ⑦ Chemical stability, strong oxidation resistance; ⑧ Good gas solubility and permeability; ⑨ Low solubility in foaming solutions; ⑩ No physiological activity, high safety
dispersant
Flat coating
Features: Low viscosity, low defoaming pressure
Alkyl modified organosiloxane
As mentioned earlier, polyether modified polysiloxanes have some shortcomings; Alkyl modified polysiloxanes have precisely these advantages.
This series of polysiloxane products also belong to the comb structure. The molecular weight of this type of product is relatively small, around 10000, and n+m is about 30-50. The main purpose of modifying with alkyl is to improve thermal stability, compatibility, and unstable foaming, and even to have defoaming functions. However, as the modified alkyl chain increases, its ability to reduce surface tension also decreases
Recommendation: Mineral oils or mineral oil modified polyethers
Elastic coating
agent
hand
dispersant
Features: High viscosity, high Free of silicone defoamers pressure
water-based
There is no unified understanding of the mechanism of defoaming agents. According to the mechanism of defoaming agents proposed by predecessors, there are generally the following types: [4]
General defoaming mechanism
Typical defoaming mechanisms with a broad overview are the Robinson defoaming mechanism and the Ross hypothesis. Among them, Robinson mechanism is the basis of Ross hypothesis, which mainly emphasizes the liquid drainage of defoamer destroying foam and Marangoni effect to realize defoaming; The Ross hypothesis is based on the fact that the defoamer particles are insoluble droplets, while some defoamers actually produce defoaming effects in a dissolved state, so the defoaming mechanism of the Ross hypothesis is not comprehensive
Recommendation: Polyether modified silicone
Surface coating and film covering adhesive
Recommendation: Polyethers, which can effectively prevent surface defects and have a small impact on gloss
Water in Water Colorful
Features: More surfactants, stable foam
India Recommendation: Use polyethers or mineral oil to modify polyethers
Precautions for use of paint Free of silicone defoamers:
Before use, stir thoroughly and mix evenly; Adding the paint while stirring; Before use, it is generally not diluted with water; The dosage should be appropriate. Excessive dosage can cause shrinkage, edge shrinkage, poor brushing performance, and other problems; Too little dosage leads to poor defoaming effect; Add it in two stages, namely, add it in the grinding stage and the paint mixing stage, generally accounting for half of the total amount each time. Use defoaming agents with good foam suppression effect in the grinding stage, and use defoaming agents with good foam breaking effect in the paint mixing stage