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Analysis of causes and solutions of polyurethane foaming

1. Foam may appear in polyurethane in the following situations:

1. In order to increase the viscosity of polyurethane dispersion, a certain amount of chemical additives such as thickeners are often added. These additives are surfactants and have foaming properties.

2. In the production and use of polyurethane, due to the mixing operation of mechanical equipment, a large amount of air is mixed in. These gases are difficult to escape, so foam will be formed.

3. The moisture in the raw materials in polyurethane is not properly treated, and the carbon dioxide produced by the reaction between water and isocyanate causes foam (chemical bubbles) to occur.

2. Some common treatment methods for bubbles produced by polyurethane adhesives

1. Vacuum degassing method

Vacuum degassing is a common process that uses the principle of expansion and annihilation of gases in a negative pressure environment to reduce the environmental pressure by placing liquid or materials containing bubbles in a vacuum container.

Make the bubbles in the liquid expand and disappear quickly, thereby achieving the purpose of removing the bubbles.

2. Add liquid defoamer

Faced with a large amount of foam in polyurethane, some manufacturers choose polyurethane defoamer to solve the foam problem. For high-viscosity polyurethane products, excessive addition will affect the stability and performance of the produced products to a certain extent. It will also increase the production ingredients and cause unnecessary waste of defoaming agents.

3. Use molecular sieve powder for physical defoaming

It has strong defoaming and anti-foaming capabilities and can quickly absorb moisture and carbon dioxide in polyurethane materials.

And it will not foam again in subsequent operations; it has strong hydrophilicity, fast dispersion, and the addition amount is only 1-5%. It eliminates bubbles without affecting the product itself, and can be used as a filler, which greatly reduces the cost and makes The quality of polyurethane products is better, more stable and more high-end.

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