What is the most important thing in the polyurethane foaming process?

In the foaming process of polyurethane foam, the most important are the gel reaction (reaction between hydroxyl groups and isocyanate) and foaming reaction (reaction between isocyanate and water) A good balance is established between the two, so that the formation of urethane and the rate of gas generation are coordinated with each other. During the gas generation reaction, the cell wall has sufficient strength to effectively encapsulate the gas in the foam body. To achieve this, the role of blowing agents, catalysts and foam stabilizers is crucial, especially the latter two. These three are also the three most important additives in foaming formulas.

The foaming agent mainly determines the total amount of gas produced, and at the same time, it reduces the viscosity of the entire system and affects the production of gas. and growth rate also have a certain impact. Choosing an appropriate composite catalytic system can not only speed up or slow down the overall reaction rate, but also effectively balance the gel reaction and foaming reaction rates and cooperate with each other to prevent the foam from collapsing and shrinking. In addition, the formation of the cell structure also requires The role of catalyst.

In polyurethane foam, the more commonly used catalytic systems are tertiary amines and organotin compounds. On the one hand, the role of foam stabilizer is to reduce the overall viscosity of the foaming system, so that a large number of small and uniform bubble nuclei can be produced in the mixed liquid, and the cells can be enlarged smoothly. On the other hand, the function is to make the surface tension inside the mixed liquid as consistent as possible, thereby narrowing the cell diameter distribution.

The above three additives will affect each other during the foaming process. For example, the catalyst that catalyzes the gelation reaction will Foam solidifies rapidly, but foam stabilizers slow down this solidification process. Therefore, if you want to obtain a foam product with uniform and fine cells and excellent comprehensive properties, you must have a deep understanding of each component in the foaming system and consider it comprehensively when formulating the formula.