Let’s talk about the pore opening agent in polyurethane foam

First of all, why do we use pore opening agents? PolyurethaneFoam glueforming bubblesThe process involves foaming and gelation reactions at the same time, especially MDI system foaming. Since the gelation rate is higher than the foaming rate, the reaction The generated gas is easily trapped in the cell structure, that is, the porosity is insufficient, resulting in poor dimensional stability of the product and defects such as foam shrinkage, stiffness, and even loss of elasticity. Therefore, an effective method is to add a certain amount of pore opening agent.

Pore opening agent is a special type of surfactant, which generally contains hydrophobic and Hydrophilic segments or groups are adsorbed on the surface of bubbles. By adjusting the surface tension of the foam wall, the gas in the bubbles can easily break through the wall membrane, thereby increasing its open porosity and solving the problem of foam shrinkage caused by closed cells. Problem, the ideal cell opener can cause the cells to rupture near the gel point of the foam. When the cells are opened, air flows between the cells. The shrinkage rate of the foam after molding is greatly reduced, and the foam is given a lower hysteresis and aeration feeling, reducing the fatigue of the foam and improving the durability of the foam.

The cell opening effect of the cell opening agent can be quantitatively characterized by the sinking rate of the foam. In the formula that adds a cell opening agent, the oxygen index of the foam decreases and the flame retardancy becomes worse. The reason is that the greater the amount of cell opening agent added, the better the cell opening of the foam, which is more conducive to the circulation of air in the material. Cell opening agents can increase the elongation at break and improve the elasticity and feel of the foam to a certain extent, but they can also lead to a reduction in the breaking strength and hardness of the foam.