As a key additive for polyurethane foam materials, polyether-modified silicone oil mainly plays the role of stabilizer and is also called a homogenizing agent. Although its usage in the formula is small, usually 0.5% to 2.0% of the polyol, its role is crucial.
Four main functions of polyether-modified silicone oil in polyurethane foam production:
Emulsification:
In the initial stage of mixing polyether polyol and isocyanate, due to the poor solubility of the two, the hydrophobic group of polyether-modified silicone oil is soluble in isocyanate, while the hydrophilic group is soluble in polyether polyol, so it can effectively promote the mixing and emulsification of the two, ensuring that the reaction starts evenly in the system.
Generate and homogenize bubbles:
Polyether-modified silicone oil can reduce the surface tension of the reaction system, so that the air can be evenly dispersed into fine bubbles to form bubble nuclei. This provides conditions for carbon dioxide and the gas generated by the foaming agent to enter the bubble nucleus to form bubbles, and low surface tension is conducive to the growth of bubbles.
Stabilize bubbles:
When the system viscosity is low, the bubble core liquid film is thin and easily broken by drainage, merging or mechanical impact. Polyether-modified silicone oil enhances the stability of the bubble core through the Gibbs-Marangoni effect, reduces bubble wall leakage and merging. In addition, its non-ionic properties help reduce the van der Waals force at the gas-liquid interface and further stabilize the bubbles.
Connect the bubbles:
In the final formation stage of polyurethane soft foam materials, the connectivity of the bubble core is crucial. When the system viscosity is low, polyether-modified silicone oil helps stabilize the bubble core wall film and promotes the wall film to reach the critical opening thickness, creating conditions for the final opening of the bubble core.