How to Produce Silicone Oil-Modified Polyurethane Flexible Foam?

In the production of polyurethane flexible foam, the cell structure directly affects the foam's properties and applications. By modifying with silicone oil, it is possible to produce foams with coarse cells, irregular cells, or pseudo high-resilience cell structures. This article explains the mechanism of silicone oil in the foaming process and provides specific formulation and process suggestions.

1. Role of Silicone Oil in Foaming

Silicone oil acts as a surfactant in the foaming process, mainly regulating the foam cell structure. Its roles at different foaming stages include:

Early stage (Cream Time): Disperses raw materials and promotes uniform mixing.

Middle stage (Foam Growth): Stabilizes foam structure and prevents cell collapse.

Final stage (Foam Stabilization): Aids in cell opening to enhance breathability and elasticity.

Figure 1 shows the relationship between gas release and foam formation:

Figure 1: Relationship Between Gas Volume and Foam Formation During Foaming

Regulating the cell structure depends not only on the type and amount of silicone oil but also on factors like gas injection rate, mixing head speed, and mixing efficiency to achieve the desired foam structure.

2. Recommendations for Producing Different Cell Structures:

① Producing Coarse-Cell Foam

 Adjust silicone oil type and dosage

 Control gas injection

 Improve mixing efficiency

② Producing Pseudo High-Resilience Foam

 Use a blend of silicone oils with different activities ("pseudo high-resilience silicone")

 Control gas injection volume

 Enhance mixing efficiency

 Note: Ensure sufficient reaction at the front end of foaming to avoid collapse.

③ Producing Irregular-Cell Foam

 Use special silicone oils such as L-501 cell modifier

 Locally disrupt conventional silicone oil at specific temperatures

 Cause localized collapse and excessive coalescence to form a chaotic and variable cell structure

By adjusting formulation and process parameters, silicone oil-modified polyurethane flexible foams with specific cell structures can be effectively produced to meet different industrial application needs.