Vacuum Decompression Foaming Technology

The expansion effect of a foaming agent is based on the pressure inside the foam cells during the foam rise process, which exceeds the external pressure applied to the foam. Reducing the external pressure can cause the cell volume to increase, thereby reducing the density. To achieve this effect, a method is needed to create a lower pressure, i.e., vacuum, in order to reduce the density without adding more foaming agent.

There are two methods to implement low-pressure production of molded parts using this technology:

1.Foaming in a Vacuum Zone

2.Special Vacuum Molding Technology (called “Vaku Foam”)

Foaming in a Vacuum Zone
In a vacuum conveyor belt or a vacuum foaming zone, the entire mold to be foamed is placed within a pressure-protective shell. Before or after injecting the reaction mixture, a lower pressure is applied to the surrounding space, reaching the new required mold density. The molded part must remain inside the vacuum chamber until the foam cell structure of the molded part is stable, which takes up most of the molding time.

For continuous production, the molded part must pass through vacuum lock doors before and after entering and exiting the vacuum section. This technology has not yet been widely adopted due to high equipment investment and high foam production costs.

Foaming with Special Vacuum Molding Technology (Vaku Foam)
The core of the Vaku Foam technology is in the mold itself. The mold is designed to be the vacuum zone, and a specially designed mold can precisely adjust the internal pressure during the rise and curing stages.

Operation Process of Vaku Foam Technology
As shown in the diagram, the entire process is similar to the conventional model production line, with the only difference being that the mold has a vacuum connection. Once the foam is injected into the mold, the vacuum system is connected, and the required internal pressure (low pressure) is adjusted.

The following table provides example data that strongly demonstrates that vacuum-molded foam not only reduces costs but also achieves low density while maintaining the best physical properties.