Visible injection mark on flexible foam part

Description:

The marks are visible through recognisable spots or dents.

Affected Foam Parts:

Affected are parts made of soft foam, high resilient foam, viscoelastic foam for automotive or furniture industry (headrests, armrests and cushions, as well as pillows and mattresses), acoustic foam, insulation foam and back foam.

What causes it:

The cause of this problem in polyurethane processing is foam that penetrates to the mould. This can be due to an insufficient release agent barrier, improper release agent, the foam being poured from unsuitable distance or the injection speed being too high.

The problem can also be caused by a release film that is not completely dry or poor mixing of the PU system.

• Not enough release agent barrier/improper release agent
• Not ideal distance when pouring the foam
• Too high injection speed of PU-foam
• Release film not completely dried
• Not proper mixing of the PU system

Solutions:

To prevent visible spots and depressions, it is important to choose the appropriate shot point and optimize the parameters of mould temperature, pressure, PU-temperature, mixing ratio, distance and injection speed. The use of release agents that provide a better barrier or use of a paste wax can also help prevent the polyurethane foam from penetrating to the mould.

• Adjust the pour spot
• Adjust distance and speed of pouring
• Use release agent with more barrier or a paste wax in pour area
• Check PU processing parameters
• Check mould temperature

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