Sources of error

Why is my PU foam not correctly hardened in the model mould?

The most common reason for this is an insufficient amount of moisture. PU prepolymer needs moisture to completely react. When making model moulds, we recommend slightly wetting the walls of the mould and later the foam itself. Alternatively, you can use a 2-K-PU foam instead of a 1-K-PU foam.

Why do PU foam cans need to be used upside down?

In contrast to classic aerosol cans, PU foam cans do not have a so-called riser tube that pumps the fluid content outwards when the spray head is pressed. Because PU foam is viscous, a transport tube of this kind would become clogged. Therefore, the can needs to be turned upside down to empty it after the pre-polymer has been mixed with the propellant by means of shaking. This causes the viscous mass to sink downwards to the valve and ensures that there is always a sufficient amount of PU foam at the valve opening and the foam can be applied evenly without interruption.

Problem: The PU foam does not foam correctly, the yield is deficient.

Possible causes:

  • Insufficient humidity (min. 30% rel. humidity) Solution: wet the surface!
  • The can was insufficiently shaken (min. 20 – 30 times) or was shaken with the valve pointing upwards. Solution: Hold the can with the valve facing downwards and shaken thoroughly.
  • The PU foam can was too cold. Solution: warm the can carefully.
  • The ambient temperature was too cold (<5° Celsius) Solution: Use winter foam if possible.
Problem: The PU foam does not expand correctly or is slightly brittle

Possible causes:

  • The processing temperature is too low (<5° Celsius) Solution: warm the can carefully.
  • The can was not shaken sufficiently. Solution: Shake the can again.

Note: Please do not press the foam in, because otherwise it cannot foam any more.

Problem: The can cannot be completely emptied

The can valve may be clogged (always store the can in an upright position)! The foam gun is soiled or clogged inside (higher propellant pressure required)! The foam gun does not close properly, propellant escapes unnoticed!

Questions and answers about PU foam

Working with PU foam

Interaction with other materials

Special application areas

Questions about the product

Ecology and recycling

Active ingredients and health