Instructions for Solving Problems in the Spraying of Polyurethane Foam

Table of Contents

• Instability in spraying
• A fog – like suspension appears during spraying
• Components take long time to react
• Nonuniform color of the mixture of the foam
• During spraying components are crumpled. They create an uneven layer once each the surface and cause equipment clogging
• Bubble formation of uneven sizes and large voids in the thickness of the foam. Bumpy surface
• Component overuse above the manufacturer's specified consumption
• Foam shrinkage is above the manufacturer’s specifications
• The foam is too fragile
• Excessive elasticity (softness) of the resulting foam
• Weak adhesion of foam to the base (foam detachment from the base)
• Bloating formation on the surface of the foam (with the formation of large "bubbles") after spraying. Bumpy surface
• Polyurethane foam’s surface is oily which results in weak material and polyurea adhesion
• Keen smell when spraying
• Component A is expired

Instability in spraying 

• Excessive or insufficient air pressure in the compressor (for low pressure) or in the mixing chamber (for high pressure).
• Non-compliance of the compressor with the technical requirements of the installation.
• Mistake in selecting or adjusting the nozzle of the spray gun.
• Contamination of the mixing chamber of the spray gun.
• Low temperature of the components resulting in their high viscosity.

• Air supply adjustment. Check the compressor for compliance with the technical requirements of the installation. According to the experience of our customers and manufacturers recommendations: for low pressure installations (Foam-98, PGM-5, NAST-7, PGM-9 at) normal pressure 6 ATM;  for high pressure, the pressure in the mixing chamber: Graco Reactor EXP-2 - 240 bar, Reactor A-25 - 140 bar, Graco Reactor E 10 - 140 bar.
• Common types of compressors used by our customers: SBS-4 (420 l/min), Remeza (320L/min), Elite-5 (350L/min), Fubon (450l/min).
• Adjust the nozzle of the spray gun
• Clean the spray gun
• Adjust components temperature in accordance with specifications  

A fog – like suspension appears during spraying

• Excessive air pressure.
• Excessive pressure when mixing.

• Reduce air supply. Check the compressor for compliance with the technical requirements of the installation.
• Reduce mixing pressure at the plant (for high pressure plants). Reduce the speed of rotation of gear pumps (for low-pressure installations).

Components take long time to react. Material drainage and formation of "icicles" when spraying foam on the ceiling surface

• Cold surface and / or components themselves.
• Low ambient temperature. Spraying of "summer" components in winter conditions.
• Components’ terms and/or conditions of storage are not actualized. Not enough foam activator.
• The barrel with component A was not mixed before spraying.

• Increase the temperature of the components to the limits specified in the TU
• Heat the hoses and air supply to the spray gun, especially when working in winter conditions. Heat the spraying surface, especially when working in winter conditions. For example, using heat guns to work with winter components to raise the surface temperature to 0-(+5°C), summer system to +15°C. Postpone the work until suitable environmental conditions have been met. The recommended surface temperature for summer systems is no lower than +15°C, for winter systems no lower than 0°C, and the ambient air to -10°C.
• If the shelf life of the components expires, consult the technical specialists of the manufacturer.
• Possible solutions:

  - order an activator for component A,
  - exchange component A for a new one.

• If component A was stored outdoors at temperatures below 20°C, components stratification might have appeared. It is necessary to heat the component A to 20-25°C and mix thoroughly.

Nonuniform color of the mixture of the foam

• Due to the differences in the component viscosity and/ or in air pressure, components have moving difficulties (congestion) which causes a bad component mixture environment.  

• Check air pressure.
• Clean the spray gun to eliminate congestion of the components.
• Adjust the temperature of the components according to the manufacturer's specifications
• Check and adjust the component ratio. The recommended ratio for the Himtrust SKN 100: for 100 (volume) or 100 component A and 115-120 parts of the component B by weight.

During spraying components are crumpled. They create an uneven layer once each the surface and cause equipment clogging

• The temperature of the components exceeded the temperature specified by manufacturer, which leads to an advanced rise of the foam.

• Reduce the temperature of the components according to the manufacturer's specifications.
  

Bubble formation of uneven sizes and large voids in the thickness of the foam. Bumpy surface

• The coating thickness is more than 25 mm in one pass.
• Application of the second layer of foam before the first layer has formed
• The quality of mixed of components is reduced
• The barrel with component A was not mixed before spraying
• No dehumidifier on the compressor

• Reduce the thickness of the spray layer of foam to 10-25 mm in one pass, depending on the density of the foam.
• Increase the formation time of the applied layer of foam before applying the next layer. Usually the drying time between the layers is 120 seconds, at a temperature of 20-25°C.
• Evaluate the quality of mixing components by color uniformity of the mixture and foam. Check the ratio of the supplied components. The recommended ratio for the components of the Himtrust SKN: 100 to 100 by volume or 100 parts component A and 115-120 parts of component B by weight.
• Thoroughly mix the barrels with component A before starting work.
• Moisture and oil significantly affect the quality of the foam. Therefore, before spraying always check the compressor for moisture and oil, and be sure to put a dehumidifier.

Component overuse above the manufacturer's specified consumption

• Polyurethane Foam over-compaction due to non-compliance with the temperature regime of spraying.
• Spraying of PU foam on the surface with a temperature above 45°C, while the gelation is ahead of the foam rise.
• Components’ terms and/or conditions of storage are not actualized. Not enough foam activator.
• The barrel with the component A was not mixed before spraying.

• Measure the density of the PU foam sample obtained by weighing it and calculating the volume. If the density obtained is higher than the manufacturer's specified density, then:

- Check the ratio of the components supplied. The recommended ratio for the Himtrust SKN:  component A is 100 by volume or 100 parts and 115-120 parts of component B by weight.

- Heat components, hoses and spray surface, especially when working in winter conditions. Observe the temperature regime of spraying. The recommended surface temperature for summer systems is not lower than +15°C, for winter systems not lower than 0°C, and the air to -10°C.

• Do not spray on the surface with a temperature above 45°C.  Usually this occurs in the summer in the corrugated board sheds. We advise to spray in the evening or at night, when the surface temperature drops to 20-30°C.
• Components have expired. It is necessary to contact the technical specialists of the plant:

  - order an activator for component A,
  - exchange component A for a new one.

• Thoroughly mix the barrels with component A before starting the work.

Foam shrinkage is above the manufacturer’s specifications

• Uneven ratio of supplied components.
• Poor mixing quality due to differences in viscosity, ratio, and/ or air pressure.
• The barrel with the component A was not mixed before spraying.

• Check the ratio of the supplied components. Recommended ratio for Himtrust  SKN components: 100 by volume or 100 parts of the component A and 115-120 parts of the component B by weight.
• Check air pressure. According to the experience of our customers and to the equipment manufacturer recommendation: for low pressure installations (Foam-98, PGM-5, NAST-7, PGM-9 at) normal pressure is 6 ATM. For installations of high pressure, the pressure in the mixing chamber is: Graco Reactor EXP-2 - 240 bar, Reactor A-25 - 140 bar, Graco Reactor E 10 - 140 bar. Common types of compressors used by our customers: SBS-4 (420 l/min), Remeza (320L/min), Elite-5 (350L/min), Fubon (450l/min). In case of component congestion, it is necessary to eliminate it and clean the spray gun. Adjust the temperature of the components according to the manufacturer's specifications.
• Thoroughly mix the barrel with the component A before spraying.

The foam is too fragile

• High flow of the component B.
• Congestion in the flow of the component A.
• Cold surface and / or components themselves. The ambient temperature is too low.
• The foam forming process is not complete.

• Check the ratio of the components.
• Clear the blockage of the component A. Clean the spray gun.
• Heat the components, hoses and spray the surface when working in winter conditions. Follow spraying temperature specified by manufacturer.
• Withstand the foam after spraying for a day until fully formed, especially when working in winter conditions

Excessive elasticity (softness) of the resulting foam

• The supply of the component A is overstated.
• Blockage in the flow of  the component B.
• The quality of mixing of components is minimal.

• Check the ratio of the supplied components. The recommended ratio for  the Himtrust SKN is: 100 to 100 by volume or 100 parts of the component A and 115-120 parts of the component B by weight.
• Remove the blockage of the component B. Clean the spray gun.
• Evaluate the quality of color and foam homogeneity Steps to improve the mixing quality are described in the table above. It is also necessary to adjust the temperature of the components according to the manufacturer's specifications. For the components of Himtrust SKN recommended temperature of the component A is 20-25°C, and component B is 40°C.

Weak adhesion of foam to the base (foam detachment from the base)

• The surface was not prepared.
• Cold surface and / or components themselves. The ambient temperature is too low.

• Prepare the surface according to the manufacturer's specifications (cleaning, degreasing, surface drying, etc.).
• Heat components, hoses, and spray surfaces when working in winter conditions. Compliance with the temperature regime of spraying. The recommended surface temperature for summer systems is not lower than +15°C, for winter systems is not lower than 0°C, and the air to -10°C.

Bloating formation on the surface of the foam (with the formation of large "bubbles") after spraying. Bumpy surface

• Presence of condensate and/or oil in the compressor. No air dryer on the compressor.
• Application of the second layer of foam before the end of the formation of the first layer.

• Check the compressor and the entire pneumatic system for moisture and oil, put a dehumidifier.
• Reduce the thickness of the foam spray layer to 5-15 mm in one pass, depending on the density of the foam. Increase the drying and formation time of the applied layer of foam before applying the next layer. The drying time between the layers should be at least 120 seconds, at a temperature of 20-25°C.

Polyurethane foam’s surface is oily which results in weak material and polyurea adhesion

• The presence of oil in the compressor receiver. If after  the application of  the PU components, the surface is oily, then there might be contamination by oil components in the receiver.

• It is necessary to check the compressor, the compressor receiver, and the entire pneumatic system for the presence of oil
• Put an oil separator.

Keen smell when spraying

• The smell of accelerants. Manufacturers of foam spraying components use catalysts that can have a keen smell.

• It is necessary to ventilate the room for 48 hours after spraying even if there is no smell. Himtrust SKN components use European catalysts Air Products and Momentive, in order to have reduced odor. 

Component A is expired 

• The recommended storage time for SKN components is 6 months. Catalysts and foaming agents in the component A lose their properties over time.

• It is necessary to contact the component manufacturer and obtain recommendations from technologists.