The success of polyurethane foam application depends on proper surface preparation, moisture control and strict adherence to the manufacturer’s technical instructions. The use of protective equipment is essential due to the chemical components and flammable propellants contained in the cylinder. For maintenance, fresh foam is cleaned with a special solvent, whilst cured foam is removed mechanically. Storing the cylinder correctly in an upright position ensures the material’s longevity. You will find all the steps for safe and effective use in the Geosantro technical guide.
Safety precautions before use
Polyurethane foam is an extremely useful building material, but care must be taken when using it. Before starting any work, it is essential to consult the Safety Data Sheet and the Technical Data Sheet for the specific material you are using.
Protective Equipment: Always wear protective gloves, safety goggles and suitable clothing. Contact between fresh foam and the skin is difficult to treat and may cause irritation.
Adequate Ventilation: Work in well-ventilated areas. The vapours released during casting must not be inhaled in high concentrations.
Sources: Any Touch: The cylinders contain flammable propellant gases under pressure. Keep the product away from naked flames, sparks, lit cigarettes or hot surfaces.
Spray foam versus hand-applied foam
The choice between spray foam and hand-applied foam depends on the frequency of use, the level of precision required and the type of job. The expansion ratio is determined by the chemical composition of each product and is specified in the technical data sheet.
Characteristic
Spray Gun Foam
Hand Wash
Flow Control
High accuracy thanks to the pistol’s trigger
Basic check via the plastic tube
Degree of Swelling
It depends on the composition as stated in the technical data sheet
It depends on the composition as stated in the technical data sheet
Reuse
Possible, provided the manufacturer’s instructions are followed
Limited, if the material in the tube dries out
Suitability
Repetitive, prolonged or precise tasks
Small, one-off and occasional jobs
Steps for correct application
Mixing times, application temperatures, expansion ratios and curing times vary from product to product. Always check the label and technical data sheet for the specific foam before use.
1. Preparing and wetting the surface
Clean the substrate to remove dust, oils, grease and loose material. In single-component polyurethane foams, moisture in the air and the substrate is essential for the polymerisation reaction to be completed. Lightly spray the surface with water before application. This improves adhesion and helps to create a more uniform cellular structure.
2. Shaking the bottle
Shake the bottle vigorously for the time specified by the manufacturer (usually 15 to 30 seconds). Shaking ensures that the propellant gases are properly mixed with the liquid polymer.
3. Orientation of the bottle
With most standard cylinders, the cylinder must be positioned with the valve facing downwards so that the lighter gases push the material towards the outlet. Follow the manufacturer’s instructions regarding orientation, as some specialist products allow application at any angle.
4. Filling the joint
Do not fill the gap completely. Take into account the secondary expansion factor specified in the product’s technical data sheet. Fill the joint partially (for example, to between one-third and half its depth), allowing the foam to expand without exerting excessive pressure on the structural elements.
5. Temperature conditions
Check the ambient and can temperature limits. Most conventional foams perform best at ambient temperatures between 15°C and 25°C. For work carried out during the winter months, use specially certified low-temperature foams.
Where is standard polyurethane foam not used?
To avoid manufacturing errors, it is important to be aware of the material’s limitations:
It is not a structural connector: Standard foam provides a seal and insulation, but does not replace mechanical fixings (such as screws or plugs) when fitting window frames.
It is not a firebreak: For applications requiring fire resistance, only specialised, certified fire-resistant foams must be used.
Traction limitations: It does not adhere to surfaces made of polyethylene, polypropylene, silicone, Teflon or greasy substrates.
Permanent immersion: It is not suitable for localised applications that are subject to constant water pressure without an additional waterproofing layer.
Removal of fresh and hardened foam
Removing foam requires a different approach depending on its physical state.
Removing fresh foam
Do not use water to clean liquid foam from tools or surfaces, as moisture accelerates the polymerisation of the material. Remove any excess with a plastic spatula. Then use the specialist foam cleaner recommended by the manufacturer.
Attention: Always test cleaning solvents on an inconspicuous area, as they may damage painted, plastic or varnished surfaces. Do not apply chemical solvents to the skin. In the event of skin contact, follow the first-aid instructions in the Safety Data Sheet, using soap, water and gentle mechanical removal.
Removing hardened foam
Once it has set, the foam cannot be effectively removed using standard fresh-foam cleaners. The main method of removal is careful mechanical scraping using a chisel, scraper or sandpaper. For sensitive substrates, there are special ointments for softening hardened foam, provided their compatibility with the surface has been confirmed. If the material has dried inside a spray gun, do not pull the trigger and avoid using sharp objects on the valves. Follow the equipment manufacturer’s maintenance instructions.
Storage and shelf life
To ensure the product remains in good condition until its use-by date:
Standing position: Always store the bottles in an upright position. If stored horizontally, the liquid contents may come into contact with the valve and block it.
Storage temperature: Store the bottles in a cool, dry place, protected from frost and direct sunlight.
Temporary storage of a cylinder in the gun: Some systems allow for temporary storage with the cylinder attached to the gun, provided that the control valve is fully closed. The permitted duration is specified by the manufacturer of the foam and the spray gun.
Protection from ultraviolet radiation
Polyurethane foam is sensitive to ultraviolet radiation. Prolonged exposure to the sun causes its structure to break down, leading to yellowing and the gradual crumbling of the material.
Once the curing process is complete and any excess has been trimmed away, the foam must be protected when used outdoors. Cover the surface with plaster, filler, silicone, acrylic sealant or a suitable protective paint.
Her team Geosantro is at your service to provide you with certified polyurethane materials, application equipment and specialist technical advice for any construction project.
Frequently Asked Questions
Why are good ventilation and protective equipment essential?;
Polyurethane foam contains chemical compounds and pressurised propellants. Ventilation prevents the build-up of vapours and flammable gases in the area. Gloves and goggles protect the skin and eyes from any unwanted splashes, as the fresh foam adheres strongly and is difficult to remove.
How does temperature affect the performance of polyurethane foam?;
The ambient and container temperatures affect the curing time, the cell structure and the final expansion volume. At very low temperatures, the reaction is delayed, whilst at high temperatures it is accelerated. Always check the product’s technical data sheet for the recommended temperature limits.
What should we do if fresh polyurethane foam gets on the skin?;
Do not use chemical solvents or acetone on the skin, as they may cause irritation or facilitate the absorption of substances. Immediately wipe off as much of the substance as possible with a cloth. Wash the area with plenty of water and soap, and allow any remaining residue to be gradually removed through the skin’s natural renewal process.
Can polyurethane foam replace the fixing screws in a frame?;
No. Conventional polyurethane foam provides thermal and sound insulation and fills gaps, but it is not a load-bearing structural material. Mechanical fixing of the frame using suitable screws or plugs is essential for the safety and stability of the structure.
