Polyurethane foams are primarily intended for insulation, sealing and filling. Foams cannot perform a bearing function and are not suitable for fixing. In different countries the construction practices are different, but mechanical fastenings are almost always strictly recommended, especially when installing windows. Once again, the exception is foam adhesive, which can also be used for fixing. In the development of foam adhesives, much attention has been paid to their good adhesive properties. Although conventional foams also have good adhesive properties, foam should not be used as an adhesive. There are specific requirements for adhesion, and using foam instead of adhesive in critical places may not work.
Polyurethane foam requires air humidity to cure, and the previously moistened surface ensures a better structure for the foam. Moistening is recommended in summer and for porous and dry surfaces. In the case of winter foams (up to -18°C), the air humidity may be lower, which has already been taken into account in the composition of the foams used at minus temperatures. However, it must be ensured that the substrates are free of ice and frost.
The joint or surface on which the product is to be installed must be moistened and not the foam itself. Water damages the structure of the foam. It is the best to use a sprayer where the liquid comes out in a gentle mist. Water droplets must not remain on the surface of the joint. If necessary, the droplets must dry before using the foam. If the foam is applied in two layers, it is also necessary to moisten the first layer of the foam. In the light of the above, polyurethane foams cannot be applied in a closed room or opening because there is not sufficient humidity required for the foam to harden.
It is necessary to shake the foam can 20 times before use in order to mix the ingredients and ensure good foam structure. Then, the can must be turned upside down and screwed on the gun. If the can is screwed on the gun without shaking it first, some gas will come out. Gas has an impact on the yield of the product and some of the foam may remain in the can.
Gas is the most hazardous ingredient in the polyurethane foam (explosion risk), and thus foam cans must be stored and transported in an upright position. As the can is under pressure and flammable, the foam must be protected against overheating and kept away from sources of ignition. Considering the safety of aerosol, the product must not be left in the sun on the construction site or in the car. The suitable storage temperature is +5°C to +30°C. It is important that the can is intact and free of any dents. After use, the cans must be emptied and taken for waste collection.
Application of polyurethane foam does not present any risks when using personal protective equipment, such as gloves and protective goggles, and the room is ventilated. Installed and hardened foam does not emit harmful compounds.
The life expectancy of polyurethane foam protected against UV radiation is very long. It does not rot or mould, it does not collapse or become brittle, and it withstands extensive temperature and humidity fluctuations.