1. Is it true that polyurethane foam in a canister has a limited shelf life?

    Yes, because of chemical reactions with the ingredients and the loss of propellants, a typical shelf life ranges from 9 to 24 months, depending on the product.

  2. Is the shelf life of polyurethane foam influenced by external conditions?

    Pronounced shortening of the shelf life will occur if the polyurethane foam is subject to storage in warm or/and humid surroundings over a prolonged period.

  3. What is the recommended optimum temperature for using polyurethane foam?

    The best results are obtained when the operating ambient and the canister is between +15 und +25 °C.

  4. How long can a partially used container be left attached to a gun?

    If the dispensing gun has been maintained well and if it is still gastight, a canister can be stored attached to the gun for a period of one to two weeks. In order to prevent unintentional operation, it is recommended to secure the gun with the screw.

  5. I have seen plastic extension tubes attached to the nozzles of other products. What is the purpose of this?

    The extension tube helps to access hard-to-reach areas. But this type of design leads to unplanned dripping from the tube end. To avoid this effect, canisters are not generally fitted with these extension tubes. Furthermore this tube has negative influence on some foam properties.

  6. Is it necessary to remove excess foam from the adapter, or can I simply insert the next canister?

    Though the adapters are constructed from a non-stick material, it is advisable to remove any excess foam straight away with gun cleaning fluid: well-maintained tools last longer. It is particulary important to keep the sealing ball inside of the adapter basket clean.

  7. Why does foam spurt out sideways when the canister is re-used?

    In such cases cured foam has partially blocked the nozzle, pushing newly-expelled foam to one side. We recommend cleaning fresh foam from the nozzle from time to time, especially if work is interrupted for any period. Usually such a canister can not be repaired again and should be exchanged by a new one.

  8. Is it OK to leave half-empty canisters attached to applicator guns?

    Yes; in fact we recommend leaving a partially-full container attached to the gun. To store the gun and canister safely, the security screw should be tightened without force to secure the trigger.

  9. Does a plastic body gun wear out quicker than a metal one?

    If both applicator guns are used in identical conditions, their life expectancy is the same. The mechanical components of a plastic gun are carefully engineered – with critical parts Teflon-coated. This ensures a  long working life for this precision instrument.

  10. Can polyurethane foam be used to fill profiles such as aluminium, steel or u-PVC section?

    The necessary curing moisture cannot generally be delivered along the entire length of the profile, a two-component foam is better for such applications.

  11. What should I do with excess foam such as that round doors and windows?

    Cured excess foam can be cut away with a knife, saw or any similar implement. The waste foam is not hazardous and can be disposed with normal household waste.

  12. Is cured foam subject to ageing?

    Cured foam does not age in the absence of UV light, hot temperatures (> 110 °C), alkalines or acidics and some special chemicals which are used to eliminate PU stains.

  13. How can foam spots be removed?

    Fresh foam can be removed with PU cleaner or solvents like acetone. Cured foam can only be removed mechanically or by using special hard foam remover.

  14. Is there any way to accelerate the curing process?

    Yes, in case of dry conditions the slight wetting of the bonding surfaces (before the foam application) and the foam surface (after the application); ideally from an atomiser. This will help to speed up the hardening process and to enhance the foam quality.

  15. Does the foam develop and exert pressure during expansion and curing?

    Yes, the foam exerts a pressure during expansion and through hardening. It is therefore advisable to fill gaps and cavities by no more than one third and to use spacers or clamps to avoid deformation of weak joint walls.

  16. What is the scientific basis of one-component polyurethane foam?

    The chemical basis is an adhesive produced from Polyols, Isocyanates, propellants and various foam additives.

  17. How does the viscosity of the polyurethane influence the output of released foam?

    The output rate depends strongly on the viscosity of the ingredients, the higher the viscosity the lower the outpit rate. The viscosity depends on the canister temperature and the shelf life of the can. A cold and aged canister decrease the output rate.

  18. Are there any special safety requirements for storing polyurethane foam canisters?

    Yes, there are important considerations in the storage of aerosol cans in general and polyurethane foam canisters in particular. Each individual canister has information on safe storage printed on the label.

  19. What happens when polyurethane canisters are stored for a protracted period in cold conditions?

    The viscosity [flow resistance] of the foam will increase significantly, making the material flow more slowly. The canisters should therefore be brought to the proper temperature before use. However there is no impact on shelf life, differently to high temperature storage.

  20. What is the problem when no foam is released when a can is re-used?

    Generally, cured foam residues which should have been removed have blocked the vent outlet.

  21. Can a polyurethane cylinder which has been properly stored and temperature-maintained explode?

    No, a correctly stored, temperature-controlled, properly used PU foam canister can not explode. It bursts only due to outer impacts like e. g. too high temperatures or mechanical impacts. PU foam canisters are produced and tested to well defined industrial standards.

  22. Are there any special conditions to be observed during polyurethane foam canister storage?

    Yes: one-component polyurethane foams must be stored dry and cool. Delivery packs and individual containers should be kept upright, with the valve pointing up. Storing horizontally leads to misfiring valves.

  23. Does the canister need to be shaken again during use?

    It is recommended to shake the can occasionally during use, and especially after interruptions, to avoid re-separation of the propellant und prepolymer.

  24. How much must the cans be shaken to ensure a homogeneous mix of the two constituents?

    A canister should be shaken 15 to 20 times.

  25. Is there a negative effect on the foam if the can is not shaken thoroughly prior to use?

    Polyurethane foam consists of a prepolymer and a propellant gas, which form two layers during storage. The can must be shaken vigorously before use to create a homogeneous mixture. Insufficient shaking will result in poor foam properties such as a coarse cell structure and reduced foam volume.

  26. How one can remove cured and uncured foam unnecessary spots?

    Please use MAKROFLEX Cleaner - cleaning agent for the removal of uncured foam. Caution: the agent is a strong solvent and can destroy also plastic and synthetic textile surfaces!
    Removal of cured foam is possible only mechanically.

  27. How much cured foam is it possible to get from a 750/1000 ml can?

    The exact volume of cured foam depends on multiple factors: the humidity of the air, outer temperature, the width and depth of the joint. Normally, straw foam expands after foaming 2 – 2.5 times.

  28. Why does already cured foam need to be protected from sunlight?

    PU foams are highly sensitive towards UV-radiation. When a joint is left uncovered. the cured foam will be quickly destroyed.

  29. Do joints have to be moisturized?

    Spraying the surfaces with water before applying foam ensures better adhesion of the foam, especially on porous surfaces like concrete. Spraying the curing foam with water during expansion is unnecessary in most cases. Such action can be recommended only when the moisture level in the air is really low.

  30. What are silicone sealants?

    Silicones are modifications of the polysiloxane molecule, which is a very large macromolecule that can be modified to a clear liquid with low to very high viscosity or a soft solid material. Silicones do not dissolve in water.

  31. What are the advantages of silicone sealants?

    Silicones used in joints to bond materials, accommodate movements due to temperature changes, moisture, shrinkage, sound, wind and vibration. Silicones ensure that construction materials stay affixed and absorb stress and movement so a structure is strong and safe. Because of their unique adhesive and durability properties, silicones bond with most materials - very porous, non-porous, sensitive materials and hard to adhere to materials like concrete, glass, granite, marble, aluminium, steel and plastics. The sealants create a strong airtight seal that not only protects but also complements building aesthetics.

  32. Why can silicone sealants not be painted?

    Because silicones are materials with high elasticity and a paint layer on the surface does not have a strong basis on which to adhere. Although most silicones will bond to most painted surfaces, paint will not adhere to silicone rubber.

  33. How do I remove silicone sealants once they have cured?

    A combination of physical scraping and a strong solvent works best. Special removers are available which soften the silicone, helping mechanical removal of that later.

  34. Which environments are silicone sealants not suitable for?

    Conventional silicone rubber is not suitable in environments where it comes into contact with oils fuels and solvents.  Silicone rubbers in general also have poor resistance to steam and super heated water.

  35. How to dispose silicone sealants?

    Silicone rubber cured or un-cured is not considered a hazardous waste and therefore can be disposed of in accordance with the local regulations regarding waste disposal.

  36. How can I remove glue?

    Removing glue can be a difficult procedure. Try to determine whether the adhesive is a water base system or a solvent base system. One way of doing this is to pour warm soapy water on the adhesive to see if it helps to soften it up. If that method doesn't work, try a little solvent such as white spirit or terpentine on a cloth to see if that helps to soften the adhesive, taking care not to damage your surface. Glue that has been in place for a long time will become quite hard and the only way to remove it may be by abrading or sanding the adhesive down.