PU adhesive foam for bonding and insulating
PU foam insulates, seals and bonds, and features particularly strong adhesive properties. It is most frequently used for mounting thermal insulation systems (TIS), which account for around 80 percent of the facade insulation used in Germany. PU adhesive foam is used to attach the insulation panels to masonry, facades, cellar ceilings and flat roofs. Its very good thermal insulation values range between 0.26 and 0.04 W/(mk), ensuring that the TIS adhesive foam acts as a second insulating layer between the insulation panel and the wall. As a result, the insulation can be mounted free of thermal bridges.
Advantages of PU adhesive
The advantage of polyurethane adhesive foam (also referred to as PU adhesive) over other cement-based adhesives is that it hardens quickly and the fitter does not require any additional tools. After just two to three hours, work can continue on walls mounted with PU adhesive. Cement-based adhesives must dry out for three to four days before the next work step is possible. When choosing the right adhesive foam, manufacturers recommend using foams that do not expand too rapidly. This ensures that the insulating elements do not shift in an uncontrolled manner during the hardening and expansion process.
It is also important to check that the foam is officially approved for use with the TIS. Approval is also required for PU adhesive foam to be used for grouting non-load-bearing walls. Partially-collapsing foams are the right choice in this case.
Avoiding thermal bridges
While PU foam is optional for TIS mounting, it is a must for filling open joints. To ensure that no thermal bridges are created in the facade, the tradesman must install the insulation panels precisely with tightly pressed butt joints. However, regardless of how exactly the panels are installed, joints cannot always be avoided. These need to be filled in carefully later on, so that the 'full insulation' can live up to its name.
Adhesive mortar may never be used because this will create thermal bridges. Instead, in the case of larger gaps, polystyrene strips are cut to fit and placed in the joint. Smaller gaps are insulated with PU foam. Likewise, these need to be approved by the system manufacturer for this application.
In addition to mounting thermal insulation systems, PU adhesive can be used quite universally. Two examples of this are bonding non-load-bearing interior walls and bonding flowerbed edgings made of natural stones. Adhesive foam is offered in customary pressurised cans as adapter foam or pistol foam and replaces classic cement. Like all other PU foam cans, the used cans can be returned free of charge for recycling at PDR.
PU adhesive foam should not be confused with assembly adhesive. Assembly adhesive is offered in plastic cartridges and in tubes. Assembly adhesive is always used when drilling, screwing and nailing should be avoided; for example, when mounting a mirror in the bathroom. Assembly adhesive is available in various chemical compositions, including a PU-based composition, but it is not actually considered a PU foam.