Reaktív ömledékragasztók (PUR, POR)
Reactive polyurethane-based hot melt adhesives (PUR) are becoming increasingly significant. These can be used to create high-strength structural bonds. Once the reactive PUR hot melt has been applied, it initially sets physically. There then follows a chemical reaction to the moisture in the air or the highly molecular polymer substrate. This enables extraordinarily high adhesion values, high degrees of temperature resistance, high flexibility at cold temperatures and solvent resistance to be achieved.
It is important to bear in mind that it may take a while for the adhesive bond to reach its final strength, depending on the moisture content available for chemical cross-linking and the PUR adhesive application strength.
To prevent undesirable reactions while the PUR adhesive is in storage, reactive hot melt adhesives are packaged in moisture-proof containers.
Another group in the reactive hot melt adhesives segment are silane-modified polyolefin-based formulas (POR). Compared with PUR hot melts, these are characterised in particular by the fact that they adhere much better to untreated substrates such as polyethylene (PE) and polypropylene (PP). Furthermore, they also contain no isocyanates and therefore do not have to be labelled. In contrast, their cohesion properties are far below those of polyurethane-based adhesives.