New method for incorporating fillers into reactive PU blends

This method opens up entirely new possibilities for the use of composite materials, regardless of whether they are hard or soft, or if the polyurethane is a solid or a foam. One possible area of application is adding flame retardants to polyurethane parts, which is required for a variety of applications.

With today's batch method, fillers are often added to the polyol component before this is blended with the isocyanate component in the high-pressure mixing head and reacted. There are two disadvantages to this method, however. First, the system components must be adequately protected against wear caused by the solid, and second, large or mechanically sensitive filler particles limit the options.

“With the SIA technology, the components – polyol, isocyanate and filler – are added separately and not blended together until in the mixing head. This avoids the disadvantages of the batch method,” said Roger Scholz, a PU expert at BMS.

The method enables the use of very light, heavy, and abrasive fillers (such as barium sulphate), or also the combination of different types. Even reactive substances or particles with porous surfaces can be used – from expanded graphite to hollow glass spheres. This significantly reduces the probability of changes to the fillers and the wear of plant components due to abrasive or corrosive additives. The technology also makes it possible to vary the filler content within a layer or between different layers, such as in a sandwich composite, for example. BMS operates a pilot plant employing the method in Leverkusen, Germany.