Foams can easily be manufactured from polyurethanes (PUR) using water or physical propellants. The result is a great variety of products: open- or closed-cell, soft or hard foams.
Processing of BASF Polyurethanes using foaming
The foaming of polyurethane (PUR) can be done either continuously (flexible slabstock foam/rigid foam) or as a batch process. In the continuous process, the liquid reactive components are fed in preselected proportions via separate strands to a mixing head, which drags the mixture out onto the conveyor. Since the foam expands freely, densities of 15 up to 50 kg/m³ are possible. In the batch process, so-called molded foams are produced in tools optimized for this purpose. Thereby, the liquid reactive components polyol and isocyanate can be mixed in high-pressure systems (counter-current injection at 150 to 200 bar) or low pressure machines (mixing by intensive stirring in the mixing chamber) and poured into the mold. The foaming reaction in the mold may be physical (low boiling propellants) or chemical (CO2 formation by the reaction of water/isocyanate) and takes place in the mold. This foaming technology enables the formation of molded parts with a density range of 42 to 1000 kg/m³, and hardness ranges of shore A to D with extremely varied physical properties.
Flexible PUR foams are used in particular as upholstery materials, for mattresses, seat cushions in furniture or car seats. They are open-cell, for the most part.
Rigid PUR foams are predominantly applied in heat insulation, for example in buildings, cooling units, heat and cold storage, as well as pipe systems. Because of the desired heat insulation effect, these PUR rigid foams are closed-cell.
Further applications for PUR foams in vehicles are steering wheels, armrests, handles, interior linings, instrument panels, and sound insulation.