The developed foaming technology with use of gas counter pressure shows a new possibility to use high amounts of CO2 as a physical blowing agent in the production of moulded PU foam. The gas counter pressure inhibits a pre-mature dissolving of the CO2 out of the reaction mixture when the mixture is injected to the mould cavity. By a defined pressure reduction inside the mould, the foaming process can be controlled independent of the PU reaction. It has been proven that the developed process technology is capable for solving pressures of the CO2 up to 2.2 MPa and for gas counter pressures up to 2.5 MPa. This allows the use of up to approx. 10 wt.-% CO2 in the polyol (PIR at 303 K). Thereby, the foam density could be reduced down to 61 kg/m³ for the FF system. The investigations of the new foaming technology with flow obstacles confirm a form filling behaviour that is competitive to chemical foaming with water. But in comparison to chemical foaming, physical foaming with CO2 doesn't cause hard segments. As a result, at a comparable density the compressive strength can be reduced to less than a third. In combination with additives or combination of physical and chemical foaming, it is now possible to adjust the flexibility and hardness of flexible foams in a larger area than before, even for parts of low density of approx. 50 kg/m³. In conclusion, the potential of the new foaming technology for important applications like automotive seat upholstery is proven.
In case of rigid foams, the ability of the foaming technology is proven as well. Therefore, new applications come into focus due to optimised fire classification in comparison to pentane as a blowing agent, but without the ecological concerns of blowing agents containing fluorine. However, how far the density of rigid PU foams can be reduced by this foaming technology and what quantity of fire protection classification can be achieved, has to be investigated in further test series.