Foam extrusion of thermoplastic polyurethanes (TPU) using CO2 as a blowing agent

The foaming of thermoplastic polyurethanes (TPU) with CO2 as a blowing agent reduces material input for existing applications and also leads to improved material properties for new applications. Therefore the correlations between process parameters and the resulting foam quality are examined in this paper. The solubility behaviour of CO2 in the polymer melt is analysed by means of a high pressure sorption balance. For the foam extrusion of the temperature and shear sensitive polymer, the influence of the screw geometry on the extrusion process is examined. First extrusion experiments have resulted in TPU foams with a density below 0,4 g/cm3.