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

The foaming of thermoplastic polyurethanes (TPU) with CO2 as a blowing agen t reduces material input for existing applications and also leads to improv ed material properies for new applications. Therefore the correlations betw een process parameters and the resultsing 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 te mperature and shear sensitive polymer, the influence of the screw geometry on the extrusion process is examined. First extrusion experiments have resu lted in TPU foams with a density below 0,4 g/cm(3).