Prof. Dr. Axel Müller

Polymer blends have the potential to be homogenously foamed since the interface area between their phases can used as bubble nucleating agents, during the foaming process. Immiscible polymer blends of Poly(2,6-dimethyl-1,4-phenylen ether) PPE and poly(styrene-co-acrylonitrile) SAN with a weight ratio of 60/40 were compatibilized by different amounts (1 to 10 wt.-%) of Janus nanoparticles (JPs). Here we report on the nucleation effect of JPs and the dispersed PPE phase on the foaming behavior of PPE/SAN blends. The plasticization of CO₂ and its solubility and diffusion behavior in the PPE/SAN blend was analyzed and correlated to blend morphologies. It is shown that partial coverage of the raspberry structure results in stress concentration at the blend interface during the saturation step. This formation of new surfaces by cleavage (and to some extent micro crazes) results in a higher sorption of the blowing agent, which affects the foaming behavior. Through temperature induced batch foaming with CO₂, the blends were foamed to find the optimum foaming conditions and relationships between the morphology of the compact and foamed blends (cellular structure) and the density were established. Finally, it was concluded that by using Janus particles, homogenous foams with small cell sizes and relatively high densities were produced.