Investigations into the foaming behavior of ABS by means of granule extrusion using expandable microspheres

The following investigations address the production of syntactic polymer foams using thermally expanding microspheres (TEM) in the extrusion process. A process model for the foaming behavior of acrylnitrile butadiene styrene (ABS) with thermally expanding microspheres as masterbatch is derived by varying the two basic process parameters extruder rotational speed and extruder temperature in a test matrix with five stages each. The investigations include the production of unfoamed and foamed strands and the measurement of process relevant properties and parameters such as extrusion mass flow, relative density of the structures, die-swelling and the characterization of the generated foam structures. The achievable density reduction is within the order of 50%. The process model resulting from the investigations allows the production of homogeneously foamed strands. These results are intended to serve as the basis for a transfer to the Large Scale Additive Manufacturing (LSAM) process.