The aim of these experimental investigations is to understand the potential for reducing foam density by the amount of Thermoplastic Expandable Microspheres (TEM) used as foaming agent, the processing temperature and the viscosity of the rubber. Two EPDM-based rubber compounds that are processed in injection moulding and extrusion processes, and therefore have different viscosities, have been the subject of investigation. A Sponge Rubber Analyzer is used to determine the timedependent reduction and thus the lowest achievable foam density. It was shown that the process temperature and the mass content of TEM added had a significant influence on the foam density reduction. © 2024, Huthig GmbH. All rights reserved.