Until today, the consumption of bead foams is steadily increasing. However, only a limited number of polymers were established for bead foams at all. This includes, (i) expanded polystyrene (EPS), which is mainly used for packaging as well as for thermal insulation in construction and (ii) expanded polypropylene (EPP), that can be found typically in automotive applications such as sun visors or in seat parts. The main issue of the established materials is their low thermal resistance (HDT - heat deflection temperature), which is approximately 80°C for EPS and 110°C for EPP, respectively. For certain applications (e.g. close to an engine – so called under the hood application) and some processes (e.g. cathodic dip painting or sandwich applications) bead foams that can withstand a long-term exposure to heat. Consequently, the interest in engineering polymers such as polybutylene terephthalate (PBT) for the use as bead foam material is growing. Köppl et al. [1] reported in an earlier work the continuous production of bead foams by foam extrusion coupled with underwater granulation (UWG). The work showed the main challenges of PBT foaming, which are (i) the poor rheological properties of this polyester, namely a low melt strength that limits the foam expansion and (ii) the narrow processing window for foaming. Another drawback was (iii) even though the production of E-PBT bead foams was possible, the foam beads failed to fuse under the conditions used in the steam chest molding (SCM) process. The present work describes the chemical modification of the PBT with a commercial chain extender (CE) as well as the production of bead foams with the UWG with a density of 170 kg/m3. Additionally, the successful fusion of the E-PBT in a modified SCM process with higher steam pressures was shown. Furthermore, we could demonstrate that E-PBT has superior properties such as a higher thermal but also chemical resistance allowing it to undergo the cathodic dip painting.