Bead foams, e.g. expanded polypropylene (EPP) show a multi-scale structure with mesoscopic microcellular beads fused into macroscopic foam parts. Due to this assembly, bead foams have a special hierarchical morphology. Thus, in contrast to other polymer foams, an additional major parameter controlling the performance of bead foams must be taken in account: the interbead bonding. Playing a crucial role, a good fusion of beads is necessary in order to achieve favorable mechanical properties.
In this contribution we discuss the influence of
(1) molding conditions on the interfacial structure and bonding quality in EPP
(2) incorporated functional components on the microstructure of the weld lines and the extend of fusion
The findings show evidence on the significant role of interdiffusion and crystallization phenomena on the fusion strength of EPP and provide a deeper knowledge about the influence of coating on EPP properties, which allows further development of novel materials with fine-tuned functional properties.