Microstructure development of PEBA and its impact on autoclave foaming behavior and inter-bead bonding of EPEBA beads

Expanded poly(ether-block-amide) (EPEBA) bead foams are a new class of advanced thermoplastic elastomer foams with low density and high resilience. Steam-chest molding realizes the fabrication of the molded EPEBA bead foams with complex geometry. However, the evolution of polymer microstructure in autoclave foaming process and the bonding mechanism behind the steam-chest molding of EPEBA beads are still unclear. In this work, the microstructure development of PEBA was characterized by DSC, SAXS and rheological methods. Then, EPEBA beads with an expansion ratio higher than 25-fold were prepared by autoclave foaming, and the molded EPEBA bead foams with a density lower than 0.15 g/cm(3) and a resilience higher than 70% were produced by steam-chest molding. According to the change about thermal properties of EPEBA beads before and after steam-chest molding, a possible inter-bead bonding mechanism during EPEBA beads molding was proposed. The amorphous soft segments and melted low-ordered hard segments promoted the welding process. However, the well-ordered hard segments hindered the interdiffusion of polymer chains at the interface, which leaded to the reduced tensile strength and the narrowed molding temperature window of EPEBA bead foams.