The effects of the saturation temperature and high-pressure dissolved CO2 on the crystallization behavior of polyether-block-amide (Pebax (R)) containing various amounts of polyamide-12 hard segment were studied. Non-isothermal and isothermal analyses were conducted using differential scanning calorimetry (DSC) to evaluate the crystallization kinetics of Pebax (R) samples. Wide angle X-ray diffraction (WAXD) was used to characterize the crystalline morphology of Pebax (R) under various conditions. A higher cell density was observed from the foams of the broader distribution of the hard segment length and the hard segment crystalline phase obtained by twin-screw compounding. It appears that the hard-segment crystals are the heterogeneous nucleating sites that govern the nucleation phenomena of Pebax (R). Therefore, the broader distribution of crystalline phase offers better foaming characteristics because of the larger number of nano-/micro-scale heterogeneous nucleation sites. (C) 2017 Elsevier Ltd. All rights reserved.