Characterization of hard-segment crystalline phase of poly(ether-block-amide) (PEBAX®) thermoplastic elastomers in the presence of supercritical CO2 and its impact on foams

•Hard segment (HS) crystallized faster in Pebax after melt compounding.•Plasticizing CO2 significantly induced a large number of HS crystals in Pebax.•HS crystallization reduces activation energy for bubble nucleation in Pebax microstructure.•Improved foaming of Pebax due to the broader size distribution of HS crystallites.

The effects of the saturation temperature and high-pressure dissolved CO2 on the crystallization behavior of polyether-block-amide (Pebax®) 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® samples. Wide angle X-ray diffraction (WAXD) was used to characterize the crystalline morphology of Pebax® 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®. Therefore, the broader distribution of crystalline phase offers better foaming characteristics because of the larger number of nano-/micro-scale heterogeneous nucleation sites.

Graphical abstractThermal behavior of Pebax after annealing at ambient pressure, gas pressure and after foaming.Download high-res image (129KB)Download full-size image