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.

Thermal behavior of Pebax after annealing at ambient pressure, gas pressure and after foaming.129