An efficient pre-foamed method to fabricate low density poly(ether-block-amide) foams

Poly (ether-block-amide) PEBA foams have been widely used in many industrial fields. However, compared with amorphous polymers, the microcellular foaming process of PEBA is more complicated due to their complex phase morphology evolution behavior. Moreover, the productivity was limited owing to the long saturation time for thick samples. In this study, we proposed an efficient pre-foamed method to fabricate low density poly(ether-block-amide) foams. PEBA foams with controlled rather high density were firstly prepared by microcellular foaming under relatively low foaming temperatures. Afterwards, the pre-foamed PEBA sample with a high density were further foamed into much lower density by using secondary microcellular foaming under relatively high foaming temperature. The microphase separation phenomenon in PEBA was clearly studied by scanning transmission electron microscopy and atomic force microscopy-based infrared spectroscopy technique. Thanks to pre-foaming process, the diffusion rate of CO2 in PEBA matrix was greatly increased, resulting in shorter saturation time in microcellular foaming process. Most interestingly, pre-foaming process can also help PEBA achieve a higher expansion ratio compared with traditional microcellular foaming process with the same foaming parameters. Pre-foaming driven foaming process was a practical way of achieving low-density PEBA foams efficiently without adding new equipment, especially for thick parts.