Evolution of cell morphology from sub-macroscale to nanoscale in modified thermoplastic polyether ester elastomer via supercritical CO2 foaming

Abstract

Modified thermoplastic polyether ester elastomer (TPEE) foams with the cell size from sub-macroscale to nanoscale were prepared by solid-phase batch foaming in the presence of supercritical CO2 (scCO2). Multifunctional epoxy chain extender (CE) with the functionality of 9 was incorporated into TPEE to form a moderate crosslinking structure. The rheological property and crystallization behavior of modified TPEE were investigated, and then the cell morphologies of as-prepared TPEE foams were analyzed. It was found that the introduction of branching and crosslinking structure led to an increased melt viscosity and a reduction of crystallinity of TPEE. Moreover, it was identified that the rheological property dominated the foamability at high foaming temperature of 185 °C, and then the fine sub-macroscale cells were seen. Conversely, the change of crystallization behavior mainly affected the evolution of cell morphology at low foaming temperature of 160 °C, and the foams with nano and/or micro cells are obtained. As a result, a series of TPEE foams with the cell morphology from sub-macroscale to nanoscale could be achieved by adjusting the crosslinking degree of modified TPEE and the temperature of supercritical CO2 foaming.