Role of chain extension in the rheological properties, crystallization behaviors, and microcellular foaming performances of poly (butylene adipate‐co‐terephthalate)

Currently, the fabrication of microcellular semicrystalline polymer foam using supercritical CO2as a blowing agent constitutes a worldwide interest. In this work, a facile approach of chain extension and batch foaming was proposed to prepare microcellular semicrystalline poly (butylene adipate‐co‐terephthalate) (PBAT) foam using CO2as a physical blowing agent. With the introduction of chain extender (CE), the weight‐average molecular weight and gel fraction of PBAT samples increased; their crystallization temperature increased from 74.2 to 86.9 °C and their viscoelasticity was improved greatly. Microcellular PBAT foams with the cell size <4 μm and the cell density more than 1010cells cm−3were fabricated successfully. With increasing concentration of CE, the cell density and volume expansion ratio (VER) of various PBAT foams increased from 3.4 × 1010to 8.7 × 1010cells cm−3and from 1.5 to 2.0 times, respectively. With increasing foaming temperature, the cell size and VER increased and the cell density decreased.