Preparation of Pebax Foam Based on Chain Extension via Supercritical CO₂-Assisted Two-Step Foaming

Polyether block amide (Pebax) is difficult to prepare high expansion ratio (ER) foam in a wide range of foaming temperatures by supercritical CO2-assisted foaming due to its weak melt strength and complex crystallization behavior. In this work, Pebax foam with a high ER was prepared by two-step foaming under supercritical CO2 after chain extension modification. The results showed that the addition of chain extender significantly increased the melt strength and improved the crystallization behavior of Pebax. At the same time, the foaming window temperature of Pebax foam is reduced from 160 to 140 °C, which realizes the large-span control of foaming ratio from 1.2 times to 39.1 times for the first time. In addition, the second isothermal process was regulated to achieve the preparation of Pebax foam with a high expansion rate at different temperatures. What is more interesting is that the Pebax foam has a minimum thermal conductivity of 30.5 mW m–1 K–1, which has good thermal insulation properties.