Preparation of biodegradable poly(butylene succinate)/halloysite nanotube nanocomposite foams using supercritical CO₂ as blowing agent

Biodegradable poly(butylene succinate) (PBS) was melt compounded with halloysite nanotube (HNT) to prepare PBS/HNT nanocomposites, and both pure PBS and PBS/HNT nanocomposites were foamed successfully using supercritical carbon dioxide as a physical blowing agent. The cell morphologiesshowed that the cell size decreased, and both cell density and volume expansion ratio increased with the addition of HNT. Within the HNT content used in this work (1, 3, 5, and 7 wt.%), the content of 5 wt.% was found to be the one that lead to the smallest cell size and highest cell density and volume expansion ratio. In addition to the HNT content, both saturation temperature and saturation pressure were found to significantly influence the cell morphology. Higher saturation pressure led to smaller cell size and higher volume expansion ratio. Interestingly, a close-celled to interconnect open-celled morphology transition occurred for PBS/HNT nanocomposites at a saturation temperature of 120 °C. The formation of interconnect open-celled morphology was mainly attributed to the stress induced by the HNT in the cell solidification process. With the increase of HNT content, saturation temperature and saturation pressure, the enthalpy of fusion of the foamed samples increased.