Shortening the Saturation Time of PBAT Sheet Foaming via the Pre-Introducing of Microporous Structures

Poly (butylene adipate-co-terephthalate) (PBAT) foam sheets prepared by foaming supercritical fluids are characterized by high resilience, homogeneous cellular structure, and well-defined biodegradability. However, the inert chemical structure and the rigid hard segments restrict the diffusion of CO₂ within the PBAT matrix, resulting in extremely long gas saturation times as long as 9 h at a thickness of 12 mm. In this study, microporous structures were pre-introduced into the PBAT matrix to provide a fast gas diffusion pathway during the saturation process. After 2 h of saturation, PBAT foam sheets with expansion ratio of 10 to 13.8 times were prepared. The interaction of CO₂ with PBAT was systematically investigated, and the CO₂ sorption process was evaluated kinetically and thermodynamically using the Fickian diffusion theory. The solubility and diffusion rate of CO₂ in pretreated PBAT sheets with different microporous sizes and densities were investigated, and the effects of pretreatment strategies on the foaming behavior and cell structure of PBAT foam sheets were discussed. The introduction of a microporous structure not only reduces saturation time but also enhances solubility, enabling the successful preparation of soft foams with high expansion ratios and resilience. After undergoing foaming treatment, the PBAT pretreated sheets with a 10 μm microporous structure and a density of 0.45 g/cm³ demonstrated improved mechanical properties: their hardness decreased to 35 C while resilience increased to 58%, reflecting enhanced elastic recovery capabilities. The pretreatment method, which increases the diffusion rate of CO₂ in PBAT sheets, offers a straightforward approach that provides valuable insights into achieving rapid and efficient foaming of thick PBAT sheets in industrial applications.