Effects of chain composition of PBAT on the supercritical CO2 foaming and degradation behavior

Poly (butylene adipate-co-butylene terephthalate) (PBAT) with different copolymer compositions and molecular weights exhibits unique foaming behavior and dimensional stability when supercritical CO2 is used as a blowing agent. With an increase in the content of butylene glycol terephthalate (BT) from 43% to 61%, the melting point and crystallinity of PBAT increase. Consequently, the foaming temperature range of PBAT shifts toward a narrower, higher temperature zone, i.e., from 70 – 120 °C to 135 –160 °C under 13 MPa CO2 pressure. Additionally, CO2 solubility and desorption rate decrease, while PBAT exhibits a higher compression modulus and better foam dimensional stability. For similar BT contents, an increase in the molecular weight of PBAT widened the foaming temperature window and increased the cell density of the foam. It is noteworthy that increasing the BT content of PBAT to 52% not only ensures good dimensional stability of the PBAT foams, but also good biodegradability of PBAT. In addition, the effect of foam structure on degradation behavior was investigated. It was found that the PBAT foams with a higher volume expansion, larger cell size, and lower cell density degrade faster.