Green preparation of biodegradable poly (butylene adipate-co-terephthalate) foam modified with bio-based epoxidized cardanol using supercritical fluid foaming

Poly (butylene adipate-co-terephthalate) (PBAT) foam is a potential alternative to conventional packaging materials. However, its wide adoption is hindered by issues such as low foaming–expansion ratios and shrinkage. A series of biodegradable epoxidized cardanol (EC)-modified PBAT foams were prepared using supercritical carbon dioxide (CO2) foaming. The addition of EC enhanced the crystallisation temperature and stiffness, and improved the rheological properties, thereby promoting polymer foamability. When the EC content reached 0.6 wt%, lightweight foams with the highest initial expansion ratio (Rv) of 48.4 were produced before shrinkage. N2 was introduced as a co-blowing agent to reduce shrinkage of the PBAT foams, resulting in the production of a microcellular foam with a stable Rv of 12.9. EC improved the foamability of PBAT while also introducing the co-blowing agent N2 to resist shrinkage. These findings can serve as valuable insights for the large-scale production of lightweight biodegradable foams.