Shape Memory Temperature-Tunable Poly(butylene adipate-co-terephthalate)/Polylactic Acid Foams Prepared by Supercritical CO₂ Foaming

Lightweight, shape memory temperature-tunable, biodegradable, and reusable poly(butylene adipate-co-terephthalate) (PBAT)/polylactic acid (PLA) foams with acetyl tributyl citrate (ATBC) were prepared by a simple, green, and efficient supercritical CO₂ foaming technique. ATBC reduces the glass transition temperature (T_g) of PLA in PBAT/PLA composites and, thus, decreases the switching temperature of the shape memory in PBAT/PLA foams. ATBC widens the shape memory applicable temperature range, and the applicable temperature shifts toward lower temperatures. The minimum shape memory applicable temperature is 50 °C. ATBC can also accelerate the shape recovery process. In addition, increased shape memory temperature favors the shape fixing ratio (R_f) and recovery ratio (R_r) and can shorten the shape recovery time. PBAT/PLA foam exhibits a low density of 0.16 g/cm³, an R_f of 93.6%, and an R_r of 95.2%. PBAT/PLA foam also has reusability; both R_f and R_r remain above 85% after 10 cycles.