A Brand New Biodegradable Foams of Poly(Propylene Carbonate‐Co‐Phthalate) With Superior Performances Fabricated by a Two‐Step Bead Foaming Process

Poly(propylene carbonate‐co‐phthalate) (PPC‐P), a fully biodegradable amorphous copolymer of aliphatic polycarbonate and aromatic polyester, exhibits excellent biodegradability and mechanical properties. However, the preparation of PPC‐P foam beads and 3D foam molded bodies with superior compression performance and dimensional stability remains challenging due to its low melt strength and poor heat resistance. In this study, the crystalline polylactic acid (PLA) was employed as a reinforcing material and methylene diphenyl diisocyanate (MDI) as a crosslinking compatibilizer to enhance the melt strength and heat resistance of the blend. The PPC‐P/PLA expanded beads with varying PLA ratios were prepared via a two‐step foaming process involving rapid depressurization followed by rapid heating. The results demonstrate that increasing PLA content elevates cell density to 5.84 × 10 9 cells/cm 3 while reducing cell size to 31.7 μm. Furthermore, the 3D foaming blocks were fabricated from those foamed beads through the confined molding method, and their structural integrity and performance were systematically characterized, focusing on inter‐bead sintering behavior, compression strength (up to 575.9 kPa), and dimensional stability (< 10% shrinkage after 240 h). Overall, this study establishes a scalable manufacturing approach for the PPC‐P/PLA expanded beads with fine cellular structures and molded blocks with high‐compression, low‐shrinkage.