Anti‐Shrinkage and Superior Oil‐Adsorption Poly(4‐hydroxybutyrate) Foam Achieved Through In Situ Fibrillation of Polyvinylidene Fluoride

ABSTRACT Owing to inherent limitations such as low melt strength and slow crystallization rate, poly(4‐hydroxybutyrate) (P4HB) exhibits unsatisfactory foaming performance and oil adsorption capacity. Herein, a shear‐induced in situ fibrillation process is integrated with supercritical CO 2 foaming to fabricate P4HB/polyaryl polymethylene isocyanate (PAPI)/polyvinylidene fluoride (PVDF) foams. This strategy enhances the crystallization behavior and melt strength of chain‐extended P4HB, suppresses foam shrinkage, and improves both foaming ability and oil adsorption performance. The resulting foam achieves a maximum expansion ratio of 45.9 and a cell density of 5.8 × 10 12 cells/cm 3 . Notably, the foam with 2 wt% PVDF exhibits the highest oil adsorption capacity, reaching 28.1 g/g for CCl 4 . This work provides an effective strategy for overcoming the challenges of P4HB foaming and demonstrates significant potential for expanding its applications in oil adsorption and related fields.