Micro‐Crosslinking and Interfacial Synergy in Polylactic Acid Blends: Balancing High Strength and Toughness With Low Content of Poly(3‐Hydroxybutyrate‐Co‐4‐Hydroxybutyrate)

ABSTRACT Blending with bio‐based elastomers is an effective strategy for toughening polylactic acid (PLA), but it often requires high elastomer loadings (≥ 20 wt%), leading to a severe loss of strength. In this study, a cascade strategy was proposed based on micro‐crosslinking synergistic compatibilization to achieve a high strength–toughness balance in PLA with only 10 wt% of poly(3‐hydroxybutyrate‐co‐4‐hydroxybutyrate) (P34HB). A micro‐crosslinked reactive P34HB (RPHA) was first constructed via in situ crosslinking initiated by bis(tert‐butylperoxy) diisopropyl benzene (BIBP). It was then melt‐blended with PLA and a multi‐epoxy chain extender (ECE) to tailor the interfacial adhesion. The resulting PLA/RPHA‐0.2 blend exhibits a high fracture energy of 141.8 MJ/m 3 —more than ten times that of the un‐crosslinked counterpart—while maintaining a high yield strength of 55.2 MPa, only 7.7% lower than neat PLA. The micro‐crosslinking strategy enables optimized interfacial strength and finely tuned dispersed phase morphology (only 0.3 μm), which synergistically contribute to the superior toughness. This work provides a novel and sustainable approach to fabricating fully bio‐based PLA materials with excellent mechanical properties for green packaging applications.