Interfacial Engineering of PLA/PBAT Blends via Peroxide‐Assisted Grafting of a Biobased Polyol

Abstract

Poly(lactic acid) (PLA) is a commercially important biodegradable polymer, yet its inherent brittleness and poor compatibility with flexible biodegradable polyesters limit its application in mechanically demanding products. In this study, the interfacial compatibilization of immiscible PLA/poly(butylene adipate‐co‐terephthalate) (PBAT) blends was achieved using a novel castor oil‐based biobased polyol (COP) synthesized via transesterification followed by esterification with itaconic acid. Reactive melt extrusion was employed, with dicumyl peroxide (DCP) used as a radical initiator to promote interfacial grafting. The effects of COP content and peroxide activation on mechanical performance, melt rheology, crystallization behavior, and thermal stability were systematically investigated using tensile testing, dynamic rheology, X‐ray diffraction, differential scanning calorimetry, and thermogravimetric analysis. The results show that COP acts as an effective amphiphilic compatibilizer, improving interfacial adhesion and stress transfer between PLA and PBAT phases. In the presence of low peroxide loading, COP is further stabilized at the interface through radical‐mediated grafting, leading to enhanced melt elasticity, refined crystalline structure, and a balanced improvement in strength and ductility. An optimum formulation containing 2.5 phr COP and 0.2 phr DCP was identified, beyond which interfacial saturation and partial softening reduced performance. Overall, this study demonstrates an effective and sustainable compatibilization strategy for PLA/PBAT blends using a renewable, multifunctional polyol, providing insights into structure–property relationships while offering a viable pathway toward high‐performance biodegradable materials for packaging and additive manufacturing applications.