Defect-Tolerant Interfacial Compatibilization of Heterogeneous Recycled Polypropylene via Binary iPP-g-MA/aPP-g-MA Masterbatches

Single-use polypropylene (PP) food containers represent a rapidly growing waste stream characterized by compositional heterogeneity and microstructural defects. Conventional reactive compatibilization using isotactic maleic anhydride-grafted PP (iPP-g-MA) provides rigid crystalline anchoring but lacks the interfacial flexibility to accommodate complex micro-defects. Herein, we propose a defect-tolerant compatibilization strategy by developing a binary iPP-g-MA/aPP-g-MA masterbatch for real post-consumer rPP derived from food-service containers. The amorphous aPP-g-MA component is proposed to provide a compliant interfacial environment that accommodates stress concentrations associated with microscale defects, whereas the iPP-g-MA component contributes crystalline anchoring with the recycled PP matrix. This soft/hard interfacial architecture is supported by grafting-degree analysis, GPC, XRD, DSC crystallization behavior, and SEM fracture morphology. The 1:1 mass-ratio binary formulation shows a marked improvement in elongation at break to 200%, representing a 203% increase relative to the single-component iMA system. The notched Charpy impact strength is enhanced to 8.98 kJ m−2, while tensile strength is retained at 20.9 MPa within the typical strength–ductility trade-off of polymer toughening. TGA shows no premature degradation within the melt-processing window, indicating adequate thermal stability for melt reprocessing. This study provides a compositionally tunable, data-supported route for high-value upcycling of heterogeneous post-consumer polyolefins. From an application viewpoint, the improved ductility-impact balance makes the material relevant to injection-moulded semi-structural products such as storage crates, appliance housings, and automotive interior panels.