Degradable Polyester Ternary Blends: Composition and Hybrid Compatibilization for Flexible Packaging

Abstract

A fully degradable ternary blend system comprising bio-based poly(butylene succinate) (BioPBS), poly(butylene adipate-co-terephthalate) (PBAT), and poly(3-hydroxybutyrate-co-hydroxyvalerate) (PHBV) was developed to achieve a tailored stiffness-toughness balance. The influence of polymer selection, relative ratios, and hybrid compatibilizer addition on blend properties was systematically investigated. Morphological analysis revealed that the blend components remained largely immiscible, consistent with solubility parameter predictions, while interfacial tension measurements indicated that BioPBS effectively separated PHBV and PBAT phases. Optimized ternary blends with 50 wt.% PHBV exhibited synergistic mechanical performance, reaching elongation at break close to 100%, tensile strength around 35 MPa, and Young’s modulus exceeding 1.6 GPa. Rheological analysis suggested enhanced interfacial interactions due to increased chain entanglement, even in the absence of a compatibilizer. Incorporation of 3-5 wt.% hybrid compatibilizer further enhanced mechanical and thermal performance, with elongation at break increasing by 8%, impact strength by 15%, and Young’s modulus by 9%, alongside improved thermal stability. These improvements were attributed to interfacial chemical interactions confirmed by Fourier Transform Infrared Spectroscopy, enhanced phase adhesion observed via Scanning Electron Microscopy, and more entangled or cross-linked networks indicated by rheology. The results demonstrate that BioPBS/PBAT/PHBV ternary blends can be tailored to produce fully degradable materials with tunable mechanical and thermal properties. Hot melt cast extrusion processing was employed to obtain a cast sheet with high barrier properties, highlighting its potential for sustainable packaging applications.