Effects of different compatibilizers on interfacial compatibility, crystallization, and mechanics of PBAT/PLA blends

Abstract

To address the narrow application range of PBAT/PLA blends caused by component incompatibility, this study selected four compatibilizers and compared the effects of different compatibilizers on the properties of the blends: these included a commercially available styrene-acrylate copolymer (HPC), as well as three synthesized compatibilizers: PBAT-g-(GMA-co-St) graft copolymer, epoxidized soybean oil–cardanol derivative (ESO–CD), and N-carboxymethyl triethylammonium bromide (CEA). The chemical structures of three compatibilizers were characterized via FTIR, ¹H-NMR and ¹³C-NMR to confirm successful synthesis. Subsequently, corresponding PBAT/PLA blends were prepared via melt blending and tested for compatibility, matrix dispersion, crystallization behavior, rheological properties, and mechanical performance. Results indicate that all prepared compatibilizers improve PBAT/PLA blend compatibility and PLA dispersion within the PBAT matrix to varying degrees. Specifically, PBAT-g-(GMA-co-St) and HPC compatibilizers enhanced compatibility by reacting their epoxy groups with the molecular chains, significantly narrowing the glass transition temperature gap between PBAT and PLA components. ESO–CD, containing both epoxy bonds and hydroxyl groups, further strengthened compatibility while markedly improving the blend's elongation at break and toughness. CEA compatibilizer reduces the ΔT_g of the blend to a minimum by increasing the interfacial strength between components in the blend, produced the most uniform PLA phase size, and substantially enhanced interfacial adhesion. This resulted in the highest tensile strength (approximately 25.5 MPa) and elongation at break (approximately 404.9%) for the PBAT/PLA/CEA blend, with the elastic modulus increasing to approximately 777 MPa. Regarding crystallization behavior, DSC and XRD tests revealed that CEA promotes PLA nucleation, inducing new α-crystalline diffraction peaks in the PLA phase of the blend. This significantly advances the crystallization temperature (T_c) and enhances crystallization capability. Furthermore, although the addition of the compatibilizer improved the compatibility of the PBAT/PLA blend, its rheological behavior remained predominantly viscous. In summary, the CEA compatibilizer demonstrated optimal performance in enhancing the comprehensive properties of PBAT/PLA blends, providing crucial insights for the optimized design of biodegradable plastics.