Incorporation of Fully Bio-Based Butylene Succinate Oligomers into Poly(butylene succinate) by Melt Mixing

In this study, fully bio-based oligomers of butylene succinate (OBS) with different molecular weights (low: L-OBS, medium: M-OBS and high: H-OBS) were incorporated into poly(butylene succinate) (PBS) by melt mixing at varying loadings of 5-15 wt%. Then, PBS/OBS films were obtained by thermo-compression and characterized to assess their suitability for sustainable food packaging. Thus, OBS were homogeneously incorporated into PBS matrix and modulated the thermal, mechanical, and barrier properties of the PBS. L-OBS (Mn = 1150 g·mol^-1) plasticized the amorphous PBS, depending on its concentration, more effectively than M-OBS (Mn: 8700 g·mol^-1) and H-OBS (Mn: 18,650 g·mol^-1), as deduced from the thermo-mechanical analysis. In every case, OBS enhanced crystallinity, mainly L-OBS, which reduced the film strength and increased water vapor permeability, depending on its concentration. In contrast, H-OBS improved mechanical strength, stiffness, and barrier performance. In all cases, X-ray diffraction confirmed the preservation of the PBS's monoclinic crystalline structure but slightly shifted the diffraction angle depending on the ratio of the end-chain groups in the blend, thus reflecting the contribution of OBS in the crystalline lattice. Finally, oligomer incorporation resulted in an overall migration increase in different food simulants, impairing their application in packaging.