Bio-based plasticization of PLA-PHB blends using chemically modified borage seed oils towards sustainable active materials

The development of sustainable and functional polymer systems for active packaging remains a key challenge in materials science. In this study, borage seed oil (BSO) was chemically modified via epoxidation and maleinization to yield bio-based plasticizers, epoxidized borage seed oil (EBSO) and maleinized borage seed oil (MBSO), which were incorporated into poly (lactic acid)–poly(3-hydroxybutyrate) (PLA-PHB) blends to tailor their mechanical, thermal, and functional performance. Both modified oils demonstrated effective plasticizing behavior, reducing tensile strength while significantly enhancing ductility and impact resistance. MBSO exhibited a more balanced mechanical response, suggesting more effective interactions within the polymer matrix, whereas EBSO induced a stronger plasticization effect through increased chain mobility and free volume. Thermal analysis revealed a decrease in glass transition temperature and alterations in crystallization behavior, consistent with enhanced molecular mobility, while maintaining adequate thermal stability for potential packaging applications. In addition, both modified oils exhibited antioxidant activity in a concentration-dependent manner, with EBSO-based systems showing the highest radical scavenging capacity. Furthermore, the time-dependent increase in antioxidant activity, alongside migration and solubility results, suggests that the availability of antioxidant-active species is influenced by the plasticizer content and is consistent with the gradual diffusion of low-molecular-weight compounds from the polymer matrix. Morphological analysis revealed changes in fracture surface consistent with the mechanical behavior of the developed formulations, with higher concentrations inducing void formation and saturation effects. Overall, chemically modified borage seed oils serve as bio-based plasticizers that simultaneously enhance mechanical flexibility and confer antioxidant activity. These results highlight their potential as bio-based additives for developing sustainable, biodegradable materials tailored for active packaging applications.