Mechanical, Thermal and Rheological Characteristics of Ternary Blended System, Poly(lactic acid)/Poly(hydroxyalkanoates)/Poly(butylene adipate-co-terephthalate) (PLA/PHA/PBAT) via the Morphological Influence

This study explores the potential of biodegradable polymer blends as environmentally friendly alternatives to conventional plastics. Single biodegradable polymers have limitations in fully replacing traditional polymer materials. To overcome these limitations, blending different polymers or using compatibilizers has been investigated. However, compatibility issues arise due to the high molecular weight and surface energy differences between materials. In this study, we aim to enhance compatibility by controlling the composites and investigating the effects of polymer surface energy in ternary blends of Poly(lactic acid) (PLA)/Poly(hydroxyalkanoates) (PHA)/Poly(butylene adipate-co-terephthalate) (PBAT). Our analysis includes the examination of morphology, mechanical properties, rheological characteristics, and a particular focus on the effects of PHA at the blend's interface. The results reveal that PHA acts as a compatibilizer, transforming the blend structure from a sea-island morphology to a co-continuous structure, with PHA encapsulating PBAT. This not only enhances impact strength but also achieves the highest tensile strength and elongation at break by optimizing the PHA content. The aggregation and reinforcement effects of PHA in the PLA/PBAT blend contribute to these improvements. The morphological prediction of the blend is conducted using diffusion coefficients, and the influence of PHA on interfacial properties is confirmed through scanning electron microscopy (SEM). The co-continuous interface achieved by encapsulating PBAT with PHA contributes to a consistent and stable structure. Rheological properties are evaluated using a rheometer, revealing a decrease and subsequent increase in complex viscosity with increasing PHA content. This behavior can be attributed to the formation of complex fluidity during the heating process, followed by the formation of a new structure. Moreover, for immiscible blends, the influence of the interface becomes more significant, resulting in a larger increase in storage modulus. However, as PHA content increases, the rate of increase in storage modulus decreases. Overall, these findings highlight the role of PHA as a compatibilizer in PLA/PBAT blends. Furthermore, by increasing the content of biomass-based PHA instead of petroleum-based PBAT, this study suggests the possibility of sustainable plastics for eco-friendly packaging materials.