Thermomechanical and mechanical analysis of polylactic acid/polyhydroxyalkanoate/poly(butylene succinate-co-adipate) binary and ternary blends†

Abstract

Research efforts are increasingly directed towards the development of biodegradable polymers derived from renewable agricultural resources. Polymer blends, which combine multiple polymers, offer enhanced properties such as ductility and toughness while being more cost-effective compared to the development of specialized copolymers. This study examines nine binary and four ternary blends of polylactic acid (PLA), poly(butylene succinate-co-adipate) (PBSA), and polyhydroxyalkanoate (PHA). The morphology of most blends was characterized by spherical inclusions. Binary blends with a 50/50 wt% ratio demonstrated distinctly different interactions between the bioplastics. The addition of PBSA increased both tensile elongation and impact strength. Notably, the PLA/PBSA blend with a 30/70 wt% ratio exhibited an elongation at break of 172%. In blends where PBSA constituted 30 wt%, there was an increase in impact strength, from 15% to 29% in PHA/PLA and PLA/PBSA blends, respectively. Overall, PBSA exhibited better compatibility with PLA compared to PHA. Mechanical testing of ternary blends was integrated with the binary blends' results to construct ternary diagrams. Dynamic mechanical analysis revealed that the glass transition temperatures in PBSA binary blends remained largely independent of the blend composition. Calorimetric analysis revealed a shift in crystallization behavior. This research highlights the potential of biopolyester blends in developing bioplastics with tailored mechanical properties for applications in automotive, agriculture, food packaging, and shape memory materials.