Recyclability and mechanical performance of PLA/PBS blends: impact of reprocessing on structural and thermal properties

This study examines the mechanical properties of PLA/PBS blends with high secondary raw materials, extending prior research on recyclability. Three formulations with 45% recycled content from previous extrusion processes simulated mechanical recycling and underwent static tensile tests over three extrusion cycles. To ensure optimal processability, extrusion processing parameters were selected in accordance with the composition of each formulation. Results show increasing PBS content enhances ductility. Young’s modulus stayed stable in L and S series during first and third extrusion cycles, while LS formulation increased. IZOD impact testing showed significant impact strength improvement, with L samples surpassing base PLA (13.3 kJ/m 2 ) to reach 21–24 kJ/m 2 . Impact resistance rose with PBS content, with 82.8%, 200.7%, and 521.3% improvements for 15.53% (L), 31.07% (LS), and 67.32% (S) PBS, respectively. Mechanical stability of thermoformed structures is crucial for tray functionality. The tray compression test of the L series showed consistent maximum loads of 542.2–862.9 N, regardless of test speed and extrusion cycles. Notably, formulation L(1) exhibited higher loads with increased testing velocities, maintaining structural integrity without premature failure. LS materials showed viscoplastic behavior with lower stiffness and loads of 455.7–677.6 N. The S series, with more PBS, exhibited elastic deformation, maintaining integrity and resisting collapse, with loads of 418.4 and 504.4 N across test speeds and extrusion cycles. These findings highlight the potential of recycled PLA/PBS blends in industrial applications, especially in thermoforming, where maintaining mechanical integrity through multiple recycling cycles is crucial.