olyethylene terephthalate (PET), a petroleum-based polyester and polylactic acid (PLA), a biodegradable polyester, were investigated in the form of nanocomposites reinforced with montmorillonite (MMT), with a particular focus on their behaviour after reprocessing. These materials, commonly used in the automotive applications, have shown significant differences in structural and mechanical performance. Melt flow index (MFI), shrinkage, crystallinity (CRF) and impact strength were analyzed according to international standards (ISO 1133 for MFR, ISO 11357-7 for CRF and ISO 179-1 for Izod impact) to evaluate the effect of mechanical recycling. The results showed that PET experienced a notable reduction in viscosity (~13–16%) with reprocessing, while PLA exhibited more stable viscosity (~3–5%). The addition of MMT affected both materials differently: it significantly reduced the impact strength of PET but had a milder effect on PLA. Shrinkage increased with recycling, particularly for PLA. Crystallinity was enhanced by the presence of MMT, especially in PLA. The findings demonstrate that PLA has better stability upon recycling compared to PET, and that MMT acts as a nucleating agent, altering crystallinity and mechanical properties. Reprocessing led to a decrease in mechanical performance in both nanocomposites, with PET more adversely affected. This work provides a direct comparison of PET and PLA nanocomposites subjected to identical reprocessing conditions, offering new insight into their recyclability and structural stability. Overall, these findings highlight the importance of balancing processability, recyclability and durability when selecting nanocomposites for applications where mechanical stability is critical, such as the automotive industry.
Taha et al. (Wed,) studied this question.