Toward a circular economy: an investigation in recycled PLA via mechanical, thermal, and morphological performances and life cycle analysis

The objective of this study is to evaluate the mechanical recycling of polylactic acid (PLA) via hot melt extrusion. Virgin PLA was extruded to produce the initial batch and subsequently reprocessed for up to three cycles, during which 20 wt% virgin material was incorporated into the recycled matrix at each stage. All batches were characterized with respect to density, melt flow index, molecular weight, color, differential scanning calorimetry, rheological behavior, mechanical performance, and morphological behaviors. The results demonstrate that the inclusion of 20 wt% virgin PLA can effectively mitigate the deteriorated effect from mechanical recycling, which can be noticed from the similar mechanical performances between all the batches and less reduced molecular weight shown between the recycled iterations compared with that after first round extrusion. Regarding the life cycle assessment, it reveals that the conducted multi-loop mechanical recycling can significantly improve the environmental performance of PLA life cycle depending on the number of recycling loops, where 30–55% reductions across key impact indicators by the third recycling loop can be achieved. In the final end-of-life, after the three recycling loops, industrial composting shows the lowest overall environmental impacts, whereas incineration remained the most emission-intensive, highlighting the pivotal role of multi-loop recycling systems in mitigating life cycle impacts and advancing circular economy objectives for biopolymer-based products.