Repetitive recycling of 3D printing PLA filament as renewable resources on mechanical and thermal loads

3D printing technology has emerged as a high value-added industry with high efficiency that has dramatically broken away from the existing material and manufacturing industry’s human-based production system. These technologies, ranging from small parts to large structures, are rapidly developing due to the challenge of various filament materials, whereas there are significant concerns about waste filler materials, and complimentary research is needed to improve them. Polylactic acid (PLA), the representative polymer of 3D printing, contributes to minimizing environmental risks. However, although thermoplastic PLA has excellent reversible properties for heat in terms of sustainable resources, it is degraded as a low value-added material afterward. Therefore, in this study, the effect of repetitive recycling on the mechanical and thermal properties of PLA filaments was analyzed to verify and re-evaluate PLA as a renewable resource. As a result, recycled PLA has decreased tensile and flexural strength by up to 69% and 53%, respectively, compared to initial neat PLA with the increase of the number of repetitive recycling, and this demonstrates the change in the thermal properties of recycled PLA.