Untersuchungen zur Degradation bei wertstofflichem Recycling am Beispiel von PLA

Abstract

The increasing popularity and use of additive manufacturing by means of Fused Filament Fabrication (FFF for short) results in an ever-growing demand for plastics. Due to the use of support structures, insufficient filament remnants and misprints, the FFF process tends to generate more waste, which in turn is also increasing due to its popularity. The recycling of plastic waste for additive manufacturing is possible in principle, but limited in frequency due to the degradation of the materials through the reprocessing process. Furthermore, various studies in the past showed widely varying results in terms of the mechanical properties of the recycled materials. For this reason, this work deals with the influence of multiple reuse of the plastic material polylactide (PLA) on its mechanical properties and general printability. For this purpose, the material passed through a filament production cycle a total of five times. During each run, two different types of test specimens were made. The remaining material served as the basis for the subsequent recycling run. Thus, the present study elaborates the influence of repeated filament production without the additional use of a 3D printer. The test specimens were used to check the mechanical properties of the material and the dimensional accuracy of the printed objects. The dimensional accuracy was evaluated with the help of a 3D scanner. The results of the study showed that repeated filament production had very little effect on the mechanical properties and printability of the material. The reduction in the determined mechanical properties from the first to the last run amounts to about 5% for Young's modulus, about 2% for tensile or yield stress, and about 7% for breaking stress. A minimal reduction was also observed for dimensional stability over the entire component. This shows that repeated use ofthe starting material is suitable for reprocessing in filament production, thus old filament remnants or insufficient filament quantities can be processed into new filament