The mechanics of extruded polylactic acid: an investigation into the effects of its multiple recycling and the inclusion of fly ash

Abstract

This study examines variations in the material properties of the 3D printed polylactic acid (PLA) components after they have been recycled multiple times. Additionally, virgin polylactic acid was supplemented with fly ash from the thermal power plant, and the material's behavior was examined after it was recycled on multiple times. By means of different tests, the impacts of filler addition on the mechanical behavior of the recycled materials are investigated. Using various forms including broken pieces, flakes, and fine powders, the filament extrusion was performed using used polylactic acid material during recycling. Under multiple recycling conditions, the mechanical characteristics of the polylactic acid and fly ash added polylactic (PLA-FA) were investigated. This work also investigates the impact of the polymer's particulate size during the filament extrusion process. After recycling, it was found that the fine powder additions during the extrusion process provided high tensile strength of 32.61 MPa and flexural strength of 47.32 MPa for the PLA specimens. After recycling processes, the maximum tensile strength of 25.64 MPa and flexural strength of 50.22 MPa were found in fly ash enriched PLA. In contrast, the hardness of both PLA and fly ash-included PLA increased following each recycling procedure. Multiple recycling of PLA material turned the ductile material into brittle material by means of amorphous phase emergence. When compared to other particle sizes which were bigger in size, the specimens developed with filaments extruded with fine powder showed maximum results in all the tests. The tensile strength of PLA material decreased by 17.25%, while the tensile strength of PLA-FA material decreased by 21.35% after recycling. In PLA, the flexural strength drop following three recycling was 17.56% while in PLA-FA material it was 9.01%. After three times of material recycling, the hardness increased by 3.52% in PLA and by 2.48% in PLA-FA.