Mechanical Properties of Specimens 3D Printed with Virgin and Recycled Polylactic Acid

Abstract

With the 26% annual growth rate of additive manufacturing, especially in the area of 3D polymer printing, the amount of waste is increasing at a rapid rate. Limited research in the area of recycling has been produced, yet there are several recycling machines being developed for home use. Despite this work there is no published mechanical data on components produced with filament recycled from 3D printed parts. There is very limited data on mechanical properties of any 3D printed materials. This article compares the properties of parts 3D printed with virgin polylactic acid (PLA) to those printed with recycled PLA. Using commercially available PLA and an entry level 3D printer, tensile and shear specimens were produced and then tested for tensile yield strength, modulus of elasticity, shear yield strength, and hardness. The specimens were then ground up and re-extruded into filament, and a second set of specimens were produced and tested using this recycled PLA filament. Mechanical testing showed that 3D printing with recycled PLA is a viable option. With the recycled filament, tensile strength decreased 10.9%, shear strength increased 6.8%, and hardness decreased 2.4%. The tensile modulus of elasticity was statistically unchanged. Although the average mechanical properties before and after recycling were similar, there was more variability in the results of the recycled filament. Additionally, when printing with the recycled filament there was some nozzle clogging, while none occurred with the virgin filament. Overall, the mechanical properties of specimens 3D printed from recycled PLA filament were similar to virgin properties, encouraging further development in the area of recycling 3D printed filament.