Towards Circular Manufacturing: Repurposing Eggshell Waste As Filler For Poly Lactic Acid Feedstock For 3D Printing

Abstract

— White eggshell (WES) waste was crushed into a fine powder (32 μm) and used as filler in poly lactic acid (PLA), a plant-based polymer, to enhance its mechanical properties such as its flexural strength and modulus. Pure PLA is a relatively brittle material that could benefit extra ductility to broaden its usage opportunities. Therefore, the influence of WES on this characteristic was also observed. Samples containing 5, 10 or 20% (w/w), respectively of WES were compared to samples containing the same proportions of limestone (LS) and to samples of pure PLA in flexural tests following ASTM D790-17. The observed mechanical properties were successfully improved using WES as filler when compared to LS or to pure PLA samples. Considering flexural strength and modulus, an approximate optimal point of 5% (w/w) WES could be determined by analyzing the data. Further, selected fractured samples were observed on a Scanning Electron Microscope (SEM) (Hitachi TM3000) to characterize and correlate the distribution of filler particles in the PLA matrix to these improvements. The SEM also allowed to characterize the fractures qualitatively on ductility compared to pure PLA. It could be concluded that the samples containing filler particles are more ductile than pure PLA. It was also possible to conclude that samples containing the highest filler content (i.e. 20%), regardless of the filler type, exhibited the most textured fracture surfaces thus indicating a more ductile fracture mode.