Fabrication of PLA-hemp 3D printing filaments

Abstract

This thesis focuses on the development and evaluation of polylactic acid (PLA) composites infused with hemp fibers for 3D printing applications. The project aims to leverage the intrinsic properties of hemp fibers and PLA to create a material that mitigates brittleness and enhances biodegradability while maintaining mechanical performance and printability. The methodology involves fabricating composite filaments from 2 mm PLA pellets and 0.4 mm hemp fiber particles. Hemp fiber at varying weight ratios (5 wt%, 10 wt%, and 15 wt%) was extruded using a single screw extruder. The optimal ratio was determined among these blends for maximum tensile and flexural strength, and the structures on the fractured surfaces were observed under low magnification. The filaments were studied under flexural and tensile mechanical testing, optical microscopy analysis, Fourier Transform Infrared thermal profiling, moisture absorption, and biodegradability analysis. The blends were compared with a commercial PLA filament for 3D printing applications. As a summary of the results, the composition of 5 wt% and 10 wt% hemp powder had lower Ultimate Tensile Strength (UTS) than 100 wt% PLA filaments; however, this blend had higher elongation and toughness. The highest tensile strength of 35 MPa occurred with the 95 wt% PLA-5 wt% hemp fiber composition. Similarly, the flexural strength for the 95 wt% PLA-5 wt% hemp fiber composition was 86 MPa, which was the highest among the composites, but lower than 100 wt% PLA. This composition showed a higher flexural modulus of 4 GPa which was greater than 100 wt% PLA. For water absorption, all the composite filaments showed the greatest rate of absorption during the first 1 hour. After the initial hour, no notable changes occurred. The 85 wt% PLA-15 wt% hemp fiber had the highest absorption rate; indicating that increasing the fiber percentage increases the water absorption. The biodegradability was studied using an enzyme-rich FABRICATION OF 3D PRINTING FILAMENTS M. UDDIN detergent which showed that 90 wt% PLA-10 wt% hemp fiber had the highest weight loss percentage across all three concentrations which was over 20% which indicates that this composition was more prone to biodegradability using this method than the other compositions. The printability of the filaments was analyzed qualitatively using a commercial 3D printer. A simple design for a “paper clip” was printed which requires both tensile and flexural strength. The products were printed with ease whereby the filaments melted and flowed through nozzles of 0.8 mm diameter for fused filament printing.