Mechanical properties and microstructure of hemp hurd reinforced polylactide biocomposites for <scp>3D</scp> printing

Abstract Polylactide (PLA) biocomposite filaments containing hemp hurd (HH) of variable particle size were evaluated in comparison with injection‐molded counterparts using single/twin screw extrusion in this study. HH particle size (35, 50, and 160 μm) was parametrically investigated for its efficacy within PLA/HH biocomposites and fused filament fabrication (FFF)‐printed parts by assessing its effect on performance through rheological, microstructural, mechanical, and surface finish analyses. In addition, melt flow indexing, rheometry, scanning electron microscopy, mechanical testing, and x‐ray computed tomography were utilized to analyze microstructure, mechanical performance, and surface roughness. With an increase in particle size of the HH, the corresponding biocomposites showed increased flowability, and the injection‐molded specimens showed increased impact strength. The FFF printing of the biocomposite filament presented no challenges, and the mechanical properties of FFF parts enhanced with a particle size smaller than the printed layer thickness. Compared with injection‐molded parts, FFF‐printed samples showed higher impact strength. The FFF‐printed PLA/HH biocomposite samples showed considerable potential over their injection molded alternatives for low‐volume specialized applications. Highlights Polylactide (PLA)/hemp hurd (HH) biocomposite filaments with different particle sizes of HH were developed. Melt flow and impact strength increased when HH particle size increased. 3D‐printed part porosity and roughness increased when HH particle size increased. Higher HH particle size enhanced the mechanical performance of 3D‐printed parts. 3D‐printed parts exhibited higher impact strength than injection molded parts