Study on pistachio shell filled PLA composites for FDM-based processing

In this research, Polylactic Acid (PLA)/Pistachio shell particles (PSP) composite filaments were developed using a single screw extruder for Fused Deposition Modeling (FDM) process. Alkali and silane treatments were applied to PSP to enhance bonding between the filler particles and the PLA matrix. FTIR analysis indicated the removal of lignin and hemicellulose from the PSP surface and formation of siloxane bonds due to the chemical treatments. XRD analysis indicated reduced crystalline organization due to treated PSP incorporation. Despite slight decreases in tensile, compressive, and flexural strengths, PSP addition improved tensile modulus and matrix stiffness. When comparing 2%, 4%, and 6% PSP additions, the 4-wt% composite demonstrated the highest tensile strength (49.81 MPa), which can be attributed to the improved dispersion of PSP particles as confirmed by SEM images. In contrast, the 6-wt% composite exhibited the maximum compressive strength (43.06 MPa) and flexural strength (58.06 MPa), likely due to the higher filler loading providing greater resistance to deformation. Hardness and impact resistance also showed steady improvement with increasing PSP content. However, the inclusion of treated PSP reduced the wettability of the PLA matrix. Interestingly, the 4-wt% composite recorded the highest Melt Flow Index (12.80 g/10 min), suggesting enhanced processability. Taken together, the 4-wt% composite with uniformly dispersed PSP offered the best balance of mechanical and thermal properties.