Experimental investigation on mechanical, flammability, wear and thermal properties of 3D printed Polylactic acid composite contain rice husk ash Si3N4 nanoparticle

This study investigates the effects of varying Si₃N₄ particle concentrations on the mechanical, wear, and flammability properties of additively printed Polylactic acid (PLA) composites with rice husk ash Si3N4 particles. The Si₃N₄ is extracted from rice husk through pyrolysis and nitration processes and found to be amorphous polycrystalline crystals with the Miller Indices plane of (110), (200), and (201) correspond to the diffraction peaks at 22.0, 26.7, and 33.69, respectively. The customized Polylactic acid -Si₃N₄ filaments were further prepared using a twin-screw extruder with varying volume ratio, and composites are printed using fused deposition modelling with specified infill ratios. According to results the composite C2, contains 1 vol% Si₃N₄ filler with a 75% infill ratio, exhibits superior mechanical properties, including the highest tensile strength of 34.2 MPa, flexural strength of 64.3 MPa, impact energy of 3.6 J, and hardness of 68 Shore-D. This enhancement is attributed to the optimal dispersion of Si₃N₄ particles, which promotes effective load transfer and minimizes stress concentrations. In contrast, specimen D2, with 2 vol% Si₃N₄ filler and a 75% infill ratio, demonstrates the best wear resistance and flammability performance, showing the lowest coefficient of friction of 0.18, minimal wear loss of 0.036 g, and the lowest flame propagation speed of 0.32 mm/min with “N0” ratings across all flammability categories, indicating excellent flame retardancy due to a denser structure and higher filler content. In thermal stability also the D4 composite performed well and stable at initial decomposition stages. Finally, scanning electron microscope (SEM) analysis further supports these findings, revealing that uniform filler dispersion as in C2 improves mechanical properties, while agglomerated particles as observed in suboptimal specimens lead to reduced performance due to localized stress points. The results highlight the potential of Si₃N₄-reinforced Polylactic acid composites in applications requiring enhanced mechanical, wear, and flammability properties.