Micronized Banyan Tree Aerial-Root Powder-Reinforced PLA Biocomposites for Fused Filament Fabrication: Processing, Structure, and Property Relationships

Polylactic acid (PLA) is widely used in fused filament fabrication (FFF), but its engineering applications are constrained by brittleness and limited thermal resistance. Here, micronized banyan tree aerial-root (BTAR) powder was incorporated into PLA at 5–25 wt.% and processed into composite filaments by single-screw extrusion for FFF printing. The composites showed a composition-dependent response. At 15 wt.% BTAR, tensile and flexural strengths increased by approximately 47% and 43%, respectively, compared with neat PLA. The highest impact energy absorption was obtained at 25 wt.% BTAR, reaching 2.93 J versus 1.07 J for neat PLA. XRD and FTIR results indicated a predominantly amorphous PLA matrix with superimposed cellulose-I features and spectral changes suggesting possible interfacial interactions. SEM revealed relatively uniform filler dispersion at intermediate loading, whereas higher BTAR contents promoted agglomeration. Thermal analysis showed a slight reduction in degradation onset temperature but increased char residue from 0.1% for neat PLA to 5.4% at 25 wt.% BTAR. These results indicate that untreated BTAR is a promising regional particulate filler for FFF-grade PLA, with 15 wt.% favoring strength and 25 wt.% enhancing impact resistance and char formation.