Enhancing Rice Straw–Polylactic Acid Biocomposites via Supercritical CO ₂ and Chemical Surface Treatments for Large‐Format Additive Manufacturing

Large‐format additive manufacturing (LFAM) enables the cost‐effective fabrication of complex components; however, its alignment with circular economy goals depends on the adoption of sustainable materials. To address this, polylactic acid (PLA) composites reinforced with rice straw (RS), an abundant agricultural residue, processed via fused granular fabrication (FGF) were developed. To improve fiber–matrix adhesion, the RS was pretreated with alkaline, oxidative, and supercritical fluid (SCF). Comprehensive characterization (FTIR, NMR, DSC, TGA, XRD, SEM, density, and mechanical testing) coupled with analysis of variance (ANOVA) revealed that these pretreatments are decisive in tuning the composite's overall performance. The findings highlight the potential of SCF–assisted modification to produce high‐performance, bio‐based composites tailored for LFAM applications.