Development of sustainable PLA bio-composites reinforced with Azolla pinnata via solvent casting method

Polylactic acid (PLA) is a widely used biodegradable polymer, yet its inherent brittleness and limited thermal stability restrict its broader engineering applicability. This study introduces Azolla pinnata (AZP), a fully renewable and lightweight aquatic biomass, as a reinforcing bio-filler to enhance PLA performance. Composites were fabricated through a solvent-casting process followed by compression moulding to achieve uniform filler dispersion across multiple compositions. The use of renewable bio-fillers in polylactic acid (PLA) has gained increasing importance due to the growing need for environmentally sustainable materials with improved functional performance. In this study, Azolla pinnata (AZP) is investigated as a natural bio-filler to examine its influence on the mechanical, thermal, and microstructural properties of PLA. The developed PLA–AZP composites were systematically characterised through tensile testing to evaluate mechanical behaviour. Morphological and structural characteristics were analysed using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Density measurements, water absorption analysis, and thermogravimetric analysis (TGA) were performed to assess the physical integrity and thermal stability of the composites. The 20 wt% AZP composites exhibited the most balanced performance, showing 20% higher tensile strength and 24% higher stiffness while maintaining a low void content of 5.96%. Thermal analysis revealed a T_onset decrease from 335°C to 282°C with increasing filler content, alongside higher char residue formation. Moisture uptake increased from 0.1% to 3.5%. These findings position AZP-reinforced PLA as a promising lightweight and sustainable composite system for structural and automotive applications.