Laccosperma secundiflorum fibres: a promising bio-based reinforcement for composites and 3D printing filaments

This study introduces, for the first time, lignocellulosic fibres derived from the stems of Laccosperma secundiflorum (LS) as a bio-based reinforcement for sustainable composites and filaments intended for 3D printing. The fibres, extracted through water retting, were characterised using scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), gravimetric, thermogravimetric (TGA), and differential scanning calorimetric (DSC) analyses, as well as tensile testing on individual bundles. The fibres exhibit a density of 0.766 g/cm 3 and a linear density of 33.3 Tex, indicating their lightweight nature. Chemical composition analysis revealed contents of 44.4 % cellulose, 30.8 % hemicellulose and 18.9 % lignin. The presence of functional groups typical of these lignocellulosic constituents was confirmed by FTIR spectra. SEM observations revealed compact bundles with semi-circular cross-sections and rough surfaces. TGA and DSC analyses demonstrated good thermal stability up to 215.2 °C, with a maximum degradation temperature of 363.4 °C and an activation energy of 81.2 kJ/mol. The fibres showed a water uptake of 213.9 % in distilled water and 123.2 % in seawater, as well as a moisture regain of 9.3 %, with sorption kinetics accurately described by the modified Page model. Under tensile loading, the fibres achieved a tensile strength of 462.3 MPa and a Young’s modulus of 5.5 GPa, with moderate losses at 200 °C (345.3 MPa; 4.0 GPa), which were not statistically significant according to ANOVA, but substantial degradation was observed at 300 °C (up to -91 %). The thermal stability observed above 200 °C confirms compatibility with low melting point thermoplastics such as PLA (≈ 180 °C) and PCL (≈ 150 °C). Overall, LS fibres stand out as a promising biological resource, capable of expanding the range of natural reinforcements for composites and sustainable filaments for 3D printing.