Sequential chemical refinement of micronized Lantana camara fibers: Size-dependent crystallinity and thermal stability

This paper examines the impact of sequential chemical treatments on Lantana camara fibers with diameters of 75 µm and 150 µm. This study presents a novel investigation on the combined effect of sequential NaOH – HCl – NaOH treatment and controlled particle sizes (75 μm and 150 μm) on the structural and thermal behaviour of lantana camara fibers. The fibers are subjected to 5% NaOH, 3% HCl and 2% NaOH chemical treatments and then characterized using X-ray Diffraction, Fourier Transform Infrared spectroscopy, Thermogravimetric Analysis - Derivative Thermogravimetry and Scanning Electron microscopy. The XRD pattern confirms the retention of cellulose I, with strong (200) peaks at 2θ = 22.5262° for the 75 µm AA sample and 22.6143° for the 150 µm AA sample, signifying enhanced crystallinity. The treated fibers exhibit a dominant peak at 2θ ≈ 22.5° and a degradation peak at 338.71°C, compared to 64.03% mass loss in raw fibers. FTIR spectra indicate the loss of lignin and hemicellulose peaks in the regions 1667-1507 cm⁻¹ and the augmentation of cellulose peaks at 1051 cm⁻¹ (75 µm) and 901 cm⁻¹ (150 µm). Thermogravimetric analysis with DTG shows that raw 150 µm fibers have an initial weight loss of 6.91% below 100°C and a maximum rate of weight loss of 64.03% at 355.31°C; However, AA-treated fibers have lower degradation and higher char residue, with a DTG peak material at 338.71°C. FESEM micrographs show reduced impurities, enhanced fibrillation and better surface morphology. The 75 µm AA-treated fibers have better crystallinity and thermal properties. This combined treatment – size approach provides a distinct advancement over existing studies on lantana camara fibers. These properties enhance stiffness, thermal resistance and interfacial bonding in composites.