Polymeric Applications of Cellulose from Tibouchina lepidota (Bonpl.) Baill Extracted from Sustainable Forest Residues

The extraction of cellulose from underutilized forest residues can diversify bio-based material supply chains and reduce pressure on commercial pulps. In this study, cellulose was isolated from <i>Tibouchina lepidota</i> (<i>Bonpl.</i>) <i>Baill</i> pruning residues through an alkaline-acid-oxidative protocol, and its suitability for polymeric applications was evaluated. Two granulometric fractions (250 µm and 125 µm) were used; the yields were 4.73 ± 0.12 g and 3.62 ± 0.11 g per 50 g of biomass, equivalent to 90.5% and 92.8% recovery, respectively (fractional remains as bleached pulp after removal of non-cellulosic components). Fourier Transform Infrared spectroscopy (FTIR) showed the disappearance of lignin and hemicelluloses bands and a pronounced β-glucopyranosic signal at 894 cm^-1, indicating high purity. Selective solubility in 17.5% NaOH classified the polymer as β-cellulose, suitable for wet spinning and film regeneration. Optical microscopy revealed smooth fibers of 25-50 µm length and 0.5-1 µm diameter, with aspect ratios ≥ 50, indicating favorable morphology for load transfer in composites. Statistical analysis (Shapiro-Wilk, F-test, and Student's <i>t</i>-test) confirmed the significant influence of particle size on yield (<i>p</i> < 10^-15). Overall, <i>T. lepidota</i> residues constitute a viable source of high-purity β-cellulose, whose molecular integrity and microstructure satisfy the requirements of sustainable polymeric manufacturing.