Functional Finishing of Textiles Using Neltuma juliflora Bark Tannins for UV Protection and Color Development

In this study, tannins extracted from Neltuma juliflora (N. juliflora) bark using a unified solvent extraction method were applied as a bio-based finishing agent to impart ultraviolet protection and coloration to various textile substrates. The unified extraction method yielded tannins with 85.91% purity and high functional consistency. Finishing was carried out with copper mordant on 100% cotton, 100% viscose, 60/40 CVC, and 100% polyester fabrics. Tannin treatment resulted in “Excellent” ultraviolet protection factor (UPF) for cotton and markedly enhanced the already strong UPF of 100% polyester, while viscose and 60/40 CVC fabrics achieved “Very Good” UPF. The color strength (K/S) increased across all fabrics, confirming a strong interaction between tannins and fibers. Fourier Transform Infrared (FTIR) spectra exhibited peak shifts, band broadening, and new bands consistent with tannin deposition and mordant-assisted interactions/surface fixation, with additional indirect evidence from the fastness results. The treated fabrics maintained mechanical integrity and demonstrated good to excellent fastness to washing, rubbing, and perspiration. GSM (grams per square meter) analysis revealed a moderate increase in fabric mass due to uniform deposition of the tannin-mordant complex, while soil burial tests confirmed that the biodegradability of cellulosic fabrics remained unaffected.