Differences of Alkali and Thermal Treatment on Cotton Residues Applicable to Green Composites

Natural fibers have been widely used in biocomposites because are renewable raw materials and improve mechanical performances. However, some components such as lignin reduce the biodegradation of these composites. This study evaluated the effects of two types of treatments (alkali and thermal) on superficial and composition of the cotton fibers. The samples were evaluated by Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), contact angle measurement (CA) and X-ray diffraction (XRD). The alkali treatment removed impurities, hemicellulose and part of lignin (using 10% wt.%NaOH). There was also a change in the crystalline structure of cellulose. Treatment with higher temperatures increased the removal of hemicellulose residues and lignin. It also decreases oxidized cellulose, which increased wettability and hydrophilicity of the cotton fiber. The most effective treatment was with 10% NaOH and 60 or 90°C as studied with delignification, wettability, and thermal stability. This process should facilitate biodegradation.