Investigation of thermal oxidative stabilization process of viscose rayon fibers by multistep heat treatment technique

This study investigates the thermal oxidative stabilization (TOS) process of viscose rayon fibers. Before stabilization, a chemical pretreatment containing ammonium sulfamate and urea was applied to the fibers, and then stabilization was carried out at temperatures between 200 degrees C-250 degrees C for different times with a multi-step heat treatment strategy. The effects of the TOS process on fiber density, tensile strength, FT-IR spectroscopy, X-ray diffraction (XRD), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were evaluated in detail. The results show that as the TOS time increased, the density increased to 1.73 g/cm3 and the carbonization efficiency increased from 15% to 64%, but the tensile strength decreased by 60%. FT-IR and XRD analyses revealed that the cellulose II crystal structure was disrupted, the structure became 100% amorphous after 5 min of stabilization and cross-linked aromatic structures increased. DSC and TGA results show that the thermal resistance of stabilized fibers is significantly improved. These findings indicate that stabilized viscose rayon fibers have attained sufficient thermal stability for the subsequent stages while also making significant contributions to the optimization processes for the efficient production of viscose rayon-based activated carbon fibers.