Flame-retardant anti-fibrillation Lyocell fibers prepared by online-treatment of coagulated filament

Lyocell fiber is a green synthetic fiber widely used in the twenty-first century. However, its flammability and fibrillation limit its further use. In this paper, we used online-treatment of coagulated fibers during spinning to obtain flame-retardant and anti-fibrillation Lyocell fibers with crosslinkers and flame retardants that penetrate the fiber surface easily and react more quickly with the cellulose molecular chains. The results of infrared spectroscopy, X-ray diffraction and birefringence showed that the coagulated filaments had more micropores, lower crystallinity and orientation compared to heat setting fibers. At lower concentrations of flame retardant (200 g/L) and cross-linking agent (60–80 g/L), the limit oxygen index (LOI) of Lyocell fibers treated on-line was about 30.2%, the char residue was increased from 7.1 to 23.0%, and the peak of heat release rate (PHRR) and total heat release were reduced by 86.4% and 49.6%, respectively. This is attributed to the better adsorption ability and accessibility of coagulated filaments and the rapid reaction between cellulose and the crosslinker to capture more flame retardant during the online-treatment. After washing 20 times, the LOI was still maintained at 28.7%, and the degree of fibrillation of the fiber was obviously reduced. Compared with conventional Lyocell fibers post-treatment technology, this work provides an industrially feasible and efficient method to continuous prepare Lyocell fibers with both favorable flame retardant and anti-fibrillation properties.