Utilizing zinc borate as an efficient and environmentally friendly flame retardant for the development of flame-resistant regenerated fibers

Reed pulp was used as the raw material for fiber spinning, with [Amim]Cl as the solvent and zinc borate added as a flame retardant, and flame-retardant cellulose fibers were produced through a dry-wet spinning process.Flame-retardant cellulose fibers were produced through a dry-wet spinning process by using reed pulp as the raw material, [Amim]Cl as the solvent, and zinc borate as the flame retardant. The fibers were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and their limiting oxygen index, combustion properties, and thermal stability were assessed. The results revealed that the fibers exhibited a near-circular cross-section with a diameter of approximately 20 μm, and the flame retardant was evenly distributed on both the surface and cross-section of the fibers. The fibers, containing 20 % flame retardant, exhibited an ultimate oxygen index of 30.5 % and demonstrated self-extinguishing behavior in a horizontal orientation. When exposed to flame in a vertical position, they maintained a complete fibrous carbon layer, and their thermal stability was significantly enhanced. The flame retardant mechanism involves zinc borate, which forms ZnO and B₂O₃ after dehydration, adhering to the fiber surface to create an inorganic char layer that reduces heat and mass transfer, promotes charcoal formation, and inhibits cellulose thermal degradation.