Abstract: To find suitable process conditions for high-speed spinning of Lyocell fibers, spinnerets with different apertures were used to spin Lyocell fibers at different air-gap lengths and 400 m/min of spinning speed. The impact of the aperture of spinneret and air-gap length on crystalline orientation, mechanical property, and fibrillation index of Lyocell fibers spun at high spinning speed were studied through XRD, sonic velocity method, birefringence anisotropic method, and wet rubbing test. Results indicated that accompanied by an increase in the aperture of spinneret, crystallinity, crystal orientation and average orientation of Lyocell fibers all increased, and the breaking strength of fibers increased as well. Excessive orientation would lead to an increase in fibrillation index, resulting in higher fiber diameter variation rate and weaker fiber quality. Spinneret with 0.10 mm aperture is suitable for high-speed spinning of Lyocell fibers. As the air-gap length increased, the strength and modulus of the fibers increased to a certain extent, but the breaking elongation of fibers dropped, so a proper increase in air-gap length could improve fiber properties.

Key words: high speed spinning; Lyocell fiber; spinneret aperture; air-gap length; fibrillation