Experimental and Theoretical Study of Rectangular Fiber Melt Spinning

Abstract

In order to study the process of rectangular fiber melt spinning, experimental and theoretical investigations are conducted. Several different values of such process variables as die dimension, flow rate, take-up speed, quench air speed and temperature, and die temperature are chosen for manufacturing poly(ethylene terephthalate) fibers. Both 1-and 2-dimensional formulations are employed under the Newtonian fluid assumption. Two separate mathematical schemes are then combined via the Picard iteration to provide a convenient tool estimating the process with all variables taken into account and with as little computational effort as possible. From this experiment, it is found that the extrudate exhibits negative swelling in the fiber width direction, which results from the negative second normal stress direction in shear flow inside the die. Fiber cross-section takes elliptical shape at the point of maximum thickness swell and then gets flat as it approaches the take-up point. As to numerical simulation, all the quantities such as fiber dimension, velocity, temperature and tension except variables related to cross-sectional area are relatively well described by this simple theory. Neglect of material elasticity and over-simplification of temperature variation along fiber cross-section are main causes for the deviation of calculated values from experimental data.

Effects of Spinning Conditions on Shape Changes of Trilobal-shaped Fibers

“…Among the various possible methods used to define the shaped fiber cross-sectional shape, the shape factor of the rectangular fibers was defined as the ratio of the fiber height to width [8], and the hollowness of the hollow fibers defined as the ratio of area of the outer circle to that of the inner circle [9]. In this work, the shape factor was defined by equation ( 1) and the spinnerets shape factor was 7.94 and 7.22 for the PP and PET trilobal fibers, respectively.…”

“…Owing to the usefulness of new fibers, functional fiber manufacturing technology has advanced greatly [5], generating new fibers usually having a non-circular cross-section, that changes bending stiffness, friction coefficient, softness, lively resilience, and appearance. Commonly used shapes for new fibers are trilobal, rectangular, and hollow [6][7][8][9][10], with factors such as viscosity, mass flow rate, spinning temperature, and take-up speed affecting the final shape of the as-spun fibers. Most research has focused on verifying the relationship between spinneret shape and the final cross-section of the as-spun fibers.…”