Numerical simulation of melt spinning of polyethylene terephthalate fibers

Abstract

This chapter presents a study that analyses high speed spinning process, employing some hybrid numerical methods combining both 1- and 2-dimensional formulations. The radius of the extrudate and the temperature on its surface are calculated under the 1-dimensional flow assumption, and then with these results specified as boundary conditions, 2-dimensional simulation is conducted to estimate the temperature profile and the morphological structure development along the fiber cross-section. Including the effect of crystallinity in the elongational viscosity and assuming the tensile stress acts only on the amorphous region enabled to observe the neck-like deformation in the spinline. From the result of numerical simulation, it can be concluded that the take-up speed plays the most determining role in the fiber structure formation. Even though the flow rate shows strong effect on diameter and temperature variation along the spinline, its role diminishes in the case of crystallinity and birefringence of the final products. The formation of the fiber skin-core structure is simulated in this numerical procedure. Effect of spinning conditions on the formation of skin-core structure is estimated by observing the birefringence distribution in the cross-section. The distinct skin-core structure builds up due to the combined effect of high-speed take-up and quench air. As the quench air velocity increases at high speed spinning and the fiber diameter becomes thicker, this structural inhomogeneity becomes severer.