Hydrodynamic resistance in wet forming of chemical fibers

Abstract

A moving model fiber of diameter 0.2-1.0 mm is used to study boundary layer formation as a function of distance, velocity of motion, and diameter of the fiber. An equation is obtained that describes the dependence of the boundary layer thickness on the viscosity, distance, radius, and velocity of motion of the fiber. In forming a complex filament, the boundary layers of adjacent filaments merge at a distance of ∼0.15 mm from the spinneret, so that the coagulation bath is immobilized (trapped) by the moving fiber and moves along with the filament at a velocity equal to 85% of the velocity of the filament. The amount of the coagulation bath drawn off from the spinneret in the form of boundary layers is equal to the product of the area of the perforated part of the spinneret times the velocity (0.85%) of the filament. This amount of the bath approaches the perforated surface of the spinneret in the form of a normal flow at a distance of ∼5 mm from the spinneret. It causes significant stress in the individual filament (jet of spin dope) and may cause the filament to break.