Dog-legging in the melt spinning process

Experiments were performed in a continuous capillary rheometry to investigate the dog-legging mechanism in a melt spinning process. The bending angle of the spinline was measured under various spinning conditions while spinning PP, PET, and PEN fibers. Experimental results indicate that obstacles inside the capillary of the spinnerette are the primary cause of bending of the spinline. The bending angle is greatly influenced by the obstacle's dimensions and position inside the capillary. An increase in the obstacle's radius or a decrease in the obstacle's length caused the bending angle to increase. The closer the obstacle was to the exit of the capillary implied the bending angle would be the wider except for the block immediately above the exit. Also at high shear rates, PEN was found to be relatively insensitive to spinline-bending than PET polymers. Ln accounting for the dog-legging behavior, our results suggest that the die swell model is more realistic than the conventional vortex model.