Methods for making morphologically stable bulked continuous filaments

The present invention relates generally to synthetic filaments and to their processes and systems for manufacture. More specifically, the present invention relates to processes and systems for making melt-spun, synthetic polymeric yarns of bulked continuous filaments (BCF), especially carpet yarns comprised of nylon BCF. BCF yarn is melt-spun, drawn and textured to provide morphologically stable BCF yarns. The yarn texturizing includes a relatively low efficiency fluid jet texturizer, that is a fluid jet texturizer operating at a sufficiently low fluid jet velocity and a sufficiently high fluid jet temperature to obtain a yarn skein shrinkage of less than about 0.50 inch, more preferably about 0.25 inch or less. Most preferably, the BCE yarns are formed of nylon-6 and exhibit an alpha-crystalline content of less than about 45%, and usually between about 45% to about 55%.