One of the most important factors in polymer processing is viscosity, which is a function of molecular weight. The number-average molecular weight of polymer suitable for textile fiber production ranges from 14,000 to 20,000. Since Polycaprolactam can be regarded at equilibrium as a polycondensation polymer, the number-average molecular weight alone is sufficient for its characterization. Two-step melt spinning, comprised of spinning and drawing, is considered to be the conventional method to manufacture nylon filaments. After melting, filtering, and deaerating, the molten polymer is extruded through a spinneret into a chamber where the melt solidifies into a filament form. At this stage, the filaments have little molecular orientation, and their slight birefringence is due to shear forces set up during extrusion. In order to achieve desirable properties through molecular orientation and crystallinity, the newly formed filaments must be drawn. Since the Tg of nylon is below room temperature, nylon can be cold drawn.Hot drawing is also frequently used. Nylon filaments are drawn approximately four times their initial length. The effect of drawing on birefringence, a measure of molecular anisotropy, can be seen in Table I. Also, the elastic modulus increases significantly with increasing orientation as shown in Table I. Other physical properties, such as density equilibrium, moisture sorption, tenacity and elongation-at-break, are also affected by drawing.