SynopsisThe structure of melt-spun nylon 6 filaments was studied using on-line x-ray diffraction and birefringence measurements. Measurements were also made on as-spun and treated filaments. On-line wide-angle x-ray scattering measurements indicated that crystallization did not occur on the nylon 6 spinline at spinning rates up to lo00 m/min when spinning was done into either ambient air of 60% relative humidity or into wet saturated air. The filaments did crystallize gradually on the bobbin to a paracrystalline pseudohexagonal (y) form. The rate of crystallization was dependent on the molecular orientation developed in the spun filaments. Crystalline orientation factors based on hexagonal symmetry were computed as a function of take-up velocity for fibers which were conditioned 24 hr in air at 65% relative humidity. Annealing in air or treatment in water or 20% formic acid solution causes a transformation from the pseudohexagonal form to the a monoclinic form. The tangent modulus of elasticity and tensile strength of spun and conditioned filaments increase with increasing take-up velocity and spinline stress, while elongatioq break decreases with these variables.

SynopsisBasic studies of the melt-spinning dynamics and rheological properties of a nylon 6 polymer are described. The magnitude of the force components on the spinline has been analyzed with special reference to the drag and rheological forces. Spinline deformation has been investigated for spinning through ambient air and through an isothermal chamber. Both sets of experiments are interpreted using an elongational viscosity. Non-Newtonian viscosity was measured at 230°, 250°, and 270% in a Weissenberg rheogoniometer and an Instron capillary rheometer. The principal normal stress difference was measured in the former instrument. The rheological properties are interpreted in terms of the theory of viscoelastic fluid behavior. The isothermal melt-spinning experiments were also interpreted in terms of the theory of viscoelastic fluids, and attempts were made to understand the spinning results in terms of basic rheological properties.