Melt spinning of nylon 6: Structure development and mechanical properties of as‐spun filaments

Abstract

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.

Microstructural investigation of high-speed melt-spun nylon 6 fibers produced with variable spinning speeds

“…Many investigations on the structural changes of nylon 6 fibers produced at various spinning speeds have been performed. Bankar et al 1 carried out quantitative studies to relate the crystalline orientation of spun fibers with their spinning speed in the range of 100 -1000 m/min. Stepaniak et al 2 described empirical methods for calculating a total crystalline index, crystalline indices for ␣ and ␥ forms, and the corresponding ␣ and ␥ orientation functions for nylon 6 fibers at spinning speeds of 20 -2435 m/min.…”

The Structure and Properties of Typical Melt-spun Fibres

“…Bankar et al [51] and Ishibashi and Ishii [52] found that the birefringence of spun fibres increased with time on the bobbin.…”

“…Bankar et a1. [51] studied fibres spun at low draw-downs and stress levels and observed wide-angle X-ray scattering patterns showing only amorphous halos.…”

Study of the structure development during the melt spinning of nylon 6 fiber by on-line wide-angle synchrotron X-ray scattering techniques

“…Conditioned data from Bankar et al 12 and Gianchandani et al 32 are also plotted for comparative purposes. Deviations from the present work to that of the two listed above can be attributed to different temperature profiles in the extruder and sample molecular weight.…”