Fiber Structure Formation in High-Speed Melt Spinning of Polyamide 6/Clay Hybrid Nanocomposite

Abstract

Polyamide 6 (PA 6)/clay hybrid (NCH) nanocomposites containing 2 and 5 wt% of clay were melt spun at take-up velocities from 1 to 5 km/min, and the effect of clay on the fiber structure formation was investigated. As the reference, neat PA 6 was spun at take-up velocities from 1 to 7 km/min. The NCH fibers showed higher crystallinity in the whole take-up velocity range, although there was no remarkable crystallinity dependence on the clay content. The birefringence of NCH fibers exceeded that of neat polymer only in the low take-up velocity region (i.e., up to 3 km/min). The orientation-induced crystallization was observed to start at about 2 km/min for NCH and at 4 km/min for neat PA 6. Also, at these take-up velocities, the peaks of α-form crystals appeared in the wide-angle X-ray diffraction equatorial (WAXD) scans, indicating that the orientation-induced crystallization was related to the direct formation of α-form crystals in the spinline. The NCH fibers were superior in Young's modulus; however, their tenacity was higher only in the low take-up velocity region in which the crystallization in the spinline of neat PA 6 did not occur yet. That variation of tenacity was attributed to the molecular orientation, whereas the modulus was supposed to be determined by the stiffness of intercrystalline regions.