Structure of Twisted Nylon 6 and Poly(ethylene terephthalate) Fibers

Abstract

Nylon 6 and poly(ethylene terephthalate) monofilaments were subjected to various levels of twist inserted under constant load. X-ray diffraction patterns of the twisted filaments were obtained and the axial dispersion of the crystalline regions was estimated from the azimuthal spreading of the equatorial diffraction arcs. The experimentally obtained values were compared with those calculated by assuming that the fiber under goes a uniform deformation. The data show that the crystalline orientation does not follow the macroscopic twist imparted to the filament. The discrepancy is largest at small twist angles, indicating that at this stage the twist is taken up primarily by regions that do not give rise to coherent x-ray scattering. At higher twist angles, there is indi cation that a tilting of crystallographic planes accompanies the reorientation of the crystallites. The effect of crystallite disorientation on the properties of the fibers is discussed.