Fibrillar and microfibrillar structures in poly(p‐phenylene terephthalamide) fibers

Abstract

The microfibrils and the microfibrillar network in poly(p-phenylene terephthalamide) (PPTA) fibers formed during the coagulation from a monodomain lyotropic fiber are stabilized by critical point drying and characterized by electron microscopy and small angle X-ray scattering. The diameter of the microfibrils varies from 20 to 49 nm depending on the PPTA concentration in the lyotropic solution used for the spinning. A formation mechanism for the microfibrils and the microfibrillar network is suggested. During the coagulation, the spinodal decomposition (phase separation) is assumed to occur before the crystallization (phase transition), resulting in the formation of the microfibrils. The formation of the microfibrillarnetwork is considered to be related to the misorientation ofmacromolecules and the density fluctuation in the crosssection of the filament during spinodal decomposition.

Microfocus small‐angle X‐ray scattering investigation of the skin–core microstructure of lyocell cellulose fibers

“…Ruland analysis 18,19 was used on the SAXS fiber data to calculate the width of the orientation distribution of the voids (B ) and the average void length projected onto the fiber axis (L 3 ). The right-hand lobe of the scatter was used in each case, in that this showed better subtraction around the beam stop than the left-hand lobe.…”

“…It was obtained in a mathematically direct analogy of Ruland analysis, 18,19 by taking the intercept of a plot of obs 2 against (1/s 2 ), where obs is the angle at which each azimuthal curve reaches a background intensity. Equation (7) was evaluated using the MATHEMATICA software package (Wolfram Research, Inc., Champaign, IL).…”

Studies of Structure and Morphology Development During the Heat-Draw Process of Nylon 66 Fiber by Synchrotron X-ray Diffraction and Scattering Techniques

“…To gain information on the morphological changes during drawing, we have adopted two unique procedures to analyze the 2D SAXS image. These procedures include the use of correlation function analysis (Strobl & Schneider, 1980) to determine the lamellar crystal and amorphous thicknesses (along the fiber direction) from the sliced meridional intensity, and Porod analysis (Porod, 1982;Balt~-Calleja & Vonk, 1989;Wang, Ruland & Cohen, 1993) to determine the crystal fibril width (perpendicular to the fiber direction) from the integrated equatorial intensity profile.…”

Morphology and structure changes of aromatic copolysulfonamide fibers heat‐drawn at various temperatures

“…Following these assumptions, we have designed a heat‐drawing experiment for pre‐drawn aromatic copolysulfonamide ( co ‐PSA) fibers to investigate the changes of the structure and properties of the fibers at various heat‐drawing temperatures below T d . From our previous study, it is known that, unlike PBO and Kevlar fibers with extended chain structure in the crystal phase, pt ‐PSA has a twofold molecule with two monomeric units forming a zigzag conformation in the crystal lattice and forming a layer structure, which is stabilized by the hydrogen bond between –NH and –CO and parallel‐displaced π–π stacking from the distortional coplanarity of the benzene rings and amide groups . The relationship between the structures developed in the heat‐stretching process and the performances of PSA fibers with such a special conformation is unknown yet.…”