Thermal- and stress-induced lattice distortions in a single Kevlar49 fibre studied by microfocus X-ray diffraction

Abstract Understanding the macroscopic physical and mechanical properties of poly(p-phenylene terephthalamide) (PpTA) fibres as a function of temperature requires an understanding of how temperature influences its microscopic structure. This study investigates lattice distortions in single PpTA fibr...
Ausführliche Beschreibung

Abstract Understanding the macroscopic physical and mechanical properties of poly(p-phenylene terephthalamide) (PpTA) fibres as a function of temperature requires an understanding of how temperature influences its microscopic structure. This study investigates lattice distortions in single PpTA fibres using the high brilliance of a synchrotron radiation microbeam. Lattice distortions are studied over a temperature range of 110–350 K and the influence of tensile deformation is also considered. The results reveal linear thermal expansion behaviour for all unit cell axes, in general agreement with literature. Expansion/contraction is greatest along the [100] direction whilst being reduced along [010] by inter-chain hydrogen bonding. During macroscopic deformation, longitudinal crystal strain dominates with respect to axial lattice distortions induced by temperature changes. There is only a small change in the [100] coefficient of thermal expansion, with the [010] and [001] directions being largely unaffected. Ausführliche Beschreibung