Small-angle X-ray scattering of aramid fibre

Aramid fibres show elongated microvoids parallel to the direction of the fibre axis, resulting in an equatorial streak in the small-angle X-ray scattering (SAXS) pattern. The scattered intensity in the equatorial direction has been measured for three samples of the same fibre: an untreated yarn specimen, yarn in which Ag₂S was precipitated and a single filament of the latter. In the case of the untreated yarn, the interpretation of the SAXS pattern is hindered by the presence of residual water in the voids, resulting in a three-phase system. The SAXS pattern of the yarn with precipitated Ag₂S follows the theoretical pattern (adapted for the two-dimensional case) for a system with random pores, but the interface between aramid and Ag₂S shows fractal properties. The single filament with Ag₂S shows a SAXS pattern analogous to that of the fibre with Ag₂S, indicating that multiple scattering and interfilament scattering is negligible. It was also found that the Ag₂S precipitates in the fibre with preferred orientation.