Abstract
X-ray total reflection by the surface of fibers produces strong streaks in the direction perpendicular to the fiber axis. In order to analyze higher-order crystalline structures in the fiber, the streaks overwhelm valuable scattering from the structures we intend to analyze. Shish-kebab structure is one of the most important higher-order crystalline structures because it plays a key role for imparting high strength to general fibers. It is known that the streaks due to the X-ray total reflection from the fiber surface can be eliminated by immersing fibers into a liquid of which electron density was matched to that of the PET fibers because the contrast between two neighboring objects is proportional to the square of the electron density difference between the two objects. For the sake of the precise structural analyses, we have conducted two-dimensional small-angle X-ray scattering (2d-SAXS) measurements at room temperature for poly(ethylene terephthalate) (PET) fibers prepared with high-speed melt spinning being immersed in non-solvent of which electron density was matched to that of the PET fibers. For this purpose, a bundle of the fibers was set in a quartz capillary of which axis is parallel to the fibers (the edge-view image). As a consequent, it was found that the spacing between the neighboring shish structures and that between the neighboring kebab structures were both increased with an increase in the spinning velocity. We also present a succeeded example of a sophisticated method for end-view 2d-SAXS measurements for the PET fibers dipped in the electron-density matching non-solvent, where the incident X-ray beam was exposed to the fibers from the direction parallel to the fiber axis. The result of this measurement was consistent with that of the measurements for the fibers in the quartz capillary.
