Crystallite regularity and void content in cellulose fibers as shown by small‐angle x‐ray scattering

Abstract

Abstract Long spacing order in the fiber axis direction is found for the majority of viscose rayon yarns, varying in repeat spacing from about 170 to 220 A. This order is interpreted as a regularity of crystallite placement such that the crystallites themselves act as diffracting centers to form a line lattice with long spacings. The diffraction found for different rayons varies in intensity and perfection as well as repeat spacing. This new structural feature can be related to the periodic length determined by the limiting degree of polymerization after hydrolysis. Current interpretations in the literature regarding the diffuse scattering at small angles are extended to include scattering due to micro‐voids or regions of low electron density. Since it is known that the materials are so dense that interparticle interference arises for the particle scattering, the reciprocity rule dictates that the voids are the source of the major amount of the scattering, not the crystallites. This interpretation is in agreement with the concepts of polymer structure from other techniques and can be used to explain the changes in scattering with swelling or the very small changes with crystallization. The micro‐voids are elongated in the fiber axes direction. For a dry cellulose fiber a distribution of sizes of the axes of the ellipsoidal voids can be obtained for relative comparisons.