Analysis of the heterogeneity of dry cellulose fibers by small-angle x-ray diffraction

We describe a technique for analysis of the specific internal surface area (SISA) of dry cellulose fibers by small-angle x-ray scattering, making it possible to rapidly evaluate the change in the polymer matrix — microvoid interface for cellulose-based materials when exposed to modifying factors. We demonstrate that treatment of cotton fibers with sodium hydroxide solutions, even under conditions ensuring exhaustive polymorphic conversion of the cellulose, leads to a decrease in SISA by only a factor of 1.16. This phenomenon is due to preservation of the fibril structure of the fibers upon mercerization. We show that dispersal of cotton fibers as a result of acid hydrolysis when microcrystalline cellulose is obtained leads to an increase in the specific internal surface area of the material by a factor of 1.32. The SISA of cotton is 7.6 times higher than the analogous parameter for viscose rayon fibers, for which during their synthesis the morphological structure of the natural material (and consequently also its microporous structure) is completely broken down.