Surface Structures of Regenerated Cellulose Fibers Observed by Atomic Force Microscopy.

Abstract

The surface morphology of various regenerated cellulose fibers was observed by atomic force microscopic method under dry and wet states. For Lyocel, long and slender microfibrils with ca. 10_??_20nm diameter were aligned along the fiber axis. Commercially available cupro (Cupro-1) had fibrils with ca. 80_??_200nm diameters. On the surface of anti-fibrillation type cupro (Cupro-2) and viscose rayon (Rayon), the well developed microfibrils were not clearly observed and anisotropy of the particles constructing the microfibril or aggregate was lower than those of Lyocel and Cupro-1. The tendency of fibrillation occurring under wet state was in the order of Lyocel>Cupro-1>Cupro-2_??_Rayon and this order was just corresponding to the degree of the anisotropy of the particles. The surface morphology was changed by wetting in the order of Rayon_??_Cupro-2>Cupro-1>Lyocel. The degree of connection of the particles along the fiber axis (DCP) was also in the latter order. The degree of crystalline orientation was just in reverse order. The decrease of the tensile strength by wetting was larger for the fiber with lower DCP. DCP and the anisotropy were considered to govern the lowering of the wet tensile strength and the fibrillation tendency for the regenerated cellulose fiber.