The Influence of Drawing on Solid Structure and Fibrillation Resistance of Cuprammonium Rayon(Cupro).

Abstract

An attempt was made to clarify the influence of drawing on solid structure and the fibrillation tendency for cuprammonium rayon, as a model of regenerated cellulose fibers. The drawing was carried out for the gel-like fiber obtained after coagulation (drawing at coagulation) and at the regeneration process of the coagulated fiber (drawing at regeneration). In the case of drawing at coagulation, the fibrillation tendency, degree of crystallite orientation (fc), and birefringence (Δn) increased, and the peak temperature of α2 dispersion (Tmaxα2) and tanαvalue (tanαmaxα2), which are the parameters representing the density and the amount of the amorphous region, respectively, decreased with drawing ratio. On the other hand, for drawing at regeneration, only fc showed very low drawing ratio dependence, while the influence of drawing on other factors was same as the case of the drawing of coagulation. The coagulated fiber with constant length showed remarkable stress relaxation at regeneration process. From these results we considered that in the case of drawing at coagulation, both crystal and amorphous phases increased in their orientation degree by drawing, because of the presence of network structure formed by cellulose-copper (II) complex. During the regeneration, such network structure is cleaved by the sulfric acid, as a regeneration reagent. Therefore the crystallization occurs under less tension than that at coagulation process and the drawing at this process may mainly lead to the orientation of cellulose molecules in amorphous region. The drawing at coagulation and regeneration processes was inferred to make remarkable break-down of bondings between fibrils, which may results in an increase of fibrillation tendency.