Cuprammonium rayon

Abstract: Cellulose was dissolved rapidly in a NaOH/ thiourea aqueous solution (95:45 in wt-%) to prepare a transparent cellulose solution, which was employed, for the first time, to spin a new class of regenerated cellulose fibers by wet spinning The structure and mechanical properties of the resulting cellulose fibers were characterized, and compared with those of commercially available viscose rayon, cuprammonium rayon and Lyocell fibers The results from wide angle X-ray diffraction and CP/MAS 13 C NMR indicated that the novel cellulose fibers have a structure typical for a family II cellulose and possessed relatively high degrees of crystallinity Scanning electron microscopy (SEM) and optical microscopy images revealed that the cross-section of the fibers is circular, similar to natural silk The new fibers have higher molecular weights and better mechanical properties than those of viscose rayon This low-cost technology is simple, different from the polluting viscose process The dissolution and regeneration of the cellulose in the NaOH/ thiourea aqueous solutions were a physical process and a sol-gel transition rather than a chemical reaction, leading to the smoothness and luster of the fibers This work provides a potential application in the field of functional fiber manufacturing

Abstract: A method for obtaining the intrinsic dielectric constant and loss factor of dry cellulose fiber along the fiber axis was developed, and the dielectric properties of viscose rayon, Bemberg (cuprammonium rayon), and cotton sliver were measured over the frequency range from 500 cycles/sec. to 3 Mcycles/sec. and the temperature range from −60 to + 20°C. by using the mutual inductance bridge. Only one dispersion could be observed in this temperature and frequency range. Cole-Cole's circular are law could be satisfactorily applied to the data obtained, and the parameters of the are (ϵ0 – ϵ∞) and β for the three samples could be determined at each temperature. The value of (ϵ0 – ϵ∞), which is proportional to concentration of the dipoles contributing to the orientation, increased with rising temperature and reached a limiting value at about −20°C. The value of β relating to the width of the distribution of relaxation times also increased with rising temperature, showing a little rise in the degree of increase at temperatures above −20°C. On the other hand, the apparent activation energy for dipole orientation, as calculated from the temperature dependence of the dispersion frequency, reached a maximum around −20°C. All these facts suggest that some transition will take place in the neighborhood of −20°C. This temperature is not considered to be likely to be the glass transition temperature for dry cellulose, since −20°C. is too low for a primary transition in stiff molecules such as cellulose, and since the observed value of the apparent activation energy is too small to activate the segmental movement of the main chains. It might be possible to expect some secondary transition, probably of a thermodynamical nature, relating to the movement of local parts such as side chains, especially methylol groups on glucose residue, at about −20°C., though there is no other support for this expectation. Moreover, the effect of the fine structures on the dielectric properties is that the magnitude of (ϵ0 – ϵ∞) at each temperature decreases in the order, viscose rayon > Bemberg > cotton sliver, and this order parallels that of the accessibility of the three samples. This fact suggests that the dipoles in the amorphous region and on the surface of the crystallite provide the chief contribution to this dispersion.

Abstract: A novel cellulose solution, prepared by dissolving an alkali-soluble cellulose, which was obtained by the steam explosion treatment on almost pure natural cellulose (soft wood pulp), into the aqueous sodium hydroxide solution with specific concentration (9.1 wt %) was employed for the first time to prepare a new class of multifilament-type cellulose fiber. For this purpose a wet spinning system with acid coagulation bath was applied. The mechanical properties and structural characteristics of the resulting cellulose fibers were compared with those of regenerated cellulose fibers such as viscose rayon and cuprammonium rayon commercially available. X-ray analysis shows that the new cellulose fiber is crystallographically cellulose II, and its crystallinity is higher but its crystalline orientation is slightly lower than those of other commercial regenerated fibers. The degree of breakdown of intramolecular hydrogen bond at C3[Xam(C3)] of the cellulose fiber, as determined by solid-state cross-polarization magic-angle sample spinning (CP/MAS) 13C NMR, is much lower than other, and the NMR spectra of its dry and wet state were significantly different from each other, indicating that cellulose molecules in the new cellulose fiber are quite mobile when wet. This phenomenon has not been reported for so-called regenerated cellulose fibers.