Introduction to Regenerated Cellulose Fibers

11.08.2015 Innovative Biofibers from Renewable Resources

Regenerated cellulose • Viscose • Rayon • Cellulose solvent

The production of regenerated cellulose fibers as early as the 1930s resulted in the generation of a new class of fibers. For several decades, the production of regenerated cellulose fibers such as viscose rayon and cuprammonium rayon was extensively done, and these fibers were considered to be ideal substitutes for the natural cellulose fibers. Traditionally, regenerated cellulose fibers were produced using wood as a source for cellulose. Regenerated cellulose fibers generally termed “rayon” were produced in various configurations and properties. Figure 15.1 depicts the cross section and Table 15.1 provides the properties of the different types of conventional regenerated cellulose fibers. As seen in the table, considerable variations in properties are observed depending on the cross section and the type (specifically degree of polymerization) of the cellulose used for fiber production. A rather distinguishing feature of the fibers which is also a major limitation of the regenerated cellulose fibers is their considerably lower wet strength compared to their dry strength, whereas the most common natural cellulose fiber cotton becomes stronger when wet. This unique behavior has been demonstrated to be mainly due to the poor crystallinity (30-35 %) of regular viscose fibers.

The advent of the relatively inexpensive synthetic fibers that also had good performance properties resulted in the gradual decline in the production of regenerated cellulose fibers. In addition, the production of regenerated cellulose fibers via the traditional xanthate process results in the generation of by-products that are harmful to the environment. Therefore, the production of regenerated cellulose fibers using the traditional approach is not being followed in developed countries. Although regenerated cellulose fibers are still being produced in considerable quantities, the raw materials used, the process of fiber production, and end uses have changed substantially. Modern methods of producing regenerated

Fig. 15.1 Type of cross-section of conventional regenerated cellulose fibers [95Woo, 01Sta]

cellulose are much more environmentally friendly and also use renewable raw materials. In this chapter, the new approaches of producing regenerated cellulose fibers, their advantages and limitations, and properties of the fibers produced are discussed in detail.