Page 360 - Handbook of Properties of Textile and Technical Fibres

Regenerated cellulosic fibers 333

Figure 10.3 Regenerated cellulosic fibers produced with different technologies: (a) viscose,
(b) lyocell, and (c) Ioncell-F (produced with the ionic liquid [DBNH][OAc]).
(a) Image is courtesy Kelheim Fibres GmbH, (b) is courtesy Lenzing Aktiengesellschaft, and
(c) is reproduced from Hummel M, Michud A, Tanttu M, Asaadi S, Ma Y, Hauru LKJ,
Parviainen A, King AWT, Kilpel€ ainen I, Sixta H: Ionic liquids for the production of man-made
cellulosic fibers: opportunities and challenges. In Rojas OJ, editor: Cellulose chemistry and
properties: fibers, nanocelluloses and advanced materials, Cham, 2016, Springer International
Publishing with kind permission of the publisher.

fibrils, and this supports the above model (Lenz et al., 1988). The arrangement of poly-
mer chains in the fibrils range from highly ordered (“crystalline”) domains to highly
disordered (“noncrystalline” or “amorphous”) domains.
In the crystalline domains, the chains are arranged side-by-side in sheets, and the
sheets are arranged in stacks. There are interchain hydrogen bonds between the poly-
mer chains in sheets, and the sheets in stacks are linked by van der Waals forces.
Further, there are also intrachain hydrogen bonds between adjacent monomeric units
in chains. The patterns of inter- and intrachain hydrogen bonding differ. In regenerated
cellulosics, the adjacent monomeric units in the crystalline domains of chains are
linked by one hydrogen bond, whereas in native cellulosics, there exist two hydrogen
bonds between adjacent monomeric units (see Fig. 10.4). In regenerated cellulosics,
each polymer chain is linked by hydrogen bonds to four others in the sheets, whereas