Viscose rayon cross-section shape

The classification of viscose rayon fibers into different types is done mostly on the basis of physical and chemical properties. Fibers produced by nonviscose processes are usually identified separately. It has already been described how the fiber can be produced to have almost any desired structure, and it is considered to be the most versatile of all human-made fibers. It is available in various cross-sectional shapes, from multilobed, serrated, and round to flat longitudinally, it may be straight or curled (crimped). It comes in fine deniers... 

Rayon (left) has a lobed cross section which is typical for fibers spun industrially by the viscose process. In contrast, Lyocell (middle) displays a round shape similar to the cellulose carbamate example (right). (In all the micrographs, the dark streaks are overlaps of sample material caused by the cutting movement of the ultra microtome knife.) Cross sectional shape and pore structure are strongly dependent on the precipitation conditions. For NMMO fibers [11] it was shown that harsh precipitation with water gave dense, round structures while softer precipitation into alcohols lead to a skin-core stmcture with dense skin and a porous inner region. StiU, cross sections are round in contrast to viscose-ty fibers. 

Fig. 3.3 Different fiber cross-sectional shapes a Round nylon b Trilobal nylon c Round polyester with lower denier d Crenulated viscose rayon...

FIGURE 2.37 Typical cross-section of fibers produced by different spinning processes (a) melt-spun nylon from various shaped orifices (b) dry-spun cellulose acetate from round orifice (c) wet-spun viscose rayon from round orifice. 

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