Man-made cellulose fibers

Rayon. Virtually all current commercial production of man-made cellulosic fibers uses the viscose process, or some modification of it (19,20) (Fig. 1). The basis for this process is the formation of a metastable, water-soluble derivative from which cellulose can be regenerated after the filament is formed. Similar technology is used to manufacture cellophane film. Traditionally the process, as outlined in the following, is a batch operation involving discrete steps more recently semlcontinuous or continuous systems have been developed. 

Dissolution of cellulose has three major purposes. The first is to prepare regenerated and man-made cellulose fibers or films from cellulose solutions at the industrial level. Environmentally friendly and cost-profitable systems to dissolve and regenerate cellulose are now required. The second purpose is to use cellulose solutions as homogeneous reaction media during chemical modifications, which have been investigated at the laboratory level. The last one is to analyze cellulose samples. Molecular mass and molecular mass distribution studies using cellulose solutions are included in this category. Numerous cellulose solvents have, therefore, been developed and studied for these purposes. 

In the present chapter, rayon and other man-made cellulose fibers wUl be introduced in terms of properties and stracture. The compounding method to obtain the composites will be described briefly. PP-rayon composites will be considered in more detail as the practically most relevant class of this type of material at present arousing interest from the automotive industry. In another section rayon composites with poly(lactic acid) (PLA) and polyhydroxyalkanoates (PHA) will be studied as a promising bio-based and biodegradable alternative to conventional materials in durable applications, transport, and automotive industry. Finally, some concluding remarks will be given concerning future prospects of rayon reinforced thermoplastics and the problems to be tackled in future work. 

Table 18.1 Mechanical properties of typical man-made cellulose fibers from single fiber measurements...

Table 18.2 Crystallinity x, crystallite dimensions Duo, and Doo4, and crystalline orientation factor/c from X-ray diffraction for selected man-made cellulose fibers...

Table 18.3 Tensile strength and modulus, unnotched Oiarpy impact strength, and heat distortion temperature (HDT-A) for PP-man-made cellulose fiber ctnnposites showing ways to increase HDT Material Strength [MPa] Modulus [GPa] Charpy [kJ/m ] HDT-A [°C]...

The ground is laid for industrial use of man-made cellulose fibers for reinforcing a series of thermoplastics. Specific recipes, including processing aids, stabilizers, color master batches, etc., remain to be developed for possible applications in various sectors of the plastics industry. 

Khan MA, Ganster J, Fink H-P (2009) Hybrid composites of jute and man-made cellulose fibers with polypropylene by Injection molding. Compos A Appl Sci Manuf 40 846-851... 

Reinforcement of thermoplastic and thermosetting composites with cellulose fibers is increasingly regarded as an alternative to glass fiber reinforcement. The enviromnental issues in combination with their low cost have recently generated considerable interest in cellulose fibers such as isora, jute, flax, hemp, kenaf, pineapple leaf, and man-made cellulose fibers as fillers for polymer matrices-based composites. 

Graupner, N. (2009). Improvement of the Mechanical Properties of Biodegradable Hemp Fiber Reinforced Poly(lactic acid) (PLA) Composites by the Admixture of Man-made Cellulose Fibers. Journal of Composite Materials 43(6), 689-702. 

Cellulose 11 as the most important from a technical and commercial point of view is formed from cellulose I by precipitating cellulose firom solution into an aqueous medium at room or slightly elevated temperature, i.e., in technical spinning processes for man-made cellulose fibers. It is also obtained in the large-scale mer-cerization process of cotton, which proceeds via the formation of sodium cellulose by interaction of the polymer with aqueous sodium hydroxide and subsequent decomposition of this intermediate by neutralization or washing out of the sodium hydroxide. It is not yet understood how the parallel chain arrangement of cellulose I undergoes transition into the antiparallel orientation of cellulose II without an intermediate dispersion of cellulose molecules. The crystalline structure of cellulose I and cellulose 11 are shown in Fig. 2. 

In 1664, Robert Hooke, predicted that silk could be produced by artificial means but man-made cellulosic fibers were not produced until Count Chardonnet used the cuprammonia process to produce rayon in 1891. Viscose rayon was produced in the UoS. from cellulose xanthate in 1910 and is still in production. ... 

Cellulose II can be obtained by sweUing cellulose I samples with alkali (known as mercerization typically, 21.5% NaOH aq. solution at 20 °C for 24 h) or by regeneration from cellulose solutions into precipitates, which is the typical process for the technical spinning of man-made cellulose fibers. 

Figure 15.13 Life cycle of man-made cellulosic fibers.

Cellulose is a fibrous material of plant origin and the basis of all natural and man-made cellulosic fibers. The natural cellulosic fibers include eotton, flax, hemp, jute, and ramie. The major man-made cellulosic fiber is rayon, a fiber produced by regeneration of dissolved forms of cellulose. The cellulose acetates are organic esters of cellulose and will be discussed in Chapter 4. 

Synthetic and man-made Cellulose Fibers Regenerated cellulose (rayon fabric, cellophane) Polyacrylonitrile, polyamides (aliphatic (nylon), aromatic (aramid) fibers), polyester (PET), polytetrafluoroethylene, polyvinyl alcohol... 

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