Synthetic chemical fiber polyvinyl alcohol

Formation of condensation structures is the reason for gelation of solutions of various natural and synthetic polymers. Gelation may be accompanied by conformational changes of macromolecules, which occur in the case of gelling of gelatin and other biopolymers, or in the course of chemical reactions. For instance, according to Vlodavets, partial acetalization of polyvinyl alcohol with formaldehyde in acidic medium under the conditions of supersaturation yields fibers of polyvinyl formals which further undergo coalescence and form a network with properties similar to those of leather (and artificial leather substitute). 

The formation of condensation structures is the main cause for the gelling of solutions of various natural and synthetic polymers. Gel formation may be accompanied by conformational changes of the polymer molecules, as is the case with gelatin and other biopolymers, or by various chemical interactions. Such is the acid-catalyzed synthesis of synthetic leather by the partial acetylation of polyvinyl alcohol with formaldehyde. Under supersaturation conditions, the fibers of the polyvinyl formal form in this system and develop into the network structure of synthetic leather. 

Fibers from synthetic polymers make up approximately 80% of the total production of chemical fibers in Germany and about 90% worldwide (2000). The most important synthetic fibers are polyamide (Wulfhorst, 1997), polyester (Tetzlafi", 1997), and polyacrylonitrile (Wulfhorst, 1998). Because of their very specific properties, polyvinyl chloride (Koch, 1968), polytetrafluoroethylene, polyolefin fibers (such as polyethylene and polypropylene) (Wulfhorst, 1989b), and polyvinyl alcohol are used mostly for technical textiles. At the end of this section, an overview is given of synthetic polymers featuring the chemical structures, specific properties, and various applications (Table 2.7). The physical characteristics of chemical fibers from synthetic polymers are summarized later in Table 2.8. 

Manufactured protein fibers, often called azlons, are man-made fibers produced from animal or plant proteins. Examples of protein sources are milk, chicken feathers, soy beans, peanuts, corns, etc. Traditionally, most manufactured protein fibers were made directly from proteins dissolved in solvents. Recent trends in the research and development of manufactured protein fibers include the use of biochemistry to modify the source proteins and the introduction of synthetic polymers such as polyvinyl alcohol and polyacrylonitrile to improve the fiber mechanical properties. Antibacterial agents are often being added during the fiber formation process to provide health benefits to the manufactured protein fibers. As a result, the chemical structure of manufactured protein fibers is becoming more complex. 

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