Physical Structure of Synthetic Polymer Fibers

The chemical structure of synthetic fibers deals with how the atoms and repeating units are arranged in polymer ehains, while the physieal strueture addresses how the polymer chains are assembled to form fibers. In general, the ehemieal strae-ture determines the maximum potential a fiber ean achieve. However, the physical structure determines how well the potential actually is achieved in practice. The chemical structure affects the physical stracture of synthetic fibers. This chapter focuses on the physical structure of synthetic fibers. 

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Part 1 of this book focuses on the chemical and physical stmctrrres of fibers, and it starts with synthetic polymer fibers. The fundamental knowledge on the chemical structure of synthetic polymer fibers is essential for rmderstanding their physical structure and properties. The chemical structrrre, such as chain stmcture and configuration, of synthetic polymer fibers is determirred when the polymer is synthesized. In general, the process for making the polymer irrto fibers does rrot change the chemical structure. The chemical structure of synthetic polymer fibers... 

The chemical and physical structures of natural polymer fibers are more complex than those of synthetic polymer fibers. Two most important building imits for natural polymer fibers are cellulose and protein. Natural cellulose fibers come from the stringy portions of plants ranging from the fine seed fibers of the cotton plant to the coarse pineapple leaf fibers. Natural protein fibers are hairs of animals, like the sheep and the dehcate filaments spun by silkworms and insects. In addition to these natural fibers, manufactured cellulose and protein fibers also are based on natural biopolymers. Although these fibers are processed like synthetic polymer fibers, they are discussed in this book together with natural cellulose and protein fibers since they have similar chemical structures. The chemical and physical structures of natural polymer fibers are discussed in Chapters 4 and 5, respectively. 

The chemistry of synthetic polymers is similar to the chemistry of small molecules with the same functional groups, but the physical properties of polymers are greatly affected by size. Polymers can be classified by physical property into four groups thermoplastics, fibers, elastomers, and thermosetting resins. The properties of each group can be accounted for by the structure, the degree of crystallinity, and the amount of cross-Jinking they contain. 

The significance of synthetic polymers, on the other hand, lies more in their mechanical, electrical, or optical properties. Their use as raw materials for plastics, elastomers, or synthetic fibers is especially important. The chemical structure of these substances plays a subordinate role for their application, and it is desirable that such substances are as chemically inert as possible otherwise the useful properties could change unfavorably with time. Since the properties of plastics depend on physical quantities, the chemistry of synthetic macromolecules is bound inseparably to the physics and physical chemistry of such substances. Thus, a clear-cut division into pure preparative chemistry and pure physics of macromolecules is inadvisable. Macromolecular science represents a true interdisciplinary science. ... 

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. 

The more fundamental aspects of fiber constitution and behavior are dealt with in Astbury s Fundamentals of Fibre Structure 27) and Textile Fibres under the X-Rays 28), Hermans Contributions to the Physics of Cellulose Fibres 39), and Physics and Chemistry of Cellulose Fibres (40 Marsh s Textile Science (40 Preston s Fibre Science 59) and the High Polymers series of monographs, three of which are concerned with natural fibers—Volume IV, Natural and Synthetic High Polymers, by Kurt H. Meyer 53), Volume V, Cellulose and Cellulose Derivatives, edited by Emil Ott 56), and Volume VI, Mechanical Behavior of High Polymers, by Turner Alfrey, Jr. 21 ... 

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