Fiber-forming polymers

NH(CH2)5C0 4 with regular sequences of six carbon atoms between the nitrogen atoms. A nylon with two numbers is termed dyadic indicating that it contains both dibasic acid (or acid chloride) and diamine moieties, in which the first number represents the diamine and the second the diacid used in the synthesis. The monadic nylons have one number, indicating that synthesis involved only one type of monomer. This terminology means that a poly (a-amino acid) would be nylon-2. 

Terylene is an important polyester. It exhibits high resilience, durability, and low moisture absorption, properties that contribute to its desirable wash and wear characteristics. The harsh feel of the fiber, caused by the stiffness of the chain, is overcome by blending it with wool and cotton. 

The acrylics and modacrylics are among the most important of the amorphous fibers. They are based on the acrylonitrile unit —CH2CH(CN)— and are usually manufactured as copolymers. When the aaylonitrile content is 85% or higher, the polymer is an acrylic fiber but if this drops to between 35 and 85%, it is known as a modacrylic fiber. Vinyl chloride and vinylidene chloride are the most important comonomers, and the copolymers produce high-bulk yams, which can be subjected to a controlled shrinking process after fabrication. Once shmnk, the fibers are dimensionally stable. 

A polymer is characterized by its molecular and supramolecular structures. On the molecular level, the properties of polymeric materials are influenced mostly by the chemical composition of the polymer and its constituent monomers. In addition, in its condensed state the conformation and configuration of the polymeric chains are important factors in the polymer structure. On the supramolecular level, the properties of polymeric materials are further influenced by the three-dimensional arrangement of the polymeric chains. Some of the key issues concerning polymer structures are discussed below. 

Monomers and repeating units Monomers are the building blocks of a polymeric chain, and polymers are often named according to the type of the constituent monomer residues or repeating units. For example, the generic name for cellulose is poly-(l,4- 3-D-glucose), based on the fact that it is derived from o-glucose units finked 

Monomer arrangement in copolymers In a copolymer, the different types of monomers are distributed along the backbone in a number of ways. In a random copolymer the monomers distribute irregularly, while an alternating copolymer possesses regularly alternating monomer residues. Block copolymers have two or more homopolymer subunits linked by covalent bonds, while graft copolymers contain side chains attached to the main polymer chains. 

Polymer architecture A polymer s architecture affects many of its physical properties, including viscosity, solubility, glass transition temperature, etc. A variety of techniques may be employed for the synthesis of a polymeric material with a range of architectures, such as star polymers, comb polymers, brush polymers, deudrimers, etc. 

Chain conformation and configuration Conformation and configuration are used to describe the geometric structure of a polymer chain, with conformation referring to order that arises from the rotation of molecules around the single bonds, while configuration concerns the order that is determined by the various chemical bonds in a polymer chain. 

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Fiber stmcture is a dual or a balanced stmcture. Neither a completely amorphous stmcture nor a perfectly crystalline stmcture provides the balance of physical properties required in fibers. The formation and processing of fibers is designed to provide an optimal balance in terms of both stmcture and properties. Excellent discussions of the stmcture of fiber-forming polymers and general methods of the stmcture characterization are available (28—31). 

Table 2. Thermal Properties of Olefins and Other Fiber-Forming Polymers...

An alternative polymerization process utilizes a slurry of calcium chloride in NMP as the polymerization medium. The solubiHty of calcium chloride is only 6% at 20°C however, the salt continues to dissolve as conversion of monomers to polymer proceeds and calcium chloride/polyamide complexes are formed. Polymer molecular weight is further increased by the addition of /V, /V- dim ethyl a n i1 in e as an acid acceptor. This solvent system produces fiber-forming polymer of molecular weights comparable to that formed in HMPA/NMP. 

The properties of elastomeric materials are also greatly iafluenced by the presence of strong interchain, ie, iatermolecular, forces which can result ia the formation of crystalline domains. Thus the elastomeric properties are those of an amorphous material having weak interchain iateractions and hence no crystallisation. At the other extreme of polymer properties are fiber-forming polymers, such as nylon, which when properly oriented lead to the formation of permanent, crystalline fibers. In between these two extremes is a whole range of polymers, from purely amorphous elastomers to partially crystalline plastics, such as polyethylene, polypropylene, polycarbonates, etc. 

Microcrystalline, fllm-and fiber-forming polymer stable to water, hydro-phobic)... 

PET is not strictly Newtonian, or else it could not be fiber-forming. Polymers with the latter property develop increasing tension due to retraction forces as they become oriented, so that localized necks do not grow and become discontinuities. At high shear rates, molecular orientation will also reduce the resistance to shearing. 

In terms of copolymerization, the addition of a comonomer to a crystalline polymer usually causes a marked loss in crystallinity, unless the second monomer crystallizes isomorphously with the first. Crystallinity typically decreases very rapidly, accompanied by reductions in stiffness, hardness, and softening point, as relatively small amounts (10-20 mol%) of the second monomer are added. In many cases, a rigid, fiber-forming polymer is converted to a highly elastic, rubbery product by such minor... 

J. S. Robinson, cd., Fiber-Forming Polymers Recent Advances, Noyes, Park Ridge, N.J. (1980),... 

This work has demonstrated that we have been successful in extruding fibers from these polymer nanocomposites, knit them into textiles, and test their flammability. These prototype nanocomposite FR fiber-forming polymers and textile materials based upon them could be taken forward by interested parties for scale-up and commercial development. 

Bryce, D. J., and Greenwood, C. T. (1966). The thermal degradation of starch. Part 6. The pyrolysis of amylomaize starch in the presence of inorganic salts. In Thermoanalysis of Fibers and Fiber-Forming Polymers, Applied Polymer Symposium, Vol. 2, pp. 159-173. Interscience, New York. 

In a previous section, data and plots were given showing the rapid rise in consumption and production of manufactured fibers at the expense of natural fibers. The principal reason for this has been the wide range of manufactured fiber variants that can be produced from a single fiber-forming polymer. The wide range of polymers available, each with its particular properties, adds yet another dimension. This is not to say that there is only one type of cotton, wool, silk, or asbestos fiber there are many varieties of natural fibers, but their supply is limited by natural factors such as climate and genetics. The relative availabilities of manufactured fiber types can be altered by controlled chemical-process... 

Synthetic fibers are generally made from polymers whose chemical composition and geometry enhance intermolecular attractive forces and crystallization. A certain degree of moisture affinity is also desirable for wearer comfort in textile applications. The same chemical species can be used as a plastic, without fiber-like axial orientation. Thus most fiber forming polymers can also be used as plastics, with adjustment of molecular size if necessary to optimize properties for particular fabrication conditions and end u.ses. Not all plastics can form practical fibers, however, because the intermolecular forces or... 

Poly(ethylenoxy benzoate) is a fiber-forming polymer produced by the following sequence of reactions ... 

The behavior of polymethacrylonitrile (PMAN) fits into this picture. In contrast to PAN, PMAN is not a textile fiber forming polymer, despite the presence of the highly polar CN groups. An atom model representation of a PMAN chain shows... 

CARLSSON AND WILES UV Light oYi Fiber Forming Polymers 329... 

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