Fibre structure synthetic fibres

As might be expected from the heterogeneous nature of their structure, synthetic fibres do not have a clearly defined melting point. Brown Textile Research Journal XXV, 1955, 891) investigated the phenomenon known as second order transition, or also as the glass rubber transition. His method was to record the stiffness of the fibre which is the load required to produce 1 per cent elongation multiplied by 100 divided by the denier of the sample at various temperatures. 

Polylactic acid (PLA), the structure of which is shown in Figure 7.10, is a polyester fibre in which there has been recent interest because of its environmental credentials. PLA may be derived from renewable resources, such as cornstarch, and it is biodegradable. PLA may be coloured using certain disperse dyes, although the dyes do not exhaust as well as on PET, mainly because of its aliphatic character. Acrylic fibres are synthetic fibres based essentially on the addition polymer polyacrylonitrile, the essential structure of which is illustrated in Figure 7.11. However, most acrylic fibres are rather more complex and contain within their structure anionic groups, most commonly sulfonate (-SOs ), but also carboxylate (-CO2 ) groups either as a result of the incorporation of co-polymerised monomers in... 

In man-made fibres, any stretching will irreversibly alter the crystallinity and there is no control of the lateral size of polymer crystals. Semicrystalline polymer networks typically consist of platelet type crystals whose width exceeds their thickness by several order of magnitudes because only the thickness is controlled by the chain folding [61]. In contrast to synthetic fibres, spider silk does not need any mechanical treatment by external forces the constituents self-assemble directly during the spinning-process. These examples clearly demonstrate the need for more detailed control of the mesoscopic structures for further development of man-made materials. 

The general properties of regenerated portein fibres include the wool like attributes of resilience, warmth and soft handle. The strength is lower than wool. These fibres do not contain cystine linkage, which results in more open structure. These fibres are far less successful than hoped and never seriously challanged wool. 1.7 Synthetic Fibres... 

Bicomponent fibres are sjmthetic fibres composed of two firmly but separately combined polymers of different chemical and physical structures. The structure of the bieomponent depends on the shape of the spinnerette orifice (side-by-side, sheath eore, matrix - fibril and multi-fibrillary) and the type of spinning method. Due to the structural differences, the two components shrink differently on heat treatment and form crimp and greater bulk in the fibre. The first fully synthetic bicomponent was an acrylic (Sayelle, Orion 21). The use of sheath-core fibres composed of nylon 6,6 and nylon 6 (Heterofil, ICI) for floor coverings is described. 

There are various kinds of synthetic fibres structurally with different melting points and with different heat-setting conditions. Even a slightest variations in heat-setting conditions, namely temperature, time and tension influence the setting effect, regardless of the system used. 

Effect of Heat-setting on Various Properties of Synthetic Fibres 8.7.1 Structural changes of polyester and nylon... 

The chemical weak spots and the corresponding types of damage vary greatly with synthetic fibres depending on their structure. Thus they are described in the next section in relation to the type of fibre. However, a general difference in chemical stability exists between fibres formed by polymerization or polycondensation. At extreme pH values polycondensate fibres are hydrolytically degraded, for example... 

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 ... 

To achieve these ends the new curricula placed particular emphasis on such concepts as periodicity and the mole. They also incorporated some major chemical ideas underlying the structure of materials, chemical bonding kinetics and energetics. These are some tunes referred to as concept-based which indicates the attention given to the principles of chemistry in their development. To make aware the students about the importance of chemistry topics like plastics, synthetic fibres, elastomers, detergents, drugs and insecticides were also included. 

NH4][N03] and [NH4]2[HP04] (which has the benefit of supplying both N and P nutrients) [NH4]2[S04] accounts for a smaller portion of the market. The remaining 12% of NH3 produced was used in the synthetic fibre industry (e.g. nylon-6, nylon-6,6 and rayon), manufacture of explosives (see structures 14.1 and 14.2), resins and miscellaneous chemicals. 

For the synthetic fibre poly(ethylene terephthalate) it is very important to impart antistatic properties to it [175]. Studies on the effect of the structure of cationic surfactants on the half-life time of static charge decay and surface resistivity (Rs) of PET fibres show best results with a methylated quarternary ammonium salt of a stearyl amine-ethylene oxide adduct or hydrochloride of a lauryl amine-EO adduct with 10 EO. 

Whereas several new products of chemical research, such as synthetic fibres and medical drugs, have appeared in everyday life, the production and use of these products has not been given a proper place in the curriculum. Since emphasis in the survey curriculum has always been on the scientific aspects of each topic, technology and its consequences for society are only discussed in the margin, say at the end of a chapter. In fact, by adopting, in the post-Sputnik period, the systematic nomenclature especially developed for scientific communication, the curriculum actually alienated students from the chemistry of everyday fife the name propanone may inform a student about the molecular structure of this substance, but it does not associate with the nail polish remover commonly known as acetone. 

Organic chemistry is the branch of chemistry in which covalent carbon compounds and their reactions are studied. A wide variety of classes of compounds such as vitamins, drugs, natural and synthetic fibres, as well as carbohydrates, peptides, and fats consist of organic molecules. Organic chemists determine the structures of organic molecules, study their various reactions, and develop procedures for the synthesis of organic substances. 

Figure 8.8 is the common method, which is clear for expression of the formulation of the curvature radius and undulation of the fibre in the textile structure, but it is not detailed enough compared to the observed properties of textile structures. Fibre sections are not perfectly circular as supposed in the schematic. They contain many irregularities. For a sample made from POFs, the fabric thickness h is smaller than the period of the POF crossing p, because the POF is a monofilament and harder than normal synthetic fibres. Therefore, the following equation is more adapted to woven OFs (Masuda et al., 2006) ... 

Low- and high-powered microscopes are used to examine the morphological features of the fibres and the initial determination of whether the fibre is natural or man-made. FTIR microscopy can be used on a synthetic fibre to provide information in relation to the functional groups present this can be used to pinpoint which synthetic fibre it is. Polarising light microscopy is used with synthetic fibres plane-polarised Ught interacts with the fibres in order to provide refractive index values (many of these fibres have two refractive indices due to the chemical structure of the fibre and are said to be birefringent). This helps in the identification of the synthetic fibre. 

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