Fibres

12 Key excerpts on "Fibres"

• 

  eBook - ePub

  Medical Textile Materials

  • Yimin Qin(Author)
  • 2015(Publication Date)
  • Woodhead Publishing

    (Publisher)

  3

  A brief description of textile fibers

  Abstract

  Textile fibers are composed of polymers with many different structures, resulting in a diverse range of chemical, physical, and biological properties. This chapter offers a brief introduction to the general characteristics of polymers and polymeric materials, and classifies the main types of natural and chemical fibers. The physical, chemical, and biological properties of textile fibers are discussed, following an introduction of the chemical, physical, and morphological structures of textile fibers. Attempts are also made to summarize the many fiber-making methods, including solution wet spinning, solution dry spinning, melt spinning, electrospinning, gel spinning, etc.

  Keywords

  Chemical fiber; Electrospinning; Fiber-making method; Fiber property; Fiber structure; Polymer

  3.1. Introduction

  A textile fiber is a unit of matter, either natural or manufactured, that forms the basic element of fabrics and other textile structures. A fiber is characterized by having a length at least 100 times its diameter or width. Fibers can be spun into yarns or made into fabrics by various methods, including weaving, knitting, braiding, felting, and twisting. The essential requirements for fibers to be spun into yarns include a length of at least 5  mm, flexibility, cohesiveness, and sufficient strength. Other important properties are elasticity, fineness, uniformity, durability, and luster.

  3.2. Fiber-forming polymers

  Polymers are the basic constituent of textile fibers. A polymer is a large molecule composed of repeating structural units which are connected by covalent chemical bonds to form a long molecular chain. For example, cellulose is a natural polymer with each single molecule comprising hundreds of glucose monomers, while polyethylene is made of repeating units based on ethylene monomers. Polymers encompass a large class of compounds comprising both natural and synthetic materials with a wide variety of properties. Because of the extraordinary range of properties of polymeric materials, they play an essential and ubiquitous role in everyday life, ranging from synthetic plastics and elastomers to natural biopolymers such as nucleic acids and proteins that are essential for life. The three main forms of polymeric materials are plastics, rubber, and fibers, which can be made into a vast number of end products.

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  Handbook of Textile Fibres

  Man-Made Fibres

  • J Gordon Cook(Author)
  • 1984(Publication Date)
  • Woodhead Publishing

    (Publisher)

  INTRODUCTION FUNDAMENTALS OF FIBRE STRUCTURE During the last half-century, all the familiar materials that the world has been using for thousands of years have come under the microscope. Science has opened up a great era of exploration which is probing into the nature of material things. We want to know why different forms of matter behave as they do: and to fina our answers we have had to study the atoms and molecules from which materials are made. In this respect, natural Fibres have proved to be one of the most interesting fields of modern scientific research. As raw materials of one of the world's greatest industries, and as peculiar forms of matter in their own right, Fibres have long excited the curiosity of scientists. Now, research into the chemistry and physics of Fibres has provided a satisfying explanation of the unusual and invaluable properties that they possess. Thread-like Molecules All Fibres have been found to share one thing in common; the fundamental particles, the molecules, are always long and thread-like. That is to say, the molecules of fibrous matter are in the form of hundreds or even thousands of individual atoms strung together one after the other. The molecule of cellulose, for example, is built up by the plant from hundreds or more of small glucose molecules, each of which in turn contains six carbon atoms. The cellulose molecule, therefore, is in the form of a long thin chain of atoms. The molecules of a fibre are thus in shape very similar to the fibre itself. And just as the fibre bestows its characteristics on the yarn of which it forms a single strand, so does the fibre derive its properties from the thread-like molecules of the substance from which it is made. One of the most outstanding properties of a fibre is its strength. Relative to its cross-sectional area, the strength of a silk fibre, for example, is extraordinarily high.

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  Physical Properties of Textile Fibres

  • J. W. S. Hearle, W E Morton(Authors)
  • 2008(Publication Date)
  • Woodhead Publishing

    (Publisher)

  Fig. 1.4 , results in a moderately strong electrical interaction. In polyester Fibres, and others based on aromatic polymers, there is an interaction between benzene rings.

  1.4 Electric dipoles in the acrylonitrile side group.

  1.1.3 The nature of Fibres

  Fibres have been defined by the Textile Institute [3 ] as units of matter characterised by flexibility, fineness and a high ratio of length to thickness. To these characteristics might be added, if the fibre is to be of any use for general textile purposes, a sufficiently high temperature stability and a certain minimum strength and moderate extensibility.

  The characteristic dimensions of Fibres are the basis of their use and need to be stressed: individual Fibres (or elements of a continuous filament) weigh only a few micrograms, and their length/width ratio is at least 1000:1, so that a single cotton fibre scaled up to be as thick as a thumb would be 100 m long. In addition to the need to be made of materials that can be produced in this special form with adequate stability for use, ordinary textile Fibres must be, at least partly, elastic up to breaking extensions between 5 and 50%. This is an unusual intermediate range of extensibility, since glasses and crystalline solids are less extensible, whereas rubbers are much more extensible. The materials that meet these needs are almost all partially oriented, partially crystalline, linear polymers. A remarkable fact is that almost all the general textile fibre market is met by six polymer types: the natural polymers, cellulose and proteins , and the synthetic (manufactured) polymers, polyamide , polyester , polyolefin and vinyl (including acrylic).

  The above comments relate to Fibres for the traditional textile uses. More recently, a second generation of high-performance Fibres has been introduced for functional applications. They have high strength and low extensibility. Some of these are linear polymer Fibres. Others are inorganic networks, which, provided that they are fine enough, have the necessary flexibility. Glass and asbestos (which is no longer used because it is a health hazard) are the two older Fibres in this group. At the other extreme, elastomeric Fibres are used where a high stretch is specially needed.

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  Fibre Structure

  • J. W. S. Hearle, R. H. Peters, J. W. S. Hearle, R. H. Peters(Authors)
  • 2013(Publication Date)
  • Butterworth-Heinemann

    (Publisher)

  STRUCTURE, PROPERTIES, AND USES in round nylon Fibres as it is in triangular silk Fibres or in serrated viscose rayon Fibres. 19.2.8 Chemical properties Two factors determine the chemical behaviour of Fibres: the affinities of the chemical groups making up the fibre molecules, and Figure 19.14. Molecule of polytetrafluorethylene the openness of the structure. For example, the extreme inertness of Teflon Fibres, which makes them so suitable for such special purposes as filter fabrics for strong chemicals, is a consequence of the inertness of the polytetrafluoroethylene molecule, which in turn depends on its compact form {Figure 19.14) and favourable electronic arrangement. On the other hand, the dyeing of natural Fibres is helped by swelling them in water, thus separating the fibre molecules and allowing the dye molecules to penetrate more easily. 637 FIBRE STRUCTURE Textile chemistry is a subject in itself and only brief indications of its ramifications can be given here. Solubility of the polymer is important in determining the means of spinning man-made Fibres, and it gives to alginate Fibres their use as scaffolding threads during the weaving of very fine fabrics. Mercerization, a treatment with caustic soda, modifies the internal structure of cotton, decreases its crystallinity, transforms the cellulose I crystal structure into cellulose II, and causes important changes in the strength and lustre of yarns and fabrics. Other chemical modifications of cotton, such as acetyla-tion, may be used to increase its electrical resistance, improve its resistance to rotting, or reduce its tendency to soil: these processes have been extensively studied in recent years (11). In general, the resistance of a fibre to degradation due to attack by light, chemicals, insects, atmospheric conditions, or micro-organisms, depends on the chemistry of its molecules. However, it is probable that the most important chemical problem associated with Fibres is their dyeing.

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  Handbook of Properties of Textile and Technical Fibres

  • A. R. Bunsell(Author)
  • 2018(Publication Date)
  • Woodhead Publishing

    (Publisher)

  1

  Introduction to the science of fibers

  Anthony R. Bunsell     MINES ParisTech, Centre des Matériaux, Evry Cedex, France

  Abstract

  Fibers are a class of materials, which cover the whole range of the science of materials. Even though their properties vary enormously, they have much in common with one another. Most forms of materials can be found in fiber form, and when they do they generally possess enhanced properties of strength and often Young's modulus than in bulk form. This makes them very interesting as mechanical reinforcements. Some fibers, particularly natural fibers, only exist in fiber form and their remarkable properties whether mechanical or of texture have been used for centuries, but today many are finding increasing applications in mechanical applications as well as recapturing markets for textiles, which had been lost to synthetic fibers. Flexibility is a characteristic of all fibers, and it is intimately linked to their small diameters. This is clearly an advantage but also a problem when characterizing the fibers. Techniques have been developed over the last few decades, which give unprecedented access to understanding the characteristics of fibers. This introductory chapter covers these aspects of fiber characteristics and provides an easy access to data that are covered in greater detail in the succeeding chapters.

  Keywords

  Environment; Fineness; Properties of fibers; Property analysis; Synthetic and natural fibers; Units

  1.1. Introduction

  This book has the intention of presenting the science of fibers. It has been inspired by the first edition but has been greatly extended to cover a much larger number of fiber types as well as expanding the information on their properties (Bunsell, 2009 ). There are other books, of course, which have dealt with fibers, and the reader is referred to Morton & Hearle

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  Concise Encyclopedia of Composite Materials

  • Andreas Mortensen(Author)
  • 2006(Publication Date)
  • Elsevier Science

    (Publisher)

  Fibers and Fiber Types 1.1 Fibers as a Material Form Fibers, which are materials in a one-dimensional form characterized by flexibility, fineness, and high ratio of length to thickness (McIntyre and Daniels 1995), perform many functions in living organisms and are used in a wide variety of manufactured structures. A list of values of the fiber form, some of which are more relevant to other fiber uses than to textiles, includes: (i) Combination of flexibility with strength, in contrast to the usual association of stiffness and strength. (ii) Crack-stopping at the discontinuities, which gives strength to composites. (iii) High surface area, which is important in ab-sorption. (iv) Large included volume between fibers in tex-tile structures. (v) Continuity over long lengths, which is vital in optical fibers. (vi) Ability to form networks. (vii) Structural control: in natural fibers, by genet-ics; in manufactured fibers, due to the rapid heating, cooling, evaporation, and stress changes. (viii) Small defect size (less than fiber diameters), typified by the high strength of glass fibers. (ix) Ability to modify chemistry or introduce ad-ditives to give specific properties. (x) Control of end-use performance at several lev-els: chemical constitution, fiber fine structure, macro-scopic fiber form, yarn structure, fabric structure, etc. 1.2 Characteristic Features of Textile Fibers For clothing and household textiles, the common fiber requirements are: Appropriate dimensions: commonly, textile fibers are in the range 1–20 dtex, which gives diameters of 5–50 m m. Coarser forms, typically 0.1–1mm, are known as monofilaments. Microfibers , down to 0.1dtex ( B 3 m m diameter) or less, have been introduced in T * Cross references marked by an asterisk are included in this volume. # Cross references marked by a hash can be found by consulting the Encyclopedia of Materials: Science and Technology. 843

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  Structural Biological Materials

  Design and Structure-Property Relationships

  • M. Elices(Author)
  • 2000(Publication Date)
  • Pergamon

    (Publisher)

  Engineering with Fibers Passage contains an image

  Chapter 8

  Biological Fibrous Materials: Self-Assembled Structures and Optimised Properties

  Emily Renuart; Christopher Viney

  8.1 INTRODUCTION

  8.1.1 Background

  A great variety of Nature’s structural materials are deposited in fibrous form. Examples include: silk, keratin, collagen, viral spike proteins, tubulin and actin (all of which are proteins), cellulose and chitin (polysaccharides), and even mucin (a glycoprotein). All are characterised by hierarchical molecular order . As a result, the influence of individual molecules on bulk physical properties is exerted through the manner and patterns in which the molecules are able to self -assemble into larger structures. The liquid crystalline state (often supramolecular) plays a pivotal role in this self-assembly process (Neville 1993 ; Viney 1993 ; Viney 1997a ; Goodby 1998 ). Water is also significant, not just in maintaining the structural and functional integrity of some Fibres (e.g. in muscle or the cytoskeleton), but also in promoting liquid crystallinity and supramolecular self assembly (McGrath and Butler 1997 ).

  Hierarchical molecular order enables Fibres and other biological materials to exhibit several optimised properties simultaneously. Such a material is said to be multifunctional . The optimised properties need not all relate to mechanical behaviour; they include characteristics such as responsiveness to electrical stimuli (muscle Fibres), to chemical information (insect antennae) or to ambient water (capture threads in spider webs). Multifunctionality is possible because different features, at different length scales, can be tailored to optimise the different properties.

  The catalogue of fibre-forming biological polymers is extended if we include those that can be spun or drawn from solution artificially. Many derivatives and analogues of biological polymers are fibre-forming as well. Again, the liquid crystalline state and / or supramolecular assembly remain important to the process of fibre assembly, and so dictate final structures and properties. Included here are DNA (

  Strzelecka et al. 1988

  ;

  Reich et al. 1994

  ; Stryer 1995 ), filamentous phage and other viruses (Marvin 1966 ; Fraden 1995 ; Tang and Fraden 1995 ; Dogic and Fraden 1997 ), bacterial polyesters (

  Brandl et al. 1990

  ; Kemmish 1993 ), synthetic polypeptides such as PBLG [poly(γ-benzyl-L -glutamate)] (Robinson 1966 ;

  Horio et al. 1985

  ), cellulose derivatives (

  Atkins et al. 1980

  ; Gray 1983 ; Gilbert 1985 ), and chimeric systems in which very small amounts of a rodlike species can be used to impose molecular order on adsorbed molecular coils (Huber and Viney 1998

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  Handbook of Textile Fibres

  Natural Fibres

  • J Gordon Cook(Author)
  • 1984(Publication Date)
  • Woodhead Publishing

    (Publisher)

  Rayon, nylon and other man-made Fibres are being manufactured in enormous quan-tities and nature's monopoly of textile fibre production has been broken. xiv INTRODUCTION Today, the importance of research and scientific understanding in the textile industry is established. The Fibres on which the entire industry is based are the subject of a vast amount of academic and industrial research. Textile progress is no longer dependent simply on inventiveness and engineering skill; textile manufacture has be-come a modern scientific industry that must keep abreast of scientific progress and discovery. The 'big four' - cotton, wool, flax and silk - are still used more extensively than any other natural textile Fibres. But the manufac-ture of rayon and synthetic Fibres has attained the status of a major world industry, and output is increasing. Moreover, the discovery of nylon stimulated research on synthetic Fibres which has given us a range of synthetic Fibres which increases year by year. What is a Textile Fibre? The use of textiles for clothing and furnishing depends upon a unique combination of properties. Textiles are warm; they are soft to the touch; they are completely flexible and thus take up any desired shape without resistance; and they are usually hard-wearing. The reason for these properties is to be found in the structure of textile materials. Textiles are derived from threads or yarns which have been interlaced in one way or another. The threads them-selves are flexible, and in their loose interweaving they remain flexible, conferring this property on the-cloth itself. In their turn, the threads or yarns are built up by twisting to-gether the long, thin, flexible but strong things we call Fibres. Ultimately, therefore, the properties of any material must depend very largely on the properties of the Fibres from which it is made. The spinning and weaving processes obviously have their effect on the final textile.

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  eBook - ePub

  Textiles for Protection

  • Richard A. Scott(Author)
  • 2005(Publication Date)
  • Woodhead Publishing

    (Publisher)

  Horrocks and Anand (2000) .

  5.1.2 Units for fineness and mechanical properties

  The fineness of Fibres is most conveniently expressed in terms of their linear density (mass/length) and the preferred unit is tex, which is g/km (106 times the strict SI unit of kg/m). Area of cross-section is less easy to measure and in fibre assemblies is ill-defined because of the spaces between Fibres. It is therefore better to express mechanical properties on a mass basis and not on the area basis commonly used in physics and engineering. The unit for stiffness (modulus) and strength (tenacity) is N/tex, which equals kJ/g and (km/s)2 . The latter two units are interesting because they relate to two factors that give good ballistic impact resistance: the specific work of rupture (energy to break) is expressed in kJ/g; the wave velocity is the square root of modulus in N/tex or (km/s)2 . Conversion to conventional units of stress is through multiplication by density: GPa = (N/tex) × (g/cm3 ). Details of the many alternative units are given in an Appendix to High-performance Fibres (Hearle, 2000 ). Two convenient bench-marks are that high-tenacity forms of nylon and polyester Fibres approach 1 N/tex in strength and that the high-modulus variants of aramid Fibres have a stiffness of around 100 N/tex.

  5.1.3 Cellulosic, protein and synthetic ’textile’ Fibres

  Cotton and other Fibres from plants are composed of cellulose, which is laid down in helical forms in plant cells in the seed coats, stems or leaves of plants. The helix angle of 21°, the helix reversals and the convolutions in cotton give it a break extension of about 7% and a tenacity of 0.1 to 0.5 N/tex. Other cellulose Fibres, which stiffen the leaves or stems of plants, have a lower helix angle and are stronger and less extensible.

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  Regenerated Cellulose Fibres

  • C Woodings(Author)
  • 2001(Publication Date)
  • Woodhead Publishing

    (Publisher)

  8.1 Introduction Among all the textile Fibres, cellulose Fibres have the most diverse range of structures and properties. Even apart from the variety of natural cellulose Fibres, with their highly crystalline fibrillar structures in various helical forms of lay-down, the less highly ordered regenerated cellulose Fibres have many different structures, which lead to different properties and applications. The dominant method for manufacturing textile Fibres, typified by nylon, polyester and polypropylene, is now melt spinning, in which the structural formation is controlled only by molecular weight, extrusion, cooling and stretching. In contrast to this, the manufacture of cellulose Fibres is also controlled by two or three other factors: always by solvent and by the means of separation from solution, and, in some methods, by chemical reactions. The choice of manufacturing conditions among the large number of parameters involved leads to the diversity of structure and properties. Table 8.1 summarises the various modes of formation of cellulose Fibres that influence the resulting structure. Within each type, technical and eco-nomic factors lead to detailed differences both between different manu-facturers and over time, so that the information in this chapter must be regarded as general and not particular. Some processes which are no longer commercial are mentioned for their historical relevance and will be referred to briefly below when there are features of particular structural or property interest. Cuprammonium rayon has had a recent revival and the lyocell Fibres, such as Tencel “ , spun from organic solvents are growing in impor-tance. However, the various forms of viscose rayon remain the largest commercial types and will receive the greatest attention. Following the pro-duction of aramid Fibres, such as Kevlar and Twaron, from liquid crystal solutions, there has been research on the formation of high-modulus and high-tenacity cellulosic Fibres by similar methods.

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  An Introduction to Textile Coloration

  Principles and Practice

  • Roger H. Wardman(Author)
  • 2017(Publication Date)
  • Wiley

    (Publisher)

  At this stage it is impossible to change one physical property without affecting others, so the degree of stretch needs to be controlled. The close alignment of the polymer chains may allow some crystallinity to develop, and this increases the brittleness of the fibre. Although crystallinity increases the strength of the fibre, if the fibre becomes too crystalline, it will fracture when bent and will have poor abrasion resistance. The fibre will also be more difficult to dye or to be penetrated by chemical reagents or water (permeability to water is an important factor in the comfort of clothing).

  Thus by adjusting the draw ratio (the ratio of the final length to the original length), these various properties can be controlled to give Fibres with the characteristics required for their intended end use. In the final state therefore, the Fibres are composed of polymer chains aligned roughly parallel to the fibre axis with varying degrees of molecular order along the length of the fibre, ranging from crystalline to highly oriented non‐crystalline to areas of low orientation (Figure 2.17 ).

  Figure 2.17

  Changes in molecular orientation in filaments during drawing: (a) at the filament emerges from the spinneret, orientation is mainly random (amorphous); (b) on cooling and stretching some crystalline order appears, with a degree of general orientation along the fibre axis; (c) further stretching aligns amorphous and crystalline regions along the fibre axis.

  2.14 Conversion of Man‐Made Fibre Filaments to Staple

  Once the filaments have been obtained, they may be twisted together to form a yarn for use in knitting or weaving. Often however, the properties required for the yarn are better obtained using a staple fibre of a predetermined length, for example, for the purpose of blending with natural Fibres. The man‐made Fibres will be cut to correspond closely with the staple length of the natural fibre so that the blended Fibres can be processed easily on spinning machines to make yarns. For other purposes, such as the preparation of Fibres for flocking

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  Synthetic Fibres

  Nylon, Polyester, Acrylic, Polyolefin

  • J E McIntyre(Author)
  • 2004(Publication Date)
  • Woodhead Publishing

    (Publisher)

  Thus an understanding of the fibre properties is useful in appreciating the Nylon Fibres 51 characteristics of a yarn or fabric, but in itself it is not sufficient. Some properties may be modified by the presence of other Fibres or depend on the particular structure. The fibre properties do, however, give a limit to what is possible in a yarn or fabric; the strength of a yarn cannot be greater than that of the component Fibres. The mechanical properties of a nylon fibre cover a large number of attributes, all of which combine to determine the characteristics of the fibre. The most quoted attributes are the breaking stress and strain. Although these are important, in practice they do not give a realistic assessment of the performance of the textile material in use. Normally textiles are not stressed to the breaking point in use. The response of the fibre to low levels of stress or to repeated stress or to prolonged stress can also be important. In choosing a fibre for a particular application, the fibre whose attributes best fit the needs of the application needs to be determined. The effect on the fibre of small amounts of stress or strain and the extent to which any elongation is recovered are often of more interest than the breaking stress and strain. When a load is applied to a nylon fibre it will become elongated. The extent of the elongation will depend on the linear density of the fibre or yarn. A coarse fibre will be more resistant to elongation than a fine one. To standardise, the tensile stress on the fibre is expressed in terms of a 1 tex fibre as the load per unit linear density, with units of N tex –1 . The tensile strain is the elongation as a proportion of the original length of the fibre. As the fibre initially comes under load, then there will be a region of the stress–strain curve where the tensile strain is proportional to the tensile stress. The slope of the graph in this region is the initial modulus of the fibre.

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