An Introduction to Textile Coloration

Name: An Introduction to Textile Coloration | Principles and Practice
Brand: Wiley
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Principles and Practice

Roger H. Wardman(Autor*in)

Wiley (Verlag)

Erschienen am 20. September 2017

376 Seiten

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Inhalt

Society of Dyers and Colourists xiii

Preface xv

1 General Chemistry Related to Textiles 1

1.1 Introduction 1

1.2 Atomic Structure 1

1.3 Periodic Table of the Elements 4

1.4 Valency and Bonding 6

1.4.1 Giving or Receiving of Electrons: Formation of Ionic Bonds 6

1.4.2 Sharing of Electrons: Formation of Covalent Bonds 8

1.4.3 Secondary Forces of Attraction 10

1.5 Chemical Reactions 13

1.5.1 Types of Chemical Reaction 13

1.5.2 Rates of Chemical Reactions and Chemical Equilibria 14

1.5.3 Effect of Temperature on Rate of Reaction 16

1.5.4 Catalysts 17

1.5.5 Thermodynamics of Reactions 19

1.5.5.1 The First Law of Thermodynamics 19

1.5.5.2 The Second Law of Thermodynamics 20

1.5.5.3 The Third Law of Thermodynamics 21

1.5.5.4 Free Energy 21

1.5.5.5 Interpreting Thermodynamic Data 22

1.6 Acids, Bases and Salts 23

1.6.1 Acids and Bases 23

1.6.2 The pH Scale 23

1.6.3 Salts and Salt Hydrolysis 24

1.6.4 Buffer Solutions 25

1.7 Redox Reactions 26

1.8 Organic Chemistry 27

1.8.1 The Hydrocarbons 27

1.8.1.1 Aliphatic Hydrocarbons 28

1.8.1.2 Aromatic Hydrocarbons 30

1.8.2 Functional Groups 32

1.8.3 Important Functional Groups of Aliphatic Compounds 32

1.8.3.1 Halides 32

1.8.3.2 Alcohols 33

1.8.3.3 Carboxylic Acids 34

1.8.3.4 Esters 35

1.8.3.5 Aldehydes and Ketones 36

1.8.3.6 Ethers 36

1.8.3.7 Amines 36

1.8.3.8 Cyano and Nitro Groups 38

1.8.4 Important Functional Groups of Aromatic Compounds 38

1.8.5 Important Compounds in Textile Dyeing 40

1.8.5.1 Sequestering Agents 40

1.8.5.2 Surface-Active Agents (Surfactants) 41

1.8.5.3 Carriers 42

1.9 The Use of Chemicals by Industry 43

1.9.1 Reach 43

1.9.2 Effluent Disposal 44

2 Textile Fibres 47

2.1 Introduction 47

2.2 Nature of Fibre-Forming Polymers 51

2.3 Properties of Textile Fibres 54

2.4 Mechanical Properties of Textile Fibres 54

2.4.1 Fibre Length 54

2.4.2 Fibre Fineness 54

2.4.3 Fibre Strength 55

2.5 Chemistry of the Main Fibre Types 57

2.5.1 Cellulosic Fibres 57

2.5.1.1 Cotton 57

2.5.1.2 Chemistry of Cotton 58

2.5.1.3 Morphology of Cotton 60

2.5.1.4 Properties of Cotton 62

2.5.1.5 Organic Cotton 64

2.5.2 Other Cellulosic Fibres 65

2.6 Protein Fibres 65

2.6.1 Wool 66

2.6.1.1 Chemistry of Wool 66

2.6.1.2 Morphology of Wool 70

2.6.1.3 Properties of Wool Fibres 72

2.6.1.4 Ecological Aspects 74

2.6.2 Hair Fibres 74

2.6.3 Silk 74

2.7 Regenerated Fibres 75

2.7.1 Early Developments 75

2.7.2 Viscose 76

2.7.3 Lyocell Fibres 77

2.7.4 Cellulose Acetate Fibres 79

2.7.5 Polylactic Acid Fibres 80

2.8 Synthetic Fibres 81

2.8.1 Condensation Polymers 82

2.8.1.1 Polyamide (Nylon) Fibres 82

2.8.1.2 Aramid Fibres 84

2.8.1.3 Polyester Fibres 85

2.8.1.4 Elastomeric Fibres 87

2.8.2 Addition Polymers 87

2.8.2.1 Polyolefin Fibres 87

2.8.2.2 Acrylic Fibres 89

2.9 Conversion of Synthetic Polymers into Fibre Filaments 90

2.10 Fibre Cross-Sectional Shapes 92

2.11 Microfibres 93

2.12 Absorbent Fibres 94

2.13 Drawing of Synthetic Fibre Filaments 94

2.14 Conversion of Man-Made Fibre Filaments to Staple 96

2.15 Imparting Texture to Synthetic Fibres 96

2.16 Fibre Blends 97

2.17 Textile Manufacturing 99

2.17.1 Yarns 99

2.17.2 Fabrics 99

2.17.2.1 Woven Fabrics 100

2.17.2.2 Knitted Fabrics 103

1
General Chemistry Related to Textiles

1.1 Introduction

This chapter provides a background to the chemical principles involved in coloration processes, which will be beneficial to those with little working knowledge of dyeing chemistry. Chemistry has been classically divided into three branches: inorganic chemistry, organic chemistry and physical chemistry. Inorganic chemistry is the study of elements and their compounds. However carbon is so unique in the breadth of the compounds it forms (chiefly with hydrogen, oxygen, nitrogen and, to a lesser extent, sulphur) that it has its own branch - organic chemistry. Physical chemistry is concerned with the influence of process conditions such as temperature, pressure, concentration and electrical potential on aspects of chemical reactions, such as how fast they proceed and the extent to which they occur.

There are no clear distinctions between the three branches. For example, organometallic compounds are important substances that combine organic and inorganic chemistry, and the principles of physical chemistry apply to these two branches as well. Fundamental to all these branches of chemistry is an understanding of the structure of matter, so the chapter begins with this important aspect.

1.2 Atomic Structure

Modern chemistry is based on the belief that all matter is built from a combination of exceedingly minute particles (atoms) of the various chemical elements. Many different elements are found in nature, each possessing characteristic properties; the atoms of any one element are all chemically identical. An element is a substance made up of only one type of atom, for example, carbon is only made up of carbon atoms, and sodium is only made up of sodium atoms. Atoms combine together to form molecules of chemical compounds. A molecule is the smallest particle of a chemical element or compound that has the chemical properties of that element or compound.

A single atom consists of a very dense central core or nucleus, which contains numbers of positively charged particles called protons and uncharged particles, called neutrons. Protons and neutrons have equal mass and together they account for the atom's mass. A number of very small negatively charged particles, called electrons, circulate around the nucleus in fixed orbits or 'shells', each orbit corresponding to a certain level of energy: the bigger the shell (the further away from the nucleus it is), the greater the energy. These shells are labelled n?=?1, 2, 3, etc., counting outwards from the nucleus, and each can hold a certain maximum number of electrons, given by 2n2. The movement of an electron from one energy level to another causes the absorption or emission of a definite amount of energy. Atoms are electrically neutral, so the number of electrons in an atom is exactly the same as the number of protons in its nucleus. The total number of electrons within an atom of a particular element is called the atomic number of the element. This is the same as the number of protons in its nucleus. It is the arrangement of the electrons around the nucleus of an atom that determines the chemical properties of an element, especially the electrons in the outermost shells.

It is possible that some of the atoms of an element have a different number of neutrons in their nucleus, but their numbers of protons and electrons are still the same. These atoms are called isotopes, and although they have the same chemical properties as the other atoms, their atomic masses are different. Also recent research into atomic structure has shown that the three subatomic particles are themselves made up of other smaller particles such as quarks, but for this book it is sufficient to only consider atoms in terms of protons, neutrons and electrons.

The simplest atom is that of hydrogen, which has a nucleus consisting of just one proton with one electron orbiting around it and has an atomic number of 1. In deuterium, an isotope of hydrogen, there is one neutron and one proton in its nucleus. So its atomic mass is 2, but its atomic number is still only 1. There are roughly 6400 atoms of 'normal' hydrogen for every atom of deuterium. Another example is chlorine, which has two stable isotopes - one with 18 neutrons and the other with 20 neutrons in the nucleus. Because each has 17 protons, their atomic weights (the combined weights of protons and neutrons) are 35 and 37, respectively. These two forms are labelled 35Cl and 37Cl. Approximately 75.8% of naturally occurring chlorine is 35Cl and 24.2% is 37Cl, and this is the reason why the periodic table of the elements shows the atomic weight of chlorine to be 35.45.

Within a shell there are orbitals, each of which can hold a maximum of two electrons. Within an orbital, the two electrons are distinguished by the fact that they are spinning around their own axis, but in opposite directions. In illustrating this diagrammatically the electrons in an orbital are often shown as upward and downward arrows , for example, as in Figure 1.3. The orbital nearest the nucleus is called an s orbital, followed by p, d and f orbitals, which are occupied in the larger atoms. These orbital types have different shapes. The s orbitals are spherical, whilst the p orbitals have two lobes and are dumbbell shaped. The three p orbitals are all perpendicular to each other, in x, y, z directions around the nucleus, so are often labelled px, py and pz (Figure 1.1). There are five d and seven f orbitals and these have more complex shapes.

Figure 1.1 The three p orbitals.

The first shell (n?=?1) can accommodate only two electrons (according to the 2n2 rule) and there is just the s orbital. The next element, that of atomic number 2 (helium), has two electrons, both occupying the s orbital. In lithium (atomic number 3), its first shell contains two s electrons, but because that is now full, the third electron goes into the s orbital of the next shell. This second shell (n?=?2) now fills up, and after the s orbital is full, further electrons go into the p orbitals, as shown in Table 1.1. The p orbitals can hold a maximum of six electrons and after they are full the third shell (n?=?3) begins to fill.

Table 1.1 Filling of the shells by electrons in the first 30 elements.

Atomic number Element Orbit, n 1 2 3 4 1 Hydrogen 1s 2 Helium 2s 3 Lithium 2s 1s 4 Beryllium 2s 2s 5 Boron 2s 2s 1p 6 Carbon 2s 2s 2p 7 Nitrogen 2s 2s 3p 8 Oxygen 2s 2s 4p 9 Fluorine 2s 2s 5p 10 Neon 2s 2s 6p 11 Sodium 2s 2s 6p 1s 12 Magnesium 2s 2s 6p 2s 13 Aluminium 2s 2s 6p 2s 1p 14 Silicon 2s 2s 6p 2s 2p 15 Phosphorus 2s 2s 6p 2s 3p 16 Sulphur 2s 2s 6p 2s 4p 17 Chlorine 2s 2s 6p 2s 5p 18 Argon 2s 2s 6p 2s 6p 19 Potassium 2s 2s 6p 2s 6p 1s 20 Calcium 2s 2s 6p 2s 6p 2s 21 Scandium 2s 2s 6p 2s 6p 1d 2s ? 30 Zinc 2s 2s 6p 2s 6p 10d 2s

Table 1.1 shows that once the three p orbitals of the third shell (n?=?3) are full in argon, the electron of the next element, potassium, goes into the fourth shell, instead of continuing to fill the third shell, which can hold a maximum of 18 electrons. However, after calcium, further electrons go into the third shell, into its d orbital, of which there are five, thus holding a total of 10 electrons. After the d orbitals are all filled, at zinc, further electrons then fill up the 4p orbitals from gallium to krypton. Thereafter electrons go on to occupy the 5th orbit in a similar...

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