Principles of Spinning

Fibres and Blow Room Cotton Processing in Spinning

Ashok R. Khare

• Publisher: CRC Press
• Year: 2021
• Print ISBN: 9781138592919
• eBook ISBN: 9780429943409
• Topic: Technology & Engineering
• Subtopic: Materials Science
• Index: Technology & Engineering

Principles of Spinning: Fibres and Blow Room Cotton Processing begins by giving basic information about the various types of fibres (natural or artificial) used as raw materials in textile manufacture, for fibre-to-yarn conversion. This information includes essential and desirable fibre characteristics along with material on cotton-growing. The book offers a brief description of conventional methods of blow-room machinery, including shortcomings and aspects of automation. Many day-to-day examples that a spinner should know are presented, and the problems solved with an aim to give the reader an idea of how to use the various technical parameters in acquiring the required working data. The book focuses on blow room sequence of machines and its functioning.

Key features:

• Discussion of the role of electronics in management of various controls.
• Review of a practical perspective of modern techniques used in processing cotton through the blow room.
• An exclusive chapter on modern blow room concept.
• Solved examples and exercises.

This book is aimed at senior undergraduates and graduate students in textile engineering, staple fibre processing, and the spinning of staple fibres.

1 Fibres

1.1 History of Fibres

Hair-like material in a continuous filament form or in a discrete elongated form, similar in length to pieces of threads, is called ‘fibres’. It can be converted into indiscrete filaments, threads or ropes. These can be used as material in composites, and also matted into a sheet to make papers or felts. There are basically of three types: natural fibres, fibres extracted from cellulose and purely synthetic fibres. The earliest evidence of humans using fibres goes with the use of wool and flax fibres which, sometimes in the dyed form, were located in prehistoric caves.

Since ancient times, therefore, the art of making yarns and fabric-like wares is known. In those days, China and Japan were specialists in making very fine silk fabrics. It was reported that some of the garments made of silk were so fine that the whole garment could easily pass through a small orifice of a wedding ring. After using fibres of animal origin, humans started using fibres with vegetable origin, which were later converted into fabrics.

Though there are a number of fibres available in nature, only a limited number can be used to make textiles. Even then, technologists are continuously trying to add a few more fibres such as banana and pineapple at a regular pace into the textile world. However, the essential properties of all such new fibres (tensile strength fineness, pliability, softness) are not entirely favourable in all respects. Therefore, their commercial usage on a normal basis is not fully seen.

Broadly, fibres can be put into four categories depending upon their origin as Vegetable, Animal, Mineral and Artificial.

1.2 Natural Fibres

Vegetable Originated Fibres: They are available in nature in three styles.

1. Outgrowth over Seed: The first is fibres from seeds (in the form of seed hair). The cotton (often referred to as ‘King Cotton’) comes under this style and enjoys the best popularity worldwide.
2. Bast Fibres: These fibres are recovered from the inner bark of the stem of the plant. The fibres like jute, flax (linen), hemp and ramie come under this style.
3. Foliaceous Fibres: These are recovered from the leaves of plants. Sisal comes under this style.

1.3 Some Other Vegetable Originated Fibres

1. Fibres from Fruit: Fibres can be recovered from fruits; e.g. coconut has got hair-like growth on its surface. When these are removed, they can be used for making ropes.
2. Fibres from Stalk: They are actually stalks of plants, e.g. straws of wheat, rice, barley and crops including other crops like bamboo and grass. Even tree-wood falls under this category.

1.4 Fibres from Animals

They are in the form of hair (wool) or filament (silk). Human hair also falls under this category. However, its thickness and surface characteristics prohibit coherence to neighbouring fibres. Hence, it cannot be bundled into rope-like structure even though it is very strong.

1.5 Fibres from Minerals

In nature, fibres are available in the form of crust. One of the fibres known in this form is asbestos. The basic elements in asbestos are silica, magnesium, lime and oxides of iron. The fibre is very tough, flexible and comparatively longer. Owing to its non-inflammable nature, it has very high potential to be used in fire-resistant and fire-retardant materials or fabrics.

Filaments from Metals: Precious metals like silver and gold have been used in the form of very fine filament in textiles since medieval times. Such fabrics were customarily used by kings and queens and by many rich people. They add excellent ornamenting appearance, thus improving the value of the fabric. Glass, though brittle in nature, also gives useful fibres that have their special application in industry. In many instances, it is used as thermal insulation material.

1.6 Artificial Fibres

These can be further divided into (1) Regenerated fibres and (2) Synthetic fibres

1. Regenerated: Cellulose is available in nature in various forms. This cellulose is extracted, dissolved in suitable solvents and then regenerated in the form of fine filaments. Viscose is one such fibre that possesses lustre similar to silk.
2. Synthetics: There are large numbers of fibres made artificially by combining chemicals to produce long-chain polymers, which are then extruded in the form of finer filaments. Nylon, polyester, acrylic and polypropylene are some of the popular varieties. These fibres are basically manufactured with an aim to develop special properties. This is done by controlling their ingredients, technical parameters and process parameters during their manufacture.

1.7 Fibre as a Molecular Chain

Basically, any fibre is a giant molecule which makes it useful for textile purpose. The elements in this long-chain molecule are – Carbon, Hydrogen, Oxygen and Nitrogen. The cotton molecule has as many as 40,000–80,000 atoms. The Degree of Polymerization (DP), which is the measure of molecular weight, is the number of repeats of cellulose units that goes into making cotton fibre. The degree of polymerization is the number of monomers (base units) that are polymerized to form the polymer. For cotton, the degree of polymerization varies from 4,000 to 10,000.

Table 1.1
Degree of Polymerization⁶

Type of Fibres	Degree of Polymerization
Nylon 6	110–120
Nylon 6.6	190–200
Polyester (PET)	100–100
Polyacrilonitrile	2000–2050
Viscose rayon	150–350
Polynosics	700–1100
Cotton	4,000–10,000
Wool	60,000–100,000
Polyethylene (HDPE)	700–1,800
Ultra-high molecular weight polyethylene	100,000–250,000

During the process of manufacture of regenerated cellulose, special efforts are made to reduce DP to about 350 to make it soluble and ease the extrusion. It also controls the viscosity of the solution, thus minimizing mechanical difficulties during processing. It was found that the length of the cellulose molecule (DP), especially with cotton, is an important factor in deciding the physical properties of a fibre. In general, increasing degree of polymerization correlates with higher melting temperature and higher mechanical strength.

1.8 Vegetable Fibres

Fibres like cotton, jute, flax ramie, sisal and hemp are formed from cellulose. Such fibres serve in the manufacture of cloth and are also used in the paper industry. As mentioned earlier, they can be categorized as Seed Fibres (cotton and kapok), Leaf Fibres (fique, sisal and agave), Bast or Skin Fibres (flax, jute, kenaf, industrial hemp, ramie, rattan and vine fibres), Fruit Fibres (coconut-coir) and Stalk Fibres (stalks of wheat, rice, barley, bamboo, tree-wood and grass).

Figure 1.1 Classification of Textile Fibres (A)^4,6.

Figure 1.2 Classification of Textile Fibres (B)^4,6.

Classification of Fibres:^4,6 The most used vegetable fibers are cotton, flax and hemp, although sisal, jute, kenaf, bamboo and coconut are also widely used. Hemp fibers are mainly used for ropes and aerofoil, owing to their high suppleness. They have heat-resistant properties and are also used in the sanitary industry.

1.9 Importance of Fibre Quality

If a fibre has to be useful for its textile purpose, it should have certain physical and chemical properties. Thus, all the substances which look like fibre in nature cannot possibly be considered as textile material. In addition, a fibre must meet the demands of textile users. Also, if it has to be used in actual field applications, it must meet industrial demands.

In addition, fibres and their subsequent forms have to undergo various processing treatments. The conversion of fibre into yarn, for example, involves opening, cleaning, individualizing, and drafting the fibre strand to finally spin the yarn to the desired fineness. Similarly, the conversion of a yarn into a fabric also involves several processes. In all these, the fibres or yarns are subjected to varying stresses and strains. Further, during finishing, several chemical compounds are applied for imparting useful properties such as crease resistance, water proofing and fire retarding. Even after a finished fabric is suitably converted and used by the consumer, the fabric has to withstand washing, laundering, exposure to sunlight, perspiration and abrasion during its lifetime.

The fibres, therefore, must provide for all these, in the form of their strength, sustaining power to processing strain and destructive action of chemicals, sunlight and micro-organisms. For considering the fibres to be useful for their conversion into textile products, there are certain properties which are essential and certain properties which are desirable.

1.10 Essential Pre-Requisites

Fibre length, strength, cohesiveness and flexibility are the four essential fibre properties.

1. Fibre Length: This is the most important property, along with its strength. If a fibre is to be spun into yarn, there needs to be a minimum fibre length of 5 mm. It is because with the traditional spinning methods, it is not possible to spin the yarn below this length. The length alone does not suffice the purpose. In addition, its relation to fibre thickness is equally important. The length to diameter (thickness) ratio needs to be at least a hundred times. Many a time, another indicator called “uniformity ratio” is also used. It is the ratio of the mean length of the fibre (50% span length) to its upper half mean length (2.5% span length), expressed as percentage.
2. Fibre Strength: It gives the fibre the ability to withstand the stress-strain caused during its conversion to yarn and fabrics. Certain fibres such as Kapok not only have very short length but also lack adequate strength. The strength is measured as force per unit cross-section when fiber breaks and is expressed as g/d, g/tex or cN/tex. When the two different fibres are to be blended, it is very important to select the components so that they have matching stress-strain curves. When the yarns are spun with this criterion, the two component fibres share the load almost equally.
3. Fibre Cohesiveness: The fibres as a bundle finally make the yarn. The ability of the fibres to form the yarn depends upon their cohesive action to hold on to each other. In fact, it is the surface characteristics which give the frictional property to the fibres with which they are able to hold on to the other fibres. The cohesiveness appears in a different form. In cotton, it is due to natural convolutions during their growth. The crimp in the woollen fibres gives them this ability. In man-made fibres, however, this needs to be specially imparted. Viscose is manufactured with serrated cross-section, while polyester fibre is crimped. This is because uncrimped synthetic fibres, as it is, are quite smooth and rod-like structures. In this form, it is very difficult to make them hold together even when twisted.
4. Fibre Flexibility: One of the most important operations in yarn forming is twisting. It binds the fibres together to form a yarn having worthwhile strength. During twisting operations, the fibres are strained. The ability of the fibre to try to spring back is flexibility. It makes the fibre pliable.

1.11 Desirable Pre-Requisites

Apart from these essential properties, a fibre becomes more useful if it also has some desirable properties. Therefore, even when a yarn can be made with a fibre only having essential properties, a still better yarn can be made when it also possesses some of the following desirable properties.

1. Fineness: It is a measure of both the diametric size and linear density of the fibres. In the case of artificially manufactured fibres, the diameter of the fibre is proportional to linear density, except in the case of “hollow” fibres. With natural fibres, the fibre maturity governs the linear density, hence it is customary to define the fibre fineness in terms of weight per unit length with such fibres. The following are some of the units of measure:
   Micron: 10^‒4 cm, especially used in the case of wool fibres to specify diameter.
   Micronaire: It is another measure of judging both the fineness and maturity of the fibres.
   Micro-grammes per inch: 10^‒6 grammes per inch for expressing linear density.
   Tex or Denier - grammes per 1000 m or 9000 m, respectively. This unit is specially used for fibres and filaments
   There is a lot of variation in diameter (20–30% for wool or silk) in the case of natural fibres, whereas man-made fibres can be manufactured more precisely (3–5% variation only).
2. Colour: The colour of the cotton is judged by two parameters – Degree of Reflectance (Rd) and Yellowness (+b). While degree of reflectance shows the brightness, yellowness depicts the degree of cotton pigmentation. The colour gets affected by atmospheric conditions, impact of insects, fungi, type of soil and storage conditions. There are five recognized groups – White, Gray, Spotted, Tinged and Yellow-stained.
3. Resiliency: Fibres exhibit a beautiful property called resiliency. This is disclosed when a fibre is stressed. Here, they try to yield; and when the stress is removed, they try to spring back, i.e. recover their shape and size. Fibres like wool show excellent resilience. During the twisting operation, this property of resiliency becomes very useful when fibres try to regain their original state. Under this condition, a constant pressure is experienced by the inner mass of the fibres, and it helps in holding the inner mass and the peripheral fibres together.
4. Uniformity: The artificial fibres can be very precisely manufactured as for their weight per unit length and length itself. But, it is not s...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Contents
• List of Tables
• Preface
• Acknowledgments
• About the Author
• 1 Fibres
• Chapter 2 Cotton and Its Cultivation
• Chapter 3 Picking, Baling & Ginning
• 4 Cotton through Blow Room
• Chapter 5 Modern Blow Room Machinery
• 6 Defects in Blow Room Product & Machinery
• 7 Blow Room Calculations
• Index