Lecture 1A.pdf

Textile Science and clothing technology C34072/44072 Production and properties on natural and synthetic fibers, yarns, fabrics and apparels  What are Fibers? Fibers are the basic units of all textiles. Textiles are a form of cloth or f...

Textile Science and clothing technology C34072/44072 Production and properties on natural and synthetic fibers, yarns, fabrics and apparels  What are Fibers? Fibers are the basic units of all textiles. Textiles are a form of cloth or fabric from which clothing and other items are made. Fibers are put together to form a continuous strand, making a yarn. Yarns are woven or knitted together to make fabrics.  Textile Fibres and their properties Fibre properties Fibers contribute to fabrics performance. Form example strong fibres contribute to the durability of the fabrics. Absorbent fibers are used for apparel that comes in contact with the skin and for towels and diapers Fire resistant fibers are used for children’s sleepwear and firefighters To analyse and predict a fabric’s performance, start with the fibre. Knowledge of fiber properties will help you understand the fibres' contribution to the performance of a fabric and the product made form it. Fiber properties are determined by their physical structures, chemical composition and molecular arrangement  Fiber Characteristics Knowledge of fiber characteristics will help you select the right fabric for your needs. ▪ Strength: the ability to withstand pulling and twisting. Tensile strength ▪ Shrinkage: the ability to maintain size. ▪ Warmth: the ability to maintain body temperature. ▪ Durability: the ability to hold up to repeated usage. ▪ Absorbency: the ability to take in moisture. ▪ Wicking: the ability to pull moisture away from the body and toward the surface of the fabric where it can evaporate quickly. Fiber Characteristic Continued (2) ▪ Wrinkle Resistance: the ability to resist creasing. ▪ Resiliency: the ability to spring back when crushed or wrinkled. ▪ Elasticity: the ability to return to its original size. ▪ Shape Retention: the ability to retain the original shape. ▪ Abrasion Resistance: the ability to withstand rubbing. ▪ Luster: the natural sheen or shine of some fibers. ▪ Static Resistance: the ability to withstand the buildup of electricity. Fiber Characteristic Continued (2) ▪ Fiber length : Staple and filament fibers ▪ Fiber count: the yarn count is used to express how fine or coarse (or thin or thick) the yarn is. We use the English count numbering system, which is part of a larger group known as indirect counting systems. Denier, a unit of measure for the linear mass density of fibers, is the mass in grams per 9000 meters of the fiber Groups of Fibers There are two main groups of fibers. ▪Natural fibers which are made from natural sources—plants and animals. ▪Manufactured fibers which are made from chemicals in factories. What is textile : Textile fiber types Fibers are classified by their chemical origin, falling into two groups or families: natural fibers and manufactured fibers. General classification of fibers based on chemical composition of fibers Natural Fibers Natural Fibers The most common natural fibers are cotton, linen, wool, and silk. Natural fibers vary in quality depending on the kind of animal or plant and the growing conditions. The fibers must be cleaned before they can be made into yarns. Supplies of natural fibers vary, according to the season. They each have unique characteristics that cannot be copied by science. There are two categories of Natural Fibers: 1. Cellulosic Fibers 2. Protein Fibers Cellulosic Fibers Cotton Cellulosic Fibers come from plant sources. There are many kinds of cellulosic fibers, but few are used in fabric. Cotton, and flax are the main cellulosic fibers that are used in the fashion industry. Flax  Cotton fibers Cotton fiber length: Fiber length is critical in processing of fibers and yarns and in the translation of fiber strength to yarn strength. In general, a longer fiber length is preferred Textile fibers are either staple or filament length. Staple fibers range from 2 to 46 cm; filament fibers are of infinite length Staple length is reported as the average length of the longer half of the fibers (normally called “upper-half-mean” length), measured by clamping a fiber sample, then combing and brushing to make the fibers straight and parallel Cotton fiber staple length depend on the country of origin of cotton seed  Cotton fibers Under a microscope, a cotton fiber appears as a very fine, regular fiber, looking like a twisted ribbon or a collapsed and twisted tube. These twists are called convolutions It is widely used natural fiber It is a soft, fluffy staple fiber that grows in a boll, or protective capsule Cotton consists typically of between 88 to 96% cellulose with the rest being protein, pectic substances (congealed gum-like carbohydrates), ash and wax. After scouring and bleaching, cotton is then about 99 % cellulose. The fiber length varies with the type and quality, within the range 10 to 65 mm; the fiber diameter ranges from 11 to 22 μm Cotton is a relatively strong fiber with a strength of 25 to 35 cN/tex and a breaking elongation of 7 to 9 %. It is stronger when wet. Cotton also absorbs moisture readily, which makes cotton clothes comfortable to wear in warm weather (water retention of 50 %, moisture regain of 7 %)  Cotton fibers Physical structure of cotton fiber The typical components of dry mature cotton fibres are shown in Figs. Most of the non-cellulosic materials are present in the outer layers of cotton fibre  Cotton fibers Physical structure of cotton fiber Cotton fibre has a fibrillar structure which consists of a cuitical, primary wall, a secondary wall and a lumen Cotton fibres have a multi layered structure that has been studied for nearly a century. The structure of the primary cell wall of the cotton fibre, and particularly the outer surface layer (the cuticle), has a major influence on fibre properties, processing and use  Cotton fibers Physical structure of cotton fiber Under a microscope a cotton fibre looks like a twisted ribbon or a collapsed and twisted tube These twists are called convolutions: there are about 60 convolutions per centimetre. The convolutions give cotton an uneven fibre surface, which increases inter- fibre friction and enables fine cotton yarns of adequate strength to be spun. The cross-section of a cotton fibre is often described as being kidney-shaped.  Cotton fibers Physical structure of cotton fiber The primary wall comprises non-cellulosic materials and amorphous cellulose in which the fibrils are arranged in a criss-cross pattern Owing to the non-structured orientation of cellulose and non-cellulosic materials, the primary wall surface is unorganized and open. This gives flexibility to the primary wall, which is required during cell growth The basic ingredients responsible for the complicated interconnections in the primary wall are cellulose, hemicelluloses, pectins, proteins and ions The secondary wall, in which only crystalline cellulose is present, is highly ordered and has a compact structure with the cellulose fibrils lying parallel to one another  Cotton fibers Physical structure of cotton fiber Cellulose molecules in the cotton yarn is arranged as amorphous region and crystalline region The hydrogen bonding between molecules makes the cotton fabrics easy to crease Anti creasing finishes makes permeant intermolecular crosslinking which will block the hydrogen bong formation  Cotton fibers Physical structure of cotton fiber The outermost layer, the cuticle is a thin film of mostly fats and waxes. The waxy layer forms a thin sheet over the primary wall that forms grooves on the cotton surface  Cotton fibers Physical structure of cotton fiber SEM images of the different layers. (a) Fibres from desized cotton fabric; (b) amorphous wax surface of the desized cotton fibre; (c) network of primary wall of cotton fibre and (d) secondary wall of cotton fibre  Cotton fibers Amount Chemical Component (dry basis)% Main location Primary wall (%) composition of Cellulose 94 Secondary wall 48 cotton fiber Protein 1.3 Lumen 12 Pectin substance 0.9 Primary wall 12 Oil, fat & wax 0.6 Cuticle 7 Ash 1.2 3 Malic, citric and other organic 0.8 Lumen 14 acids Total sugar 0.3 Primary wall Pigment Trace Others 0.9  Cotton fibers Chemical composition Cellulose (approximately 90% of cotton composition): Cellulose content of the raw cotton fiber ranges from 88 to 96 %. Cellulose is a polymer of ß-D-glucose with a specific configuration shown in figure. The cellobiose, repeating unit of cellulose, consist of two beta glucose molecules linked together at the 1:4 carbon atoms. Each successive glucose unit is rotated 180 degree around the molecular axis. This gives a linear polymer chain that is almost flat therefore suitable for fiber formation. About 5000 cellobiose units are present in cotton that is degree of polymerization of cotton is 5000.