Anúncio
Monjurul sir-syllabus
Monjurul sir-syllabus
Monjurul sir-syllabus
Monjurul sir-syllabus
Anúncio
Monjurul sir-syllabus
Monjurul sir-syllabus
Monjurul sir-syllabus
Monjurul sir-syllabus
Monjurul sir-syllabus
Anúncio
Monjurul sir-syllabus
Monjurul sir-syllabus
Monjurul sir-syllabus
Monjurul sir-syllabus
Monjurul sir-syllabus
Anúncio
Monjurul sir-syllabus
Monjurul sir-syllabus
Monjurul sir-syllabus
Monjurul sir-syllabus
Monjurul sir-syllabus
Anúncio
Monjurul sir-syllabus
Monjurul sir-syllabus
Monjurul sir-syllabus
Monjurul sir-syllabus
Monjurul sir-syllabus
Anúncio
Monjurul sir-syllabus
Monjurul sir-syllabus
Próximos SlideShares
Fibre science ppt by b.aFibre science ppt by b.a
Carregando em ... 3
1 de 26
Anúncio

Mais conteúdo relacionado

Anúncio
Anúncio

Monjurul sir-syllabus

  1. Textile A term originally applied only to woven fabrics, but the term textiles are now also applied to fibers, filament, yarns and the products (natural or synthetic) of fibers. Fiber Fiber or fibre is a natural or synthetic substance that is significantly longer than its diameter. So, the material which has a high length to diameter ratio is known as fiber. Textile fiber Textile fiber can be spun into a yarn or made into a fabric by various methods including weaving, knitting, braiding and twisting. The essential requirements for fibers to be spun into yarn include high length to diameter (at least 1000:1), cohesiveness, flexibility, uniformity and sufficient strength. Other important properties include elasticity, fineness, uniformity, durability, luster etc. In another way, Any substance, natural or manufactured with a high length to diameter ratio and with suitable characteristics for being processed into fabric, the smallest component hair like in nature, that can be separated from a fabric. Classification of Textile fibers 1. Natural fibers: Fibers which grow or develop and come from natural resources like plant and animals. Example: Cotton, jute, flax, hemp, silk, wool etc Natural fibers may be classified as three types a) Animal fiber (Protein fiber) example: silk, wool, hair of camel, horse, goat. b) Vegetable fiber (Cellulosic fiber) Example: i) Seed fiber (cotton fiber), ii) Bast fiber (flax, jute, hemp) iii) Leaf fiber (Sisal, abaca) c) Mineral fiber Example: Asbestos Asbestos is the only naturally occurring mineral fiber that was used extensively for making industrial products but is now restricted due to its suspected carcinogenic effect. 2. Manufactured (or man-made) fibers:
  2. Fibers produced by industrial processes, whether from natural polymers transformed upon the action of chemical reagents (regenerated fibers) or through polymers obtained by chemical synthesis (synthetic fibers). Examples: Regenerated fibers: viscose rayon, acetate,triacetate, modal etc Synthetic fibers: Polyester, Nylon, acrylic, elastane etc. Length of Textile fiber All the fibers are classified according to their staple length into two categories, such as staple fiber and filament. Staple fiber It has limited length that varies according to the type, such as cotton, wool, jute etc. there are two types of staple fiber, one is short staple fiber and another is long staple fiber. Cotton is mainly short staple fiber and other maximum natural fibers are long staple except silk. Silk is only natural fiber that is filament. Filament A filament is a very long, continuous fiber strand of indefinite length. The length of filaments may range from a few hundred meters, as in the case of silk, to several kilometers in the case of man-made fibers. The thickness of filaments is similar to that of fibers. They exist either in monofilament or multifilament. Primary properties of Textile fiber 1. Length to diameter ratio This ratio decides suitability of a fiber for spinning into yarn, provided, it first meets the fiber length and thickness requirement. The smallest appropriate ratio of fiber length to fiber width (diameter) is about 350:1. Ratio less than this indicate a fiber which will not permit twisting of fiber into a yarn structure. But fiber ratio of 1000:1 or more spins into a useful yarn. Fiber shorter than 1.3 cm (1/2 inch) are seldom used in yarn manufacturing. 2. Cohesiveness With the current methods of yarn formation, stable fiber must be able to adhere to each other. This property is known as cohesiveness or spinning quality. The surface contours of fibers directly affect cohesiveness. 3. Strength A fiber must possess enough strength to with-stand processing by available textile machinery and provide the desire durability in its end use. 4. Tenacity or specific strength
  3. The tenacity of a material is the mass stress at break, the unit being, of course, g/denier or g/tex. An alternative term for tenacity is specific strength. In general strong fibers produce strong fabrics. 5. Flexibility The ability of a fiber to resist repeated bending or bowing without rupture is flexibility. 6. Uniformity: Fibers that are similar in length, strength, fineness, cohesiveness and flexibility can be processed together with less difficulty than can dissimilar fibers. Fibers conforming to the same specifications for those properties are said to exhibit uniformity. Secondary properties of Textile Fiber 1. Luster: The gloss, sheen, or shine of a fiber is referred to as its luster. The way in which light is reflected from the surface of the fiber determines the amount of luster observed. A round fiber is shiner than a fiber with irregular cross-section because we can see more of the light reflected by the round fiber. 2. Color: Although most are white and cream, fibers are available in a wide range of color. Wool may be off-white, tan, brown, gray, or black; cotton is usually white or cream, but there are brown varieties. 3. Moisture Absorption: The amount of water a fiber can absorb from the atmosphere or an immersion pool may affect apparel comfort, Fabric care, textile processing and fiber price. Fibers are usually categorized as hydrophilic, those that “like” or absorb water, and hydrophobic, those that “dislike” or do not absorb water. 4. Moisture Regain: Moisture regain is defined as the weight of water in a material expressed as a percentage of the oven dry weight. Fibers Moisture Regain (MR%) Cotton 8.5 Wool 15-18 Silk 11 Viscose 11 Nylon 4 Polyester 0.4 Jute 13.75 5. Moisture content: Moisture content is defined as the weight of water in a material expressed as a percentage of the total weight. Let, Oven dry weight = D, Weight of water = W, Moisture Regain = R, Moisture Content = M Then, R = W*100/D, M = W*100/(D+W). Why MR% is is different in different fibers? 6. Density: To compare substances of different volumes, it is important to express in volumetric units-for example g/cm3 . The term density means the mass per unit volume of a substance. The mass of most textile fibers is reported as density.
  4. 7. Fineness: Relative size, diameter and linear density are measures of fineness of the fiber. Cotton fiber fineness express in micronaire it means weight in microgram of one inch fiber. 8. Linear density: Linear density express in terms of denier, tex and decitex, is the most common method for comparing fiber fineness. Denier is the weight in grams of 9000 meters of fiber or yarn. It gives the fineness or coarseness of fibers. Small numbers refer to fine fibers; large number describes coarse fibers. It is related with end use of fiber. Tex is the weight in grams of 1000 meters of fiber or yarn. Organic cotton fiber Organic cotton fiber is the fiber that is grown without pesticides from plants which are not genetically modified. Though organic cotton has less environmental impact than conventional cotton, it costs more to produce. What is the difference between natural cotton and organic cotton? Organic cotton is grown from non genetically modified seeds. And the farmer didn't use synthetic fertilizers or pesticides on the cotton crop. Transition cotton Organic cotton must be grown in fields that have been free of synthetic pesticides and fertilizers for three years. As farmers switch over to and use organic farming methods the cotton grown during this three year period is called transition cotton. Wal-Mart has been purchasing millions of pounds of transition cotton. This has greatly help farmers to make the transition to organic farming methods. Green cotton Green or natural cotton is not organic. When you see cotton products labeled "natural", you are getting conventional cotton grown with large inputs of chemicals, pesticides, and herbicides to control weed growth. The only difference between green and conventional cottons, is in the processing: final product is not supposed to be treated with formaldehyde or chlorine bleach. Dye ability: Direct, Reactive, Vat dyes are used to dye cotton fiber. Mixing When same kind but different grades of fibres are mixed together then it is termed as mixing Example: mixing of Indian cotton fiber with American cotton fiber.
  5. Blending When different types of fibers are mixed together are within a particular ration then the mixture is known s blending. Example: Nylon and cotton Blending Polyester and nylon Blending Differences between mixing and blending Mixing Blending Here, same kind but different grades of fibres are mixed together. Here, different types of fibre are mixed together within a definite ratio. Example: Low graded cotton with high graded cotton Example: 35% polyester with 65% cotton Yarn count Count
  6. The yarn count is a numerical expression which defines its fineness or coarseness i.e. whether the yarn is thick or thin. A definition of yarn count is given by Textile Institute “count is a number indicating the mass per unit length or the length per unit mass of yarn”. Basically there are two types of yarn counting system – 1. Direct system: Tex, denier, pound per spyndle. 2. Indirect system: English, metric, worsted. 1. Direct system In this system the yarn count express the number of weight unit in one length unit. Thus higher the count, coarser the yarn. This is used for man made fibre such as polyester, nylon etc. Here, N = yarn count W = the weight of the sample L = the length of the sample l = the unit of the length of the system. Tex The yarn number or count in the tex system is the weight in grams of 1000m or 1 km or yarn. Denier The number or count in the denier system is the weight in grams of 9000m or 9km of yarn. 2. Indirect system: In this system the yarn count express the number of length unit in one weight unit. Thus higher the count, finer the yarn.
  7. Here, N = yarn count W = the weight of the sample L = the length of the sample w = the unit of the weight of the system l = the unit of the length of the system English It is defined as the number of hanks (840 yards) per pound. If one pound of yarn contains 20 hanks of 840 yards, then in English system count will be 201s or 20 Ne. it is denoted by Ne. Metric It is defined as the number of hanks (1000m) per kg. If one kg of yarn contains 40 hanks of 1000m, then in metric system count will be 40 Nm. It is denoted by Nm. Worsted It is defined as the number of hanks (560 yards) per pound. If one pound of yarn contains 20 hanks of 560 yards, then in worsted system count will be 20 worsted. The measurement of yarn number or count The yarn count can be measured by the following four systems. 1. Wrap reel and balance method (indirect reading balance). 2. Quadrant balance method (direct reading balance) 3. Knowles balance method (direct reading balance) 4. Beesleys balance method (special balance) Yarn Manufacturing Technology Flow chart of carded yarn production: Input Process/ Machine Output Bale → Blow room → Lap
  8. Lap → Carding m/c → Sliver Sliver → Breaker Draw Frame → Sliver Sliver → Finisher Draw Frame → Sliver Sliver → Roving Frame /Speed Frame/Simplex → Roving Roving → Ring Frame → Yarn Flow chart of combed yarn production: Input Process/ Machine Output Bale management ↓ Fibre → Blow room → Lap Lap → Carding m/c → Sliver Sliver → Pre comb drawing → Sliver Sliver → Lap former → Lap Lap → Combing → Sliver Sliver → Post comb drawing → Sliver Sliver → Simplex → Roving Roving → Ring Frame → Yarn Flow chart of Rotor yarn: Input Process/Machine Output Bale management ↓ Fibre → Blow room → Lap Lap → Carding m/c → Carded sliver Carded sliver → Draw frame → Drawn sliver
  9. Drawn sliver → Rotor spinning → Rotor yarn Bale management: Testing, sorting & mixing bales according to properties of fibre for producing specific good quality yarn at minimum cost is called “Bale management”. Importance of bale management: If bale management is absent-  Lot to lot variation will produce fabric barre effect.  After weaving, shade variation will be found in case of dyed fabric.  After knitting, colour variation may be found in case of dyed fabric. Mixing: If different grade of same fibres are kept together, then it is called mixing. e.g. 50% of 1 1 8  staple length of cotton + 50% of 1 1 4  staple length of cotton. Types of mixing: Volume mixing, Wt. mixing, Hand stock mixing., Bin mixing, Mixing by hopper, Lap mixing, Card mixing, Sliver mixing, Automatic mixing. Blending: When different fibres of different grades are kept together, then it is called blending. Blending is possible in different stages of Processes: Blending type Process stage Bale mixing - Before the blow room Flock mixing - Within the blow room Lap ,, - Using doubling scutchers Web ,, - At the ribbon lap m/c or the blending draw frame Sliver ,, - At the draw frame & sliver
  10. Blending type Process stage Lap or the comber Fibre ,, - At the card or Rotor spgn m/c Roving ,, - At the ring spgn m/c Blow Room: Blow Room consists of a number of machines used in succession to open and clean the cotton fiber to the required degree. 40 to 70% trash is removed in this section. Operation in Blow Room: I. Opening: a. To open the compressed bales of fibers & b. To make the cotton tuft a small size as much as possible. II. Cleaning: To remove the dirt, dust, a broken seed broken leafs, stalks and another foreign material from the fibers. III. Bending or Mixing: To make good value of yarn and to decrease the production cost by mixing different grade of fibers. IV. Lap forming: a. To transfer the opened and cleaned fibers into a sheet form of definite width and uniform unit length which is called lap. b. To roll the lap of predetermined length in a cylindrical shape around a lap pin. c. To transfer the lap from the lap pin to a rod to suitable handle and feed it to subsequence processing carding m/c. Objects or Functions of blow-room: The basic purpose of blow-room line is to supply following qualities of fiber tufts to the carding process.  Small fiber tufts  Homogeneously mixed or blended tufts
  11.  Clean fiber tufts  Convert fiber tufts into a fibrous sheet, is called lap. Action in blow-room: The actions of the machines in any blow room range fall into one or more of four main groups namely: 1. Action of opposite spike: (opening) The action of opposite spikes is opening the cotton fiber. By this action, the large pieces of cottons have been reduced in size. 2. Action of Air current: (Transport + Cleaning) During processing, the movement of cotton from machines to machine is done by air current. It also helps the separation of lint and trash. 3. Action of Beaters: (Cleaning & Opening) Beaters are responsible for removing almost all of the impurity extracted in the blow room. Beater also helps in opening of cotton fiber. 4. Action of regulating motion: (Uniform output) The action of regulating motion gives the uniform output of cotton fiber by the help of swing door and swing paddle Carding: Heart of Spinning: Carding is the one of the most important process in cotton spun yarn manufacturing, because it determine the quality of yarn. This is the process, by which fiber are prepared to manufacture a yarn. In this process, fibers are opened at almost single, removal of dust, trash, neps and short fiber to produce a continuous strand of fiber called sliver. Carding machine is called heart of spinning, because it prepares the fiber in such a way, which is ready to manufacture yarn because disentanglement, cleaning and intermixing of fiber are happened here. Objectives or Functions or Tasks of carding machine: 1. Opening the tufts into individual fibers and individualization of the cotton fiber at a single fiber staple state. 2. Elimination of Impurities and dust: Elimination of foreign matter occurs mainly in the region of the taker in. 3. Disentangling of neps i.e. removal of neps. 4. Elimination of short fibers. 5. Fiber blending. 6. Fiber orientation.
  12. 7. Finally produce a continuous strand of fibers called sliver of. Draw frame Drawing: It is a process of yarn manufacturing in which the sliver is elongated when passing through pairs of rollers, each pair faster than the previous one. This permits combination of several slivers and drawing and elongating them to straighten and to create greater uniformity. Necessity of draw frame or objectives of using Draw frame:  Crimped, curled and hooked fibers are straightened,  Parallelization of fibers,  Reduction of sliver weight per unit length,  Reduce irregularities of fibers by doubling and drafting,  Remove remaining dust from sliver,  Blending of fiber to provide compensation of raw material variation. To parallisation of fibre and blending carded→ Carded sliver. In carded sliver, fibre present in hook form i.e. trailing hooks and leading hooks. To parallel those hook, draw frame is used. Majority of the fibre hooks in a carded sliver are trailing while leading hooks are comparatively less. Trailing hooks are also known Major hooks. While leading hooks are known as Minor hooks. Tasks of draw frame: I) Equalizing. II) Parallelizing. III) Blending. IV) Dust removal.
  13. Actions involved in Draw frame: I) Drafting: The process of attenuating or increasing length per unit weight of sliver. It is mainly due to peripheral speed of the rollers. II) Doubling: The process of combing two or more carded sliver into a single form is called doubling. In draw frame m/c generally six slivers are fed and converted into one i.e. six doubling. III) Drawing: In the cotton Industry, the term is applied exclusively to processing on the draw frame, where the operation is one of doubling and drafting. Drawing = Drafting + Doubling. Combing: Combing may be defined as to removed of short fibres , neps and remaining impurities of card sliver by using comb with the help of knives , brushes and rollers. Objects of combing: 1. To remove short fibres below a pre selected length so that the spinner enables to produce finer/ better yarn. 2. To remove reps and foreign matter from the sliver. 3. With the help of drawing and doubling, combed sliver is uniform and the fibres are straight and parallel. 4. Improve the uniformity and strength of yarn 5. Improve yarn smoothness and lusture. 6. Reduce hairiness of yarn. Objects / Necessity of lap former: 1. To reduce the strain to delicate comber reduce. 2. To reduce fibre damage. 3. To reduce chance of good fibres waste. 4. To reduce short fibres. 5. To reduce thick and thin places in the sliver. 6. To control wastage. 7. To parallel and straight of fibre in corded sliver by changing pushing of fibres . 8. Not freely opening of fibre from sliver.
  14. M/c’s used for lap preparation : 1. Conventional system – i. Sliver lap m/c. ii. Ribbon lap m/c . 2. Modern System – 1) Super lap former Object of pre comb drawing:  To parallelize the hooked fibres  To reduce the loss of long fibres  To convert the leading hook into trailing hook  To remove short fibres Objects or functions of speed frame:  Attenuation of drawframe, sliver to form roving of required hank by drafting,  Insert small amount of twist to give required strength of roving,  Winding the twisted roving on to bobbin,  Build the roving in bobbin such a form, which will facilitate handling with drawing and transfer to the next process. Advantage of Ring spinning system:  Any type of material (fibre) can be spun  Wide range of count can be processed  It delivers a yarn with optimum characteristics.  Idealized twisting system  It is uncomplicated and easy to operate  Higher yarn strength can be achieved Disadvantage of Ring spinning system:  Low production  Machine generates more heat Limitations:  In ring spinning machine twisting and winding are done simultaneously. That’s why
  15. the power consumption is higher Operation involved in ring frame The Following Operation Are Involved: I Creeling II Drafting III Twisting IV Winding V Building VI Doffing Main Features of Rotor spinning process:  Yarn Coarser than carded or combed yarn  Low count. Generally 12 to 20 English count  Yarn Use for coarser fabric  Low manufacturing coast.  Produced by low graded fiber  High productivity  Less wastage percentage  No need of Simplex machine  Less labor  High capital cost  Mainly use to manufacturing Denim jeans fabric  Low price  Machine speed very high
  16. Wet Processing Technology Flow chart of wet process for woven fabric Grey Fabric Inspection & batching Singeing De-sizing Scouring Bleaching Mercerizing Dyeing Printing Finishing Final Inspection (QC) Ready for delivery Inspection: To check the fabric for naps, warp& weft missing, End breakage, Hole, Spot.
  17. Batching: To Weight the fabric according machine capacity on the basis of shade, yarn lot & production planning. Singeing: To remove the loose hairy fibers from woven fabric. De-sizing: To remove the size material. Scouring: To remove the impurities & increase fabric absorbency. Bleaching: To improve whiteness of fabric or yarn by destroying natural color. Coloration: Dyeing & printing. Finishing: To improve the overall quality & to satisfy the consumers. Steps of Wet processing Pretreatment Coloring Finishing 1. Singeing 1.Dyeing 1. Chemical finishing. 2. Desizing 2.Printing 2. Mechanical finishing. 3. Scouring 4. Bleaching 5. Mercerising.
  18. Singeing: Singeing is the process carried out to remove loose hairy fibres from surface of the yarn or fabric. It is necessary for level dyeing and to increase lusture of the fabric. It is generally carried out for woven fabric. Objects of singeing: 1. To remove loose hairy fibres from surface of yarn or fabric. 2. To obtain smooth surface. 3. To increase lusture of finished fabric. 4. For level dyeing and printing. Machines used for singeing: 1. Plate singeing machine. 2. Roller or Rotary cylinder singeing machine. 3. Gas or Flame singeing machine. Desizing: Desizing is the process of removal of size materials (starch, gum etc) from the warp yarn of woven fabric. Desizing is the first treatment of wet process in textile. Objectives of desizing: 1. To remove sizing materials from the warp yarn of woven fabric. 2. To increase absorbency of the fabric. 3. To reduce stiffness, 4. To make soft and pliable. 5. To make the fabric ready for the next process like scouring, bleaching, dyeing and printing.
  19. Chemicals used in desizing: a) amylase enzyme b) acid c) alkali d) water. Scouring: Scouring is the process where all natural and added impurities such as oil, wax, fat etc are removed to make hydrophilic and clean the textile materials. Objects of scouring: 1. To remove natural and added impurities such as oils, wax, fat etc. 2. To increase water absorbency of fabric or yarn without undergoing physical and chemical damage. 3. To produce clean material. 4. To make the fabric ready for uniform dyeing, printing and finishing. Chemicals used in scouring: 1. Alkali. 2. Wetting agent. 3. Detergent. 4. Sequestering agent. 5. leveling agent. Bleaching: Bleaching is the process for improving the whiteness of textile materials by removing the natural colouring matters. Bleaching produces a pure and permanent white effect on fabric which is suitable for level dyeing, and sharp printing. During bleaching it should be carefully observed that the bleaching agent does not reduce the tensile strength of fabric.
  20. Object: 1. Destruction of natural colouring matters from the fabric. 2. To impart a pure and permanent white effect to the fabric or yarn. 3. To obtain permanent white colour of the fabric or yarn. 4. To increase absorbency of textile material for uniform dyeing, printing and finishing. Bleaching agent: Substance which carry out the bleaching process is called bleaching agent. 1. Hydrogen per oxide, H2O2. 2. Bleaching powder, Ca(OCl)Cl,Ca(OH)2 3. Calcium hypochlorite, Ca(OCl)2. 4. Sodium hypochlorite, NaOCl. Mercerization: Mercerization is a physio-chemical treatment of cellulosic textiles in yarn or fabric form where it is treated with a concentrated solution of caustic alkali (550 – 650 Tw) at a temperature of 200 – 300 c. It is necessary to hold the fabric under tension and wash thoroughly while still under tension. Benefits obtained by mercerization: Mercerization is a beneficial process to cotton textile material except that it occurs shrinkage if it is not carried out under tension. The benefits obtained by mercerization are mentioned below: 1. improved tensile strength. 2. improved hygroscopicity. 3. improved dye affinity. 4. improved surface smoothness and handle. 5. improved lusture. 6. improved dimensional stability.
  21. Difference or Comparison between Dyeing and Printing: The differences between dyeing and printing are as below: Sl.No. Dyeing Printing 1 In dyeing process color is applied uniformly all over the fabric. In printing process, color is applied in one side according to the design only. 2 There is no localized application. There is localized application. 3 Color is applied in form of solution. Color is applied in form of thick paste. 4 Thickener is not used. Thickener must be used. 5 In dyeing process, color penetrates through the fabric. Color is applied only on the surface. 6 A particular temperature is maintained during dyeing process for knit fabric. There is no particular temperature controlling system in printing. 7 Generally after dyeing, steaming, and curing are not required for knit fabric. After printing, steaming and curing is must for fixing the dye molecules to the goods. 8 Huge amount of water is required. Less amount of water is used. Dyes A Dye is a coloring substance, either from natural or synthetic that imparts its color throughout a material by penetration. It is a colored, unsaturated organic chemical compound that is responsible for the color of dyed & printed textile materials. They are made to react with or deposit within a substrate in order to impart colour to that substrate with some degree of permanence. Dyes are soluble or dispersed in its medium of application (usually textiles) and are designed to be absorbed by that medium. Dyes can be formed synthetically from relatively cheap products where specific functional group in the dyes determines or affects the applicability & fastness. Pigment Pigment is a substance in particulate form which is substantially insoluble in a medium but which can be mechanically dispersed in that medium to modify its colour and light scattering properties. Pigment is a coloring matter, usually in the form of insoluble fine powder mostly from mineral origin & used from the earliest time for the coloration of metal, wood, stone & other surface as paints in association with oils or water & applied by means of a binding agent.
  22. Characteristics of dyes 1. Must have a chromophore group or ability to give color to a substance. 2. Must be soluble in water at some point or make a solution by any means. 3 must have substantivity or affinity for textile fibres. 4. Should have some good fastness properties. Differences between dyes and pigments The followings are the differences between dyes and pigments – Dyes Pigments 1. Most of the dyes can are organic compounds and some are inorganic. 2. Most of the pigments are inorganic mineral matters. 2. All dyestuffs are made by longer chemical reactions. So they are costly 2. Pigments are derived from mineral compounds. So they are cheap. 3. All dyestuffs are soluble in water. Some are insoluble. 3. Pigments are mostly insoluble but in some special cases soluble.
  23. Color Theory 1: Additiv e color Additiv e color u ses the primar y colors found in light (red, green and blue) and adds them together (i.e., combines them) to create all other colors. White results from combining red, green and blue light in equal intensities. The secondary colors of additive color are magenta, yellow and cyan. Red + Green = Yellow Red + Blue = Magenta Green + Blue = Cyan Color Theory 2: Subtractive Color Theory or pigment color theory Subtractive color is the basis for creating colors when mixing paint, dye or ink. Color is created when some wave lengths of light are subtracted (i.e., absorbed) while others are reflected. The color display on a surface (a wall, a piece of cloth, a sheet of paper) depends on which colors are reflected by it and therefore made visible. 4. Dyes contain both chromophore and auxochrome groups. 4. Pigments have chromophore groups but not have auxochrome group. 5. All types of fabric can not be dyed by dyestuffs. 5. Pigments can dye all types of fabric. 6. No binder is required for dyeing with dyes. 6. Binder is required for dyeing with pigment. 7. Dyes are absorbed by fabric. 7. Pigments diffuse on fabric surface.
  24. Printing Printing is the production of a design or motif on fabric or garments by the use of colorant and other chemicals in paste form in a predetermined pattern. Printing may be also regarded as localized area of dyeing. Thickener Thickener is the main ingredient of the print paste. It is a thick, viscose substance which imparts stickness to the print paste. The main functions and objects of a thickener are –  To maintain a sharp outline of printed design.  To prevent bleeding or spreading of color.  To prevent the premature reactions among the various chemicals of the print paste.  To hold the ingredients of the print paste on the surface of fabric and in print paste. Example: Na-alginate, fine gum, starch tragacanth, British gum, C.M.C etc. Printing paste The purpose of thickener is to produce a medium for the dye paste and the resultant product is called the printing paste. The printing paste is an emulsion of thickener and hydrocarbon (e.g. spirit or very light hydrocarbon oil) plus a surface active agent.
  25. Style of Printing: The different styles of printing are – 1. Direct style of printing 2. Discharge style of printing: a) white discharge, b) color discharge 3. Resist style of printing: a) white resist, b) color resist Methods of Printing: 1. Hand block printing 2. Hand screen printing 3. Semi-automatic screen printing 4. Automatic Screen printing 5. Rotary Screen Printing 6. Roller printing 7. Heat transfer printing 8. Ink jet printing Classification of different types of screen printing machines: There are four types of screen printing machines. They are – 1. Hand screen printing machine (flat) 2. Semiautomatic screen printing machine. 3. Automatic (fully) flat screen printing machine.
  26. 4. Rotary screen printing machine. Finishing: In broad sense all the processes after weaving or knitting fall in the wide range of finishing. It is a very wide range of operation carried out by 3 different stages as below: 1. First stage: pre-treatments such as scouring, bleaching, desizing etc. 2. Second stage: colouration such as dyeing, printing. 3. Third stage: finishing. This is the final stage of treatment of fabrics to prepare them for consumers, such as raising, calendaring and mercerizing. Objects or effects of finishing on fabric properties: By finishing the following effects are produced on fabric – 1. To improve the attractiveness. Fabric attractiveness is improved by the following ways – a) By modification of fabric appearance e.g. by calendaring, by using optical brightening agents etc. b) By alteration of fabric handle e.g. by softening, stiffening. c) By controlling fabric dimension e.g. by shrink resistant treatment, sanforizing, resin treatment, chemical setting. 2. To improve serviceability of fabric. Serviceability of fabric is related to weather, time, fashion, durability and many other aspects. It can be improved by different ways.
Anúncio