Textile printing

Today's traditional textile and fashion market place is going through creative, technical and product development changes. Change is defined as verb meaning to make it different.

The five  printing methods are distinguished by the method of image transfer and by the ordinary types of image bearer employed. Depending upon the process, the printed design is transferred to the substrate either directly nor indirectly. In direct printing, the image carrier to the material, example of direct printing are, flexography, screen printing and letterpress printing processes. In indirect or offset printing the image is transferred so quickly.

Textile printing is the process of applying color to fabric. In printing block and stencils plates, rollers, are used to place colors on the fabric. To prevent the color from spreading by capillary attraction beyond the limits of the pattern or design.

 

Some techniques were separately fashionable in 19th century, since were combination techniques in which indigo resist was used to make blue background prefer to block printing of other colors. Most modern industrialized printing uses direct printing techniques.


The general theory of printing

The printing of textile materials is the application of color according to a predetermined design.
The printing paste which is applied to textile material consists of dye, water, thickener and hydrocarbon solvent or oil. After the printing paste is applied the textile material is usually steamed. This is to enable the dye molecules to migrate from the surface of the fibers and to enter the fiber polymer system. Steaming swells the fibers and ensures better penetration of the dye and improved color fastness properties of the textile material.

The general theory of printing explains the interaction, on steaming, between the dye, fiber, water, thickener and hydrocarbon solvent. More specifically, it explains how within the printing paste:
1) Forces are repulsion are developed between the dye molecules and the constituents of the printing paste; and
2) Forces of attraction are developed between the dye molecules and the fibers of the textile material to be printed.      

Textile orientation is an ancient art. It refers to the different processes by which fabrics are printed in colored design print fabric. Example of Greek fabrics from the 4th century B.C have been found. India exported block prints to the Mediterranean region in the 5th century B.C.

The invention of a dyed cotton fabric dating backward to the Indus Vally civilization demonstrates that the art of dyeing with the use of mordants was well known to the Indian dyers 5000 years ago. This form of dyeing was responsible for making India famous all over the world for its dyed and printed fabrics.

The dye molecule
The dye molecules are organic molecules which can be classified as:
1) Anionic - in which the color is caused by the anionic part of the dye molecule;
2) Cationic - in which the color is caused by the cationic part of the dye molecule;
3) Disperse - in which the color is caused by the whole molecule.
The first two molecule types are applied from an aqueous solution. This third is applied from an aqueous dispersion.

The role of the thickener

The purpose of the thickener is to produce a medium for the dye paste and resultant product is called the printing paste. The printing paste is an emulsion of thickener and hydrocarbon, such as white spirit or very light hydrocarbon oil, plus a surface active agent. This surface active agents enables the emulsification of the thickener with the hydrocarbon to form printing paste of uniform consistency. The uniform consistency of the printing paste is referred to as its viscosity. The viscosity of the printing paste is very important as it influences the clarity and appearance of the printed pattern. The success of printing textile materials depends very much on the type and quality of the thickener.

Thickeners can be any of the following:
1) Natural gums, such as gum arabic, acacia gums or gums prepared from starches and other polysaccharides;   
2) The man-made, natural polymer-based gums, for example, water soluble cellulose ethers, such as carboxymethyl cellulose, methyl and ethyl cellulose, and sodium alginate; or
3) Occasionally, made-made, synthetic compounds such as polyvinyl alcohol.

Methods of textile printing
         i) Hand printing
         ii) Block printing
         iii) Screen printing
         iv) Spray printing
         v) Kalamkari
         vi) Batik
         vii) Discharge printing
         viii) Tie and dye

The trying of cloth with thread and then dyeing it is the simplest and perhaps on the plain piece of cloth. It is also the earliest forms of decorated textiles.
The fabric is washed. Often it is dipped in the mordant so that it can absorb the dye.The cloth is folded, first lengthwise then width wise into four fold. The patterns on the body are then indicated all over the surface with the use of blocks dipped in grue, a red mud color. The cloth is then printed with the left hand, one knots follow another, using the same thread.     

 

Introduction with man made fibres and protein fibres

• Wool

Wool is a epidermal in origin. Wool fibers grows from the small follicle of the skin of sheep. The sheep are primarily raised where the climate permits them to winter in the open.

Wool may be sheared from the living animal or pulled from the hide after the animal has been slaughtered for its meat. Traditionally felts have been made from wool and from other animal hair fibers, all of which have an lubricated scale structure so that the frictional coefficient root to tip is much lower than in the tip to root direction the difference between the two being described as the directional frictional effect.

Chemical composition

Keratin-33%

Dust-26%

Suit-28%

Fat-12%
Mineral matter-1%

Classification by fleece

Lambs wool: The first fleece sheared from a lamb about six to eight. months old is known as lambs wool and some time referred to as fleece wool.
Hogget wool : comes from sheep twelve to fourteen months old that not been previously shorn.
Wether wool: Any fleece clipped after the first shearing is called wether wool.
Pulled wool: When sheeps are slaughtered for meat, their wool is pulled from the pelt by the use of chemical.

• Silk

The silk polymer is folded linear fibrin polymer. It has no crystalline linkage like wool polymer and has high degree of orientation. It contains anion acid.
Functional group -COHO, -CONH-

The techniques used to process these fibers in yarn are essentially the same as with natural fibers, modification have to be made as these fibers are of great length and have no texture such as the scales in cotton and wool that aid meshing.

Chemical composition
Fibrin-62.2-67%
Sericin-30%
Mineral matter-1%
Wax-0.5%

Silk scouring is know as degumming. The main impurities of silk is one kind of gum and this is soluble by hot soap solution. Alkali is made during soap washing. This alkali react with the carboxyl group of cericine and convert it into soluble form. This is the basic principle of silk scouring.

• Nylon

The term nylon was derived from 'no-run', the name originally considered by its inventors to emphasize the durability of ladies hosiery manufactured from it. The most important polyamide fiber is nylon 6.6, that is polyhexamethylene adipamide. Nylon 6 is the second most important polyamide fiber. It is extruded from polycaprolactam.  The notation 6 denotes that only one monomer containing six carbon atoms is required to polymerize this type of nylon.

Chemical effect: 

Effect of acids: Nylon is less resistant to acids than it is to alkalies. The  amide groups in the nylon polymers are readily hydrolyzed under acidic conditions.


Effect of alkalies: Prolonged and frequent exposure to alkalies will cause significant alkali hydrolysis of nylon polymers.This is noticed as a weakening of the nylon textile material. 

• Polyester

The word ester is the name given to salts formed from the reaction between an alcohol and an acid. Esters are organic salts and polyester means many organic salts. Polyester is a man made, synthetic polymer, polyester filament or staple fiber. The most common polyester apparel or staple fiber is usually composed of ployetylene terephthalate polymers.

Chemical properties:

Effect of acids: The ester groups of the polyester polymers resistant to acid hydrolysis, as are the other chemical groups of the fiber polymer. This resistance is further enhanced by the extreme crystallinity of the polyester polymer system which prevents the entry of any acid and water molecules into the filament of staple fiber. 

Effect of alkalis: Alkaline conditions as encountered during laundering may hydrolyse the polyester polymers at their ester groups. The extreme crystallinity of the polyester polymer restricts the hydrolysis to the surface of the polyester filament or staple fiber.

Effect of bleaches: Normally polyester textile materials do not need to be bleached. If  bleaching is required this is effected using sodium chlorite.    

• Acrylic

    The term acrylic is derived from the Latin word acryl, which means bitter, irritating or pungent and descriptive of the compound, acrylic acid. Acrylonitrile is chemically related to acrylic acid and the term acrylic is short  for polyacrylonitrile.    
The acrylic fibers are man made, synthetic polymer based, polyacrylonitrile filaments or staple fibres. They are divided into two types:
1) Polyacrylonitrile fibers are generally referred to as the acrylic fibers.
2) Modified polyacrylonitrile fibers generally referred to as the modacrylic fibers.

Chemical composition: 


Effect of acids: The acrylic fibers are resistant to acids because their polymers do not contain any chemical groups which will attract or react with acid radicals.

Effect of alkalis: The very crystalline nature of the acrylic polymer system prevents the ready entry of alkaline substances. However, surface alkaline hydrolysis or surface saponification will occur.


Effect of bleaches: Acrylic fibers are not usually bleached in practice. As a result, little is known about the effect of bleaches on acrylic polymers.

Yarn production from cotton

Harvesting
The cotton plant grows best in light loamy soil in areas with plentiful rainfall or irrigation and a long growing season. The seeds are usually shown by machine, in a continuous stream in row three to four feet apart. When the plants are a few inch high, the rows must be thinned by cutting out the undesired plants.
Upland cotton grows to a height of about four feet and blooms two to three months after planting.

Ginning
From the feild seed cotton moves to nearby gins for separation of lint and seed. The cotton first goes through dryers to reduce moisture content and then through cleaning equipment to remove foreign matter. This operation facilitate processing and improve fibre quality. The cotton is then air conveyed to gin stands where revolving circular saws pull the lint through closely spaced ribs that prevent the seed from passing through.
A typical gin will process about 12 bales per hour, while some of today's more modern gins may process as many as 60 bales an hour.

Object of ginning:
        i)  To separate fibers fully from its seeds.
          ii) To collect seeds and waste together.
          iii) To collect fiber without any faults.
          iv) To separate whole fiber.

Types of ginning:
1) Saw ginning.
2) Roller ginning
3) McCarthy ginning 

Importance of fiber properties in cotton spinning

1) Fiber fineness: Fineness is one of the most important parameter  determining the yarn quality characteristics. Fiber fineness influences the number of fibers in the cross section of yarn.

2) Maturity : The maturity of cotton is defined in terms of the development of cell wall. A fully mature fiber has a well developed thick cell wall.

3) Fiber length: The average length of spinnable fiber is called staple length. Staple length is also one of the most  important fiber characteristics.

4) Length uniformity: Length uniformity influences on-

                   Yarn irregulrrity
                    Ends down
                    High wastage in combing
5) Strength: Toughness of fiber has a direct effect on yarn and fabric strength.

6) Color: Color is particularly important as a measure of how well a yarn or fabric will dye or bleach.

7) Fiber elongation: Elongation is specified as a percentage of the starting length. The elastic elongation is of decisive importance since textile products without elasticity would hardly be usable.

Yarn production

Cotton is grown anywhere with long, hot dry summers with plenty of sunshine and low humidity.

When the plants are a few inch high, the rows must be thinned by cutting out the undesired plants.
Upland cotton grows to a height of about four feet and blooms two to three month after planting. When they fall off, the boll begins to develop. These seeds or bolls contain the seeds to which the fibers are attached. When the cotton must be picked soon after the bolls open to prevent the fibers from beaming discolores and dirty from exposure to the sun and weather.
Modernization efforts have brought major changes to the textile industry. Equipment has been streamlined and many operations have been fully operated with computers. Machine speeds have greatly increased.

Mixing: 
Mixing is done for the same kind of fibers e.g, cotton and cotton fibers of different grades or origin.

Blending:
Blending is  the mixing of two or more different fibers e.g, polyester and cotton fiber mixing.

Yarn preparation from fiber

The blow room contributes only about 5-10% to production cost in the ring spinning mill. From a cost accounting point of view, the installation itself is not a relevant cost factor; however the loss of raw materials that arises here is a factor. Blow room machines must eliminate foreign matter, but they can do this only with the simultaneous elimination of some of the good fibers.

The proverbs of the expert- 'The card is the heart of the spinning mill' and ' well carded is half spun'- demonstrate the immense significance of carding for the final result of the spinning operation.. The importance of carding is still greater where new spinning systems are concerned. The considerable influence of the card on yarn quality arises from the vary complex series of events in the process itself.

Within the overall spinning process, the combing operation serves to improve the raw material. Its use in production of medium, medium-fine and fine yarns enable a positive influences to be exerted primarily on the following yarn characteristics: 

• Yarn evenness
• Strength
• Cleanness
• Smoothness 
• Visual appearance                                                                                                                                                     From a purely commercial viewpoint the draw frame is of little significance- it usually contributes less than 5% to production costs of the yarn. However, its influence on quality, especially evenness, is all the greater for this. Further, if the draw frame is not properly adjusted, there will also be effects on yarn strength and elongation.                                                                                                                                                                                                                                                                                  The draw frame produces a sliver that already exhibits all the characteristics required for the creation of the yarn, namely an ordered, clean strands of fibers lying parallel to another. It is a fair question to ask why this sliver is not used as in feed material for the ring spinning machine., instead of being processed in an expensive manner to create a roving as feed for spinning.                                                                                                                                                                                                                         The ring spinning machine was invented in the year 1828 by the American Thorp. In 1830, another American, Jenk contributed the traveler rotating on the ring. In the more than 150 years that have passed since that time, the machine has experienced considerable modification in detail, but the basic concept has remained unchanged.                                                             

Yarn manufacturing

Yarn is a long continuous length of inter-locked fibers suitable for use is the production textiles.
Yarn may be defined as arrangement of fibers uniformly to a continuous mass of fiber bound together by trust. The yarn may be spun from staple fiber or continuous filaments.
A genetic term for a continuous strand spun from a group of natural or synthetic staple fibers or filaments used in weaving, knitting to torn fabric.

        Classification of yarn
Yarn can be classified according to

a) Length of fiber
         i) Spun yarn-- Short staple, Long staple
         ii) Filament yarn-- Mono filament, Multi filament
b) No of strand
         i) Single yarn
         ii) Double yarn or ply yarn
         iii) Cable yarn

• Ply yarn

All yarns are single ply unless twisted with another yarns. Terms used are two ply if two yarns are twisted together and three ply if three yarns are twisted together.

• Cable yarn

A cable yarn is made smaller plied yarns twisted together. The easiest cable yarn is a four ply and it is a nice way to use up a bunch of singles you have got lying around.
c) Spinning system
         i) Ring yarn
         ii) Rotor yarn
         iii) Worsted yarn
         iv) Woolen yarn
d) Types of blend
         i) Cotton + Polyester
         ii) Cotton + Viscose
         iii) Cotton + Acrylic
e) Process sequence used
         i) Carded yarn
         ii) Combed yarn

• Sliver

A loose of continuous untwisted strand or a strand of loose untwisted fibers produced in carding.

• Roving

A collection of relatively fine fibrous strands used in the later or final processing of preparation for spinning.

Flow chart of carded yarn

Blow room---> Carding--->First drawing frame---> Second drawing frame---> Speed frame---> Ring frame

Flow chart of combed yarn

Blow room---> Carding---> First drawing frame---> Lap former---> Comber---> Second drawing frame--->Speed frame---> Ring frame
   
Object of blow room

i) To open compress fiber tufts into smallest tufts.
ii) To mix or blend of fibers.
iii) To remove foreign materials like trash, dust, leaves or others.
iv) To produce a lip of definite weight per unit length.
v) To feed fiber tufts directly to the carding process.

Defects of blow room

1) Poor cleaning efficiency
      i) Poor cleaning efficiency is due to the less beater speed.
      ii) Irregular feed.
      iii) Higher distance between to beater to grid bar.
      iv) Blockage the cage.
      v) Damaged striker of beater.
     vi) Excessive moisture containing in fiber.
2) Soft lap
      i) Less calender roller pressure.
      ii) Low amount of moisture.
3) Conical lap
      i) Irregular suction in the cage.
      ii) Excessive moisture.
4) Barrel shaped lap
5) Lap licking
      i) Excessive moisture
      ii) Too low calender roller pressure.
6) High neps generation
      i) Condition of beater and associated components.
      ii) High moisture content
      iii) Closer settings
      iv) Excessive fan speed

Object of carding

i) To open the fibers tufts and clean again.
ii) To individual the fibers by carding action, reduction of neps.
iii) To produce a continuous strand of fibers slivers of definite weight per unit length.


Parts of the carding machine
i) Lap feed                                   
ii) Lap
iii) Feed plate
iv) Feed roller
v) Motes knife
vi) Licker in
vii) Under caging
viii) Back plate
ix) Cylinder
x) Revolving flats
xi) Front plate
xii)Doffer
xiii) Doffer comb
xiv) Trumpet
xv) Calender roller
xvi) Sliver guide
xvii) Coiler head
xviii) Sliver can
xix) Sliver can drivers

Action involved in carding machine

1) Carding action: When two closely space wire surfaces moves against each other and the surfaces have relative speeds for the reduction of fiber mass is called carding action e.g, cylinder and doffer; flats and cylinder action.

2) Stripping action:When two closely space wire surfaces move some direction and the surfaces have relative speeds for the reduction of fiber mass is called stripping action.

Object of drawing frame
i) To straight the hook fibers along the axis of the sliver.
ii) To parallel the fiber to each other.
iii) To reduce the weight per unit length of the sliver.
iv) To improve the regularity of the sliver.
v) To blend or mix the fibers for the homogeneous sliver. 

Object of comber

i) To remove short fibers below a preselected length so that the spinner enable to produce finer yarn then that can be spun from the same cotton in the carded step.
ii) To remove neps and impurities.
iii) To improve fiber parallelization and to make strength.

Object of simplex or speed frame

i) Attenuation of drawn sliver to roving form of required hank by drafting.
ii) Insert a small amount of twist to give required strength of roving.
iii) Winding the roving onto bobbin.
Build the roving such a form which will facilitate handling and transfer to the next process.

Object of ring frame

i) Draft the roving until the required count is achieved.
ii) Twist the drafted strand to form yarn of required count and strength.
iii) Wind the twisted yarn on to bobbin for suitable storage, transportation and further processing.   

Wet processing

• Desizing

Desizing is the first wet processing technology employed to remove sizing material from the surface of the fabric.

• Scouring

The term scouring applies to the removed of impurities such as oil, fats, waxes, soluble impurities and any particles or solid dirt adhering to the fibres. This is the heart of the wet process applied to textile material.
If the appropriate reagents are used , scouring will also remove size from the fabric although desizing often precedes scouring and considered to be a separate process known as fabric preparation.

• Bleaching

Bleaching is a process of destruction of natural coloring matter to produce white fabric band be accomplished with a minimum damage to the cloth being bleached.Cotton being a vegetable fiber will be bleached using an oxidizing agent, such as dilute sodium hydrochloride or dilute hydrogen peroxide. If the fabric is to be dyed a deep shade, then lower levels of bleaching are acceptable.

This is done by bleaching in different ways-
        i) By using dilute hydrochloride solution at room temperature.
        ii) By using hydrogen peroxide at 80-85 degree celcious.
        iii) Using sodium chlorate solution.

        Bleaching agent:
1) Oxidizing agent
        i) Sodium hydrochloride (NaOCl)
        ii) Calcium hydrochloride
        iii) Hydrogen peroxide
        iv) Sodium chloride
        v) Ozone
        vi) Potassium permanganate
        vii) Potassium dichromate
2) Reducing agent
        i) Zinc dust
        ii) Spontaneous chloride
        iii) Ferrous sulfate
        iv) Sodium hydrosulphate

• Mercerizing

Mercerization is a physio-chemical process where cotton yarn or fabric is treated with 15-22% caustic soda solution at the temperature 20-30 degree celcious. It is necessary to hold the fabric under tension during the process and wash thoroughly while under tension.

Benefits obtained by mercerization-
         i) Improved strength
         ii) Improved hygroscopicity
         iii) Improved dye affinity
         iv) Improved smoothness
         v) Improved luster

• Singeing

Singeing is an operation carried out to remove hairy fibers protruding from surface of the cloth.

• Raising

Another finishing process is raising. During raising, the fabric is treated with sharp teeth to lift the surface fiber, thereby imparting hairiness, softness and warmth.

• Dyeing

The molecules of the organic compounds called dyes are responsible for the color of dyed and printed textile fiber materials. For improved fastness and washing, rubbing and light other dyes such as vat dyes and reactive dyes are commonly used.

The dye molecules

Dye molecules are colored because they are selectively able to absorb and reflect incident light. Light is a form of energy; it is also the visible portion of the electromagnetic spectrum.

Organic molecules become colored and thus useful dye molecules, if they contain at lest one of each of the radicals called chromophores and auxochromes.

Classification of dye:
1) According to chemical structure
          i) Nitroso dye
          ii) Nitro dye
          iii) Azo dye
          iv) Stilbene dye
          v) Anthraquinone dye
          vi) Indigoid dye
2)According to mode of application
          i) Acid dye
          ii) Basic dye
          iii) Direct dye
          iv) Mordant dye
          v) Vat dye
          vi) Ingrain dye or developed dye
          vii) Reactive dye
          viii) Disperse dye
          ix) Pigment dye

Acid dyes

Acid dyes are so called because they are usually applied under acidic conditions. The fibers most readily colored with acid dyes are man-made, synthetic, nylon fibers and natural protein fibers.

Azoic dyes

Azoic dyes are so called because their molecules contain an azo group. Azoic dyes are also called napthol dyes, ice colors or developed colors.

The fibers most readily colored with azoic dyes are the man-made and natural cellulose fibers, e.g. viscose, cotton, etc.

Basic dyes

These are also called cationic dyes, because in solution the basic dye molecule ionizes, causing its colored component to become a cation or positively charged redical.

When they were first synthesized, the basic dyes were used on wool and silk but they had very poor color fastness properties. They were therefore displaced for these fibers by acid dyes.

Direct dyes

Direct dyes are also called substantive colors because of their excellent substantivity for cellulosic textile materials.
The fibers most readily colored with direct dyes are the man-made and natural cellulose fibers; that is, cotton and viscose fibers.

Disperse dyes

These dyes derive their name from their insoluble aqueous properties and the need to apply them from an aqueous dispersion.
The fibers most readily colored by disperse dyes are the man-made ester-cellulose and synthetic fibers, especially the acetate fibers and polyester, and less often acrylic and nylon.

Mordant dyes

The term mordant is derived from the Latin mordeo, which means to bite or to take hold of. The mordant dye is attached to the textile fiber by a mordant, which can be an organic or inorganic substance. The most commonly used mordant is inorganic chromium. Other inorganic mordants, such as aluminium, copper, iron and tin, and organic mordants, such as tannic acid, are rarely used. Since chromium is used so extensively, mordant dyes are sometimes called chrome dyes.
Fibers most readily dyed with mordant dyes are the natural protein fibers, particularly wool; and sometimes the synthetic fibers modacrylic and nylon.

Reactive dyes

Reactive dyes are so called because their molecules react chemically with the fibre polymers of some fibres to form a covalent bond between the dye molecule and fibre polymer.
 The fibres most readily colored with reactive dyes are the man-made and natural cellulose fibers, synthetic nylon and natural protein fibers.

Sulphur dyes

These dyes are so called because they contain sulphur atoms in their molecules. The fibers most readily colored with sulphur dyes are the natural and man-made cellulosic fibers.

Vat dyes

The name vat was derived from the large wooden vessel from which vat dyes were first applied. Vat dyes provide textile materials with the best color fastness of all the dyes in common use.
The fibers most readily colored with vat dyes are the natural and man-made cellulosic fibers.       

• Printing

Printing, on the other hand, is the application of color in the form of a paste or ink to the surface of a fabric. It may be considered as localized dyeing. Printing designs on to already dyed fabric is also possible.

Production methods of fabric

Weaving is a textile production method which involves interlacing a set of longer threads is called warp threads which is crossing with weft threads. This is done on a frame or machine known as a loom. Some weaving is still done by hand but the majority is machinesed.

Knitting is a process of manufacturing a fabric by the interloping of yarn.
Weft knitting is a method of forming a fabric by knitting means in which the loops are made in a horizontal way and inter meshing of loops taken place in a circular or flat form on a course wise basis,

Warp knitting is a method of forming a fabric by knitting means in which the loops are made in a vertical way along the length of the fabric form each warp yarn and inter meshing of loops takes place in a flat form or a length wise basis.

Lace is made by interlocking threads together independently using a backing and any of the methods described above, to create a fine fabric with open holes in the work. Lace can be made by either hand or machine.

Non woven textiles are manufactured by the bonding of fibres to make fabric. Bonding may be thermal, mechanical or adhesives can be used.

The evaluation of hand knitting

The term knitting describes the technique of constructing textile structures by forming a continuous length of yarn into columns of vertically intermeshed loops.
It relies heavily on the availability of fine, strong, uniformly spun yarn. The term knitting dates from the mid-sixteenth century, earlier words such as the Saxon.

The principles of frame knitting 

After the weft yarn has been laid by hand across the horizontally mounted needle bed, thin metal sinkers descend individually between each pair of adjacent needles to kink or sink it into a loop shape around each needle stem. Each sinker is caused to descend because it is hinged at its upper end to a pivoted jack that is lifted at its outer end by a wedge shaped piece of iron termed slurcock.

The development of warp knitting

Warp knitting the second and smaller section of machine knitting was never a hand manipulated craft. It was first developed by Crane and Porter in 1769 as a method of embroidery plating, by means of multiple warp thread guides, onto stocking fabric as it was being knitted on the hand frame.
As the technique improved, purely warp intermeshed loop structures without the weft knitted ground began to be knitted and Crane patented his warp loom in 1775.

The potential knitting technology

i)Using a minimum number of yarns.

ii)Easy flow of yarn from one loop to another under tension.

iii)Varying the size of loops.

iv)Loop distortion when under tension.

v)Loop transfer.

vi)Knitting single face, double face, open-work and surface interest structures.

vii)Increasing or decreasing the number of loops in width or depth.

viii)Knitting to shape either fabric pieces or separate articles.

ix)Knitting from a selection of yarns.      

  

Principle of weave structures                                                                

It is also essential to know the basic principles of fabric forming and weave structures before we go ahead with the mechanisms. The most common and simple interlacement of warp and weft threads is represented by a plain weave. Each individual thread of warp and weft is called end and pick respectively. It is seen that two ends and two picks complete one repeat of the plain weave. Most of the commonly used apparel fabrics use this simple weave, though the ornamentation or decoration of this weave can be achieved by a number of ways. From the thinnest light weight fabric known as muslin to the thickest and the heaviest fabric such as canvas cloth, can be formed by using plain weave. The same plain weave can be represented on a point paper or a graph paper represent the warp thread on the top of the weft thread, while the blank positions represent the reverse, that is, the weft thread on the top of the warp thread.Thus, in a plain weave there are two different ways of lifting the ends. On the first pick end number one and all odd ends are lifted and on the second pick end number two and the even ends are lifted. As there are two different liftings minimum two healds are required for drawing the ends-all the odd ends through, say the first heald and all the even ends through the second healds. This is shown at the top of the design by two horizontal spaces of graph paper. The cross in the squares indicates the ends drawn through the particular heald. This is called the draft on the loom. In the given illustration the first and the other odd ends are drawn through the second heald. This order of drawing the ends through the healds is called a draft. In order to get the interlacement of ends and picks as per the weave shown in the design, a certain order of lifting and keeping the healds down is required.           All these preliminary terms of design, draft and peg plan should be understood properly before the fabric forming on the loom could be discussed.                                                                                                                                                                     

Fibres

Fibers are pliable hair like substance that are very small in diameter in relation to their length. They are fundamental units in the making of textile yarns and fabrics. "Fiber" of "Textile fiber" means a unit of matter, which is capable of being spun into a yarn or made into a fabric of any nature or character.

According to Textile Institute "Fibers are defined as the units of matter characterized by fineness, flexibility and high ratio of length to thickness."

Classification of textile fibers
(a) According to their generation process-
         1) Natural fibers
                  i) Vegetable fibers
                       ==> Bast fibers ( Jute, Hemp, Kenaf, Flax)
                               All the fibers which are extracted from the stems of plants are classified as bast fibers.
                       ==> Leaf fibers ( Sisal)
                       ==> Seed fibers ( Cotton, coir)
                  ii) Animal fibers (Wool, silk)

                  iii) Mineral fibers (Asbestos)
          2) Man made fibers
                  i) Natural polymer based
                      ==> Cellulose
                      ==> Cellulose (Esters)
                      ==> Protein
                      ==> Miscellaneous
                  ii) Synthetic fibers
                      ==> Polyamides (Nylon)
                      ==> Polyester
                      ==> Polyvinyl-derivatives
                      ==> Polyolefins
                      ==> Polyurethanes
                      ==> Miscellaneous

b) According to their forms--
Depending on their form fibers are subdivided into following groups
            1) Fibril : A fibril is a very small cell or fiber, a long cell or a component of a cell wall.
            2) Staple fibers : They are also called staple short lengths of fibers which have been chopped from continuous filament in lengths of approximately 15-500 mm.
            3) Continuous filament : A manufacturer fiber of indefinite length extracted from the spinneret during the fiber production process
            4) Flocks fibers: Flock fibers are very short in length (>15mm) and therefore are not spinnable.

Requirements of fiber- forming polymer
Fiber forming polymers of apparel should be0
1) Hydrophilic
2) Chemically resistant
3) Linear
4) Long
5) Orientation
6) Able to form high melting point polymer systems
An explanation of these requirements is now given,

Hydrophilic properties

Fiber polymers should be hydrophilic. This means that the polymers should be polar, enabling them to attract water molecules. A fiber is comfortable to wear if its polymer system consists of hydrophilic polymers.

There are, fibers whose polymers are not hydrophilic and yet these fibers are used for the manufacture of apparel. In order to make the textile materials of these fibers more absorbent and, hence, more or less comfortable, hydrophilic polymer fibers need to be blended with the hydrophobic polymer fibers. Nylon and polyester, for example, are hydrophobic polymer fibers and are often blended with cotton, viscose or wool.

Chemical resistance

Fiber polymers should be chemically resistant for a reasonable length of time against the common degrading agents such as sunlight and weather, common types of soiling, body exudation, laundry liquors and dry cleaning solvents. Chemically resistant polymers should also not be toxic or hazardous wear against human skin; this is a most important requirement which is usually taken for granted.

Linearity

Fiber polymers should be linear, only linear polymers allow adequate polymer alignment to bring into effect sufficient inter-polymer forces of attraction to give a cohesive polymer system and, hence, useful textile fiber.

The atactic polymer: This is a stereo- irregular polymer. It has its side groups arranged at random, above and below the plain of the polymer backbone.
The syndyotactic polymer: This is a stereo-regular polymer. It has its side groups arranged in a regular alternating fashion above and below the plane of the polymer backbone.
The isotactic polymer: This is also a stereo- regular polymer. It has, however, all its side groups arranged on the same side or plane of the polymer backbone.

Length

Fiber polymers should be long. It has been found that the length of the polymers constituting the commonly used apparel fibers is an excess of one hundred nanometers.

Having the polymers oriented can give rise to sufficiently effective inter-polymer forces of attraction to form a cohesive polymer system and hence, a useful fiber.

Orientation 

Fiber polymers should be capable of being oriented. T his means that the polymers are or can be arranged or aligned into more or less parallel order in the direction of the longitudinal axis of the fiber or filament.

Perfect orientation of polymers is usually not oriented, nor is it desirable. The orientation of polymers in the polymer system of any fiber consists of two distinct, yet integrated forms. The two forms of polymer orientation are called the amorphous and the crystalline regions.

Formation of high-melting point polymer systems

A fiber consisting of a high melting point polymer system tends to have adequate heat resistance to enable it to withstand the various heat treatments of textile finishing, apparel manufacture and the heat subsequently applied to it during laundering and pressing or ironing during its useful life as a garment.

It appears that a fiber's melting point needs to be above 225 degree celcious if it is to be useful for textile manufacture and apparel use.