Yarn Quality Requirements for knitting

The yarn characteristics have a major influence on the performance of knitting as well as on the apperance of finished fabric. Improvements... thumbnail 1 summary
The yarn characteristics have a major influence on the performance of knitting as well as on the apperance of finished fabric. Improvements in the performance of knitting industry demand improvements in the knitting machines as well as optimisation of yarn properties. Various hosiery yarns are manufactured using the range of fibres available to suit different end uses. In Bangladesh, India majority of the knitted products are made from cotton yarn.

The following are the important yarn quality requirements for efficient running on knitting:


  • High work of rupture value.
  • antial elongation at break.
  • Low flexural, torsional and initial stretch resistance.
  • Good resilency.
  • High ratio of parimary to secondary creep.
  • Reasonable tenacity and loop strength.
  • Resistance to fatigue due to cyclic stress and strain.
  • Regularity of physical characteristics such as twist, evenness, moisture content.
  • Smooth and low frictional properties.
Conditioning at yarn prior to kintting at a standard atmosphere of 65±2% RH at 27∘C temperature for 24 hours to 48 hours will give good results in knitting. Moisture content of cotton and cotton blended yarns not only affects knitting performance but also helps in maintaining consistency of fabric weight. Hence a moisture meter should be used so as to quickly establish yarn fabric moisture. 

To prevent snarling, steam setting is essential for polyester blends. The recommended steam setting conditions are:

Vacuum Gauge - 740mm Hg
Temperature - 95 - 110 c
Time Duration - 15 to 30 min

In high speed knitting the knitting performance with respect to yarn hairiness is to be considered o the following accounts:
  • Excessive yarn hairiness causes excessive yarn friction between yarn and metal , which hinders proper loop formation and particularly with cotton yarn, general lots of fly.
  • It spoils the fabric appearance and causes excess pilling.
  • It also gives improper dyeing.

Introduction of Textile Printing

 Printing is one kind of dyeing. When different types of color used to make a particular design on the textile goods is called printing. N... thumbnail 1 summary
 Printing is one kind of dyeing. When different types of color used to make a particular design on the textile goods is called printing. Normally printing is performed on the textile goods in dry condition.



Flow Chart of Printing:

Grey Cloth
↓
Brushing and Shearing
↓
Singeing
↓
Desizing
↓
Scouring
↓
Bleaching
↓
Mercerizing
↓
Stentering
↓
Washing
↓
Drying
↓
Winding/Beaming
↓
Printing
↓
Finishing
Printing Methods:

Printing effect is performed by using some instruments like screen, roller, block etc. The procedure of creating printing effect according to the design by using different types of instrument is called method of printing. The methods used for printing is given below:
1)      Block printing method
2)      Flat press printing method
3)      Stencile printing method / Spray printing method
4)      Screen printing method
5)      Roller printing method
6)      Transfer printing method
7)      Flock printing method
8)      Engraved roller printing method
9)      Batik printing method
10)   Photographic printing method
Style of Printing:

Sometimes we used various types of technique in different printing methods to perform the printing effect easily. This effect of printing is called style of printing. Style of printing mostly depends on the behavior of the dye and chemicals and the material to be printed. Style of printing can be divided into following groups:
1)      Direct style of printing
2)      Dyed style of printing
3)      Azoic style of printing
4)      Metal style of printing
5)      Block style of printing
6)      Crepe or Crepon style of printing
7)      Printing of Lining
8)      Discharge style of printing:
a)      White Discharge style of printing
b)      Color Discharge style of printing
9)      Resist Style of printing
10)   Raised style of printing
Ingredients of Printing:

It is required to produce printing pest before printing. A good printing pest is mainly responsible for good printing effect. So it is very important to make a printing pest carefully. There are different ingredients used in printing pest for different purposes. Generally following ingredients are used in printing pest:
  •  Dye stuffs or pigment
  • Wetting agent
  • Thickener
  • Solvents Dispersing agents
  • Defoaming agents
  • Oxidizing and reducing agent
  • Catalyst and oxygen carrier
  • Acid and alkali
  • Carrier and swelling agent
Steps in printing process:

  •     Preparation of print paste
  •     Printing of fabric
  •     Drying
  •     Fixation of dyestuff
  •     Washing


Difference between dyeing and printing:

Dyeing
Printing
The process by which a textile material is changed physically or chemically so that it looks mono uniform colored is called dyeing.
When different types of color used to make a particular design on the textile goods is called printing.
In dyeing process, the goods dyed is one color uniformly all over the fabric.
In printing process, color is applied according to the design only.
Dyeing is performed in wet condition.
Printing is performed in dry condition.
Fiber, Yarn and fabric are used for dyeing.
Only fabric is used for printing.
For dyeing there is no design.
For printing there is a particular design.
Only one color is generally used in dyeing process.
One or more colors are used in printing process.
A particular temperature is maintain in dyeing process.
There is no particular temperature controlling system in printing.
Thickener is not used in dyeing process.
Thickener must be used in printing process.
The density of dye solution is low.
The density of dye solution is high.
Generally after dyeing , steaming and curing are not required.
After printing , steaming and curing is must for fixing the dye molecules to the goods.
Dyed fabric is respectively soft in feeling.
Printed fabrics is respectively harsh in feeling.
Respectively low cost.
Respectively high cost.
There is no localized application.
 There is localized application.
Much amount of water is required.
Less amount of water is used.
Liquor ratio is high.
Liquor ratio is less.


Automatic Flat Screen Printing:
A.      Approximately 17% of printed goods.
B.      Advantages
a.       Large repeats
b.      Multiple strokes for pile fabrics
C.      Disadvantages
a.       Slow
b.      No continuous patterns
Rotary Screen Printing:
A.      Approximately 50% of printed goods
B.      Advantages
a.       Fast
b.      Quick changeover of patterns
c.       Continuous patterns
C.      Disadvantages
a.       Design limitations
b.      Small repeats
Engraved Roller Printing:
A.      Approximately 26% of printed goods
B.      Advantages
a.       High design capability
                                                                 i.      Fine detail
                                                               ii.      Multiple tones
C.      Disadvantages
a.       Copper cylinders very expensive
b.      Not economical for short runs
c.       Requires highly skilled workers
Heat Transfer Printing:
A.      Approximately 7% of printed goods
B.      Advantages
a.       High quality prints
b.      Fewer seconds
c.       Economical for short runs
d.      Practically pollution free
C.      Disadvantages
a.       Slow
b.      Primarily only for polyester

Thickener:

Thickener or Gummy Substance:
Thickener is used in textile printing which is a main part of high molecular weight compound giving viscose paste in water. This imparts stickiness and plasticity to the printing paste so that it can be applied to a fabric surface without color spreading. All about 50% to above amount is used to prepare a printing paste.
  • Function of Thickener:
  • It is soluble in water.
  • It is comparatively cheaper and available in the market.
  •  It has great attractive towards dyestuffs i.e it acts as a dye carrier.
  •  It also has viscosity properties for binding.
  • It will not react with any dyestuffs or chemical.
  •  It bears physical and chemical stability.
  • It can be easily removed or withdrawn after printing.
  • It prevents bleeding effects and retain the surface of print design.

Finishing:

Finishing Progress:
The treatment applied to the textile goods after dyeing and printing process is normally called finishing process.
Objects of Finishing:
  1.         I   To increase the attractiveness of fabric.
  2.                     To increase the service ability
  3.             To increase the beauty and glitter ness of the fabric.
  4.                     To increase the fineness and to ensure smoothness.
  5.                   To ensure softness of the fabric.
  6.                  To free from hairiness of the fabric.
  7.             To increase attractiveness to the fabrics paying customers.


Finishing agents:


Starch, gum, glow, dextrin, china clay, epsum salt, gypsums salt, glycerol, soap, soluble oil, etc. were the finishing agent in previous time. Now long chain fatty acid compound, synthetic resin, cellulose derivatives, quandary ammonium compound etc. are using as finishing agents.

Introduction of Garments Manufacturing

Historical development of garments industry: Garments is the second basic need of human. It is very difficult to say the exact time of th... thumbnail 1 summary
Historical development of garments industry:
Garments is the second basic need of human. It is very difficult to say the exact time of the use of garments. In 1755 the first sewing machine developed by Charles Frederic of England. In 1851,
commercially sewing machine is developed by Isaac Merit Singer. In 1829, the first garments factory was established at Paris with 80 sewing machine to produce uniform for military forces.



Flow Chart of Garments Manufacturing:


Design or Sketch
↓
Basic Block
↓
Working Pattern
↓
Sample Making
↓
Approved Sample
↓
Costing
↓
Production Pattern
↓
Grading
↓
Marker Making
↓
Fabric Spreading
↓
Cutting
↓
Sorting and Bundling
↓
Sewing
↓
Ironing or Finishing 
↓
Final Inspection
↓
Packing
↓
Cartooning
↓
Send to Buyer or Dispatch




Briefly Discuss:


Design or Sketch:
It is nothing but one kind of engineering art including all measurements of particular style.

Basic Block:
It is an individual component of garments without any design or style.

Working Pattern:
To make pattern for a particular style with net dimension.

Sample Garments:
The gmt which is needed for bulk production is called sample garments.


Problems of production or Production Related Matter:
Production related problems should be eliminated in this step.

Approved Sample:

The sample which is approved by buyer is called approved sample.


Send to buyer:

When all process are done then the gmt are sent to buyer.

Production Pattern:

To make pattern for a particular style with net dimension along with allowance.
Sample Flow Procedure of a Buyer

A. Offer Sample:

a. Offer sample refers first sample without technical assessment.
b. This sample created by supplier.
c. May have already pre-given measurement or sketches.
d. Ordered by team via designer or product manager.
e. This offer sample may be approved in first time or will have to be revised.

B. Fitting Sample:

Fitting sample is done for:
a. Fitting approval
b. Measurement approval
c. Workmanship approval
d. Size approval
e. This fitting sample may be approved in first time or will be advised to revise.

C. Quotation Sample:
Quotation sample is done for:
a. Price approval
b. Order confirmation.

D. Style Sample:

Style sample is done for:
a. Order confirmation
b. Prepared for specific style

E. PP Sample: 

a. Made of bulk materials before production start.
b. Prepared for approval purposes for production.
c. Prepared to be identified by buying team.
d. To be advised for replace or will be accounted as counter or seal sample.

F. Size set Sample:

a. Size set sample refers the size wise samples of an order.
b. This sample created by supplier for getting approval.
c. Size wise fitting.
d. Size wise measurement.
e. Size wise quality.

G. Production Sample:

a. Production sample refers the sample from actual production.
b. Replace shipment sample.
c. Size and color according to counter sample as a basis for quality control(measurement and workmanship)

H. Advert Sample / Photo Sample:

a. For promotion purposes.
b. Advert or photo shooting etc.
c. Correct materials, color, workmanship, measurement.
d. Size defined by buying team.

I. PR / Fashion Show Sample:

a. For all presentation and fashion show purposes.
b. Replace fashion show samples.

PATTERN:

Pattern is a hard paper which is made following each individual component for a style of garments.

Pattern Making:

The pattern which is used in gmts industry are as follows:

I. Block Pattern or basic block.
II. Working pattern or gmts pattern.

Block Pattern or Basic Block: Block Pattern or basic block is an individual components of garments without any design or style. It can be made in two ways . Such as –

I. Flat Method
II. Modeling

Flat Method: In this method, the pattern of different parts of garments especially body and sleeve are made by technical drawing. Actually this method comes from modeling method and by this method fast pattern making is possible.

Modeling: It is primary and first method and is widely still used in garments industry. In this method block is made with standard body measurement of dummy is called toile. Toile is worn on the body of dummy to check fittings. Then toile is worn out from the body of dummy and individual parts of toile are drawn on hard paper or board paper. In this method, more time is required but most efficient.

Garments Pattern: Garments pattern is made on the basis of block pattern or basic block. Individual block pattern are drawn on hard paper or board paper. Allowance i.e. sewing allowance, trimming allowance, center front line, bottom hole, dart and pleat is considered in this pattern.

Factor Upon Which Pattern Making Depends:

1. Skill ness.
2. Technological knowledge.
3. Analysis of design and
4. Experience of gmt making.

MARKER:

Marker is a thin paper which contains all necessary pattern pieces for all sizes for a particular style of garments in such a way that fabric wastage would be least.

Constraints of Marker Making:

The work of the marker planner is subjected to a number of constraints. These are related with:
a) The nature of the Desired result in the finished garments. These are:
   a. Pattern alignment in relation to the gain of the fabric.
   b. Symmetry or asymmetry and
   c. The design characteristics of the finished garments.

b) The requirements of quality in cutting

c) The requirements of production planning.

Methods of Marker Making: There are two types of marker making. Such as:


a) Manual Method
b) Computer Method

Manual Method: Manual methods are two types. Such as:
a) Marker planning with full size in a full size pattern and
b) Marker with minimized pattern.

 Marker Planning With full size in a full size patterns: In this method all patterns are in full dimension according to standard measurement. Hard paper are placed on paper or fabric and then all patterns are rounded to reduce the marker length. The top of table on which marker making are fixed or fitting and the fitting table top are placed in various angle. Arrangement of vacuum system under table top which are suitable for table cloth.

 Marker with minimized pattern: Full size patterns are minimized 1/5 part by a pantograph and minimized patterns made by pantograph are plastic sheet or hard and coarser. Maker is planned by minimized pattern. After marker making, marker is taken snap by camera. The marker efficiency is measured by marker area and pattern area. Marker photograph and minimized pattern are stored.

Advantages of Manual Method: 

a) It suitable for small production.
b) Investment cost is low.

Dis advantages of Manual Method:

a) More time is required.
b) High labor cost.

Computerized Method: This is the best method and it gives the higher marker efficiency. It is also two types. Such as:

a) Automatic marker making
b) Inter active marker making

Automatic Marker Making: In this method, computer makes marker itself. According to given commands, computer can make marker. In this method the most efficient marker can be got but it takes more time as the computer makes marker with the help of permutation and combination.

Inter Active Marker Making: It is a common process of marker making. The operator’s plans marker by interacting directly with the system through a computer screen. All the pattern pieces are displayed in a miniature of the screen. In this method, data per and tablet used for transferring of patterns.

Computerized Marker Making Technique:

a) Monitor→ Size + Sketch → Computer Monitor Enter
b) Computer Monitor → Small Size → Show
c) Grade rule to computer monitor
d) By applying grade rule , we all find all size of pattern pieces i.e. S, M, L and , XL.
e) Marker width
f) Number of pieces per marker

Advantages Of Computerized Marker Making:


a) Suitable for large scale production
b) Marker efficiency is higher than manual
c) Least wastage fabric
d) Low Production cost
e) Print out of the marker could be got in need
f) Grading of the pattern could be done automatically
g) Few time consumption
h) Can be prepared marker quickly.

Disadvantages of Computerized Marker Making:

a) Initial investment cost is high and
b) Skilled operator is required.

Introduction of Knitting and Industry

The art of knitting has been rapidly progressing in the development countries of the world. Unlike woven fabrics, knitted fabrics are pop... thumbnail 1 summary
The art of knitting has been rapidly progressing in the development countries of the world. Unlike woven fabrics, knitted fabrics are popular for their shape fitting properties, softer handle, bulkier nature and high extension at low tension. The hand knitting was a much older technology.
The application of knitting was popular by the term hose to produce a complete covering of the legs and since then the word hosiery is conveniently used for a series of articles on stockings, socks and knitted leg coverings, and even to the general circular knitted goods. Though the invention of the first knitting machine is attributed to the Reverend William Lee of England in the year 1589, the growth of machine knitting in Britain was not spectacular. The Lee hand stocking machine established the principle of bearded needle with sinkers, knock over bits etc. In nineteenth century, many inventors struggled to convert the hand operated into steam power by which the knitting speed attained 100 percent greater. The invention of latch needle and its introduction to circular knitting (first machine 1808) simplified the knitting action and enabled circular knitting machines, to be built plain, rib and purl fabrics.

Comparison of woven and knitted fabrics:

Knitting began with wool knitting and expanded fast to cotton and lately into the synthetics including all types of blends. Knitting is comparatively faster and more economical process to convert yarn into fabric, even straight into apparels, socks etc. Piece knitting is possible whereas piece weaving is not yet known. Besides being economical , knitted fabric being stretchable offers more comfort and better fitting in the most type of apparels. Designing possibilities are also larger though at times difficult. The mass production of knits have overriding advantages. The apparel of knitted fabrics lies in part in the very nature of the knitted as compared to the woven structure-its superior draping powers, its ready pack ability and its ease and excellent comfort.

Besides better appeal, popularity of knits in principles stems from the nature of knitting technology. Basically cloth can be turned out more economically on a knitting unit than on a loom. The knitting machine also has some distinct advantages over the loom in terms of patterning potential, the speed and case of patterning \. Modern living style is becoming more and more informal, go as you like and easy going. Man's life in these days is full of tension and informality helps him relax and case tension to a great extent. It is for these reasons that knitted casual wear, sportswear, T-shirt, Ladies tops, skirts, overalls, jackets, suits and what not are catching up fast and replacing woven wear years back.

The following gives the general comparison of woven and knitted fabrics:


  • The woven fabrics are produced by the interlacement of warp and weft yarns and thus require at least two yarn systems for their production. In knitted fabric production one yarn is sufficient; however a group of yarns are required for warp knitting.
  • Elasticity as well as stretch-ability of woven fabrics are much less and unless special elastic yarns are used, there is almost no elasticity. Knitted fabrics show high amount of stretch and elasticity due to their loop structure. Thus they have the ability to warp the body and confirm to body movement.
  • The lesser inherent tension and good dimensional stability of woven fabrics results in minimum shrinkage and loss of size. The formation of loops by the given yarn causes inner tension which  higher shrinkage values in knitted fabrics.
  • The woven fabrics are more durable than knits as their durability depends on yarn strength, yarn twist, yarn structure and fabric weave. The durability of knitted fabrics is based on yarn strength, loop size , stitch density and the kind of knit. Due to the elasticity character of the loop, tensile and tearing strength tests are not performed for knitted fabrics. Their bursting, wear and other resistance performances are good.
  • Moisture absorption of knitted fabrics is more than that of woven because of their comparatively loose and voluminous in construction.
  • Tight cond\struction and intersecting of yarns at right angles provide good stability to woven fabrics and hence there are no much problems of slackening and loosening of the g\fabrics. Because of the loose structure by the loops and also because of their inability to return back to their original form after stretching in knitted fabrics, there is the problem of slackening and loosening after wearing a long time.
  • Though the air permeability, heat conductivity and insulation properties are depended on fie structure fabrichickness, fabric construction and finishing processes, the open and voluminous structure of knitted fabrics makes them advantageous with respect to the above characteristics.
  • As the woven fabrics are more inclined to crease, their ironing and iron retention properties are better than knitted fabrics. Knitted fabrics are more resistant to crease and their garments can be worn without ironing. Their ironing and ironing retention properties are also poor.

The process in which fabrics are produced by set of connected loops from a series of yarn in weft direction is called knitting. There are two types of knitting process like:


1. Warp knitting.

2. Weft knitting.

Warp Knitting:


In a warp knitted structure each loop in the horizontal direction is made from a different thread and the number of threads used o produce such a fabric is least to equal to the number of loops in vertical direction.


Weft Knitting:

In a weft knitted structure a horizontal raw of loop can be made by using one thread and the threads runs in horizontal direction.

The potential of knitting technology:
Structure of knitting provides opportunities for-

1. Using a minimum number of yarns.
2. Daisy flow of yarn from one loop to another under tension.
3. Varying the size of loops.
4. Loop distortion when under tension.
5. Loop transfer.
6. Knitting single face, double face, open-work and surface interest structures.
7. Increasing or decreasing the number of loops in width or depth.
8. Knitting to shape either fabric pieces or separate articles.
9. Knitting from a selection of yarns.
10. Engineering extensibility of stability.
11. Informing yarns suitable for knitting.

Basics elements of knitting:
Basic elements of knitting machine –

Needle 

1. Beard Needle
2. Latch Needle
3. Needle Compound.


Cam

1. Engineering cam (circular)
2. Knitting cam (Knit cam, Tuck cam, Miss cam)


Sinker

1. Loop forming sinker
2. Holding Down sinker
3. Knitting over sinker.

Rayon Fibres and Uses of Rayon

Rayon and acetate fibres are not fibrillar in structure because the natural cellulose morphology is eliminated during the manufacturing pro... thumbnail 1 summary
Rayon and acetate fibres are not fibrillar in structure because the natural cellulose morphology is eliminated during the manufacturing process of these regenerated fibres. The regenerated fibres are much weaker and more extensible than cotton, reflecting principally the ower degree of structural regularity and perfection and also lower degree of polymerisation (molecular weight) of the cellulose chains.


Rayons are the first man-made fibres. Several types of rayons are being produced currently. Rayons are regenerated cellulose fibres. Viscose and cuprammonium produced by dissolving alkali-cellulose (obtained by reaction of wood pulp or cotton waste with caustic soda) in carbon disulphide and cuprammonium hydroxide respectively., passing the solution through spinnerets and then solidified by precipitation in mineral acid solution.

Viscose is normally dope dyed or mass coloured by adding pigments to the viscose solution before spinning, This is preferred rather than conventional dyeing due to better uniformity of shades, better fastness, lower coloration costs etc. However, the shade range is greatly limited as compared to conventional dyeing processes. Delustrants like titanium dioxide, fire-resistant chemicals etc. can also be incorporated to improve the appearance and properties of the viscose yarn.

In the regenerated fibres prepared by the conventional method, the cellulose molecules are not very highly oriented and the proportion of the amorphous region is large. Consequently, the fibre has poor dry strngth and very poor wet strength.

High-wel-modulus rayons or polynosic rayons are produced from high grade cellulose and the precipitation is carried out under milder conditions to prevent degradation of cellulose. Cellulose sodium xanthate is prepared from unripened alkali-cellulose and dissolved in water insted of caustic soda solution. It is then spun from a dilute sulphuric acid solution containing no additives. The thread is stretched three times its original length durring coagulation. It has a microfibrilliar structure not very different from that of cotton. Polunosic fibres have a very high tensile strength, less extension at break and reduced swelling in water.

The majority of viscose rayon has a serrated surface and irregular cross-section due to skin (higher orientation) formation during precipitation. The viscose fibre is long and straight unless the fibre has been crimped. The fibre is much less crystalline (30%) than cotton (70%). High-tenacity rayons are more crystalline.

Since rayons are essentially cellulose, the properties are very similar to those of cotton. The differences in properties are due to differences in the degree of polymerisation, crystallinity and orientation within the fibre. Unlike cotton, the wet strength is less than the dry strength, and the reduction in strength after wetting is less in case of polynosic fibres.

Rayons possess greater luster than cotton and are often delustered by adding suitable pigments before spinning.

The chemical properties are similar to those of cotton. However, these fibres are less chemical-resistance than cotton. Prolonged exposure to sunlight causes degradation and subssequent loss of strength. The fibre is less expensive and hence is used as a substitute of cotton, especially for blending with synthetic fibres. Rayons are resistant to common household solvents and to light and heat except under extreme conditions.

Both carbon disuplhide and cuprammonium hydroxide cause environmental problems, hence attempts have been made to develop an alternate process. As a result, lyocell fibres have been developed which are made by regeneration of cellulose from its solution with organic solvents, e.g. N-methyl morpholine -N-oxide (NMMO) or from cellulose carbamate solution a reaction product of cellulose and urea. NMMO is recovered after spinning. A number of lyocell fibres are available in the market such as Tencel (Courtaulds, USA). Lyocell (Lenzig, Austria), New cell (Akzo-Nobel, Germany) etc. The viscose fibres have a folded or serrated cross-section, homogeneous and skin-core morphology is as in viscose. The crystallinity and orientation are higher than those of viscose. The dyeing behaviour is, in general, like other cellulosic fibres. The dye yeild for selected dyes are higher than that of viscose, but less than that of mercerised cotton. The substantivity towards dyes is similar to viscose.

Water for Various Textile Process

In a textile processing plant, water is a vital raw material not only for the boilers supplying steam for heating and drying purposes, but ... thumbnail 1 summary
In a textile processing plant, water is a vital raw material not only for the boilers supplying steam for heating and drying purposes, but also for all the wet processes such as scouring, bleaching, dyeing, printing and finishing. The success of these processes largely depends on the quality of the water being used. Generally two qualities of water are to be maintained separately - very pure quality for feeding to the boiler and moderately pure quality for processing purpose.

Sources Of Water

Water with a high degree purity is rarely obtained from natural sources. The mineral constituents differ in amount and relative proportions depending on the source. Supplies of water may be broadly classified into three groups.

Surface Water

It is mainly accumulation of rainwater in streams, rivers and lakes. As it passes over the surface of the earth, it carries organic matters of varying stages of decomposition, a part of which is converted into nitrates by nitrifying bacteria. It also dissolves varius mineral matters, depending on the nature of the soil or rock coming in contact , or may be turbid due to their suspensions. Generally it contains sulphates and chlorides as well as bicarbonates of calcium and magnesium. Decaying vegetables may distinctly discolour surface water.

Subsoil Water

Water, collected from shallow wells or surface springs, is actually surface water percolated a small distance through the soil or rock. It is generally free from suspension as water is being filtered by the passage through soil. It howeve contains dissolved organic matters. Subsoil water is often rich in carbon dioxide arising from metabolism of vegetable life. It converts insoluble calcium carbonayes of rock into water-soluble bicanbonates. The impurity content of subsoil waters may vary significantly.

Deep Well Water

Water from deep wells or deep tube-wells is collected from a considerable depth below the ground and such water has percolated through several layers of ground. Such water is generally free from organic matters due to filtration and bacterial action. The mineral content, however may be very high because of prolonged contact with several layers of rocks and soil. It may contains sodium biacarbonate in addition to the bicarbonates and other salts of calcium, magnesium and iron.

Impurities in Vegetable Fibres

Vegetable fibres contain various impurities in different quatities. A few important impurities are discussed below Impurities in Veget... thumbnail 1 summary
Vegetable fibres contain various impurities in different quatities. A few important impurities are discussed below

Impurities in Vegetable Fibres

Hemicellulose

Hemicellulose is a substance with the general properties of carbohydrates and is a mixture of a variety of compounds, the proportions of which vary according to the source of origin. It is soluble in 18% caustic soda solution and this suggests that it may probably have a much lower degree of polymerisation than cellulose.

Mectic Acid and Pectin 

Pectic acid occurs in vegetables as calcium/mahnesium salt or pectin (i.e. methyl pectate) They are abundant in many fruits as apples, pears and sugar beet. Pectic acid is a long chain polymer similar to polysaccharide having one carboxyl group for every sixth carbon atom. It consists of a polygalacturonic acid backbone, which may be partially methylated and often han rhamnose, arabinose, galactose and xylose and other sugar bonded as side chains. It is insoluble in water but soluble in alkaline solutions. 

Lignin

This substance is absent in cotton but occurs in considerable amounts in bast fibres and is responsible for their yellowing. It is associated with woody tissues in plants as cementing materials. The constitution is not well established , its low hydrogen content in relation to carbon suggests that it may be composed of aromatic nuclei 3,3 dihydroxyphenylpropane is a degradation derivative and is probably one of its basic structural units. It is soluble in sodium hypochlorite or sodium chlorite solution. 

Fats and Waxes 

Th chemical nature of fats and waxes has never been investigated exhaustively, because the actual amounts present in the fibres are very small. Waxes are the product of monohydric alcohols, such as ceryl alcohol, gossipyl alcohol, montanyl alcohol etc. While the oils can be made water-soluble by saponification, waxes are not saponifiable but can be removed by emulsification with soap at high temperature.

Nitrogenous Compounds 

These impurities are degradation products of protoplasm, which are contained in the cell when it was still living. They are basically protein and polypeptides. Though they are present in small amounts, they can produce undesirable effect in finished materials. They are readily soluble in boiling alkali.

Mineral Matters

The quantity and composition of water-soluble mineral matters vary according to the nature of soil on which cotton is cultivated. Silicon is always present. The metallic salts commonly present are of iron, aluminium, calcium and magnesium. All these salts are convertes into respective carbonates when burnt.

Natural Colouring Matters

The yellow or brown colour of cotton still remains even after scouring. These natural colouring matters can be effectively destroyed or made colourless by oxidising bleaching agents. They are present in traces and are probably related to the flavone pigments of cotton flowers.

Classification of Textile Fibres

As the physical and chemical properties differ largely among fibres of different origin, it is necessary to classify textile fibres based o... thumbnail 1 summary
As the physical and chemical properties differ largely among fibres of different origin, it is necessary to classify textile fibres based on the source of origin. The types of textile fibres available globally are exceedingly large and apparently, it is very difficult to categories them under a few classes.

Thextile fibres are broadly divided into two classes - natural and man-made. Nture provides us a large number of excellent fibrous materials that can be used directly for yarn and fabric manufacture. Natural fibres may be obtained from plant, animal or mineral sources. All plant fibres are composed of primarily cellulose and secondarily other components like hemicellulose, lignin etc. Plant fibres can be further divided into various sub-group depending on the portion of the plant from where the fibre is obtained e.g. seed, stem or bast (flax, jute etc) or ;eaf (Sisal).

Fibres obtained from animals are mostly composed of amino acid resisues or protein. The most important animal fibres are silk and wool. In addition, there are a large number of lesser-known hair fibres such as camel hairs, goat hairs, rabbit hairs etc.

Classification of Textile Fibres 



The fibre obtained from mineral is asbestos.

Man- made fibres can be subdivided into three sub-classes:


  • Regenerated fibres are manufactured by dissloving natural fibre forming polymers and regenerating the polymer in the form of fibre (truly continuous filament) by passing it through a fine orifice called spinneret. Examples are various rayons namely viscose and acetate fibres.
  • Synthetic fibres are made by chemical synthesis from simple chemicals (i.e. monomers). After polymerisation, the melt or solution of the polymer is passed through spinnerets and spun into filament. They can be further classified as polyesters, polyamides, polyurethenes(spandex), polyvinyls, polymerised hydrocarbons or polyolefins(polypropylene) and synthetic rubbers, depending on the chemical composition of the fibres. Polyvinyls may have different substitution (chloro, fluoro, cyano and hydroxyl) products, the most important being mono-cyano substituted acrylics.
  • Refractory (ceramic) and indutrial fibres like carbon, glass, metal etc.
Another method of classifying fibres would be according to chemical structure, without regard to their origin. Fibres of similar chemical structure can be grouped together.

The annual world-wide fibre used in 1996 was 47 million tons with fibre-wise break-up as follows:

Cellulosic - 44.7%
Plyester    - 27.2%
Polyolefins - 9.6%
Polyamide - 8.6%
Acrylic - 5.7%
Wool - 3.1%
Others - 1.1%

This indicates the overall importance of cellusic and polyester fibres alone or in blends. These two fibres account for 72% of world fibre consumption. It is estimated that by the year 2010, the consumption of polyester will be more than that of the cellulosic fibres.

Classification of Textile Fibres as Per Chemical Constitution

Cellulosic - Cotton, flax and other bast fibres, leaf fibres, rayons.
Modified Cellulosic- Acetate (cellulose ester)
Protein (Natural) - Wool, silk, hair fibres, casein
Polyamide - Nylon, aramid (aromatic nylon)
Polyester - Terelene, Dacron, CD (cationic dyeable) polyester
Polyacrylic - Acrylic fibres, modacrylics
Polyolefins - Polyethylene, polypropylene
Vinyl - Saran, Teflon (polytetrafluoroethylene)
Polyurethene - Spandex

Classification Of Fibre Properties

Fibres have wide variations in chemical, electrical, mechanical, optical and other properties and the properties of a fibrous product natur... thumbnail 1 summary
Fibres have wide variations in chemical, electrical, mechanical, optical and other properties and the properties of a fibrous product naturally depend on the properties of the fibres of which it is composed. Not only the average values but also the range or statistical distribution is important. A typical classification of such fibre properties with some examples is given below:


Classification Of Fibre Properties

  • Geometric

  1. Length
  2. Cross-section
  3. Crimp

  • Physical

  1. Density - Linear, bulk
  2. Thermal - melting, transitions, conductivity
  3. Optical - birefringence, refractive index, lustre and colour
  4. Electrical - dielectric constant, resistivity
  5.  Surface - roughness, friction
  6. Mechanical - tension, compression, torsion, bending, shear


  • Chemical 


  1. Response to acids, alkalis, oxidation, reduction and heat 
  2.  Sorption - moisture, dyes
  3. Swelling - anistropy 

Essential Properties Of Textile Fibre

It was realised long back that the natural fibres consist of polymers held together by various links or forces. The first step in the devel... thumbnail 1 summary
It was realised long back that the natural fibres consist of polymers held together by various links or forces. The first step in the development of man-made fibre was the manufacture of regenerated fibre using natural fibrous raw materials. For example, cellulosic materials from plants or trees are regenerated into viscose, which can be spun into yarn.


The next step was to produce chemicals, which have the ability to form links giving rise to polymers called synthetic fibres. It must be realised that only a few of organic chemicals can be used in the production of synthetic fibres. The properties of the polymer necessary for fibre formation are as follows:

Essential Properties Of Textile Fibre


  • Molecular weight - a ploymer should have high molecular weight, which consequently results in considerably longer fibre. The length of polymer contributes to the strength of the fibre by holding crystalline region together. To produce fibre of adequate strength, the length of a polymer molecule in the range of 100 nm is required. Many naturally available cellulosic materials can not be used as textile fibres as they are much shorter in length.
  • Linearity - only predominantly linear polymers will form sufficient crystalline regions, permitting an adequate number of inter-chain forces of attraction to occur within the polymer system. The molecular chains, which are bulky and / or branched, can not pack closely enough together to form a crystalline region resulting in a week fibre.
  • Inter-fibre forces of attraction - there should be a sufficiant degree of inter-molecular links or bonds of one or more of the following types:
  • Hydrogen bonds, which occur between positively charged hydrogen atoms in one polymer molecule and negatively charged oxygen, nitrogen or chlorine atoms in an adjacent polymer molecule. Natural fibres are rich in hydrogen bonds.
  • Van der waals forces are similar but weaker than hydrogen bonds. They occur when polar groups are absent. The polymers are to be closely packed so that attraction can occur between slight charges of opposite character in the polymer chains. Both the hydrogen bonds and van der waals forces of attraction are weak, but the presence of these forces in large numbers in case of closely packed polymers significantly contributes to its strength.
  • Strongest and chemically most stable covalent bonds or corss-links are formed when any two atoms share a pair of electrons . The greater the number of cross-links, the more rigid the fibre becomes. However, a low degree of cross-links, as in case of wool or elastomeric fibres, imparts a good to excellent elasticity. 
  •  Ionic bonds are formed between oppositely charged polar groups in polymers and are stronger than hydrogen bonds and van der waals forces. They occur principally in protein fibres like wool and silk, and polyamide fibres like nylons.


  • Orientation - a fibre consists of a large number of individual polymer chains arranged in either highly ordered form called crystalline region or randomly called amorphous region. In afibre, the extent and proportion of crystalline and amorphous regions mayvary- in natural fibres, the variation is created by nature and in case of man-made fibres, the variation can be controlled during production. In some polumers, the crystalline regions are formed during extrusion and subsequent drawing process merely aligns the crystalline regions parallel to the fibre axis; whereas in other systems, the polymers are first formed in amorphous state and become crystalline fibres have harsh handles and poor abrasion resistance, i.e. quickly damaged on rubbing.
  • Melting point - when a polymer is highly crystalline or when the intermolecular attraction between the polymer molecules is strong, its resistance to heat will be high. Most textile fibres are subjected to heat treatment during production or during use. Hence the fibres should have high resistance to heat. Synthetic fibres have specific ranges of temperature during which and the degree of crystallinity of the polymer. Natural fibres do not melt as they have storng inter-chain bonding and long chain-length. However, they turn yellow and are damaged above certain temperature depending on the chemical structure of the fibre.

Chemistry of Textile Materials

The dyeing and printing processing of textile materials. Textile materials called fabrics or cloths are prepared by weaving or by knitting ... thumbnail 1 summary
The dyeing and printing processing of textile materials. Textile materials called fabrics or cloths are prepared by weaving or by knitting with continuous strands of textile materials called threads or yarns. Yarns are prepared from short length materials called staple fibres or continuous materials called filaments . Fibrics called non-woven are prepared from fibres directly by special methods.



For successful chemical processing through knowledge of the chemical constitution, physiochemical structure and chemical properties of the textile materials is extremly essential. One may wonder at the many and varied properties of fibres, yarns and fabrics that have been produced , particularly since the advent of man made fibres. One may ask what makes a material suitable for use as a textile fibre. Why fibre properties like strength , elasticity, thermal properties, dyeability, resistance to chemicals vary so widely. To answer all these questions pne must closely examine the structure of textile fibres.

Textile Fibres:

Textile fibres are defined as units of matter characterised by flexibility, fineness and a high ratio of length to thickness. They should have sufficiant strength to resist breakage due to stress applied during manufacture and use. They should also processes enough thermal and chemical stability to withstand the environment to which the fibres are exposed. Moreover, an extensibility of 5-50% is required, depending on the end-use of the final product.

Until the introduction of man made fibres, one had to rely ob fibres from natural sources. Not all of these fibres were suitable for use as textile fibres because they lacked certain characteristics, for example many were not long,flexible or strong enough. Soil, feed and other climate and environmental conditions affect natural fibres. These result in non-uniform properties of natural fibres. Man-made fibres are not much influenced by these factors and greater control can be exercised over their production. However, even with greater control, slight variations in the production of man-made fibres can give rise to significant variation in dyeability, strength and some other properties.

Each individual fibre is made of millions of individual long molecular chains of discrete chemical structure. The morphology i.e. the arrangement and orientation of these molecules within the individual fibre as well as the gross cross-section and shape of the fibre influence the fibre properties. However, the basic physical and chemical properties largely depend on the chemical structure of the long molecular chains constituting the fibre. The total number of units that repeat themeselves in a chain vary from a few units to several hundreds and is termed as the degree of polymerisation for molecules within the fibre.

Cotton for example, has a DP of about 10000 and viscose rayon, a regenerated fibre, about 300-350. The DP of man-made fibre is determined by various factors during production of these fibres.

Fibre Structure: 

With the exception of a dew speciality fibres based on inorganic substances like glass, asbestos etc, fibres are a class of solid organic polymers that are distinguised from other polymers by their physical properties and by their characteristic geometric dimensions. A fibre is readily identifiable as a substance that is extremely long with respect to its width or diameter is flexible and has high anisotropic physical properties. However, fundamental difference between fibres and other solid substances is in their molecular structure , which in turn, decides the differences in their chemical and physical properties.

For a complete description of fibre structure, it is useful to consider three levels of molecular structure, each realting to certain aspects of fibre behaviour and properties. The organochemical structure defines the structure of the reoeating unit in the base polymer and the nature of polymeric link. This is directly related to chemical properties, dyeability, moisture absorption, swelling characteristics and indirectly to all physical properties. The macromolecular structure describes the family of polymer molecules in terms of chain length, chain length distribution, chain stiffness, molecular size and molecular shape. A supermolecular structure provides a description of the arrangements of the polymer chains, primarily in terms of factors like orientation crystallinity and fibrillar structure.

In general, all fibres that are useful in textile applications are semi crystalline, irresversibly oriented polymers. This means that the fibres have certain region in which the molecular chains are highly oriented, closely packed and near-perfectly arranged. These region are usually refered to as crystalline regions or crystallites. The degree of orientation and the degree of crystallinity are important quantities that strongly influance the physical properties of fibre . In other regions, the molecular chains are not well ordered, tending to a random-coil configuration and these are usally referred to as amorphous region. In the case of natural fibres, there are various identifiable aggregates of polymer chains, which are very pften reffered to as micelles, fibrils, microfibrils and also macrofibrils.

Polymer System:

The basic unit of the textile fibre is a molecular segment called monomer which is repeated a large number of times to form a long chain or a molecule called polymer. A polymer may also be formed from two or more different monomers. Such polymers are called copolymer. There is no definite regularity in the order of monomers, which make up a copolymer. Some fibres may contain additional monomers , which do not form part of the polymer chain and are incorporated to improve certain properties of the fibre such as dye affinity. Those are grafted onto the polymer chain as side group or branch. The homopolymers, copolymers and grafted polymers, which can be prepared from the three monomers.
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