Nomenclature of dyes:

Certain letters appear after the words indicative of the color of the dye. These represent the tone of the dye and also the intensity of the tone. This G indicates GELB= yellowish tone, R indicates ROT= reddish tone, and B indicates BLEU=bluish tone. Alkali fast Green 3B is a green acid dye with considerable bluish tone. (This is indicated by the suffix 3B.)

In case of Vat dyes the names would appear as Indanthrene Yellow RK, here R indicates ROT= reddish tone and K indicates that the dye is of IK class. If the letter N appears instead of K then it indicates that the dye is of IN class.


In case of reactive dyes the letter C indicates that the dye is cold brand dye. H indicates the dyes are hot brand dye.

Suffix or addition	Meaning	Example	Class of the dye (if specific)
G, R, B	Gelb=yellowish, Rot=reddish, Bleu=bluish tone indication	Cloth red G, red dye with yellowish tint	------
2G, 3G etc	Indicates the increasing tone	Indanthrene yellow 4GK, and IY 5GK	------
L	Indicates that the dye is fast to light	Basacryl yellow 7GL	------
C, H	Cold brand dye, Hot brand dye	Premative C, Procion H	Reactive dyes
HE ME etc	High exhaustion, medium exhaustion etc		Reactive
HE ME etc	High energy etc		Disperse

Natural dyes classified on the basis chemical nature of colouring matter

Natural dyes can be classified on the basis chemical nature of colouring matter:-

Flavones:-
The yellow colours are derivatives of hydroxy and methoxy substituted flavones or isoflavones. Eg: - jackfruit bark

Indigoid:
The dyestuff is extracted from Indigofera tinctoria, a bush of the pea family. The dye is extracted from the leaves of the plant.

Dihydropyrane :-
These are principal colouring matters of logwood and they give dark shades on cotton, silk, and wool.

Anthraquinone:
Some of the most important red dyes are based on the anthroquinone structure. These are obtained from both plants and insects. These dyes have good fastness to light. They form complexes with metal salts and the resultant metal–complex dyes have good fastness.eg. Manjitha


Anthocyanidins: -
This class includes carajurin, obtained from the leaves of Bignonia chica and Awabanin. It dyes silk in blue shades eg. Beet Root

Carotenoid :-
This class includes the orange pigment carotene found in carrots. The dyes based on carotenoid structure are annatto and saffron.


Alpha-hydroxy naphthoquinones:-
The Lawsone or Henna is the most prominent member of this class. It is obtained from the leaves of Lawsonia inermis. Another similar dye is Juglone obtained from the shell of unripe walnuts.

Author : Supriya Sagar Kanzarkar (SGGS I.E & T, Nanded)

carrier dyeing of polyester fabrics

The dyeing of polyester fabric using disperse dyes can be carried out by four methods
Carrier dyeing method

* High temperature dyeing method
* Thermosol dyeing method
* Solvent dyeing
Carrier dying
Certain hydrocarbons, amino acids, amides, alcohols, phenols, and esters accelerate the rate of dyeing of polyester fibres with the disperse dyes from aqueous medium at temperature of up to 100C. the dyeing assistants alter the dispersing properties of the dyes and the physical properties of the fibre so that more of the dye transfers from the dye bath liquor to the fibre substrate. These additives are called as carriers, which swells the fibre and ultimately cause relaxation. They reducing intermolecular forces operating in the fibre and act as molecular lubricants thereby allows the dye molecule to force itself inside the fibre. The carrier that are used are also called swelling agents for the polyester fibre.

Typical dyeing procedure with carriers is as follows
The dye bath is set at 60C temperature and with pH 4-5. Fabric material is run for 10 min and aqueous dispersion of dye along with carrier (3-5 gpl) is added in two stages with a gap of 15 min. Carrier is dispersed in water at least for 30 min before use to avoid insoluble particle of carrier, which may cause a carrier mark in the fabric. dyeing is continued for about 60-90 mins. Other auxiliaries such as dispersing agent 0.5to 1 mg per lit. is also added to ensure good dispersion throughout the dyeing.


Disadvantages of carrier dyeing
1. Centre selvage variation may occur
2. Carrier mark problem
3. Tailing effect
4. This method is suitable only for light and medium depths
5. Complete removal of residual carrier is difficult
6. Most of carriers are toxic, gives unpleasant smell to fabric
7. Dyeing process takes more time as compare to other methods
8. It may turn out to be costly process due to high prices of carrier themselves.

Industrial application of textile fibres

Technological developments have broadened the scope of applications of the textile fibres. High performance Textiles are gaining importance day by day due to their versatile applications in endless areas. The advent of areas like Geo – Textiles, Industry, and Building – construction, Medical field, Automotives, Agriculture, Sports, Clothing, and Packaging have widened the reign of textile fibres-The Emperors of Industry.
The world production of textile fibers has risen to 57.7 million tons in the year 2000. This corresponds to per capita consumption of 9.5 kg/year. A production volume of 77 million tons has been predicted for the year 20101. Technical textiles are generally recognized to be one of the most dynamic and promising areas for the future of textile industry. They are mostly defined as the textile materials and products manufactured primarily for their technical performance and final properties rather than their aesthetic or decorative characteristics.
The application of high performance textiles is increasing drastically because of their versatile properties. The necessary properties engineered into these fibers include those of antibacterial, deodorant, temperature control, elasticity, absorbency, and sensitivity to light and heat. This paper focuses on some of the important high performance and unconventional textiles, which finds specialized uses in the present scenario 2, 12 The tensile strength of the textile fibres is the most important for their industrial applications. The strength characteristics of the textile fibres can be improved by various developments in the manufacturing processes and the processing stages, e. g. The breaking length of the Aramid fibre was 190 Km in 1990, but it was improved to 223 Km in 1996. This is possible because of continuous research and developments in the field of manufactured fibres. The lightweight construction potential of fibres for the reinforcement of plastics is shown in Fig: 1 Fig. 1. The lightweight construction potential of fibres for the reinforcement of plastics
Some of the most widely used high performance textile fibres have been discussed below in brief:

• Aramid:

The most important property of these industrial purpose fibers is their resistance to the actions of various chemical agents. They are distinguished by their good resistance to dilute acids and bases, while better chemical resistance is seen in Kevlar fibers. The common drawback of the aramid fibers is their low resistance, which is caused by absorption of ultraviolet radiation. Amongst aramid poly (p -phenylene terephthalamide) is the most successful high performance fiber. They are particularly used in reinforcement of radial tires both in the belt where the modulus contributes to tire performance and is the characteristics where the strength contributes to the durability. The tire system should have impact and fatigue resistance, durability and high-speed performance.
The necessary reinforcing fiber properties are high strength and modulus strength retention after fatigue and adhesion to rubber 3. They are used in filter bags for hot state gases, press cloths for industrial presses (e.g.: application of permanent press finishes to cotton and cotton/polyester garments) and insulation papers for electrical motors and transformers.
P-aramid fiber excels in these applications as compared to steel because in order to impart same strength as that of aramids, steel has to be 3-4 times heavier than the corresponding fiber. The combined attributes of low density, high strength, and stiffness of Kevlar fiber has led to numerous current aerospace composite uses, including exterior structure of aircraft and helicopters, interior aircraft structure, missile and space application.

Pre-Treatment of Cellulosic Textiles

Textile fabrics, either in yarn form or fabric form or hank form, are subjected to different processing procedures depending on its textile end use. The grey cloth is chemically and mechanically processed to give a marketable finish. The sequence of the preparatory process depends on the machinery available, the ease of the availability of water, the type of fabric and the composition of the blend.

A good preparatory process has several objectives, which are given as follows:
a) Removal of loose hairy protruding fibres from the surface of the fabric to give a smooth, even and clean looking face.
b) Removal of natural impurities like oils, fats, waxes, greases, natural matter, lignin and sizing material like starches.
c) To obtain an absorbent fabric, which is ready for dyeing or printing process.
d) To obtain softer and proper white fabric, depending on its application.5

Desizing:
A sized warp is a weaver’s necessity, but a great drawback for the processing department. Warp sized removability depends on the film forming size. Size mainly consists of starch, wax and tallow. All these remain on the warp yarns after weaving the cloth. The process of removal of starch sized from the cloth is known as desizing.

Factors affecting desizing:

1. Concentration of desizing agent.
2. Resolution of size.
3. Alkaline and acidic condition
4. Mechanical properties

Mechanism of desizing:
Chemically, starch is a poly-ά- glucopyranose containing straight chain (amylase) and branch chain (amylopectin) water insoluble polymers. The breaking of these long chain compounds to a shorter one is due to hydrolysis or due to oxidative degradation.

Desizing methods:
1. Hydrolytic method of desizing
2. Oxidative method of desizing

Hydrolytic desizing, which is most prefered over the Oxidative desizing, again classified into three methods. These are
1. Rot steep
2. Acid steep
3. Enzymatic desizing

Rot steep: This is the least expensive and oldest method of desizing in which no special chemicals are added. Here starch-sized fabric is passed through a padding mangle and saturated with water at 400 C to give 100% pick up. Then the fabric is allowed to remain for 24 hours, during which starch becomes solubilised in water because of fermentation.

Limitations:
1. This method does not yield uniform results.
2. It requires large floor space area and longer duration of time.

Acid steep: Dilute sulphuric or hydrochloric acid may also be used to hydrolyse the starch from the sized fabric. A 0.25 % (w/v) solution of the acid at room temperature (300 C) is sufficient for the purpose. By using acid solution, the duration of the desizing process may be reduced to 8-12 hours.

Limitations:
1. Local evaporation of water during the storage period may cause hydrolysis of cellulose itself leading to weakening of cotton at the places where evaporation has taken place.
2. This method does not yield uniform results.

Enzymatic Desizing
Enzymatic desizing is a more advanced method for removing the starch. Enzymes are complex, protienaceous substances, which are secreted by the cells of the living organisms and they have a very good water solubility. Three principal types of starch splitting enzymes used for desizing are ά-amylase,ß-amylases and amido glucosidase The origin of these enzymes also plays an important role in the activity of enzymes. These enzymes are highly specific and work at different specific temperature and pH.

Natural dyes

Natural dyes comprise those colourants that are obtained form animal or vegitable matter without chemical processing. Natural dyes are generally non-substantive and hence must be used in conjunction with mordants.



CLASSIFICATION OF NATURAL DYES: -

Based on chemical structure:
Indigoids: -
The dyestuff is extracted from Indigofera tinctoria, a bush of the pea family. The dye is extracted from the leaves of the plant.
Anthraquinones: -
Red dyes are based on anthraquinone structure. These dyes are characterized by good fastness to light.
Alpha napthaquinones: -
Lawsone or Henna is the most prominent member of this class. It is obtained from the leaves of Lawsonia inermis. Another similar dye is Juglone obtained from the shell of unripe walnuts.
Flavones: -
The yellow colours are derivatives of hydroxy and methoxy substituted flavones or isoflavones. Eg: - jackfruit bark
Dihydropyrans: -
These are principal colouring matters of logwood and they give dark shades on cotton, silk, and wool.
Anthocyanidins: -
This class includes carajurin, obtained from the leaves of Bignonia chica and Awabanin. It dyes silk in blue shades.
Carotenoids: -
This class includes the orange pigment carotene found in carrots. The dyes based on carotenoid structure are annatto and saffron.

Based on Color
Blue Dyes: Natural indigo, sulphonated natural indigo and the flowers of the Japanese “Tsuykusa”
Red Dyes: The colour index lists 32 red natural dyes. The prominent among them are madder (Rubia tinctorum L), Manjeet (Rubia cordifolia), Brazil wood/Sappan wood (Caesalpina sappan L), Al or Morinda (Morinda citrifolia L).
Yellow Dyes: Colour index lists 28 yellow dyes. Some of the important yellow dyes are, black oak (quercus velutina), tumeric (curcuma longa), and weld
(reseda luteola) and Himalayan rhubarb (rheum emodi).

Natural dyes

CI Natural No. of Dyes
Yellow 28
Orange 6
Red 32
Blue 3
Green 5
Brown 12
Black 6
__________
92

Structures of only 67 are known
Many dyes have more than one colouring compound
Some dyes have identical structures
Some dyes have structures similar to synthetic dyes.



Extraction: -
In general the extraction of the dye is carried out by boiling the contents in water for optimum time (found out by optimization of parameters) which is 45 to 60 minutes in most cases. The solution is filtered and cooled. The filtrate is used as a dye.
Apart form this there are two other methods of extraction of dyes. These are 1) solvent extraction e.g., Alkamin Natural Red 24,
and 2) supercritical fluid extraction.

MORDANTS
Natural dyes are either substantive, needing no mordant, or adjective requiring one. The majority of natural dyes need a chemical in the form of a metal salt to create an affinity between the fibre and the dye these chemicals are called as mordants, thus mordant is a chemical, which can fix itself on the fibre and also combines with the dyestuff. A link is therefore formed between the dyestuff and the fibre, which allows certain dyes with no affinity to be fixed on to the fibre. Tannins, metallic salts and oils are used as mordants.

Tannins
In the dyeing of textiles with natural dyes, tannins are used as natural mordants. These are high molecular weight compounds (between 500 to 3000) containing phenolic hydroxyl groups to enable them to form effective cross-links between proteins and other macromolecules.
The stability of the tannin treated fibre depends upon the pH, ionic strength and metal chelators. Tannins may be further classified into two on the basis of their chemical structure as:
- Hydrolysable tannins obtained from myrobalan fruit, oak bark, gallnuts,
pomegranate rind, sumac leaves.
- Condensed tannins like catechin obtained from acacia catechu.

Metallic mordants
There are several different metal salts that can be used for mordanting. The most effective ones are: -
Alum – potassium aluminum sulphate
Copper – copper sulphate
Chrome – potassium dichromate
Iron – ferrous sulphate
Tin – stannous chloride, stannic chloride.

Oils
Oil –mordants are mainly used in the dyeing of Turkey Red Colour from madder. The main function of the oil-mordant is to form a complex with alum used as the main mordant. Since alum is soluble in water and does not have affinity for cotton it is easily washed out from the treated fabric. The naturally occurring oils contain fatty acids such as palmitic, stearic, oleic, ricinolic etc. and their glycerides. The –COOH groups of fatty acids react with metal salts and get converted into –COOM, where M denotes the metal, for instance in the case of alum it would be Al. subsequently, it was found that the treatment of oils with concentrated sulphuric acid produces sulphonated oils which possess better metal binding capacity than the natural oils due to the introduction of sulphonic acid group, -SO3H. The sulphonic acid can react with metal salts to produce –SO3M. The bound metal can then form a complex with the mordant dye such as madder to give Turkey Red colour of superior fastness and hue.

Methods of mordanting
The three methods used for mordanting are: -
- Pre-mordanting: - The substrate is treated with the mordant and then dyed.
- Meta - mordanting: - The mordant is added in the dye bath itself.
- Post-mordanting: - The dyed material is treated with a mordant.
The methods have different effects on the shade obtained after dyeing and also on the fastness properties. It also depends upon the dye and the substrate. It is therefore necessary to choose a proper method to get the required shade and fastness by optimisation of parameters.
Cotton:
Since metallic mordants are soluble in water and are loosely held by the cotton fibres, these mordants have to be precipitated on the fabric by converting them into insoluble form, or by first treating the fibres with oil or tannic acid and then impregnating treated fabric with solution of mordant, whereby the metallic mordants are held on to cotton via oil or tannic acid.
Wool:
Unlike cotton, wool is highly receptive towards mordants. Due to its amphoteric nature wool can absorb acids and bases equally effectively. When wool is treated with a metallic salt it hydrolyses the salt into an acidic and basic component. The basic component is absorbed at –COOH group and the acidic component is removed during washing.
Wool also has a tendency to absorb fine precipitates from solutions. These precipitates are superficially sorbs onto surface of fibres and the dye attached to these gives poor rubbing fastness.
Silk:
Like wool, silk is also amphoteric and can absorb both acids as well as bases. However, wool has thiol groups (-SH) from the cystine amino acid, which act as reducing agent and can reduce hexavalent chromium of potassium dichromate to trivalent form. The trivalent chromium forms the complex with the fibre and dye. Therefore potassium dichromate cannot be used as mordant effectively.

Effects of mordanting
 Some of the natural dyes can form metal-complexes and thereby yield different colours with different metal salts.
 Mordanting improves the wash fastness of the dyes as the dyes are fixed on to the textile substrate.
 Treatment with tannins makes the dyeings dull. Alternatively, if a water-soluble salt such as alum is applied on to a cotton substrate and is then insolubilised by treatment with alkali then the insoluble salt of aluminum is deposited in the material. This provides metal chelating areas for the natural mordant dye. This kind of treatment can form the basis to get bright shades of natural metal complexing dyes.

Environmental problems posed by mordants: -
There is a tendency to use all types of metal salts for the purpose of mordanting disregarding the restrictions laid on the permissible quantities of different metals by the German ban. Accordingly the indicative maximum permissible quantities of different metals in the ultimate product are as follows: -

METALS LIMIT (ppm)
Arsenic 1.0
Lead 1.0
Cadmium 2.0
Chromium 2.0
Cobalt 4.0
Copper 50.0
Nickel 4.0
Zinc 20.0
Mercury 0.02

The upper limits of the presence of metals vary from product to product and are different for different eco-marks. However there is no upper limit on aluminum, iron and tin. Hence one can use these salts for complexing and mordanting.
According to eco-standards copper and chrome are red- listed and hence are not to be used. Another problem posed by a mordant is that a substantial proportion of it is left unexhausted in the residual dyebath and may cause serious effluent problems Researchers claim that the use of heavy metals is not necessary because the resulting shades can be obtained from other natural dyes and also advocate the use of environmental friendly mordants by craft workers. Aluminum and iron are relatively innocuous; they are abundantly available and produce excellent dyeings.

MERITS AND DEMERITS OF NATURAL DYES:-

ADVANTAGES OF NATURAL DYES: -
1) Health and safety aspects of natural dyes: Though all natural dyes are not 100% safe they are less toxic than their synthetic counterparts. Many of the natural dyes like turmeric, annatto and saffron are permitted as food additives. Many natural dyes have pharmacological effects and possible health benefits.
2) They are obtained from renewable sources.
3) Natural dyes cause no disposal problems, as they are biodegradable.
4) Practically no or mild reactions are involved in their preparation.
5) They are unsophisticated and harmonized with nature.
6) Many natural dyes have the advantage that even though they have poor wash fastness ratings, they do not stain the adjacent fabrics in the washing process because of the non-substantive nature of the dye towards the fabric. An exception to this is turmeric, which shows substantivity for cotton.
7) Natural dyes are cost effective
8) It is possible to obtain a full range of colours using various mordants.

LIMITATIONS OF NATURAL DYES

The limitations of natural dyes that are responsible for their decline are: -

 Availability
 Colour yield
 Complexity of dyeing process
 Reproducibility of shade
Besides these there are other technical drawbacks of natural dyes: -
These are: -
 Limited number of suitable dyes
 Great difficulty in blending dyes
 Non-standardized
 Inadequate degree of fixation
 Inadequate fastness properties
 Water pollution by heavy metals and large amounts of organic substances.

Textiles in Shoe

In the revolution of branded footwear industry role of textiles has been very important. It played a vital role in manufacturing and functioning of shoes such as wedding shoe, running shoe, rain boots, etc, but more specifically sports shoes. A shoe can contain wide range of textile material such as nylon, rubber, membrane, latex and neoprene for its coatings and finishes
If we can look at these within the shoe can be explain with various parts of shoe such as upper (everything above the sole i.e., it is the part of the shoe that keeps the sole attached to the foot), Linings
(inner surfaces of the upper to protect the foot and enhance comfort, non-wovens and more recently combinations of hydrophilic and hydrophobic fabric layers are used),Body of the upper (abrasion-resistant fabrics and impregnated fabrics are often used in), Shoelaces and other closures (most often either braided or woven from cotton, nylon or polyester). Footbed (as top covers, most commonly laminated nylon, polypropylene, or polyester fabrics).

Polyester

Polyester/ Polyethylene terephthalate (PET) is a category of polymers which contains ester functional groups in their main chain. Polyester includes naturally occurring chemicals, such as in the cutin of plant cuticles as well as synthetic such as in the polycarbonate and polybutyrate. Polyester may be produced in numerous forms such as fibres, sheets and three dimensional shapes. (200)
Polyester fibres are man-made fibres in which the forming substance is a long chain polymer composed of at least 85% by weight of an ester of dihydric alcohol and terephthalic acid. (201)

Polyesters are the polymers in the forms of fibres having hydrocarbon backbone which contain ester linkages. Hydrolysis of polyester by acid catalysed using dilute hydrochloric acid or sulphuric acid is a reversible process. But using alkali is the usual way of hydrolysing esters. By using alkali the reactions are irreversible and products are easier to separate.

Properties of polyester fibres.
Physical Properties:
The moisture regain of polyester is 0.2 to 0.8 and specific gravity is 1.38 or 1.22 depending on the type of polyester fibres is moderate. The melting point of polyester is 250-300°C. A wide of polyester fibres properties is possible depending on the method of manufacture. Generally as the degree of stretch is increased, which yields higher crystallinity and greater molecular orientation, so are the properties e.g. tensile strength and initial Young’s modulus. Shrinkage of the fibres also varies with the mode of treatment. If relaxation of stress and stain in the oriented fibre occurs, shrinkage decreases but the initial modulus may be also reduced.

Miscellaneous Properties:
Polyester fibres exhibit good resistant to sunlight and it also resists abrasion very well. Soaps, synthetic detergents and other laundry aids do not damage it. One of the most serious faults with polyester is its oleophilic quality. It absorbs oily material easily and holds the oil tenacity.
Chemical Properties:
Effect of alkalies: Polyester fibres have good resistance to weak alkalies high temperatures. It exhibits only moderate resistance to strong alkalies at room temperature and is degraded at elevated temperatures.
Effect of acids: Weak acids, even at the boiling point, have no effect on polyester fibres unless the fibres are exposed for several days. Polyester fibres have good resistance to strong acids at room temperature. Prolonged exposure to boiling hydrochloric acid destroys the fibres, and 96% sulfuric acid and causes disintegration of the fibres.
Effect of solvents: Polyester fibres are generally resistant to organic solvents. Chemicals used in cleaning and stain removal do not damage it, but hot m-cresol destroys the fibres, and certain mixtures of phenol with trichloromethane dissolve polyester fibres. Oxidizing agents and bleachers do not damage polyester fibres.
Polyester fibres have taken the major position in textiles all over the world although they have many drawbacks e.g., (a) low moisture regain (0.4%), (b) the fibres has a tendency to accumulate static electricity, (c) the cloth made up of polyester fibres picks up more soil during wear and it also difficult to clean during washing (d) the polyester garments from pills and thus, the appearance of a garment is spoiled, (e) the polyester fibres is flammable. Thus, it has been suggested that surface modifications can have an effect on hand, thermal properties, permeability, and hydrophilicity.
Polyester fabrics have been widely accepted by consumers for their easy care properties, versatility and long life, Inspite of such acceptance, complaints concerning their hand, thermal properties and moisture absorbency have been cited
Improved moisture absorbency of polyester fibres can be achieved by introducing hydrophilic block copolymers. However, this modification can lead to problems of longer drying time, excessive wrinkling and wet cling In addition, penetration of water into the interior of the fibres has not been clearly shown to improve perceived comfort
Polyester fibres are susceptible to the action of bases depending on their ionic character. Ionizable bases like caustic soda, caustic potash and lime water only effect the outer surface of polyester filaments. Primary and secondary bases and ammonia, on the other hand, can diffuse into polyester fibre and attack in depth resulting in breaking of polyester chain molecules by amide formation
One of the surface modifications is the controlled hydrolysis of polyester. The action of strong base leads to cleavage of ester linkages on the fibre surfaces the result is the formation of terminal hydroxyl and carboxylase groups on the fibre surface. Hydrolysis is believed to increase the number of polar functional groups at the fibre surface.

Cotton Fibre Morphology

Cotton Fibre Consists of four regions

Cuticle : Very thin outer layer containing wax amd pectic material

Pectin:

1. A peculiar group of carbohydrates of very complex composition.They are usually present as C and Mg salts.In immature fibres there is relatively high amount pectins (6%).
2. In mature fibres it is relatively high amount pectins (0.9-1%).
3. Decrease in pectin content with parallel increase in cellulose content proves that pectin is the parent substance from which cellulosic is formed
4. Function is to protect the fibre from atmospheric oxidation


Primary wall:

1. Composed of cellulose, Pectic and fatty matter
2. Formed in the first phase of growth
3. Cellulose fibrils are disposed transversely or circularly to produce high peripheral strength and also makes it weaker in length wise direction of the fibre and account for the low strength of immature fibre
4. In all native-cellulose fibres, the molecules are highly oriented parallel to one another, but they spiral round the fibre, thus reducing the degree of orientation parallel to the fibre axis.
5. In flax, ramie, hemp, and other bast fibres, the spiral angle is small – less than 6° - so that these fibres are highly oriented and give high strength and low extensibility.
6. In cotton, however, the spiral angle lies between 20° and 30°, and the fibres can extend more easily by stretching the spiral.


Secondary wall:

1. Formed during second phase of growth and makes up about 90% of the total weight.
2. This wall is composed of successive layers of cellulose deposited on the inner side of the primary wall without increase in diameter
3. Strength of the fibre is determined by secondary wall


Lumen:

* Central hollow canal whose dimensions varies over a wide range
* Contains protein, mineral salts and pigments

Course Hero

Just few days back I came across a good educational site 'course Hero'. What is Course Hero? This is how they describe themselves:"Course Hero was built by students to help students! Its an open social learning network for students, educators and self-learners to publish, share and view academic resources online. Course Hero provides critical and timely learning assistance through our user-contributed materials and most importantly online study groups comprised of students, educators and self-learners." Course Hero facilitated our studying process.
This website provides a lot of downloadable learning materials and exam modules with various topic, from many sources. With Course Hero, we can also learning in a group, directly communicate with people from different countries, and discussing a topic together in a real time. One can sign-up for free, but if you want to search for their complete archives, you need to be their premier member first. For example, you can learn from ACCT 108 Lehigh University or ACCT Lehigh Class Notes.

Fibre Classification, Cotton fibre 1

What is Fibre

Fibre is a unit matter, which possesses the properties of fineness, flexibility and a high ratio of length to thickness to be used in textile. It is a smallest unit used in a textile structure. It may be combined with others to make yarn or fabric.

Classification of Textile Fibres Based on Origin
Classification of Textile Fibres based on its chemical constitution



Cotton Fibre

- It is Natural, Vegetable, Cellulosic fibre

- It is the Oldest fibre reportedly found in found in Indus valley

- Account for more than 50% of total world fibre production

- Botanically belongs to Gossypium Family

- Productive regions accdg. to importance

1. US 2. India 3. Russia 4. Brasil 5. Egypt 6. China

Friction Spinning

The need to rotate the package at the twist insertion rate coupled with rapid increase in spinning tension with spinning speed sets a limit to the spindle speeds achievable in ring spinning. Open end spinning methods where open-end of the yarn alone needs to be rotated for imparting twist was therefore, developed to achieve high delivery rates. Rotor spinning which is one of first methods developed on this principle has well established itself as an alternate to ring spinning in course count range for certain end uses. Friction spinning represents an alternate open-end spinning method to rotor spinning which holds promise of still higher delivery rates.

Frictions spinning technologies works on the principle of open-end or wrap (Fasciated)/core spinning. The general principle of working of friction spinning in its simplest form can be described as below.

As in the above diagram, separating them from slivers generates a stream of fibres, which is transported through a duct. The fibres are then directed towards the nip of two rotating drums called friction drums .The fibres are collected close to the nip of these drums. The friction drums have perforations on it and suction from inside holds the fibres on the surface. There is a long slot inside the friction drums located close to the nip point along the length of friction drums and the rest of the area inside the perforated drum has a shield. So, the yarn at the nip of the friction drum is subjected to a radial force generated as a result of airflow over yarn.

This is shown in figure 2 , This radial force serves as a normal load and frictional force is generated between the yarn and the surface of friction drum. It can be observed from the same figure that at the closest proximity of the friction drums they rotate in opposite direction and the frictional force thus developed, produces a torque on the yarn tail. Continuous rotation of the drum produces twist in the yarn leading to gradual integration of fibres in the yarn tail. The yarn is withdrawn in the direction of the axis of the friction drums and is wound on a bobbin.

Fig.2 : Forces acting on the yarn tail and the vector diagram.

Textiles and Apparel Industry- Global Challenges and Opportunities 2009 and beyond

The “International Textiles Conference and Exhibition 2009” organized by the Team tech Textiles, India and supported by the leading Textile Associations, who are working for the development of Textile industries in India, Corporate Garment Industries, Leading Textile and Apparel Industries, Textile & Garment Machinery Manufacturers & allied industries, Will be held from 16 April 09 (Thursday) to 18 Apr 09 (Saturday) in Bangalore. Under the theme of “Textiles and Apparel Industry- Global Challenges and Opportunities 2009 and beyond”

Speakers from world-renowned fashion industry, Academics, Textile and apparel industry will be participating to share their thoughts on textile technology, R&D, Policy making, marketing to face the challenges, opportunities 2009 and beyond…

for more details visit event website teamtechtextiles

Colour and Colour Mixing

A coloured surface appears the coloured because light is reflected from it in that colour's wavelengths only. All other wavelengths predominantly are absorbed by it. A blue object reflects blue light but absorbs most of the red, orange, yellow, green and violet. Black and white is slightly different. They are not, strictly speaking, colours. White surfaces reflect all or nearly all wavelengths and black surfaces absorb them totally. Response curves for the rods (colour sensitive photoreceptors of the human eye). The peak response values occur at 580 nm for red, 540 NM for green, and 440 NM for blue. There is no excitation of the blue cones above 550 NM .The overall response of all three cones together is at 560 NM (yellow-green).

Additive Colour Mixing
The absence of light is darkness, add light to it
Superposition (lamp overlap)
Rapid alternation (biased LED) "persistence of vision"
Small elements (TV pixels, halftones)

The basic rules of additive colour mixing.
red + green = yellow;green + blue = cyan
blue + red = magenta ; red + green + blue = white

Subtractive colour mixing
Subtractive colours are produced when white light falls on a Coloured surface and is partially reflected. The reflected light reaching the human eye produces the sensation of colour. Subtractive colour is based on the three colours Cyan, Magenta and Yellow. Varying the mixture of these primary colours produces other colours. When these three colours are mixed together at 100% they produce black. The absence of CMY pigments would result in white.

Metamerism :
When two object with different spectral graphs present identical coloured appearance in specific lighting and observation conditions, and different appearance when lighting or observation conditions are changed ,then metamerism is said to be in existence. Metameric index (D65 ~ A) = { (LD-LA)2 + (a*D65-a*A)2 +( b*D65 - b*A)2 }1/2

Chitosan

Textile industry is an omnipresent industry. It has found applications over such wide range, which perhaps no other industry, except Information technology and Computers, could found. This is the reason various branches of Science and technology have been collaborated with this industry. This collaboration makes the application of various fundamentals and materials possible in textile industry. The field of Biomaterials is one such field, which provides various new materials to textile industry for obtaining better results in most ecofriendly and economical ways. Successful application of enzymes on shop floor in textile wet processing is a very good example. Now another biomaterial is about to enter in the textile industry, this material called, as “Chitosan” is not a new biomaterial; however, some lateral thinking of research workers has found some novel application of this biomaterial.

A glance at Chitosan:

Chitin is one of the most abundant polysaccharides found in nature. It is a white flaky material, found in the exoskeletons of arthropods such as insect spiders, some fungi, crabs, and shrimp. Chitosan is a derivative of Chitin produced by N-acetylation of the chitin molecule. It is often considered a cellulose derivative, although it does not occur in organisms producing cellulose. The difference between cellulose and Chitosan is that the 2-hydroxy group of the cellulose has been replaced with an acetamide group. This results in several Beta-(1 -> 4)-2-acetamido-2-deoxy-D- glucopyrnaose structural units (GlcNAc).Chitin and Chitosan have the potential to reduce and to solve some problems for creating "Greener" environment.

The chemical structure of Chitin and Chitosan are shown in Fig.

Chitosan in Wool Processing:

Additives and additional processes for bet

ter wool processing are being researched extensively for better dyeing, anti-felting, and anti-shrinking properties. Chitosan and Chitin have also enticed the attention of the research workers for their application in this area. In protonated form, Chitosan behaves like a polyelectrolyte, forming a viscous solution and interacting with oppositely charged molecules. However, it has weak binding properties for the fibre, in addition the even distribution on the fibre is very difficult obtain.

The binding properties of Chitosan on wool using a solution containing a non-ionic surfactant have been studied and it has also been shown that the oxidative treatment with the help of hydrogen peroxide and enzymes before the application of Chitosan, gives better binding properties uniform distribution.

Soil release finish

The purpose of soil release finishes is to improve soil removal from hydrophobic of durable press finished fabrics. Soil release does not include detergency of particulate soil but it reduces soil redeposition.
Soiling can be of two types, dry soiling (actual use) and wet soiling (during laundering operations where soil redeposition occurs). Soil is transported to the fabric and then deposited on to it by

• Air currents
• Electrostatic attraction
• Contact transfer from soiled surface to cleaner surface by pressure, abrasion, impingement.

The soil release finishes are available as emulsion, solutions or dispersions and they are either hygroscopic or increase hydrophilicity on water immersion. they also function as antistats. The soil release activity of finish should last for 20-50 home launderings and they should be stable to abrasion. The finish should not be toxic, irritant and should not affect the durablity and wear life of the garment.

The soil release effect may be imparted by a) topochemical reactions such as grafting, hydrolysis or oxidation, b) durable physical adsorption of surfactnats on fibre surface and c) coating with soil release polymers.

Denim Jeans

In the growing world market for leisure wear, denim holds a dominating position today. In the 1950’s when Marlon Brando and James Dean made blue jeans respectable, denim began its progress round the world. Since then it developed into a fashion unequaled in its variety. It is one of the most successful textile fabrics ever developed. This classic fabric has been in use for a long time across the world. Traditionally, denim has been referred to as a heavy grade cotton twill fabric with indigo dyed warps. Today, denim jeans is available in a rainbow of colors and in black color as well, in addition to without any color at all.
Denim continues to be mainly used for jeans both women’s jeans and men’s jeans. Denim is bleached, brushed, sanded, ice-washed, ripped, torn and even shot with bullets to give character to what is otherwise a rather mundane material. Denim jeans is truly a fabric that appeals to all classes of people of all ages. For women’s jeans, it comes in various sizes depending on the body type such as slim, curvy, athletic, full figure, short and long which can be found on various online shoping sites.

Flame retardant textiles

Flame retardant textiles are found in a variety of textile products ranging from clothing, to automotive textiles, to home furnishings. Depending on chemical nature, there are four main classes flame retardants. These are inorganics (e.g. aluminum trioxide and magnesium hydroxide), nitrogen-based organic, organophosphorus (e.g. phosphate esters), and halogenated flame retardants Flame retardants may also be classified depending on their fastness to laundering as non-durable, semi-durable, or durable. A nondurable finish does not withstand laundering and must be reapplied. Semi-durable treatments fall in between nondurable and durable. Depending on the end use of the product, the durability of the treatment is important. For example, apparels should have durable flame retardant treatment since they are washed regularly while home textile fabric would not.

Flame retardants are evaluated for many properties during burn testing including char length, after-flame and afterglow times, and melt drip. ASTM D 6413-99 defines char length as the distance of visible fiber damage beginning at the bottom edge where the flame was applied. After-flame time is a measurement of how long a substance continues to flame once the ignition source is removed and afterglow is how long a substance glows after the ignition source is removed. Self-extinguishment is defined as when the glowing or flaming of a specimen goes away after the flame source is removed.