Thursday, December 31, 2009

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

Wednesday, December 30, 2009

Natural dyes classified on the basis chemical nature of colouring matter

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

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

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.

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 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)

Friday, December 18, 2009

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.

Wednesday, December 2, 2009

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.