Bdtextileblog| Textile Engineering Guide

Water softening process - Demineralization process

noreply@blogger.com (Rony) — Fri, 16 Mar 2012 00:48:00 +0600

Demineralization process is the modern water softening process. By applying this process the water obtained may be as pure as distilled water. Because not only the ions are removed those are responsible for water hardness but also some dissolved salt i.e. FeCO₃, CaCl₂ etc. can be removed. In this process strong acid cation resin and strong base anion resin are used. Cation in water like Sodium, Calcium, Magnesium removed by cation resin. And for anion like Chloride, Sulphate anion resin are used.

Process: The demineralization plant consist of both cation and anion unit. Control over cation and anion unit is essential. Predetermined amount of resin bed are taken according to the composition of hard water. Then, the process is done by two steps:

1. Hydrogen Cation exchanger: Cation resin can be in Hydrogen (R-SO₃H) or Sodium form (R-SO₃Na). Sulphonated resin (Cation acid resin) in Hydrogen form is used as cation exchanger for water softening.

CaCl₂ + H₂R --> CaR↓ + 2HCl

Ca(HCO₃) + H₂R --> CaR↓ + 2H₂O + 2CO₂

2. Anion exchanger: Amino resin (anion base resin) is used and produced HCl is removed.

HCl + HOR₁ --> ClR₁↓ + H₂O (soft water)

Regeneration: We know, regeneration is done to get back the resins which are used to softening water are exhausted and we have to apply some acid & alkali to regenerate them again.

For step1, regeneration is performed by using acid. Less than 2% H₂SO₄ is used.

CaR + H₂SO₄ --> CaSO₄ + H₂R (regenerated resin)

For step2, regeneration is done by using 1% solution of NaOH.

ClR₁ + NaOH --> NaCl + HOR₁ (regenerated resin)

Water softening process - Base Exchange process

noreply@blogger.com (Rony) — Sun, 11 Mar 2012 00:26:00 +0600

It is the most simple and used process. Water obtained by using this process has a hardness of 0-2⁰. Water is softened by exchanging Ca²⁺ and Mg²⁺ ion with the help of zeolite. That’s why it is also called Zeolite or permutit process. While water is passed into Zeolite the ions are exchanged. Zeolite is the Hydrated silicate of sodium and aluminium. The general formula is:

(Na₂O)_x(Al₂O₃)_y(SiO₂)_z(H₂O)_n

Let, Zeolite = Z = (Al₂O₃)_y(SiO₂)_z(H₂O)_n

For temporary hardness:

Ca(HCO₃) + Na₂O.Z --> CaO.Z+ Na₂CO₃ + H₂O

Mg(HCO₃) + Na₂O.Z --> MgO.Z + Na₂CO₃ + 2H₂O

For permanent hardness:

CaSO₄ + Na₂O.Z --> CaO.Z + Na₂SO₄

MgSO₄ + Na₂O.Z --> MgO.Z + Na₂SO₄

MgCl₂ + Na₂O.Z --> MgO.Z + NaCl

Process:

Zeolite are taken into the tank. Then hard raw water is entered into the inlet pipe. While water comes to the contact of Zeolite in Zeolite bed, the water softened. Then soft water is collected from downward outlet.

Regeneration:

When water is softened by this process for many times Zeolite is exhausted. For this reason, Zeolite is not used for every time while softening water. 10% NaCl is used through the Zeolites and the Zeolites are regenerated again.

CaO.Z + 2NaCl --> Na₂O.Z + CaCl₂

Water softening process - Lime soda process

noreply@blogger.com (Rony) — Fri, 9 Mar 2012 00:25:00 +0600

Hydrated lime Ca(OH)₂and sodium Carbonate are used in this method to precipitate Calcium and Magnesium ions. Particularly, Ca(OH)₂is used for Carbonateions and NaCO₃ is used for non Carbonate ions.

For temporary hardness,

Ca(HCO₃) + Ca(OH)₂ --> 2CaCO₃↓+ 2H₂O

Mg(HCO₃) + Ca(OH)₂ --> 2MgCO₃↓+ 2H₂O

Here, the solubility of Ca(HCO₃) is lower than that of Mg(HCO₃). CaCO₃ precipitate first while water is treated with Ca(OH)₂ and at 100⁰C temperature the solubility of CO₃ is 12-75 ppm.

For permanent hardness.

CaSO₄ + NaCO₃ --> CaCO₃ + Na₂SO₄

MgCl₂ + Ca(OH)₂ --> CaCl₂ + Mg(OH)₂

In 2^nd reaction from above CaCl₂ is produced which is replaced by CaCO₃ by using Na₂CO₃.

CaCl₂ + Na₂CO₃ = CaCO₃ + NaCl

The main parts of the process are:

Reagent tanks (Soda lime + Coagulants)
Reaction tank
Filter
Soft water storage tank.

Process:

The lime and soda are entered into the reagent tank. At the same time, predetermined amount of raw hard water is pumped into the Reaction tank. A large propeller acts as an agitator into the Reaction tank. The agitation is increased to get more amount of ppm, steam is passed through the sideway pipe to increase the temperature of the mixer. The water is filtered to remove CaCO₃ after precipitation is completed and finally passed to the soft water storage tank.

Precipitation rate can be increased by:

By increasing Temperature.
By using excess reagent and stirring.
By using sand grain.

The residual hardness that presents in water as CaCO₃ can be decreased by either hot or cold method. For cold method it can be reduced to 5-20 ppm and for hot process it is 5-15 ppm.

After processing with lime soda method if the water contains some hardness, then it can be removed by adding phosphate. In this process, some NaOH are also used.

10CaCO₃ + 6Na₃(PO₄) + 2NaOH --> {Ca(PO₄)₂}₃Ca(OH)₂ + NaCO₃

Soft water - water softening methods

noreply@blogger.com (Rony) — Tue, 28 Feb 2012 00:40:00 +0600

Soft water:

The water which does not contain HCO₃^-, Cl^-, SO₄^2- salt of Ca²⁺, Mg²⁺, Fe²⁺, Al³⁺ & form foam easily by reacting with soap is called soft water e.g. Rain water.

Water softening methods:

Water softening process is done in order to remove Ca²⁺and Mg²⁺ ions from water. Since, Na and Mg are nonvolatile salt, it is needed to separate them from water by precipitation or any other way.

There is a simple process of softening temporary hardness of water and it is boiling. When water is boiled the dissolved Calcium & Magnesium salt converted to Calcium Carbonate and Magnesium Carbonate & precipitated. That way they can be separated from water. The reaction is here:

Ca(HCO₃) --> CaCO₃ + CO₂ + H₂O

ppt.

Mg(HCO₃) --> MgCO₃ + CO₂ + H₂O

ppt.

For both temporary and permanent hard water there are three industrial softening methods. These are:

Soda lime mthod
Base exchange method (permutit)
Demineralisation method.

Problems caused by hard water in textile industry

noreply@blogger.com (Rony) — Sun, 26 Feb 2012 12:51:00 +0600

Hard water can create so many problems during wet processing from desizing to finishing in textile mills. Since every process is related to the next process, so all processes should be done precisely to get best result. To do it first we have to know what problems hard water can create in different stage of wet processing.

In Boiler: If hard water is used in boiler, then a layer is formed on the inner surface of the vessel or in the inner side of tube. This layer is very hard just like as stone which is not removed without hammer or chesser or tessel. This is called scale. In boiler, temporary hard water produce CaCO3 & Mg(OH)2, the combination of CaCO3 & Mg(OH)2 is called scale.

Ca(HCO3)2 --> CaCO3 + CO2 + H2O

Mg(HCO3)2 --> Mg CO3 + CO2 + H2O

MgCO3 + H2O --> Mg(OH)2 + CO2

[CaCO3 + Mg(OH)2 ] --> Scale.

As a result, in boiler more heat will be needed & for that, more fuel will be required. For scale formation, equally heat transformation in boiler tube is not possible very often. As a result, for excess heat of a particular part of the tube, the tube may burst.

Heat loss of tube up to 40% according to the diameter of the tube. Heat loss by pipe scaling up to 40% for 20 mm scale.

SCALE THICKNESS HEAT LOSS

1 mm approximately 10%

3 mm „ 17%

5 mm „ 22%

10 mm „ 30%

20 mm „ 43%

Corrosion can be a serious problem in boiler, if hard water is used in it. Dissolved O2 in the presence of CO2 is the common cause of corrosion. Fe present in hard water reacts with CO2 to form Fe CO3, which is the main process of corrosion. This Fe CO3 is hydrolyzed & produce Fe(OH)2, this agent / component damage the boiler.

Fe + H2O + CO2 --> Fe CO3 + H2O

Fe CO3 + H2O --> Fe(OH)2 + CO2

Desizing: Hard water de-active enzymes & insolubilize size materials such as starch, PVA etc.

Scouring: Hard react with soap during scouring. Soap is the Na & K salt of higher fatty acid (C17H35COONa). The Hard water does not easily form lather by reacting with soap. The Ca & Mg salt of hard water react with soap and produce insoluble organic salts which becomes the wastage of soap.

CaSO4 + 2 C17H35COONa --> (C17H35COO)2Ca + Na2SO4

Insoluble organic salt

If we use hard water in wet processing, then they produce insoluble salt which is deposited with the fabric. As a result, the surface of scoured fabric become harsh, hard & non-flexible which creates problem in the next process like produced uneven dyeing.

Bleaching: Hard water decompose bleach bath.

H2O2 --> H2O + [O]

Mercerizing: It forms insoluble metal acid, reduce absorbency and luster.

Dyeing: Ca2+ and Mg2+ ions of hard water react with dye molecules and precipitated the dye. As a result dyestuff are spoilt. Hence, uneven shade (depth of dyeing) of color is produced.

Printing: It break the emulsion, change it’s thickness and efficiency and it is also harmful for thickener. Hard water cause problems in printing process like dyeing.

Finishing: Hard water interfere with catalysts, cause resins and other additives to become non reactive, break emulsion and deactives soap.

From above, we saw that hard water causes problems in every process of wet processing. So, we have to use such water that is suitable for wet processing and don’t create any problem. Ideal quality of feed water for textile industry is :

pH should be in the range of 7 – 8.
Water should be odorless & colorless.
Water hardness: maximum 5° dH.
Solid content: < 50 mg/L.
Dissolved solids : < 1 mg/L.
Inorganic salts: < 500 mg/L.
Organic salts: < 20 mg/L.
Iron (Fe): < 0.1 mg/L.
Mn : < 0.02 mg/L.
Cu: < 0.005 mg/L.
Nitrate: < 50 mg/L.
Nitrite: < 5 mg/L.

Hard water expression method

noreply@blogger.com (Rony) — Fri, 24 Feb 2012 21:25:00 +0600

Hard water is water that has dissolved mineral (Bi-Carbonate, Sulphate, Chloride of Calcium and Magnesium). Hard water is not health risk. But it creates problem during wet processing.

Hard water may be classified into two types:

Temporary hard water
Permanent hard water

Temporary hardness of water can be removed quite easily i.e. by boiling. But permanent hardness can be removed by applying some process. I will discuss these later.

Hardness expression method:

The hardness of water is expressed by the amount of Calcium present in water. In this methods, chloride, sulphates and bi-carbonates of calcium and magnesium are not taken into consideration. Because, it is difficult to measure the components. Hardness is expressed:

PPM (parts per million): PPM is the way to express the dilute concentration of substance. In case of hard water, PPM is the number of grains of calcium carbonate which is present in one million grains of water. It is usually defined as 1mg CaCO₃ per liter and used in America.

In Degree (grains per gallon): The number of grains of Calcium carbonates which are present in 1 gallon (70,000 grains) of water.

Parts per 10⁵: This is the weight of calcium carbonate present in 100000 unit water. It is used in England, France.

So, we find a relationship between PPM and Degree. That is

1000000 grains hard water contains X grain CaCO₃

1 ,, ,, ,, ,, X / 1000000 ,, ,,

70,000 ,, ,, ,, ,, 70000 * X/1000000 grains

Hence, Degree of hardness = 0.7 * PPM

PPM = Degree /0.07

Now, let’s take a look about the scale used in different methods to measure the hardness of water.

1⁰dH hardness (German) --> 10mg of CaOper 1L water.

1⁰fH hardness (French) --> 10mg of CaCO₃per 1L water.

1⁰eH hardness (English) --> 1 grain or 68.4mg of CaCO₃per 4.455L

water.

10mg of CaCO₃per 0.7L water.

1⁰aH hardness (American) --> 1mg of CaCO₃per 1L water.

gpg hardness --> 1 grain or 68.4mg of CaCO₃per gallon (US) water.

10mg of CaCO₃per 0.58L water.

If we convert the different system, then we get a table like this:

	Ppm	Gpg	⁰dH	⁰eH	⁰fH
Parts per million (ppm)	1	0.058	0.056	0.07	0.1
Grains per gallon (gpg)	17.118	1	0.96	1.2	1.7
German degree (⁰dH)	17.80	1.04	1	1.25	1.78
English degree (⁰eH)	14.30	0.83	0.798	1	1.43
French degree (⁰fH)	10	0.584	0.56	0.702	1

You can also use a converter to convert the hardness into different method. To convert click here.

Measurement of Hardness of water:

Classification	mg/l or ppm	grains/gal
Soft	0 – 17.1	0 – 1
Slightly hard	17.1 – 60	1 – 3.5
Moderately hard	60 – 120	3.5 – 7.0
Hard	120 – 180	7.0 – 10.5
Very Hard	180 & over	10.5 & over

Properties and uses of cotton

noreply@blogger.com (Rony) — Tue, 21 Feb 2012 20:56:00 +0600

Properties of cotton mean mainly physical and chemical properties. These are here:

Physical properties of cotton:

Length: 0.5-2.5 inch or 0.3-6 cm.

Diameter: 16-20microns.

Cross section: Kidney shape.

Color: White, grey, cream.

Luster: High.

Dimensional stability: Good.

Tenacity (gm/den): In dry state 3.0-5.0, In wet state 3.6-6.0

Elasticity: 74% recovery at 2% deformation and 45% at 5% deformation.

Elongation at break: 3.0-7.0%

Co-efficient of friction: 0.25.

Drapability: Good.

Resiliency: Low.

Moisture regain: 8.5% and raised to around 25-30% at 100% Relative humidity.

Specific gravity: 1.54

Chemical properties of cotton:

Effects of Acid and Alkalis: Concentrated acid or hot but low concentrated acid damages cotton. Cotton dissolved in high concentrated mineral acids such as HCl, H₂SO₄ but high resistant to alkalis. That’s why NaOH, Na₂CO₃ are used for scouring of cotton. Concentrated NaOH is also used for cotton mercerizing.

Effects of Bleaches: Resistance to bleach, but H₂O₂, NaOCl, NaOCl₂, Ca(OCl)Cl are used as bleaching agents for cotton processing.

Effect of heat: Cotton has an excellent resistance to degradation by heat. It begins to turn yellow after several hours at 120⁰C and decomposes at 150⁰C as a result of oxidation. It damaged at 240⁰C, flame at 390⁰C and burns in air and smell is like paper burning.

Effect of organic solvents: Have resistant ability to most organic solvents such as dry cleaning agents. A little organic solvents can damage cotton.

Dyeability: Have affinity to Direct, Reactive, Sulphur, Vat dye, Mordant, Indigo and natural colorant.

Effect of sunlight: There is a gradual loss of strength when cotton is expressed to sunlight and the fibre turns yellow. Ultraviolet ray is harmful for cotton.

Effect of weather: Acidic air spoils the strength of cotton. If cotton is stored carefully on dry condition it lasts for many years.

Effect of insects: Cotton is not attacked by moth grubs or beetles.

Micro-organism: Cotton is attacked by fungi and bacteria.

Uses of cotton:

Apparel - Wide range of wearing apparel: blouses, shirts, dresses, separates, children-wear, active wear, skirts, pants, sweaters, swimwear, suits, jackets, hosiery, neckwear.

Home Fashion - curtains, draperies, throws, sheets, bedspreads, comforters, towels, napkins, table mats, table cloths.

Medical and cosmetics – Bandage, wound plaster.

Others - fishing nets, coffee filters, cotton paper, in bookbinding, Fire hoses, tents.

Characteristics of cotton

noreply@blogger.com (Rony) — Sat, 18 Feb 2012 23:53:00 +0600

Characteristics of Cotton

Cotton is a natural fibre of vegetable origin like linen, jute or hemp. Cotton is the fruit of a shrubby plant commonly referred to as the "cotton plant". Cotton fiber has natural twists along the entire length of the fiber called convolutions. The convolutions help the fibers interlock when it is spun into yarn. Long fibers have about 300 convolutions per inch and short fibers have 200 or less. Sea Island cotton has highest number of convolutions per inch than the others:

Sea Island cotton --> 300

Egyptian cotton --> 230

American cotton --> 210

Indian cotton --> 150

Long fibre is required to produce higher and fine count. For long staple cotton fibre the ratio of length and thickness is 6000:1 where in short fibre the ratio is 3500:1. When the ratio is high than it is suitable and more easy to spun yarn.

Cotton has a diameter of 16 to 22 micron. But surface of cotton fibre is not regular. Its middle portion is thick and tip is thin and there is no convolution at tip region. Therefore, cotton consists of a irregular surface that increases the friction between the fibres during spinning and yarn becomes strong.

Cotton is not circular in cross-section. It looks like kidney in cross-sectional view under microscope. Due to its convolution and kidney like cross-section air, can pass through the cotton fabric and we feel comfort.

Color of cotton is ranges from white to grey. The color of the fibers is affected by climatic conditions, impact of insects and fungi, type of soil, storage conditions etc. There are five recognized groups of color: white, gray, spotted, tinged, and yellow stained. As the color of cotton deteriorates, the process ability of the fibers decreases.

Cotton has about 55% -70% crystalline region and 30%-35% amorphous region. That’s why the molecules of cotton polymer are arranged in a specific sequence and probably no part is 0.5nm far from the crystalline part. 0.5nm is the maximum distance to form Hydrogen bond in a polymer. These Hydrogen bonds among the polymers make the fibre strong. When cotton is wetted some molecules of amorphous region arranged in a balance way. As a result, 5% Hydrogen bond increases and that’s why wet cotton has greater strength than dried cotton.

Due to higher crystalline region cotton has less elasticity and its tendency of creasing is higher than any other natural fibre.

Cotton fabric becomes dirty easily because of its uneven surface but can be removed quite easily as it has good resistance to bleaching agent and not damaged into hot water.

Chemical structure of cotton

noreply@blogger.com (Rony) — Wed, 15 Feb 2012 14:42:00 +0600

To explain the chemical structure of cotton first we have to know about the chemical composition of cotton. I tried to discuss the structure in a very easy way to understand:

Component	Amount	Main location
Oil and waxes	0.7	Cuticle
Cellulose	86.8	Winding layer and Secondary wall
Pectins	1.0	Primary wall
Carbohydrate	0.5	Primary wall
Salts	1.0	Lumen
Proteins	1.2	Lumen
Water	6.8
Others	2.0

From above table we see Cellulose is the main chemical component of cotton, means it is a cellulose fibre. Each fiber is made up of 20 to 30 cellulose strands and is arranged into a way where it will become absorbent, strong, and durable. Cellulose is a polymer of Beta-D glucose. So, the elements that make up Cotton are: Oxygen (O), Hydrogen (H), and Carbon (C). When arranged in this specific way, these elements make up cotton.

Glucose is the basic unit from which cellulose is made. Here from the picture, we see there are two “Beta-D glucose” linked (as –O is above the C-1 atom) linked by a Beta-glycocydic bond (O-C-O bond is called glycocydic bond). When two glucose react, they produce a compound which is called Cellubiose. A chemical reaction is given for you:

C₆H₁₂O₆ (Beta glucose) + C₆H₁₂O₆ (Beta glucose) = C₁₂H₂₂O₁₂ (Cellubiose) +H₂O

So, it is sure that Cellubiose is composed of two Beta-glucose and Cellubiose is the repeating unit of cellulose polymer of cotton. In a cellulose molecule there are 1000 Cellubiose unit or 2000 Beta- glucose unit in an average. Therefore, degree of polymerization (the total number of structural unit uncluding end groups) is 20000 (average). Generally, it ranges from 2000-10,000.

Moreover, CH, OH, and CH₂ are all covalent compounds because all of the elements are non-metals. Since they are all non-metals so they make covalent bond. All of the bonds are all single bonds. All these compounds are also organic compounds since in each compound there is either Carbon or Hydrogen. There are two functional groups: Alcohol (-OH) and Ether (-O-).

Finally we can say, Cotton is a carbohydrate disaccharide, meaning that it is made up of two hydrocarbon rings. The carbon makes a ring with itself along with oxygen because it wants to fill up all of the spaces in it's last shell. Carbon has four valence electrons, while Oxygen has six, and Hydrogen has one. All these bond in specific ways to have all their empty spaces filled with each other's valence electrons.

Physical structure of cotton

noreply@blogger.com (Rony) — Tue, 14 Feb 2012 00:24:00 +0600

Under microscope cotton looks like a bean or lace and it is not circular in cross section. Physical structure of cotton comprises of several cell walls. The structure is described as follows:

Cuticle: The outermost layer of cotton is known as the cuticle. The cuticle is a few molecules thick and covers the primary wall with a waxy film. The waxy film is a mixture of fats, waxes, and resins.

Primary cell wall: The primary wall is the original thin cell wall and has felt-like reticular structure and consists of crossed cellulose crystalline fibrils. Fibrils are bundles of linear polymer which form the small fibrous structure. In primary cell wall fibrils are about 20 mm thick .

Winding or transition layer: This is the first layer after primary cell wall and between the primary and secondary wall. It differs in structure from either the primary wall or the remainder of the secondary wall. Its fibrils are more wider angle about 20-35 degree than secondary wall and in this region the fibrils periodically reverse the direction of the spiral.

Secondary cell wall: The secondary wall has several layers of spiraling fibers, which make up most of the weight of the cotton fiber. Secondary cell wall is situated inside the winding layer, accounts for the bulk of the cellulose content and in this case, the fibrils are in the form of helices with an angle of 20-30 degree.

In very mature fibre the Tertiary layer can be found adjacent to the linning of the lumen and it consist of the mineral salt and the proteins.

Lumen: The hollow central core of cotton fibres is known as the lumen. Initially there is no lumen in cotton fibre. When cotton becomes mature then lumen is noticed but it gradually begins to smaller and contains the dried out protoplasm and nucleus when the cotton boll development is complete.

Types of Cotton

noreply@blogger.com (Rony) — Sat, 11 Feb 2012 22:43:00 +0600

Cotton can be classified into various class according to commercial, botanical, staple length, maturity. All kinds are given briefly below:

According to Botanical classification:

(a) Gossypium harbaceum: This kind is usually cultivated in Asian Countries like India, Pakistan, China and Bangladesh. Its length is from 0.8 inches to 1 inch, height of the plant is of 3 feet to 6 feet, flower color is yellow.

(b) Gossypium hirsutum: This kind is cultivated in North and South America (90% of world production). Its length is from 0.5 inches to 1.20 inches, height of the plant is from 6 feet, flower color is Red.

(c) Gossypium peruvianum: This is mainly produced in Peru and other South American countries.

(d) Gossypium arboretum: It is widely cultivated in America, also in India, Pakistan,

Russia

. Its length is from 0.5 inches to 1.20 inches, height of the plant is fro 10 feet to 15 feet.

(e) Gossypium barbedense: This type is mainly produced in Egypt and Sudan which is known as Sea Island cotton. It is a high quality cotton but production is low (8% of world production). Its length is from 1.2 inches to 2.4 inches, height of the plant is of 6 feet to 15 feet, flower color is yellow.

According to commercial point of view:

(a) Sea Island cotton: This is the highest valuable cotton in the market for its high quality. Sea Island cotton grows on the coast of the Gulf of Florida, Barbados and in other adjacent islands where the climate is suitable. The length of the cotton is from 1.5 inches to 2.5 inches and diameter is 0.017nm. It can be used for spinning finest count of about 2.94Tex and sometimes mixed with silk. It is famous for its uniformity, maturity, highly developed luster, twist, soften and silk like texture. Its color is white to cream. It was also grown on the uplands of Georgia, where the quality was inferior and was soon surpassed in commercial production by another native American species, Upland cotton (Gossypium hirsutum), which today represents about 95% of U.S production.

(b) Egyptian cotton: There are two kinds of Egyptian cotton:- one brown and the other is white. Egyptian cotton is usually produced in Egypt with extra long staple length. It is very regular and contains few immature or dead fibres. The staples of Egyptian cotton can range from 1 .5 inches to 1.75 inches. Their long length (about twice the size of other cotton fibers) allows them to be spun into very fine yarns but not more than 2.95Tex. These yarns are soft and lustrous yet are very strong and durable.

(c) South American cotton: This has a staple length of 1 inch to 1.5 inches and diameter is .0195mm. It is very suitable to mix with regenerated man made fibre.

(d) American cotton: This is cultivated in the United States. Its staple length is 0.9 inches to 1.25 inches and diameter is 0.021mm. It has good natural color and cannot be used for the extremely fine counts(8.43tex).

(e) Indian cotton: This is short fibre of 0.6 inches to 0.8 inches. Therefore, it is only suitable for producing coarser counts.

(f)

China

cotton: This is the lowest commercially acceptable grade. Its staple length is short and its from 0.5 inches to 0.7 inches. Its twist is not highly developed and rather than harsh. It is not suitable for spinning a good yarn and is usually used in mixture with better quality.

According to fibre length:

(a) Long staple: This is the best and finest quality and has luster. Length of the cotton is longer than the others and it’s from 1 inch to 2.5 inches (25-65mm). Diameter is 10-15 microns. Sea Island cotton, Egyptian, American pima cotton etc. are example of long staple cotton.

(b) Medium staple: This fibre is medium grade, has medium strength and luster. Its length is from 0.5 inches to 1.3 inches (12-33mm) and diameter is from 12 microns to 17 microns. American upland and Peruvian cotton etc. are the example of medium staple.

(c) Short staple: Short staple cotton fibre is low grade coarser fibre, low strength no or little luster. This type of fibre has a length from o.375 inches to 1 inches (9-26mm) and diameter is from 13microns to 22microns. Asiatic cotton and Indian cotton are the good example of short staple cotton.

According to maturity:

(a) Mature fibre: We know mature fibre has well developed cell wall and very small lumen. Like that mature cotton has small lumen and it is the best in quality.

(b) Immature fibre: Fibre with thinner secondary cell wall, larger lumen is Immature fibre. They cannot exhaust the dye molecules properly in dyeing or printing. As a result, they produce uneven shade during dyeing.

(c) Dead fibre: Dead fibre has a only a primary cell wall. The lumen occupied the bulk of fibre. They remain undyed in dyeing.

Cotton | History of Cotton

noreply@blogger.com (Rony) — Wed, 8 Feb 2012 00:04:00 +0600

Cotton

Cotton is a soft natural pure cellulose fibre (vegetable fibre) that surrounds the seed and comes from seedpot of cotton plant, used to manufacture cloth. It is the most widely used natural fibre all over the world.

History of Cotton

No one knows exactly the origin of various species of cotton. But scientists found bits of cotton bolls in cloth while searching the Tehuaca’n Valley of Maxico and that is about 7000 years old. The plant has certainly been grown and used in India for at least 5000 years ago and probably for much longer that was found in Valley of Pakistan. About the same time, people in Egypt also woven and used cotton fabric.

Arab Merchant brought cotton to Europe Countries about 800 AD. When Columbus first discovered America in 1492, he found cotton growing in the Bahamas. By 1500, cotton was known generally throughout the world. One of the earliest crops grown by European settlers, planted at Jamestown colony in 1607.

Cotton was first spun by machine in 1730 in England. Eli Whitney first invented the cotton gin in 1793. Cotton was the most important crop in South before the American Civil War (1861-1865). Slaves usually worked all day long to pick cotton for their masters while overseers watched from their horses. England was one of the south’s largest customers.

Now cotton is produced commercially in more than 60 countries where America, China, Russia, India, Pakistan, Brazil are the largest producers.

From earlier Bangladesh is cultivating cotton. The finest cotton fabric Moslin was produced in Bengal during British rule, most famous all over the world that time. But cotton wasn’t cultivated widely for commercial purpose and the production is only around 4-5% to the requirements. Therefore, the Textile Industries have to depend on the exported cotton.

Admission result of B.Sc. in Textile Engineering 2011-2012

noreply@blogger.com (Rony) — Tue, 3 Jan 2012 16:33:00 +0600

Admission Test Result of B.Sc. in Textile Engineering 2011-2012 (Zorargonj, Begumgonj, Pabna, Barisal, Savar, Saymoli) are published. To download the result click here.

Impurities in water

noreply@blogger.com (Rony) — Wed, 28 Dec 2011 01:00:00 +0600

The brightness of color, performance of dye, whiteness etc. depends on water used in wet processing. So, it is essential to know what type of water is suitable for wet processing. To know this first we should understand about the impurities in water. There are mainly four types of impurities in water:

1. Turbidity and color: Turbidity is the presence of small and large particles in water which are soluble in water. These particles may be inorganic (silica, calcium carbonate) or organic (fats, vegetable mater, micro-organism) in nature. Large particles are removed by sedimentation. Filtration is used for small particles.

Colors dissolve in water or colloidal organic mater disperse in water. These organic compound are not visible normally. A Tintometer is used to measure the amount of color in water.

Turbidity and water stain the fabric.

2. Ions of Heavy metals: Ions of heavy metals like iron, manganese, copper are harmful during wet processing. These causes following problems:

Act as catalyst in the decomposition of bleaching agents and cause activated attack with subsequent degradation of fibre.

Produce slight yellow color during scouring and bleaching and it is difficult to remove the color.

It may insolubilise the metal oxide during mercerization and reduce lusture, absorbency.

In the dyeing stage, metal ions may combine with some dyes and cause dulling of shade.

3. Alkalinity: Generally when water contains carbonate and bicarbonate then water shows alkalinity. Amount of carbonate and bicarbonate is measured by Titration method.

4. Hardness: The presence of calcium, magnesium salt i.e. bi-carbonates, sulphates, chloride in water causes the hardness of water. The water which contains these salts is called hard water. Hard water does not easily form lather with soap as the salt of calcium and magnesium react with soap to form insoluble organic salts. There are two types of water hardness:

(a) Temporary hardness: Temporary hardness is due to the presence of bicarbonates of calcium and magnesium. The types of hardness is called temporary hardness as it can be removed by boiling.

(b) Permanent hardness: It is due to presence of chlorides or sulphates of calcium and magnesium. This type of hardness is called permanent hardness. These salts do not decompose on boiling. So permanent hardness cannot be removed easily.

Count in different system

noreply@blogger.com (Rony) — Fri, 23 Dec 2011 03:15:00 +0600

There are many types of count which are classified under direct and indirect system. Various types of count in direct and indirect system are as following:

Direct system

Tex: Count in the Tex system is the weight in grams of 1000m or 1km of yarn. From an example we will understand it easily.

If the weight of 3000meters yarn is 2.5grams, then what will be the count in Tex for the yarn?

We know that Tex is calculated in direct system. For direct system, Count, N = (W×l)/L

Where,

N = The yarn number or count.

W = The weight of the sample = 2.5gm

L = The length of the sample = 3000m

w = The unit of weight of the system = 1gm

l = The unit of length of the system = 1000m

Now, Count, N = (W×l)/L = (2.5×1000)/3000 = 0.83

So, count is 0.83Tex.

Denier: The number or count in the denier system is the weight in grams of 9000m or 9km of yarn.

Pounds per spindle: The yarn number or count in the pound per spindle system is the weight in pounds of 14400 yards of yarn. This count is used for jute.

Millitex: Count in Millitex system is the weight in milligram of 1km of yarn.

Kilotex: Count in the kilotex system is the weight in kilogram of 1 km of yarn.

Wollen: Count in wollen system is the weight in grain of 20 yards of yarn.

Indirect system

English count: The yarn count is defined as the number of hanks of 840 yards per pound. We should know that, the length of 840 yards yarn is called 1 hank. By the same way, 2520 yards yarn is equal to 3 hank.

If one pound of yarn contains 30 hanks of 840 yds, then in English system count will be 30 Ne. It is denoted by Ne. Here, length of the 30Ne yarn is (840×30) = 25200 yds as hank is 30 and unit length is 840yds.

For example, If the weight of 3000meters yarn is 2.5grams, then what will be the English count for the yarn?

We know that English count is calculated in indirect system. For indirect system, Count, N = (L×w)/(l×W)

Where,

N = The yarn number or count.

W = The weight of the sample = 2.5gm = 0.00551lb

L = The length of the sample = 3000m = 3270yds

w = The unit of weight of the system = 1lb

l = The unit of length of the system = 840yds

Now, Count, N = (L×w)/(l×W) = (3270×1)/ (840×0.00551) = 706.5 Ne.

So, count is 706.5Ne.

English count is used for cotton.

Metric: It is defined as the no of hanks(1000m) per kg e.g. if one kg of yarn contains 40 hanks of 1000m, then in metric system count will be 40 Nm. It is denoted by Nm.

Worsted: It is defined as the number of hanks(560yds) per pound e.g. if one pound of yarn contain 30 hanks of 560 yds, then in worsted system count will be 30 worsted.

Yarn count| Types of counting system

noreply@blogger.com (Rony) — Thu, 22 Dec 2011 00:09:00 +0600

Yarn Count| Types of count

Yarn count is a term used to express the thickness of yarn. In spinning process, there is a relation between the weight of the original fibres and the length of yarn. This relation is indicated as thickness. Thickness of yarn is determined by the extent of drawing process (varying draft) and designated by number. The number is called count.

So, when we say what is yarn count? The answer will be, yarn count is the weight per unit length or length per unit weight which expresses the fineness or coarseness of yarn.

According to Textile Institute, “Count, a number indicating the mass per unit length or the length per unit mass of yarn.

Types of count system
Basically, two types of yarn counting system:
1. Direct system
2. Indirect system.

Another system is classified as third type of count and that is “Tex”. Tex is also called Universal count. International Organization for Standardization (ISO) fixed the relationship between weight and length for Tex. The greater the weight, the thicker the yarn and Tex will be greater number. We will discuss it under Direct system.

Direct System

In this system, the count of yarn expresses the no of weight units in one length unit. Higher the count, coarser the yarn. This system is generally used for Man made fibre, jute, silk etc.

Now, let’s see the how count is mathematically calculated.
Let,
N = The yarn number or count.
W = The weight of the sample.
w = The unit of weight of the system.
L = The length of the sample.
l = The unit of length of the system.
Now, Count, N = (W×l)/L

Indirect System

In this system, the count of yarn is expresses the no of length unit in one weight unit. Here, when count is higher, then yarn will be finer. The system is usually used for cotton, worsted, metric, french, linen (wet spun) etc.

Let,
N = The yarn number or count.
W = The weight of the sample.
w = The unit of weight of the system.
L = The length of the sample.
l = The unit of length of the system.
Now, Count, N = (L×w)/(l×W)

Source of water

noreply@blogger.com (Rony) — Tue, 20 Dec 2011 03:21:00 +0600

Main Source of water

Main sources of water are:

1. Rain water: Rain water is the purest water of all natural sources. The water may contain traces of gases dissolved out small amount of finely divided solid matter derived from the air. It also contain dissolved impurities such as shoot traces of SO₂, NO₂, NH₃, H₂SO₄, CO₂ and other by products of industrialization. Suspended in it can be filtered by using sand bed. Rain water is suitable for boiling, washing and dyeing process.

2. Subsoil water: This type of water is collected from shallow springs and wells which are about 50ft(15cm) or so deep. It is usually free from suspended impurities because it has been filtered by its passage through the soil. It will, however, contains dissolve organic matter. Subsoil water is often rich in dissolved carbon dioxide, a gas abundantly present in the sin of the soil. Subsoil waters are very variable with regard to the impurities which they contain. It is not suitable for dyeing and finishing.

3. Surface water: Surface water consist of rain water which is collected from streams, rivers or laks. This type of water contains organic and inorganic matters which are dissolved in it and also contain suspended impurities. Then the Nutrifying bacteria will in time convert the organic substances into nitrates which are not objectionable in dyeing and finishing. Surface waters may receive considerable additions of dissolved mineral salts from shallow springs which feed the streams. It contains chloride, Sulphate, Carbonate, Bicarbonate of Sodium, Potassium, Calcium and Iron.

4. Deep well water: This type of water is obtained 500m below the surface. This is free from organic matters. The soluble impurities in water may be composed of a variety of substances, soluble organic compounds, ammonium salts, nitrites of animal or vegetable for quantities, the sewage contamination is undesirable for many textile purpose. The presence of salts of calcium or magnesium in solution can be most undesirable in many finishing process.

Other source

Other sources are:

1. Municipal or public water system.

2. Reclaimed waste streams.

The common compounds presents in almost all water supply in some extent are:

· Acidity, alkalinity.

· Aluminum.

· Chlorine.

· Heavy metal such as Iron, Copper, magnesium etc.

· Calcium and magnesium.

· Suspended matters.

· Dissolved solid.

· Oil, gases etc.

Water| Water consumption in Textile Industry

noreply@blogger.com (Rony) — Tue, 20 Dec 2011 01:32:00 +0600

Water

Water is a liquid substance in room temperature which contains Hydrogen and Oxygen. It is a complex compound. The total amount of water in the world is about 75%. Natural water is obtained in 3 steps. They are solid, liquid & vapour. Water has a incomparable power to dissolve other compound. It is very difficult to obtain pure water in nature. Water is consists of two part Hydrogen & one part Oxygen. Its chemical formula is H₂O. Water is converted to ice at 0°C & converted to vapour at 100°C the concentration of water is highest at 4°C.

Water is called universal solvent, because the solvency power of water is very high and most of the solute of this world is easily dissolved in the water.

Water consumption in Textile Industry

Textile Industry is one of the top ten Industry which consume high amount of water. The raw materials used greatly in textile wet processing is water. The quantity of water varies in different stages. Some textile mills have high water cost as they purchase water from municipal system. Therefore, quantity of water is a point to be observed in textile processing.

Water Consumption by different materials in Total Wet processing

Substrate Type Quantity(gallon/pounds)[Approximately]

Cotton 24.9-34.9

Wool 20-40

Nylon 12.5-15

Rayon 12.5-15

Polyester 10-20

Acrylic 10-20

Woven other 2-50

Knit other 3-40

Non woven 0.3-9

Water Consumption in Textile Mills

Process Consumption of water(%)

Spinning 6

Weaving 9

Bleaching, finishing 38

Dyeing 16

Printing 8

Boiler 14

Others 9

Corrected Admission Notice for B.Sc. in Textile Engineering

noreply@blogger.com (Rony) — Wed, 14 Dec 2011 20:18:00 +0600

Admission notice for four Government Textile Engineering Colleges (Zorargonj Textile, Begumgonj Textile, Pabna Textile, Nittrad) and Shyamoli Textile Engineering College is corrected in a meeting held on 08/12/2011 by the Admission Committee. To download the corrected notice click here
OR,
For details you can visit the following official website:
1. www.dot.gov.bd
2. www.pabtec.gov.bd
3. www.arstecb.com
4. www.nittrad.edu.bd
5. www.stecbd.com

Process sequence of Wet processing Technology

noreply@blogger.com (Rony) — Tue, 13 Dec 2011 20:30:00 +0600

Grey fabric: Grey fabric is the term used for a fabric which is directly collected from weaving or knitting machine. The quality of grey fabric can effect from handle to the result of dyeing and printing.

Inspection: After manufacturing fabric it is inspected in an inspection Table. It is the process to remove neps, warp end breakage, weft end breakage, hole spot.

Stitching: To increase the length of the fabric for making suitable for processing is called stitching. It is done by plain sewing m/c.

Brushing: To remove the dirt, dust, loose fibre & loose ends of the warp & weft threads is known as brushing.

Shearing / Cropping: The process by which the attached ends of the warp & weft thread is removed by cutting by the knives or blades is called shearing. Shearing is done for cotton & cropping for jute. After Shearing or cropping fabrics goes under singeing process.

Singeing: The process by which the protruding / projecting fibres are removed from the fabrics by burning / heat to increase the smoothness of the fabric is called singeing. If required both sides of fabric are singed.

Desizing: The process by which the sizing mtls (starch) are removed from the fabric is known as desizing. This must be done before printing.

Scouring: The process by which the natural impurities (oil, wax, fat etc) & added/external/adventitious impurities (dirt, dust etc) are removed from the fabric is called scouring. It is done by strong NaOH.

Souring: The process by which the alkali are removed from the scoured fabric with dilute acid solution is known as souring.

Bleaching: The process by which the natural colours (nitrogenous substance) are removed from the fabric to make the fabric pure & permanent white is known as Bleaching. It is done by bleaching agent.

Dyeing: See the previous post.

Printing: See the previous post.

Mercerizing: The process by which the cellulosic mtls/substance are treated with highly conc.NaOH to impart some properties such as strength, absorbency capacity, lusture is known as mercerizing. It is optional. If the fabrics are 100% export oriented then it is done by highly conc. NaOH (48-52° Tw).

Finishing: See the previous post.

Flow chart of Wet Processing Technology

Wet Processing| Its importance| Main operation of Wet Processing

noreply@blogger.com (Rony) — Mon, 12 Dec 2011 22:33:00 +0600

Wet Processing
The fabric produced from weaving or knitting is called Grey fabric as it contains natural color and not suitable for marketing. So there are required some treatment i.e. Singeing, desizing, bleaching, dyeing, printing, finishing etc. To make a fabric presentable to customer some chemical treatments are essential and the processes are called Wet processing. So, wet processing is the process where the textile materials are treated with some chemicals and wetted with water. In wet Processing water plays a great role. Most of the processes are done with water. So pure water is required in wet processing. The importance of water will be discussed later.

Importance
Wet processing is a process related to water. Here all the processes carry importance. For example: Desizing is a process which is required to remove the sizing materials(starch, wax, tallow, oil, carboxylic acid, sago etc.). Then scouring is done to remove the natural impurities, protein, pectin etc. to make the fabric white. Thus fabric undergoes such important process before finishing. Therefore if any fault in these process it will be very difficult to produce a quality fabric.

Main operations

Pretreatment: The process which is done to make the textile materials suitable for dyeing and printing. Such as singeing, desizing, scouring, bleaching etc.
Dyeing & printing: The process by which textile materials are colored by different types of dyes or pigment, related chemicals required water is called dyeing. Localized application of dyestuff or pigment on fabric according to predetermined design is called printing.
Finishing: The process by which textile materials are made suitable for marketing to satisfaction or attraction of buyer is called finishing i.e. calendering, anti-creasing, leveling etc.

Admission Notice of B.Sc. in Textile Engineering 2011-12

noreply@blogger.com (Rony) — Sat, 19 Nov 2011 17:16:00 +0600

Admission Notice for the four Government Textile Engineering Colleges (Begumgonj, Zorargonj, pabna & Borisal) and two Public-private Engineering Colleges have been announced. To know the admission procedure in detaiils and to downlaod click here.

Function of Twist in yarn structure | Why twist is important for yarn

noreply@blogger.com (Rony) — Wed, 14 Sep 2011 22:25:00 +0600

A question may arise why twist is given to yarn or what is the function of twist. Actually twist plays a vital role in yarn manufacturing which is given below -

1. The main function of twist is to give a round shape to the yarns, increase the strength of yarn. As in sliver no twist is given, therefore it is easy to open the fibre, but it is difficult in case of roving or yarn.

2. Without twist a strand of fibres has very little strength and in the first instance a yarn must have sufficient tensile strength to withstand the stresses of preparation and fabric manufacture.

3. The main function of twist is to give coherence to the yarn. In order to develop strength in a twisted strand of discontinuous fibres and so resist breakage, the individual fibres must grip each other when the strand is stressed. This cohesion arises mainly from the twist, which presses the fibres together as the stretching force is applied and so developing friction between adjacent fibres.

4. If the twist is low, the fibres can be made to slide past one another, but if it is large they cannot. The twist can be termed as twist angle that means when twist angle is high, then yarn strength is high. An experiment shows that, when twist is increased then yarn strength increases within a certain limit and at a point called critical point the maximum strength of yarn is obtained. But after critical point at the end increasing the tension goes to the rupture the strand by breaking the component fibres.

Amount of Twist | Importance of Twist

noreply@blogger.com (Rony) — Mon, 12 Sep 2011 20:51:00 +0600

Amount of twist

The amount of twist means the number of turns in unit length in a twisted yarn. If “n” be the number of turns in “L” length of yarn, then amount of twist will be n/L. Amount of twist is expressed in -

a. Twist per inch (TPI)

b. Twist per meter (TPM)

c. Twist per centemeter (T.P.C.m)

Here, twist per inch means the number of turns in unit inch and in the same way twist per meter and twist per centimeter is the number of turns in unit meter & unit centimeter. TPI of a yarn is 40 means the number of turns in 1 inch length of yarn is 40.

Amount of twist depends on the yarn count, for which purpose the yarn will be used and on the length of yarn. Without these the amount of twist depends on the types of fabric i.e. for soft surfaced fabrics slack twist is given and such kind of yarn is called soft twisted yarn.

Importance of twist

a. Twist increase the tensile strength of yarn as well as the strength of yarn.

b. The yarn shape becomes round i.e. shape factor goes near 1 due to twist.

c. The inter-cohesion affinity of fibres increases due to twist and do not open easily.

d. The more twist increased under the constant value, the yarn become so strength.

Yarn Twist | Twist direction

noreply@blogger.com (Rony) — Thu, 8 Sep 2011 19:35:00 +0600

Yarn Twist

According to Morton, “When a strand is twisted the component fibres tend to take on a spiral formation, the geometric perfection of which depends on their original formation.”

According to Skinkle, “Twist is the measure of the spiral turns given to a yarn in order to held the constituent fibres or threads or threads together.”

According to WIRA, “Twist may be defined as the rotation about the yarn axis of any line drawn on the yarn which was originally i.e. before twisting parallel to the yarn axis”.

According to Textile Institute, “Twist is the spiral disposition of the components of a thread which is usually the result of relative rotation of the two ends”.

Twist direction

The direction of twist is indicated the use of the letters ‘S’ and ‘Z’ in accordance with the following convention:

(a) S-twist: A single yarn has S twist when it is held in the vertical position, the fibres inclined to the axis of the yarn conform in direction of slop to the central portion of the letter S.

(b) Z-twist: The yarn has Z-twist if the fibres inclined to the axis of the yarn conform in direction of slope to the central portion of the letter Z.