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ETHIOPIAN INSTITUTE OF TEXTILE AND FASHION TECHNOLOGY (EiTex)

BAHIR DAR UNIVERSITY

MSc. PROGRAM IN TEXTILE CHEMISTRY

Advanced pretreatment and processing assignment --1

On quality assurance in textile pretreatment

BY: TAAME BERHANU (MSc. Student)

SUBMITTED TO: Dr. Saminatan

Submission date: 07/12/2015

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Contents pages

1. Introduction ……………………………………...……………………..4

2. Testing for quality of raw materials and other inputs…………..…...5

2.1. Test for water quality hardness...................................................................................5

2.2. Quality of auxiliary chemicals used…………..…………………………….……….8

2.2.1. Quality of sequestering agents.....................................................................................8

2.2.2. Test for quality of surfactants.................................................................................... 10

2.2.3. Test for quality of peroxide stabilizers…………………….………………………...12

2.2.4. Test quality of peroxide killers……………………..………………………………..13

2.2.5. Testing soda ash & hydrogen peroxide……………………/..………………………14

2.2.6. Test for quality of sodium hypochlorite ……………………………………………..17

2.2.7. Test for copper and iron content in the fiber………………………………..…….….17

3. Test for quality of pretreatment process at different stages …..………19

3.1. Quality examination of fabric at gray stage ……………………………...……….....19

3.2. Test for desizing quality ……………………………………………………………..20

3.2.1. Desizing efficiency ……………………………...…………………………………..20

3.2.2. Iodine test ……………………………...……………………………………………20

3.2.3. Absorbency test………………………………………………………………….…..20

3.2.4. Weight loss…………………………………………………………….……….……21

3.3. Test for scouring quality ………..………………………………………..……….…21

3.3.1. Immersion test …………………………………………………………………..…..21

3.3.2. Drop test ……...…………………………………………………………………..….21

3.3.3. Spot test ……………………………..……………………………………….………22

3.3.4. Column test/wicking test …………………………………...…………………….….22

3.3.5. Determination of weight loss………………………...………………………………23

3.3.6. Absorbency ………………………………………………………………………….23

3.3.7. Ash content …………………………………………………………...……………..23

3.3.8. Wax content …………….……………………………………………………….…..24

3.4. Test for bleaching quality ………………………….…………………………..……25

3.4.1. absorbency …………………………………………………………………….……25

3.4.2. Cuprammonium fluidity..……………………………………………………………25

3.4.3. Whiteness ……………………………………………………………………..……..26

3.5. Test for the quality of mercerized fabric…………………………………….………27

3.5.1. Barium activity number ………….………………………………………………….27

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3.6. Test for heat setting quality …………………………………………………….…...28

3.6.1. Shrinkage in boiling water ……………………………………………………….….28

3.6.2. iodine absorption test ………………………………………………………......…..28

4. Process control in pretreatment ……………….…………………..……29 4.1. Control desizing process ………………….………………………………...……….29

4.2. Control scouring process ……………………………….……………………………3o

4.3. Control bleaching process …………………………….………………...…………...31

Conclusion ……………………….……………………………………………32

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1. Introduction

Quality Control system is to control the quality almost after the particular operation or process

is finished. Whereas Quality Assurance is taking proactive steps to get the desired results.

Eg. Making the fabric to a higher width keeping sufficient allowance for shrinkage, selecting

the right Chemicals for acquiring the demanded quality levels etc. In any good pretreatment

process Quality Control and Quality Assurance systems should go hand in hand. The

knowledge of QC operations should lead to the formation of good QA system.

Quality Assurance Elements:

In QA elements we should consider the quality of all raw materials, right from the processing of

fabric or yarn to all the dyes and chemicals used and in QC elements we should test the quality

of finished products for the required level of standards. In both cases the following Textile

Testing Methods can be applied for.

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2. Testing for quality of Raw Materials and other inputs:

2.1. Test for Water Quality Hardness

Water is due to metal ions (minerals) that are dissolved in the ground water. These minerals

include Ca2+

, Mg2+

, Fe3+

, SO42-

, and HCO3-. Our hard water in the southern Indiana area is due to

rain moving through the vast amount of limestone, CaCO3, that occurs in our area to the aquifer.

This is why we measure hardness in terms of CaCO3; The concentration of the Ca2+

ions is

greater than the concentration of any other metal ion in our water.

Hard water does cause soap scum, clog pipes and clog boilers.

Soap scum is formed when the calcium ion binds with the soap. This causes an insoluble

compound that precipitates to form the scum you see. Soap actually softens hard water by

removing the Ca2+

ions from the water.

When hard water is heated, CaCO3 precipitates out, this then clogs pipes and industrial boilers.

This leads to malfunction or damage and is expensive to remove.

Types of Hardness

There are two types of water hardness, temporary and permanent.

Temporary Hardness is due to the bicarbonate ion, HCO3-, being present in the water. This type

of hardness can be removed by boiling the water to expel the CO2, as indicated by the following

equation: HCO3 ¯ == H2O + CO2

(THIS IS TEMPORARY HARDNESS DUE TO BICARBONATES)

Permanent hardness is due to the presence of the ions Ca2+

, Mg+2

, Fe3+

and SO4-. This type of

hardness cannot be eliminated by boiling. The water with this type of hardness is said to be

permanently hard.

Complexometric Titration

Permanent hardness is usually determined by titrating it with a standard solution of

ethylenediamminetetraacetic acid, EDTA. The EDTA is a complexing, or chelating agent used

to capture the metal ions. This causes the water to become softened, but the metal ions are not

removed from the water. EDTA simply binds the metal ions to it very tightly.

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EDTA

EDTA is a versatile chelating agent. A chelating agent is a substance whose molecules can form

several bonds to a single metal ion. Chelating agents are multi-dentate ligands. A ligand is a

substance that binds with a metal ion to form a complex ion. Multidentate ligands are many

clawed, holding onto the metal ion to form a very stable complex. EDTA can form four or six

bonds with a metal ion.

It is frequently used in soaps and detergents because it forms complexes with calcium and

magnesium ions. These ions which are in hard water are bound to the EDTA and cannot interfere

with the cleaning action of the soap or detergent.

EDTA is also used in foods. Certain enzymes are responsible for food spoilage. EDTA is used to

remove metal ions from these enzymes. It is used to promote color retention in dried bananas,

beans, chick peas, canned clams, pecan pie filling, frozen potatoes and canned shrimp. It is used

to improve flavor retention in canned carbonated beverages, beer, salad dressings, mayonnaise,

margarine, and sauces. It inhibits rancidity in salad dressings, mayonnaise, sauces and salad

spreads.

Total Permanent Hardness

In this lab you will be asked to determine the total permanent hardness. EDTA grabs all the

metal ions in the water, not just the Ca2+

ions. This gives us a value that is not truly the

concentration of Ca2+

ions. This causes an experimental error of about 1% which is acceptable

due to the "fuzzy" endpoints in this type of titration.

Eri-chrome Black - T Indicator

EDTA ENDPOINT COLOR CHANGE

Erio - T indicator or Eriochrome Black-T indicator is used in this titration. When it is chelated or

acidifies, it produces a PINK RED solution. When it is not chelated and under basic conditions

it is BLUE.

The three pictures show the end point in this titration. There is a 1 drop difference of 0.01 M

EDTA between the first and second pictures and between the second and third pictures. Two or

three seconds were allowed for colors in the second and third pictures to develop after adding the

additional drop. In each case the solution was thoroughly mixed. This color change from wine

red to violet to blue is due to the compact nature of the complex.

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Sample Analysis

You are using EDTA with a molarity of .0080 for the titration. You titrate 50.00 ml of water

sample using 10.68 ml of EDTA.

What is the CONCENTRATION of Ca2+

ion?

What is the hardness?

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2.2. Quality of Auxiliary Chemicals used.

2.2.1. Quality of Sequestering Agents

A sequestering or chelating agent is a complex forming auxiliary chemical with metals such

as Iron, Copper, Nickel, Zinc and Magnesium that are present in water and affects the textile

processing in many way.

Chelating agents are used to eliminate water hardness and heavy metals, such as iron and

copper which can affect the scouring process. These agents bind polyvalent cations such as

calcium and magnesium in water and in fibres, thus preventing the precipitation of soaps. If

polyvalent ions are present, insoluble soaps may form, settle on the fabric and produce resist

spots. There are four major types of sequestering agents to choose from: inorganic

polyphosphates, aminocarboxylic acids, organophosphonic acids, and hydroxycarboxylic

acids. The inorganic polyphosphates such as sodium tripolyphosphate and sodium

hexametaphosphate are probably the best overall in that in addition to sequestering most

metals they also aid in cleansing the fibres. They may, however, hydrolyze at high

temperature and loose their effectiveness.

The aminocarboxylic acid types such as ethylenediaminetetraacetic acid (EDTA)-

(−O2CH2)2NCH2CH2N(CH2CO2

−)2are very good in that they sequester most metal ions and

are very stable under alkaline conditions. They are the most used types. The

organophosphonic acid types such as ethylenediaminetetra (methylene phosphonic acid) are

also very effective but comparatively expensive. Oxalates and hydroxycarboxylic acids

(citrates, etc.) are excellent for sequestering iron but not effective for calcium and

magnesium. In order to quickly and effectively bring the chemicals to the textile material, i.e.

to improve their wettability and to ensure that the fibrous impurities will be removed as far as

possible, it is necessary to add surfactants with good wetting and washing/emulsifying

properties. A surfactant of optimal versatility to be used for preparation, and in particular for

the scouring and bleaching processes, ought to meet the following requirements

How one can test the strength of a sequestering or chelating agent?

We can test the strength of a chelating agent by a simple method! - (Volumetric Estimation of

Make a solution of Calcium Carbonate or Calcium Sulphate in distilled water. Say for example

dissolve 500 mg of Analar grade Calcium Carbonate in pure distilled water of 1 liter. So you

have prepared a known solution of 500 ppm of hardness. Ascertain the hardness by regular

EDTA and Erchrome Black indicator method.

Now take a 10ml micro-burette and fill it with the solution of Sequestering agent. Titrate and

find out the end point. If 5 ml of a particular brand of sequestering agent is required to treat 1

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liter of 500 ppm water, then the Chelating value (CV) of this sequestering agent is 1. If 1 ml if

enough to reach end point the CV is 5.

Normally the textile sequestering agents are supplied with CV of 1 to 3 and priced accordingly.

Quality Control Method for Calcium Sequesteration Organo Phosphates

Type: This method can be used to keep a check on the quality of various sequestering agents.

Apparatus:

1. Analytical Balance

2. pH meter

3. Burette 25 ml cap

4. Volumetric flask, 100 ml cap & 1000 ml cap.

5. Beakers 150 ml cap

6. Titration flasks 250 ml capacity.

7. Measuring cylinder

8. Black Tile.

Reagents:

1. Calcium Acetate Monohydrate solution: Dissolve 44.1 gram of Calcium Acetate

Monohydrate in distilled water and make up the volume to 1 liter in a volumetric flask. 1

ml of this colution corresponds to 24m.grams of Calcium Carbonate.

2. Sodium Carbonate 2% solution

3. Sodium Hydroxide 1 N solution

4. Acetic Acid 0.1N solution.

5. Distilled Water

Procedure:

Weigh accurately about 2 grams of the sequestering agent in a 150 ml beaker. Add about 50 ml

of distilled water and dissolve the material. Adjust the pH to 8 with Sodium Hydroxide and

Acetic Acid. Add 10ml of 2% Sodium Carbonate by means of a measuring cylinder. Adjust the

pH to 11. with Sodium Hydroxide / Acetic acid. Bring the total volume to 100 ml in a volumetric

flask. Pour in to 250 ml titration flask and titrate against calcium acetate monohydrate solution to

a distinct and permanent turbidity. Keep the black tile on the table and place the titration flask on

it. The black background helps in determining the exact end point. During titration maintain the

pH constant at 11, by addition acid or alkali.

Result calculation:

Milligrams of Calcium Sequestered per gram of sample

= (Volumel of calcium Acetate Monohydrate / Weight of the sample in grams)

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2.2.2. Test for Quality of surfactants :

I. Solid Content: Weigh accurately 10 grams of the material to be tested in a pre-weighed

porcelain crucible; let the weight be "A" grams. Dry the crucible in a high temperature

electrical over at 95C for 2 hours. Take out the crucible and re-weigh it; let the weight

after drying be "B" grams. Then the solid content of the material = 100 x (B-Empty

Crucible wt) / (A-Empty Crucible weight).

II. Wetting Time: Various methods have been used for testing wetting agents. A simple

test is to determine the number of seconds required for a 1-inch square piece of No. 6

canvas to sink in a 1 per cent solution of the wetting agent at 22 to 23 C. Another method

is that described by Draves ( I ) , in which a 5-gram skein of cotton yarn is used.

Although these simple sinking tests give an ../default of the properties of a wetting agent,

they are not conclusive and do not give a full picture of their value in treating baths. This

is true since so-called wetting agents usually have other properties besides their wetting

properties, and in some cases these other properties may be of much greater importance

than their wetting properties.

III. Ionic Nature:

Ionic nature of a wetting agent may be decided by a very simple test. Dissolve 2 grams of the

wetting agent in 100 ml of distilled water. Call this as Solution 'A'.

1. Anionic: Take about 10 ml of this solution (A) in a 20 ml test tube. Add 10 drops of

2N Hydrochloric acid in to this and shake well. If a white cloud or precipitate is

formed, then the surfactant tested is Anionic in nature.

2. Cationic: Take about 10 ml of the solution (A) in a 20 ml test tube. Add 10 drops of

2N sodium hydroxide solution and shake well. If a White cloud or precipitate is

formed, then the tested product is Cationic in nature.

3. Non-ionic: If no precipitate or cloud is formed either with acid or alkali, then the

material tested is Non-ionic in nature.

4. Amphoteric: Amphoteric wettings will make a very slight white precipitate with

acids and the precipitate will not settle down to the bottom or the test tube even after

few hours. It will remain in suspension

IV. Cloud Point: The non-ionic surfactants exhibit a property called cloud point. Upon

slowly raising the temperature of 2 grams per liter of solution (prepared using distilled

water), at a particular temperature the clear solution becomes cloudy. That temperature is

called the cloud point of that non-ionic wetting agent. After the cloud point temperature it

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is said that the nonionic products do not exhibit its intrinsic properties, such wetting,

scouring, rewetting, emulsifying etc. So if a wetting agent's cloud point is 70C, then it

should be understood that above 70C, it should not used as wetting agent. For example if

you are doing scouring and bleaching at 90C, then a 70C cloud point wetting agent is not

suitable for this purpose. Most of the non-ionic wetting agents have the cloud of more of

less 70°C.

V. Foaming Test: Formation of foam during processing especially in jet and soft-flow type

of machineries is a big headache for the dyer. So in these machines people prefer only

no-foaming or very low foaming wetting agents only. Compare two wetting agents by

making .01% solution, in two 500 ml measuring jars. Shake the jars for about 3 minutes

and keep them intact for some time. Compare the height of the foam. Lower the height

better the wetting agent

Test Methods for quality and consistency:

Specificgravity:

Accurately weigh 10 ml of the leveling agent. Specific gravity = Volume/Mass. Note down the

value and do this test whenever your receive a new consignment and compare against the first

supply.

Solid content :

Refer procedure of wetting agents

pHof1%solution:

Dissolve 1 gram of the leveling agent in 100 ml of distilled water.

IonicNature:

Check the stability of this product against the addition of acid and alkali under processing

temperature of 70C

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2.2.3. Test for quality of peroxide stabilizers

To know what is a peroxide stabilizer we should know a little more about what is peroxide

itself and what are its behaviors?

Hydrogen peroxide is the most commonly used bleaching agent for natural vegetable and

animal fibers. It is necessary to activate the hydrogen peroxide for effective bleaching.

Stabilization of the bleaching solution is also essential to minimize the loss of active oxygen.

Hydrogen peroxide (can be considered as a very weak acid) dissociates in aqueous solution

only to a small extent. H2O2 = H+ + HO2.

In pure water, particularly in acid solutions hydrogen peroxide exists mostly in un-dissociated

form and is very stable. For the same reason, commercial concentrated products are maintained

acidic.

Since hydrogen peroxide is very active in alkaline medium and dissociates in to nascent oxygen

and water in large extent, even before it bleaches the fiber, a catalyst is necessary to reduce the

dissociation level. These catalysts are called Peroxide Stabilizers.

Generally inorganic salts like MgCl2, CaCl2, MgSO4 etc and some silicates are considered to be

best stabilizers for peroxide bleaching.

But these salts after bleaching leave a harsh feel to the fabric due to the deposition of the

hydroxides of these salts and hence are not suitable for peroxide bleaching.

Now there are many organic peroxide stabilizers available in the market. Generally the quality

of these products vary from manufacturer to manufacturer. One can ascertain its quality only by

conducting actual bleaching process using these materials and assessing the whiteness ../default

of the bleached material, its feel and other physical properties.

However the following tests may be used to keep record of a particular product. The batch to

bath variation of from the same manufacturer's product can be monitored.

Test Methods for quality and consistency:

Specificgravity:

Accurately weigh 10 ml of the peroxide stabilizer. Specific gravity = Volume/Mass. Note down

the value and do this test whenever your receive a new consignment and compare against the

first supply.

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Solidcontent:

Refer procedure of wetting agent.

pHof1%solution:

Dissolve 1 gram of the peroxide stabilizer in 100 ml of distilled water and check the pH.

IonicNature:

Check the stability of this product against the addition of acid and alkali under processing

temperature of 70C.

AnalyticalMethod:

You can test the concentration of peroxide in a bleaching for every 10 minutes and plot a graph.

Compare the same against the competitor's product.

2.2.4. Test Quality of peroxide killers

After bleaching the cellulosic fiber with hydrogen peroxide, the fiber is subjected a thorough hot

wash cold wash and neutralization processes. These operations would remove all superficially

available chemicals that were used in bleaching process.

However in practice it is found that the core alkali i.e. the alkali due to the use of caustic soda or

soda ash and hydrogen peroxide, wetting agents and other auxiliaries would remain in the core

of the fiber processed even after 2 or 3 washes. These residual chemicals like alkali's and

peroxide are detrimental to the production of uniform flawless fabric production.

The core residual alkali would lead to immature hydrolisation of the reactive dyes and results in

streaky and uneven dyeing.

The residual peroxide present in the fiber will oxidize the reactive dyes' chromophore that

contain the metal ions and lead to tonal variation and sometimes uneven dyeing. In some cases

the chrmophore itself is getting destroyed into a colorless product and lead to pale or white

patchy dyeing.

Hence the removal residual alkali and peroxide are very much essential before starting a good

dyeing operation.

So any chemical that kills the residual peroxide in the fiber is called a peroxide killer. All

reducing agents are in fact peroxide killers. Again we should note that excess presence of

reducing agent in the fiber also lead to destruction of dyestuff molecule. Hence a careful

selection of a peroxide killer is very much essential.

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Now in the market there are many enzymatic peroxide killers available that will remove the

residual peroxide and die-off during subsequent dyeing operations at higher temperatures.

Test Methods for quality and consistency:

Specificgravity:

Accurately weigh 10 ml of the peroxide killer. Specific gravity = Volume/Mass. Note down the

value and do this test whenever your receive a new consignment and compare against the first

supply.

Solidcontent:

Refer procedure of wetting agent.

pHof1%solution:

Dissolve 1 gram of the peroxide killer agent in 100 ml of distilled water and check the pH.

IonicNature:

Check the stability of this product against the addition of acid and alkali under processing

temperature of 70C.

2.2.5. Testing Soda Ash & Hydrogen Peroxide

In Textile Processing the following materials are considered to be basic chemicals or bulk

chemicals used in processing. The quality of each product whether basic or auxiliary chemical

would certainly affect the final quality of textile processing. So a good dye-house should have a

continuous quality monitoring procedure like one shown below. As and when a new product or

chemical enters your dye-house, its quality should be compared with the previous supply without

fail.

Soda Ash:

Weigh accurately 1 gram of Soda ash and dissolve in 50ml of distilled water. Titrate this slowly

with 1.0N HCl, using methyl orange as indicator.

Total alkalinity as Na2CO3.% by weight = 5.3 x V x 1 / Wt where 'V' is the volume of HCl

consumed and 'wt' is the exact weight of soda ash taken for titration.

Repeat the above titration for 3 times, tabulate and take the average reading as the %

concentration of Soda ash as Sodium carbonate.

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Hydrogen Peroxide:

Take 10ml of Hydrogen Peroxide solution and dilute it to 500ml using distilled water. From this

diluted solution of Hydrogen peroxide take 10ml and add 20ml of 1.0N H2SO4.. Titrate against

0.1N KMNO4 (potassium permanganate). The end point is the appearance of light pink color.

Repeat this titration 3 times and tabulate the readings. Find out the average titration value (V).

the reader would be aware of the volumetric titration principles. Titrating two solution of

standard known strength and unknown strength, one can easily find out the strength of the other.

The simple formulae used for this purpose is;

V1N1 = V2N2

where V1 = Volume of Standard Solution, N1 = Normality of Standard solution, V2=- Volume of unknown solution, N2 =

Normality of unknown solution.

Concentration of the unknown solution in grams / liter = Normality of unknown solution x Equivalent weight of the

substance.]

In the above example, if V is the volume of KMnO4 consumed for titrating 10 ml of 10/500 or 1/50 ml of H2O2; Eq.Wt of H2O2

= 17.

Applying the formula V1N1 = V2N2

N1 = V2N2 / V1

Normality of H2O2 [N] = V [KMnO4] x 0.1 / [1/50]

Strength of Hydrogen Peroxide = V x 0.1 x 50 x 17/ 10 x 3.03 [volumes].

Commercially Hydrogen Peroxide is available in two concentration - viz., 35% and 50%.

In the above calculation please note that 1 ml of 0.1N KMNO4 is equal to 0.0017g 100% H2O2.

To find out the concentration of Hydrogen Peroxide in terms of % strength, follow the simple

procedure below:

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About 1.5 gram of H2O2 is accurately weighed and made up to 250 ml in a standard flask. To 10

ml of this solution, 50 ml distilled water and 30 ml of 20% Sulphuric acid added. The mixture is

then titrated against 0.1 KMNO4 .

Calculation:

% H2O2 = Volume of KMNO4 X N x 17

/ Weight of Sample in 10 ml X 10

The result is in percentage strength.

Determination of Hydrogen Peroxide content in bleach bath:

Hydrogen Peroxide content can be determined by titration against standard potassium

permanganate solution.

Procedure:

To carry out the titration, measure 100ml dilute (10%) Sulphuric acid solution into a 250ml

conical flask.

Titrate with KMNO4 (0.1N) to a faint pink color.

Pipette a suitable quantity of aliquot (Vml) of hydrogen peroxide bleach bath solution, usually 2

or 10 ml, into the beaker containing the dilute acid and titrate immediately with potassium

permanganate to the same faint color. Let the titre be A ml of 0.1N KMNO4.

Calculation:

Since 1 ml of KMNO4 (0.1N) is equivalent to 0.0017g H2O2 100%, then V ml bleach bath

solution will contain 0.0017 x A gram of H2O2 100%.

The strength of the bleach bath is therefore = 0.0017 x A x 1000 / V g/l H2O2 100%.

Example: Titration of 10 ml of bleach liquor sample required 8.5 ml of 0.1N KMNO4. What is

the H2O2 content of the bath in grams/liter?

Calculation: H2O2 content = 0.0017 x 8.5 x 1000/ 10 = 1.445 g/l H2O2 100%

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2.2.6. Test for quality of Sodium Hypochlorite

Determination of active chlorine in Commercial Sodium Hypochlorite:

Active Chlorine is not liberated as such from alkaline hypochlorite bleach liquors.

The effective amount of Chlorine liberated by acidification of hypochlorite solution is defined by

the equation as below.

NaOCl + 2KI + H2SO4 I2 + NaCl + K2SO4 + H2O

2Na2S2O3 + I2 2NaI + Na2S4O6

Procedure:

5 ml of concentrated hypochlorite is diluted to 100 ml with distilled water.

Pipette 10ml of the above solution in to a 500 ml conical flask containing about 200 ml

distilled water and 20ml Potassium Iodide solution ( approximately 166 g/l)

Add 50ml dilute (10%) Sulphuric acid and titrate with 0.1N Sodium Thiosulphate until

the solution is pale yellow color.

Add 5ml starch solution (soluble starch 1% w/w) and continue titration until the blue

color formed is discharged. Let the Titre value be A ml of 0.1N Sodium Thiosulphate.

Calculation:

1 ml 0.1N Sod. Thiosulphate = 0.00355 gram active chlorine

Gram/liter Active Chlorine = 0.00355 x A x 1000 x 100/(10 x 5)

2.2.7. Test for Copper and Iron content in the fiber

A. Test for Iron on the fiber:

Reagents: Nitric Acid 5% or 10% w/w Analytical grade.

Potassium Thiocyanate Solution 10% w/w made by dissolving 10 g Potassium thiocyante

in 90 gram distilled water Potassium bisulphate, analytical grade.

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Hydrogen peroxide 35% w/w.

A small sample 0.5 to 1.0 gram of fiber is placed on a watch glass and then spotted with 1-2

drops of nitric acid (5%) and allowed to stand for 2-3 minutes so that any iron present is

oxidized to ferric ions. To detect ferric ions, 2 to 4 drops of potassium thiocyanate (10%) are

added.

If no color forms then no iron is present. A red color indicates iron is present and the

intensity of the color indicates the amount. A pink color indicates low concentrations and a

wine red color high concentrations.

Potassium Ferrocyanide test:

A small sample of fabric on a watch glass is spotted with dil Hydrochloric acid(10%). The

acidified area of the fabric is then spotted with dil.Pot.ferrocyanide (1% solution freshly

prepared). A dark blue color indicates the presence of iron.

B. Test for Copper:

Copper tetramine test:

The fabric sample is properly ashed using an oven and the cooled ash is spotted with 5 to 10

drops of nitric acid (10%) or hydrochloric acid or by melting with pot.bisulphate.

Add dil. Ammonia (1:1) until the ash is alkaline. A blue color shows the presence of copper.

A white background e.g. a sheet of paper helps in observing the shade changes.

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3. Test for quality of pretreatment process at different stages

3.1. Quality examination of fabric at gray stage

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3.2. Test for Desizing quality

3.2.1. Desizing efficiency

3.2.2. Iodine test

Drop iodine solution on the desized fabric to check the absence or presence of starch within the

fabric.

If the color of the iodine solution on the fabric presence blue color it indicates absence of starch.

While if the color is changed to brown or yellow color it indicates presence of starch within the

fabric.

3.2.3. Absorbency test

To test the absorbency of desized fabric , drop small amount of water on the surface of the

desized fabric and absorb the tendency of water absorbency with time.

If the fabric is absorb the dropped water within 2-3 minute it is good.

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3.2.4. Weight loss

Measure weight of sample before desizing and subjected to desizing process .after desizing

measure weight the fabric to know the weight loss after desizing by using the following

formula.

3.3. Test for Scouring quality

3.3.1. Immersion test

3.3.2. Drop test

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3.3.3. Spot test

Solution of 0.1% direct red

Pure uniform drop on fabric

Size of droplet is observed

3.3.4. Column test/wicking test

Solution of 0.1% direct red

Sample size “5cm x 18cm”

Observation time 5 minutes

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3.3.5. Determination of weight loss

3.3.6. Absorbency

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3.3.7. Ash content

3.3.8. Wax content

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3.4. Test for Bleaching quality

3.4.1. Absorbency

3.4.2. Cuprammonium fluidity

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3.4.3. Whiteness

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3.5. Test for the quality of mercerized fabric

3.5.1. Barium activity number

In addition mercerization efficiency could be tested by:-

o Deconvolution count

Luster Meter

Cross Section

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3.6. Test for Heat setting quality

3.6.1. Shrinkage in boiling water

2.6.2. Iodine Absorption test

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4. Process control in pretreatment

THE MAIN FUNCTIONS OF PROCESS CONTROL ARE AS FOLLOWS:

1) Obtaining and maintaining optimum process condition.

2) To minimize the wastage during process and form reproducible results.

3) Establishing correct operating procedure.

4) Carrying out adequate machinery maintenance.

5) Controlling production yield and waste.

6) Setting up of testing sequence.

7) Providing thorough documenting system

8) Accessing the department’s effectiveness.

4.1. CONTROL DESIZING PROCESS :

Nature of Size: Prior to desizing spoofing test.

Action: Select correct method of desizing

%Wet pickup during Desizing: Pick up should not be less than 110%.

Action: If pickup variation is there then adjust pressure.

Concentration of desizing agent and other ingredients: HCl-5gpl, Cellulase enzyme 3-5gpl.

Impregnation and dwell time: Non ionic wetting agent 3-5gpl.

Dwell time checked during padding. Ensure optimum dwell time.

Temperature: During desizing in the bath (exothermic reaction ) may rise the temperature. Acid

desizing is done at room temperature. Enzyme desizing is done depending on the enzyme.

Action: Regulate the steam supply. In acid desizing replenish the acid solution or provide water

cooling system.

pH: Depending on the Enzyme.

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Desizing efficiency: Standard- Not less than 85%.

4.2. CONTROL SCOURING PROCESS :

1) Kier Lining: Prior to filling the fabric in kier.

i) Standard: No cheeping of interior wall of kier.

ii) Action: Ensure proper cementing of interior wall of kier.

iii) Filling density: 7-8Kg/Cubic feet during filling of kier.

2) Removal of Air:

i) Action: Air removal before raising pressure

ii) Standard: No air, ensure complete removal of air.

3) Circulation:

i) During scouring, circulation is tested by flow rate method.

ii) Standard: Smooth circulation.

iii) Action: Cleaning of circulation pump.

4) Recipe:

i) Concentration of scouring liquor: Check by titration before and during process.

ii) Action: Adjust the concentration.

iii) Pressure: 15psi or as per quality and regulate steam supply.

iv) Time: Previous time record or as per quality.

v) Concentration of blend liquor: Standard 90% must be consumed.

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4.3. CONTROL BLEACHING PROCESS :

By Kinetic study of bleaching, take 3 titration at 5 minutes. If decomposition in 2nd and 3rd

titration is fast then metallic impurity is present.

Remedy: Hexametaphosphate (7-8gpl to 15-20gpl is taken. It does not chelate Fe ion. If Fe ion is

present then EDTA is used. If hardness of water is around 250-300 PPM, then 3gpl EDTA is

sufficient, but in presence of Fe Ion 6-8gpl is needed at 250-300 PPM Hardness. EDTA chelate

is stable at higher temperature).

Concentration of Chemical:

Concentration is selected from uniformity and reproducible results of previous processing.

Adjust the feeding concentration of chemical as required.

Stock Solution Quantity:

Take study of MLR of process or nature of fabric quality.

Standard: Full consumption of Stock solution should be there, nothing should remain back as

wastage.

Temperature:

Check temperature during process. Temperature depends on bleaching process and bleaching

chemical. Regulate steam supply as needed.

Time: Method: Dwell time record, concentration of bleaching method and process selected.

pH:Adjust the pH during the process by pH indicator or pH paper.

Standard: For Hypochlorite 9.5-10.5 and for Hydrogen peroxide 10.5-11.5.

Concentration of Drain:After bleaching, with the help of titration ensure optimum utilization.

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Conclusion

• Quality assurance is An overall management plan to guarantee the integrity of data (The

“system”)

• In any good pretreatment process Quality Control and Quality Assurance systems

should go hand in hand. The knowledge of QC operations should lead to the formation of

good QA system.

• QA consists of planned and systematic activities, implemented within the quality system

and demonstrated as needed, to provide adequate confidence that an entity will fulfil

given requirements for quality

• Quality assurance then assures that incoming materials meet requirement standards,

products meet their design specifications, orders are processed as per customer demands