Bleach Wash of Woven Denim: Analysis of before & after Wash Properties

Last Updated on 01/04/2021

Bleach Wash of Woven Denim: Analysis of before & after Wash Properties

S.M. Bappy Rana
Dept. of Textile Engineering
Bangladesh University of Business & Technology
Cell: +8801781630519

 

ABSTRACT
Denim garments are most preferred of today’s youth. From special wear to regular wear, woven denim has barged into the acceptance of kid, women and men. But the fashion trends favor the faded woven denim that can only be achieved through apparel washing. The aim of this project work was to study the effect of bleach wash using bleaching powder on 100% cotton indigo dyed woven denim apparels (jeans). Jeans were washed using three parameters, bleach concentration 5 g/l, temperature 60°c and time (10 to 30 minutes). The effect of each parameter is discussed. It was achieved that bleach wash method is very effective method for woven denim apparels to achieve required color depth. It was also revealed that there are big differences in wash properties between bleach washed and raw jeans. Wash properties between the bleach washed and raw jeans that were monitored include: tensile strength, Shrinkage, EPI, PPI, Count, GSM, color depth comparison. Obtained results are discussed and found that tensile strength, GSM, dimensional stability, color depth are decreased due to bleach wash. On the other hand count, EPI, PPI are increased for bleach wash treatment.

Keywords: Bleach wash, woven denim, wash properties.

1. INTRODUCTION
Denim
is very strong, stiff and hard-wearing woven fabric that uses colored warp and white weft yarn. But without finishing treatments, denim garment is uncomfortable to wear due to its weaving and dyeing effects. Denim is produced using very coarser yarn in both warp and weft. In addition, warp yarns are mostly dyed with indigo and sized. As a result, denim is very stiff fabric and hard. So, denim apparels need a finishing treatment to make them soft, smooth and comfortable. Washing practice is the best choice to achieve these purposes.

Bangladesh is a textile-based country. Denim apparels (jeans) are being produced with other apparel to meet its demand in the competitive market of the world. Today’s youth are very fashion concern. It is very challenging to meet their quick change of current demands. At present, the demand of denim apparel with faded look is increasing rapidly. Various types of washing have been used on denim apparel to give them used look. Common washing practices are bleach wash, acid wash, enzyme wash, normal wash, bleach with stone wash etc. Among the washing methods the bleach wash is the widely used method in the washing industry.

It has been investigated by the many researchers that bleaching treatment is successful for achieving desirable color shade and soft hand feels of cotton denim apparels. That’s why bleach wash with bleaching powder is chosen for this project work. The major objective of this work is to examine the effect of various duration of washing in bleach wash with a fixed amount of bleaching powder (5gm/l) and temperature (60°C).

2. LITERATURE REVIEW

2.1 Definition of denim:
Denim is a sturdy cotton twill textile in which the weft passes under two or more warp threads. This twill weaving produces the familiar diagonal ribbing of the denim that distinguishes it from cotton duck.

It is a characteristic of any indigo denim that only the warp threads are dyed, whereas the weft threads remain plain white. As a result of the warp-faced twill weaving, one side of the textile then shows the blue warp threads and the other side shows the white weft threads. This is why blue jeans are white on the inside. This type of dyeing also creates denim’s fading characteristics, which are unique compared to every other textile.

2.2 History of denim:

Denim
Figure: Denim

The word ‘jeans’ comes from the French phrase ‘bleu de Genes’ meaning ‘the blue of Genoa’. The denim fabric originated in the French town of Nimes and owes its name to the location, which was quickly known as ‘denim’ abroad.

Spunky Genoese Navy sailors first strutted around in denim back in the 1500’s but it wasn’t until the 1870’s in the gold rush boom that denim took off. This was when Levi Strauss – a name now synonymous with denim – created a strong style of workers pants with rivets that was quickly adopted by Californian coal miners. Originally made from uncomfortable hemp, Strauss eventually discovered and started using the twilled cotton cloth that originated from the French town of Nimes and denim, as we know it, was born.

For a long time, it was largely worn by workers but become popular in American Pop Culture when jeans became symbolic of protest against conformity. Worn by teenagers and young adults they were often refused admission to movies, restaurants and other everyday haunts when wearing them. But the trend grew and during the 1960’s wearing blue jeans become more acceptable and by the 1970’s they were truly established as a fashion trend. The 80’s brought with it “designer jeans” and denim took to the catwalks.

Today jeans are a staple of everybody’s wardrobe and often a key element in seasonal trends and fashion around the world. Each season brings with it new cuts, features, treatments and embellishments.

2.3 Characteristics of denim fabric:

  1. It is for long wearing.
  2. It is hard wearing.
  3. It is very strong and durable.
  4. It resists snags and tears
  5. It creases easily.
  6. Warp yarns are colored (usually with indigo, vat, blue or sulphur black).
  7. Structure: Right hand or left-hand twill, i.e. z/s-twill of 2/1 or 3/1construction.
  8. Usually made of cotton yarns of coarser count (7s, 10s, 14s, 16s, etc.)
  9. Coarser cloth (weight lies between 6-14 oz/sq. yds) and used for pant and warm jackets.
  10. Rotor yarn are usually used.

2.4 Classification of denim fabric:

1. As per weight /unit area:

  • Light weight: 4.5 to 7 oz/sq.yd
  • Medium weight: 7 to 10 oz/sq.yd
  • Heavy weight: 11 and above.

2. As per hue and color:

  • Indigo vat.
  • Sulphur black.
  • Pigment.

3. As per slub yarns:

  • Warp yarns are slub only.
  • Weft yarn is slub only.
  • Cross Hatch: both way slub i.e. both warp and weft yarn are slub.

4. As per fabric structure /design:

  • Plain.
  • Twill (S-twill, Z-twill, herringbone or zigzag twill)

2.5 Denim washing:
In today’s trend denim has achieved much preference to teenagers as well as baby to adult as blue jeans. According to the fashionable denim garments, subjected to versatile washing techniques to obtain a worn, vintage look with various effects like as hand sand, whiskers, 3D, Nicking, Destroy etc. To produce a fading effect is the main object of denim washing without affecting the main body fabrics and patchiness, crinkles, seam puckering, hairiness, de-pilling, softened-hand feel, stabilized dimensions etc.

Denim pant
Figure: Denim pant

2.6 Types of apparel washes:

  • Wet process
  • Dry process

Wet process:

  1. Normal wash
  2. Enzyme wash
  3. Bleach wash
  4. Caustic wash
  5. Acid wash
  6. Pigment wash
  7. Super white wash
  8. Stone Wash

Dry process:

  1. Hand Scrapping
  2. Whiskering
  3. P.P. Spray
  4. P.P. Sponging
  5. Permanent Wrinkle
  6. Tagging
  7. Destroy
  8. Grinding

2.6.1 Denim bleaching:
In the process a strong oxidative bleaching agent like sodium hypochlorite or KMnO4 is added during the washing with or without stone addition. Discoloration produced is usually more apparent depending on strength on the bleach liquor quality, temperature and treatment time. It is preferable to have strong bleach with short treatment time.

Care should be taken for the bleached goods so that they should be adequately antichlored or after washed with peroxide to minimize yellowing. Materials should be carefully stored before processing for color uniformity.

2.6.2 Enzyme wash:
It is environmentally friendly wash. It involves the application of organic enzymes that eat away at the fabric, i.e. the cellulose. When the desired color is achieved, the enzyme can be stopped by changing the alkalinity of the bath or its temperature. Post treatment includes final ringing and softening cycle. The effects produced by cellulose enzyme are:

  1. Use of cellulose making the seams, hems, and pockets more noticeable;
  2. Salt paper effect is color contrast effect.
  3. Faded garment washed with acid cellulose enzyme provides less color contrast in proportion to garment washed neutral cellulose enzymes.

Garment load size of the m/c is 35-40 jeans per m/c and it cannot be overloaded.

2.6.3 Acid wash:
It is done by tumbling the garments with pumice stones presoaked in a solution of sodium hypochlorite or potassium permanganate for localized bleaching resulting in a non-uniform sharp blue/white contrast. In this wash the color contrast of the denim fabric can be enhanced by optical brightening. The advantage of this process is that it saves water as addition of water is not required.

It consists of soaking pumice stones with chlorine and using their abrasive power to bleach jeans into sharp contrasts. Also known as moon, fog, marble, ice and frosted.

2.6.4 Stone wash:
In the process of stone washing, freshly dyed jeans are loaded into large washing machines and tumbled with pumice stone or volcanic rock to achieve a soft hand and desirable look. Variations in compositions, hardness, size shape and porosity make these stone multifunctional. The process is quite expensive and requires high capital investment. Pumice stone give the additional effect of a faded or worn look as it abrades the surface of the jeans like sandpaper, removing some dye particles from the surfaces of the yarn.

2.6.5 Microsanding:
A fabric finishing process where fabrics are sanded (real sandpaper) to make the surface soft without hair. Can be performed before or after dyeing. In this fabric treatment process, a series of cylindrical rolls in a horizontal arrangement, either wrapped with an abrasive paper or chemically coated with an abrasive are used to create a soft, sueded hand. The denim is pulled over the face of the sand rollers creating a raised surface finishing. Some color reduction is experienced.

There are 3 ways for this technique:

  • Sandblasting.
  • Machine sanding.
  • Hand sanding or hand brushing.

2.7 Bleach:
2.7.1 History of bleach:
The earliest form of bleaching involved spreading fabrics and cloth out in a bleach field to be whitened by the action of the sun and water. Modern bleaches resulted from the work of 18th century scientists including Swedish chemist Carl Wilhelm Scheele, who discovered chlorine, French scientists Claude Berthollet, who recognized that chlorine could be used to bleach fabrics and who first made sodium hypochlorite (Eau de Javel, or Javel water, named after a quarter in Paris where it was produced) and Antoine Germain Labarraque, who discovered the disinfecting ability of hypochlorite’s. Scottish chemist and industrialist Charles Tennant first produced a solution of calcium hypochlorite, then solid calcium hypochlorite (bleaching powder).

Louis Jacques Thénard first produced hydrogen peroxide in 1818 by reacting barium peroxide with nitric acid. Hydrogen peroxide was first used for bleaching in 1882, but did not become commercially important until after 1930. Sodium perborate as a laundry bleach had been used in Europe since the early twentieth century, but did not become popular in North America until the 1980s.

2.7.2 What is Bleach?
Bleach is a chemical that removes colors or whitens, often via oxidation. Common chemical bleaches include household chlorine bleach, a solution of approximately 3–6% sodium hypochlorite (NaClO), and oxygen bleach, which contains hydrogen peroxide or a peroxide-releasing compound such as sodium perborate, sodium percarbonate, sodium persulfate, tetrasodium pyrophosphate, or urea peroxide together with catalysts and activators, e.g. tetraacetylethylenediamine and/or sodium non anoyloxy benzene sulfonate. To bleach something is to apply bleach, sometimes as a preliminary step in the process of dyeing. Bleaching powder is calcium hypochlorite.

Many bleaches have strong bactericidal properties, and are used for disinfecting and sterilizing. Most bleaches are hazardous if ingested or inhaled, and should be used with care.

2.8 Bleach washing:
This way be considered as a preparatory process of mercerizing, dyeing, or printing. therefore, proper bleaching should be carried out other wish the subsequent process would be fault.

Objective:

  • To remove the size material from the garments.
  • To remove the starch present on the garments.
  • For soft feeling to wear the garments.
  • To increase the color fastness and rubbing fastness.
  • Especially develop the “Bio-polishing’’ affect cotton/Denim.

2.9 Bleaching powder (CaOCl2):
Bleaching powder is a mixture of calcium hypochlorite, CaOCl2 and calcium chloride CaCl2. Thus, its chemical composition is CaOCl2 + CaCl2 or can be written as CaOCl2 or Ca(OCl)Cl (Calcium chloro hypochlorite).

Bleaching powder is manufactured by passing chlorine gas over dry slaked lime at 400C.

Ca(OH)2 + Cl2 ← CaOCl2 + H2O

Properties:
1. It is a yellowish white powder with strong smell of chlorine and is soluble in water. Aqueous solution of bleaching powder contains chloride and hypochlorite ions.

CaOCl2 ↔ Ca2+ + Cl- + ClO-

2. In presence of small quantities of dilute acids, it liberates nascent oxygen. Thus, it acts as oxidizing agent.

2CaOCl2 + H2SO4 → CaCl2 + CaSO4 + 2HClO

HClO ← HCl + [O]

3. When bleaching powder is treated with excess of dilute acid or CO2, whole of the chlorine present in the molecules is evolved. The amount chlorine so liberated is called available chlorine. A good sample of bleaching powder contains 35-38% available chlorine.

CaCl2 + 2HCl → CaCl2 + H2O + Cl2

CaOCl2 + CO2 → CaCO3+ Cl2

2.10 Mechanism of bleaching action:
Color in most dyes and pigments is produced by molecules, such as beta carotene, which contain chromophores. Chemical bleaches work in one of two ways

  • An oxidizing bleach works by breaking the chemical bonds that make up the chromophore. This changes the molecule into a different substance that either does not contain a chromophore, or contains a chromophore that does not absorb visible light.

A reducing bleach works by converting double bonds in the chromophore into single bonds. This eliminates the ability of the chromophore to absorb visible light.

2.11 Different type of bleaching agent:

1) Oxidizing Agent:

  • Ozone (O3)
  • Hydogen peroxide (H2O2)
  • Sodium hypochloride (NaOCl)
  • Sodium chlorite (NaClO2)
  • Potassium dichromate (K2Cr2O7)
  • Sodium Peroxide
  • Sodium perborate
  • Potassium permanganate
  • Peracetic acid
  • Bleaching powder
  • Lithium hypochlorite
  • Chloramine

2) Reducing agent:

  • Zinc dust (ZnO)
  • Sodium hypo-sulphite (Na2S2O2)
  • Hydrogen sulphide (H2S)

3. METHODOLOGY
The methodology of this project work was experimental. To perform a successful experiment, the following materials, instrument and methods were used in our project work.

3.1 Raw Materials:
Denim Apparels (leg panels): Leg panels are made of 100% cotton woven denim of Z twill (2/1), Construction: (75 X 45) / (10 X 9). Warp yarn is Indigo dyed and Weft yarn is White.

  • Desizing agent
  • Antistaining Agent
  • Bleaching powder
  • Soda Ash
  • Softener
  • Sodium hyposulphite

3.2 Working Places:

  • Testing laboratory in Bangladesh University of Business and Technology (BUBT).
  • Apparel Manufacturing laboratory in Bangladesh University of Business and Technology (BUBT).
  • Testing laboratory in Bangladesh University of Textiles (BUTEX).
  • Jamuna Washing Plant LTD, Plot-24, Block-k, section-2, Rupnagor I/A, Mirpur, Dhaka-1216.

3.3 Types of machineries used for washing:

  • Sample washing machine
  • Hydro-extracting machine
  • Dryer

3.3.1 Sample washing machine:
Specification:

  • Machine Name: Sample Washing machine
  • Brand: Dongel
  • Origin: Korea
  • Capacity: 125 lb
  • RPM: 600-2800
  • Temperature: 40-100°c
Sample washing machine
Figure: Sample washing machine

3.3.2 Hydro-extracting machine
Specification of hydro-extracting machine:

  • Machine Name: Hydro-extracting machine
  • Brand: Dongel
  • Origin: Korea
  • Capacity: 125 kg Garments
  • RPM: 2800(usually) – 4000
  • Temperature: Room temperature
  • Time: 5 minutes
Hydroextractor machine
Figure: Hydroextractor machine

3.3.3 Dryer
Specification of dryer:

  • Machine Name: Gas dryer machine
  • Brand: Dongel
  • Origin: Korea
  • Capacity: 250-350 kg
  • RPM: 250
  • Temperature: 40- 100°c
Gas dryer
Figure: Gas dryer

3.4 Types of instrument used for testing:

Testing Instrument Used for
Horizontal Tensile Strength testing machine Tensile Strength measurement
GSM cutter GSM measurement
Beazley’s yarn balance Count measurement
Counting Glass/ Magnifying Glass EPI & PPI
Color controller machine  Color depth comparison

3.5 Washing Condition:

No. of Sample 10
M: L 1:25
Material Weight 1000 gm
Temperature 60°c
Time 10, 15, 30 minutes
pH 10.5

3.6 The process of bleach washing:

Desizing Treatment:

  • Batch: 1 kg
  • M: L: 1:25
  • Desizing agent: 1 g/l
  • Antistaining agent: 4 g/l
  • Time: 25 minutes
  • Temperature: 60°c
  • pH: 10.5
  • Drop the liquor
  • Hot wash is done at 70°C for 5 mins, then two times rinsing is done.

Bleaching treatment:

  • Add bleaching powder: 5 g/l
  • Add soda wash: 4 g/l
  • Temperature: 50°c 5. Drop the liquor & Rinsing 2 times.
  • Time: 10- 30 minutes
  • After 10 minutes 2 samples are unloaded
  • After 15 minutes 3 samples are unloaded
  • After 30 minutes 3 samples are unloaded

Neutral wash:

  • Add Sodium hyposulphite: 4 g/l
  • Temperature: 40°c
  • Time: 5 min
  • Drop the liquor & Rinsing 2 times.

Softening process:

  • Add silicon softener :3 g/l
  • Temperature: 40°c
  • Time: 10 minutes

Hydro-extracting and drying:
After softening 5 minutes hydro-extracting is done. then we dried the samples in gas dryer at 70°c for 20 mins. Then cold drying is for 5 mins to back the apparels in normal position.

3.7 Working process:

Apparel (Denim leg panel) .8 kg

Desizing

Hot wash

Cold wash

Bleach washing

Cold wash

Softening

Hydro extracting

Dryer

Bleach washed Apparel

3.8 Testing & its procedure:

3.9 Following tests are done:

  1. Tensile Strength test.
  2. GSM measurement.
  3. Shrinkage Test.
  4. Count measurement.
  5. EPI and PPI measurement.
  6. Shade variation comparison.

3.10 Testing Procedure:

3.11 Tensile strength test:
Tensile strength test is done by grab test principle. The sample size is 6″ ˟ 4″.

3.11.1 Apparatus:

  • Heavy fabric.
  • Fabric strength tester.
  • Scissors.

3.11.2 Machine specification:

  • The horizontal tensile Strength Tester
  • Good brand & Co. Ltd.
  • Capacity: 2000lb

3.11.3 Sample:

  • Size – 6inch × 4 inch.
  • No. of sample – 8; Warp Way- 4, Weft way- 4

3.11.4 Working procedure:

  • At first 6 inch × 4-inch fabric was cut out from a leg panel of fabric. The excess amount of fabric was cut because the two jaws will require at least 2inch each to grip the fabric. Thus 4 samples were cut down for testing warp way strength and 4 samples for weft way strength.
  • Now, the first sample is fixed with the upper jaw J1 and the lower jaw J2.
  • The m/c is started and observed the dial until the sample is torn out.
  • When the sample is torn out the m/c is stopped and the reading is taken.
  • By this way the others’ reading are taken.

3.11.5 Tensile strength test is done by horizontal tensile strength testing machine of Bangladesh University of Textiles (BUTEX).

Horizontal tensile strength testing machine
Figure: Horizontal tensile strength testing machine

3.12 GSM measurement:

3.12.1 Apparatus:

  • GSM cutter
  • Electric balance.

3.12.2 Machine Specification:
Specification of a GSM Round cutter:

  • Area of Specimen: 100 cm²
  • Diameter. Of Specimen: 113 mm.
  • Type of Cut: Standard
  • Blades: Heavy duty Reversible Blades
  • Fine Brass safety Lock
  • Hand Wheel (Handle): Special Bakelite Handle
  • For repetitive test without fail the cutting pad should be new rubber-foam pad.

3.12.3 Working Procedure of Measuring GSM of a Fabric:

  • For Measuring GSM, fabric sample is cut by GSM cutter
  • Now weight is taken by electric balance.
  • By this way we get the weight in gram per one square meter fabric.
  • Here GSM of the fabrics by the GSM cutter is obtained by the multiplying the sample weight with 100.

3.12.4 GSM measurement test is done by GSM cutter from Bangladesh University of business and technology (BUBT).

GSM Cutter
Figure: GSM Cutter

3.13 Shrinkage test:
Shrinkage is the process in which a fabric becomes smaller than its original size, usually through the process of laundry. Cotton fabric suffers from two main disadvantages of shrinking and creasing during subsequent washing.

There are two types of shrinkage occurs during washing:

  1. Length wise
  2. Width wise

3.13.1 Working procedure:

  • For Shrinkage test Fabric sample is marked 8″*8″ with square.
  • Then Sample is washed with bleaching powder 10, 15 and 30 minutes. And dried in dryer machine.
  • Then the shrinkage is measured of the sample.

3.13.2 Apparatus:

  • Denim Apparels

3.14 Count measurement:

3.14.1 Apparatus:

  • Bessley balance
  • Template
  • Dead weight

3.14.2 Working procedure:

  • For count measurement warp and weft way yarn is collected from before washed and after washed (10, 15, 30 minute) sample.
  • Then the yarn count is measured by Beasley’s balance.

3.14.3 Count measurement test is done by Beasley’s balance of Bangladesh University of Business and Technology (BUBT).

Beasley’s Balance
Figure: Beasley’s Balance

3.15 EPI & PPI measurement:

3.15.1 Apparatus:

  • Counting glass,
  • Needle.

3.15.2 Working procedure of EPI & PPI measurement:

  • For measuring EPI & PPI measurement the fabric sample – Before washed & after washed (10, 15, 30 minute) is taken.
  • Then the EPI & PPI is measured by counting glass.

3.15.3 EPI & PPI measurement test is done by Counting glass from Bangladesh University of Business and Technology (BUBT).

Counting glass
Figure: Counting glass

3.16 Comparison of color depth variation:

3.16.1Apparatus:

  • Color Controller machine
  • Grey Scale
  • Denim fabric (Before Wash & After Wash Sample)

3.16.2 Working Procedure:

  • To compare of shade variation, we take the before and after wash sample.
  • Shade variation is notified by the color controller machine.
  • We note down the result which is notified by grey scale.

3.16.3 Color depth comparison is done by color controller machine from Bangladesh University of business and technology (BUBT).

Color controller machine
Figure: Color controller machine

3.16.4 Snap shot of bleach washed denim:

bleach washing treatment
Figure: Color depth comparison after bleach washing treatment

4. RESULT AND DISCUSSIONS

4.1. Tensile Strength Test:

4.1.1. The Results of Tensile Strength Test:

Observation no. Before Wash After 10-minute wash After 15-minute wash After 30-minute wash
Warp Weft Warp Weft Warp Weft Warp Weft
1. 350 lb 200 lb 320 lb 180 lb 290 lb 170 lb 200 lb 150 lb
2. 350 lb 210 lb 300 lb 180 lb 280 lb 160 lb 180 lb 150 lb

4.1.2 Graphical Comparison:

4.1.2.1 Comparison of tensile Strength in warp way:

warp way Strength Measurement
Figure 4.1.2.1.1: Bar charts of warp way Strength Measurement
warp way Strength Measurement
Figure 4.1.2.1.2: Bar charts of warp way Strength Measurement

4.1.2.2 Graphical comparison of strength loss % in warp way:

Graphical comparison of strength loss % in warp way
Figure: Bar charts of strength loss % in weft way from observation no. 1

4.1.3 Comparison of Strength in Weft Way:

weft way strength Measurement
Figure 4.1.3:1: Bar charts of weft way strength Measurement
Bar charts of weft way Strength Measurement
Figure 4.1.3:2: Bar charts of weft way Strength Measurement

4.1.3.1 Graphical comparison of Strength loss % in weft way:

Graphical comparison of Strength loss % in weft way
Figure: Bar charts of strength loss % in weft way from observation no. 1

4.1.4 Discussion:
Washing causes a huge change in strength of apparels. Strength has fluctuated randomly in different sample. In weft direction strength is lower than warp direction. More difference (warp) (350-200) ˟ 100/350= 43% in case of observation 1 in warp way. (200-150) ˟ 100/200 = 25 % in case of observation 1 in weft way. It was investigated from the project work that strength is reduced when duration of washing is increased when the bleach concentration and temperature remain same.

4.2. GSM Measurement:

4.2.1 The results of GSM measurement:

No. of Observation Before Wash After 10-minute wash After 15-minute wash After 30-minute wash
Value Average Value Average Value Average Value Average
1. 3.4 3.43 3.38 3.376 3.35 3.356 3.303 3.298
2. 3.5 3.37 3.36 3.29
3. 3.4 3.38 3.36 3.301

4.2.2 Graphical comparison of GSM measurement:

Bar charts of GSM measurement
Figure 4.2.2.1: Bar charts of GSM measurement
Bar charts of GSM measurement
Figure 4.2.2.2: Bar charts of GSM measurement
Bar charts of GSM measurement
Figure 4.2.2.3: Bar charts of GSM measurement

4.2.3 Graphical comparison of weight loss %:

Graphical comparison of weight loss %
Figure: Weight loss% from observation no. 1

4.2.4 Discussion:
Bleach washing increases the weight loss% of woven denim apparels. We know damage % should not be more than 30%, All of the tests are remain within the limit. More difference in observation 2, the weight loss% is (3.5-3.29)/3.5 ˟ 100= 6%. It has been explored that due to long time washing the weight loss % is increased.

4.3 Shrinkage test:

4.3.1 The results of Lengthwise shrinkage Measurement:

Lengthwise shrinkage Measurement

4.3.2 Graphical Comparison of lengthwise shrinkage:

Graphical Comparison of lengthwise shrinkage
Figure 4.3.2.1: Bar charts of lengthwise Shrinkage measurement
Bar charts of lengthwise Shrinkage measurement
Figure 4.3.2.2: Bar charts of lengthwise Shrinkage measurement

4.3.3 The results of Width wise shrinkage measurement:

Widthwise shrinkage measurement

4.3.4 Graphical Comparison of width-wise shrinkage:

width wise Shrinkage measurement 1
Figure 4.3.4.1: Bar charts of width wise Shrinkage measurement
Bar charts of width wise Shrinkage measurement
Figure 4.3.4.2: Bar charts of width wise Shrinkage measurement

4.3.5 Discussion:
From the result it was explored that dimensional change is occurred due to bleach wash. In the lengthwise the shrinkage% is 4.375% that means length is decreased in a small amount due to washing. On the other hand, the shrinkage% in width wise is 3.75% that means is width decreased but less than length wise.

4.4 Count Measurement:

4.4.1 The results of warp Count measurement:

No. of Observation Before Wash After 10-minute wash After 15-minute Wash After 30-minute Wash
Value Average Value Average Value Average Value Average
1. 9 9 10 10 11 11 11 11
2. 9 10 11 11
3. 9 10 11 11

4.4.2 Graphical Comparison:

warp Count Measurement
Figure 4.4.2.1: Bar charts of warp Count Measurement
Bar charts of warp Count Measurement2
Figure 4.4.2.2: Bar charts of warp Count Measurement
Bar charts of warp Count Measurement
Figure 4.4.2.3: Bar charts of warp Count Measurement

4.4.3 The results of Weft Count measurement:

No. of Observation Before Wash After 10-minute wash After 15-minute Wash After 30-minute Wash
Value Average Value Average Value Average Value Average
1. 10 10 11 11 12 12 12 12
2. 10 11 12 12
3. 10 11 12 12

4.4.4 Graphical comparison:

weft Count Measurement
Figure 4.4.4.1: Bar charts of weft Count Measurement
charts of weft Count Measurement1
Figure 4.4.4.2: Bar charts of weft Count Measurement
Bar charts of weft Count Measurement2
Figure 4.4.4.3: Bar charts of weft Count Measurement

4.4.5 Discussion:
It has been noticed that bleach washing has a little effect in count. As the denim is 100% cotton, count is measured in English count Ne. It is cleared that there is a difference in warp way and weft way count. Warp way count is lower than weft way count that means weft way yarn is finer than warp way yarn. Due to washing size materials are removed and the yarns become finer. That’s why count increases after washing. Denim becomes soft after washing.

4.5 EPI and PPI Measurement:

4.5.1 The results of EPI Measurement:

No. of Observation Before Wash After 10-minute Wash After 15-minute Wash After 30-minute Wash
Value Average Value Average Value Average Value Average
1. 75 75 75 76 76 77 76 77
2. 76 77 77 77
3. 75 77 77 77

4.5.2 Graphical comparison:

Bar charts of EPI measurement
Figure 4.5.2.1: Bar charts of EPI measurement
Bar charts of EPI measurement
Figure 4.5.2.2: Bar charts of EPI measurement
Bar charts of EPI measurement
Figure 4.5.2.3: Bar charts of EPI measurement

4.5.3 The results of PPI Measurement:

No. of Observation Before Wash After 10-minute Wash After 15-minute Wash After 30-minute Wash
Value Average Value Average Value Average Value Average
1. 44 45 46 46 47 46 46 47
2. 45 46 46 47
3. 45 47 46 48

4.5.4 Graphical Comparison:

Bar charts of PPI measurement
Figure 4.5.4.1: Bar charts of PPI measurement
Bar charts of PPI measurement
Figure 4.5.4.2: Bar charts of PPI measurement
Bar charts of PPI measurement
Figure 4.5.4.3: Bar charts of PPI measurement

4.5.6 Discussion:
It was revealed that bleach washing has a little effect in EPI and PPI of woven denim apparel. it is further noted that due to different duration of washing EPI, PPI was little changed.

4.6 Comparison of color depth

4.6.1 The results of color depth comparison:

No of Observation Before wash parameter After 10-minute Wash parameter After 15-minute Wash parameter After 30-minute Wash parameter
1. 5 3 2 1
2. 5 3 2 1

4.6.2 Graphical comparison:

Bar charts of color depth
Figure 4.6.2.1: Bar charts of color depth
Bar charts of color depth
Figure 4.6.2.2: Bar charts of color depth

4.6.3 Discussion:
It was investigated from the project work that there was a huge change in color depth due to bleach wash on woven denim apparels. When duration of washing increases, shade becomes lighter even temperature and concentration remain same at the whole process.

5. CONCLUSION
Bleaching powder (Calcium chloro hypochlorite) is an effective bleaching agent for denim washing. Bleaching treatment has become successful for achieving desirable color shade and soft hand feels of cotton denim apparel (jeans).

Popularity of apparel washing especially on denim apparel (jeans) in the world market has been increasing day by day. In this project work it has been explored that, bleach washing with a bleaching powder gives a used look appearance on jeans. The effects of bleach washing on jeans under investigation could be realized by the comparison of before and after wash properties namely tensile strength, GSM, EPI, PPI, Dimensional stability, count and color depth variation. Tensile strength, GSM, dimensional stability, color depths are decreased and count, EPI, PPI are increased due to bleach wash treatment. It is further noted that pre- washed jeans are almost stiff and harder than the bleach washed jeans.

It has also been explored that as a cost-effective method bleaching treatment with a bleaching powder can produce a fashion apparel and a value-added product with a high wear performance. So, in order to meet the quick change of customer demand for fashion apparel, bleach washing can be an effective way.

6. REFERENCES

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  9. Cookson, P. G., Relationships Between Hygral Expansion, Relaxation Shrinkage, and Extensibility in Woven Wool Fabrics, Textile Res. J. 62: 44-51 (1992).
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  13. Sangita, S., Kumar, P. S. and Chandran, M.R., Types of Stone Wash & Their Effects on the Denim Fabric, The Indian Textile Journal, (2010).
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