Now You Know Performance Analysis of Denim Garments by Bleach Wash (Part-9)

Performance Analysis of Denim Garments by Bleach Wash (Part-9)

Authors: Md. Anwarul Haque¹
Ariful Hassan²
Shantonu Paul Shuvra Md. ShagorHossain
Textile Engineering College, Begumgonj, Noakhali.
Email: haquebd2014@gmail.com¹ , arifulhassan034@gmail.com²

Previous Part


Result and discussion

Effect of washing on feel of fabric:
The hand feeling of the fabric improves a lot after performing the washing and this improvement has been found in each successive stages of processing. After desizing process the hand feel become soft than the before stage, but the fabric has become more soft after the bleaching process. After softening the fabric exhibited the soft test hand feel.

Effect of bleach wash and softening on fabric specification:

It is clear from Table that the desizing, bleaching a softening imparts significant change in the fabric properties. It has been found that, during these specific processing, the value of fabric surface density has been decreased. The Ends per Inch (EPI) and Picks per Inch (PPI) increased in a lower degree. The Shrinkage property has been found decreases, most significantly in warp way. Cotton fabrics are generally subjected to a considerable tension during weaving especially in the warp direction. This stretch was increased in subsequent finishing processes like calendaring and thus the stretch temporarily set in the fabric. The fabric is then in a state of dimensional instability. 

BLEACHING STAGES		EPI	PPI	Warp count Ne	Weft count Ne	Shrinkage (%)
Before washing		79	55	10	11	-
After washing	Sample01	77	50	9	10	L=5.5 W=0.5
	Sample02	76	53	9	10	L=6.0 W=1.0
	Sample03	75	51	9	10	L=6.0 W=1.0

When the bleach washing has been performed, the thorough wetting of the denim tends to bring the fabric back to its more stable dimensions which result in the contraction of the yarns. This effect is generally greater in the warp direction compared to the weft. This is known as relaxation shrinkage. EPI (Ends per Inch) and PPI (Picks per Inch) was increased than untreated denim garments due to this relaxation shrinkage.

Effect of bleach wash on fabric GSM:

Bleaching stages		GSM
Before washing		379
After washing	Sample 01	371
	Sample 02	373
	Sample 03	376

Discussion:
It can also be observed seen from Table that, treatment of the denim garments with hypochlorite bleach at 5g/l concentration cause significant decreased the GSM (fabric weight) of the garments, whereas weight loss (GSM decreased) results have previously been obtained with direct and reactive dyed cotton fabric substrate. During weaving cotton fabrics were subjected to considerable tensions, particularly in the warp direction. In subsequent finishing processes such as calendaring this stretch was increased and temporarily set in the fabric. The fabric is then in a state of dimensional instability. Subsequently when the denim garment was thoroughly wetted in bleach washing, it tended to revert its more stable dimensions which results in the contraction of the yarns. This effect is usually greater in the warp direction than in the weft direction. This is known as relaxation shrinkage. Due to relaxation shrinkage, PPI (picks per inch) was increased than untreated denim garments, as a result fabric weight loss is slightly minimized and 10g/l concentration is optimum result for bleach washing. Although decomposition occurred in hypochlorite bleach washing, at the same time relaxation shrinkage happened, and the GSM /fabric weight loss of denim garments were minimized slightly. This was observed that 10g/l concentration exhibits the minimum decrease in the fabric weight as compared with the other concentrations. Thus, 10g/l bleach wash is optimal and this concentration of bleach exhibited the maximum decrease in fabric stiffness; and maximum increase in water absorption, elongation at break and GSM as compared with the other concentrations.

Effect of washing on color shade of denim fabric:

Processing stage	Grey scale ratting
Before Wash	5
Sample 01	3
Sample 02	2/3
Sample 03	2

Discussion:
It is obvious from Table that, bleaching has changed the color of the denim significantly. A higher degree of color fading is achieved after the bleaching treatment. After desizing, a slight change in the color is observed compared to the before wash sample but the change in the color is vast after bleaching. The difference in color change is minimum in softening.

Effect of washing on tensile strength of fabric:

The effects of bleaching powder on denim garment washing with different concentrations from 5g/l to 15g/l of KCI bleach for 20 min were investigated. It can be seen from Table that, treatment of denim with bleaching powder at 5g/l concentration cause significant decrease of tensile strength and this decrease was higher at higher bleach concentrations. It is observed that 15g/l concentration exhibited the highest decrease in the loss of tensile strength as compared with the other concentrations. Bleaching powder decomposed cotton under the conditions used. Bleaching powder first attacked on dyed yarn portion, decomposed them slowly and fibers are partly degraded from the yarn chain and step by step penetrated inside fabric. Therefore, the chemical bonds of primary wall (outer layer) are broken by the decomposition of the aqueous solution of hypochlorite bleach. After that it attacked on secondary wall. The result of this reaction is that the primary wall (outer layer) of the cotton fiber is loosened and broken down quicker with the frictional action (mechanical forces) of rotating cylinder of the washing machine. The effect also depends on the conditions of washing.

Bleaching stage		Tensile strength(warp)	Tensile strength(weft)
Before wash		545	280
After wash	Sample 1	455	250
	Sample 2	460	260
	Sample 3	440	260
	Sample 4	445	255

Effect of washing on stiffness (Bending Length) of denim fabric:
The cotton fibers are loosened by bleaching treatment as the fibrils are degraded and partly detachedfrom the main fiber chain and softness increased. Moreover the size materials (Starch) are also removedfrom the warp yarns. As a result bending length was less and softness was increased. A significant change can be seen after the desizing as this step reduces most of the size materials from the fabric. As the size materials are removed from the warp yarns (as only warp yarns are sized), the reduction in the stiffness is very much significant in the warp way.

Raw fabric:

Direction	Face left	Face right	Back left	Back right	Average
Warp	3.5	3.5	3	3	3.25
Weft	2.5	2.45	2.85	2.78	2.645

After bleaching:

Sample 01:(conditions: D=15min,B=5min)

Direction	Face left	Face right	Back left	Back right	Average
Warp	3.1	3.1	2.9	3.05	3.0375
Weft	2.3	2.3	2.8	2.75	2.5375

Sample 02:(condition:conc.12.5g/l,50oc,15min)

Direction	Face left	Face right	Back left	Back right	Average
Warp	3.2	3.1	2.85	2.75	2.975
Weft	2.2	2.2	2.55	2.6	2.3875

Effect of moisture content and moisture regain:

Washing condition		Moisture content	Moisture regain
Before wash		3.80	4.10
After wash	Sample01	5.74	6.09
	Sample02	5.79	6.15
	Sample03	6.09	6.48

Moisture content is a measure of the level of water in the denim samples. It can be seen from Table that the moisture contents of the bleach treated samples with various concentrations from 5g/l – 15g/l are similar and are the range of 8.3-8.51%, whereas untreated sample was 7.5%. Same holds true for the elongation at break also. Elongation at break of the treated denim garments with various concentrations is similar and the range of elongation 41-48% lengthwise and 21-22% widthwise, whereas untreated sample was 24% and 16% respectively.

Conclusion
The bleaching and softening treatment have a great influence on the mechanical and color properties of denim fabric.

The fading effect can be increased by the bleaching but bleaching also reduces thefabric weight, tensile strength and seam strength which might reduce the serviceability of the garments. So an optimum bleaching action is required to get the required fading effect and softness without compensating some important properties of denim.

Finally, in denim washing our country has a bright future due to wide spread market of denim garments. We need thorough knowledge on denim treatment process and also on the fashion going around the world. And this project will be a guideline for them who are interested in the sector. pioneer in the field of hard washing. And we believe that this project will be a guideline for the washing plants in understanding and doing various treatments.

References:

1. HAMS washing & dyeing Ltd.
2. www.wikipedia.Com
3. Class lectures
4. Technology of bleaching & mercerizing (v.a.Shenai)( Book)
5. "How jeans conquered the world". BBC News. 2012-02-28.
6. Mogahzy, Y. E. (2009). Engineering Textiles: Integrating the Design and Manufacture of Textile Products (First Edition ed.). Woodhead Publishing Ltd. p. 362. ISBN 978-1-84569-048-9.
7. In 1789 George Washington toured a Beverly, Massachusetts factory producing machine-woven cotton denim. (Massachusetts Foundation for the Humanities: Mass Moments)
8. Bellis, Mary. "Levi Strauss - The History of Blue Jeans". About.com. The New York Times Company. Retrieved 2010-08-04. "Levi Strauss had the canvas made into waist overalls. Miners liked the pants, but complained that they tended to chafe. Levi Strauss substituted a twilled cotton cloth from France called "serge de Nimes." The fabric later became known as denim and the pants were nicknamed blue jeans." In INDIA jeans was introduced by famous model Reddeppa. In French of Nimes or De Nimes shortened to Denim
9. Coe, Nick. "The Essential Raw Denim Breakdown – Our 100th Article!". RawrDenim.com. Edmonton, Alberta, Canada: RawrDenim.com. Retrieved 2012-03-28. I had read somewhere that a pair of raw denim is like an individualized canvass. Indeed the fade results and any other visible marks, rips, or tears are specific you and your body. For a dramatic illustration of what we mean, hop over to Takayuki Akachi’sdocumentary on the “Traveling Denim“.
10. Slater, Sean. "When Should I Wash My Raw Jeans? – A Rough Guide". RawrDenim.com. Edmonton, Alberta, Canada: RawrDenim.com. Retrieved 2012-03-28. If you’re able to wear your jeans all day, every day then 6 months may be long enough (or perhaps even too long). But if you’re like many folks who have to wear a uniform or dress professionally for 5 days of the week, then you’ll need more time to achieve the same results, maybe 9 months or more.
11. Coe, Nick. 1  2  3  4  5  6  7  8  9

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