Bleach Wash of Woven Denims: Analysis of before and after Wash Properties (Part-1)

Bleach Wash of Woven Denims: Analysis of before and after Wash Properties (Part-1)
S.M. Bappy Rana
Dept. of Textile Engineering
Bangladesh University of Business & Technology
Cell: +8801781630519



ABSTRACT
Denim apparels 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.


CHAPTER- 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 practises 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).

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