Now You Know Effect of Random Wash on Denim Fabrics by Using Different Techniques
Friday 25 May 2018
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Effect of Random Wash on Denim Fabrics by Using Different Techniques
Muhammad Rizwan1
Muhammad Adeel
Bahauddin Zakariya University College of Textile Engineering, Multan, Pakistan
Email: rizwan.malik93@yahoo.com1
Muhammad Adeel
Bahauddin Zakariya University College of Textile Engineering, Multan, Pakistan
Email: rizwan.malik93@yahoo.com1
Abstract
Industrial washing is one the finishing method applied on Denim. As it is applied on already sewn garment, so it is important to know the effect of washing on garment. Our aim is to study effect of random wash on denim by using different techniques and study their Mechanical properties. We selected non-stretchable rigid denim fabric and stretchable rigid denim fabric. We apply different washing techniques i.e. Random wash with rags, used stones and chemicals are Potassium permanganate and Sodium hypochlorite. We performed GSM, Tensile Strength and Tear Strength and noted the effect on properties. We observed that as the concentration of the chemicals increases Tear Strength, Tensile Strength and GSM of the fabric is decreased. We also noted from experiments that Potassium permanganate is highly effective than Sodium hypochlorite.
CHAPTER 1
1 Introduction:
Denim has a lot of demand in the market of regular garments as well as in the fashion market. People of all ages, especially the youth have a great interest on the denim. Different values by adding processes like industrial washing make denims not only look beautiful but also impart some functional properties to the garments. Denim has been used as clothing material for centuries due to its high durability. But today’s fashion arena likes denim jeans due to its attractive shades, designs, and attractive styles[1].
1.1 What is denim?
A name given to a fabric in which warp is dyed yarn and weft is un-dyed. Denim is a twill textile in which the weft passes under two or more warp threads[2]. 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[3].
1.1.1 Characteristics of denim:
Denim is actually cotton twill weave. Usually, warp yearns are dyed or colored with indigo, vat, blue or sulphar black. Here some characteristics of denim are given below[3].
- It is for long wearing.
- It is very strong and durable.
- It resists snags and tears.
- It creases easily.
- Router yarns are usually used.
Nowadays, many types of denim are used. It depends upon the customer demand that what type of the denim him /her demands. A lot of varieties of denim are present in this era[4].
1.1.2.1 Dry denim:
It is a type of denim fabric which is not washed after being dyed. Mostly, denim fabrics are dried after washed in order to make the fabric softer feel and remove any shrinkage which causes any problem for customer. Dry denim can be identified by its lack of a wash, or "fade". It typically starts out as the dark blue color pictured here[4].
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| Figure 1: Dry denim |
Selvage denim is also called selvedge. It is a type of denim fabric in which clean natural edges are present that does not unravel. The selvage edges will be located along the out seam of the pants, making it visible when cuffs are worn. The word "selvage" comes from the phrase "self-edge" and denotes denim made on old-style shuttle looms. The selvage edge is usually stitched with colored thread: green, white, brown, yellow, and red (red is the most common). Fabric mills used these colors to differentiate between fabrics[4].
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| Figure 2: Selvage denim |
It is another type of denim which consists of 98% cotton and 2% spandex. Due to this blend denim is stretched. Ease of movement is done by using this type of denim fabrics. Stretch denim jeans are one of the fastest growing segments of the women’s market for jeans manufacturers[4].
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| Figure 3: Stretch denim |
This type of denim fabric contain polyester blend that wash and dry quickly. It is lighter weight and a bit dressier. These usually appeal to a slightly older market, but are also finding favor for pantsuits, etc. when the look is meant to be “dressy but casual”[4].
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| Figure 4: Poly denim |
In fashion history, No one truly knows the perfect answer to where jeans began. As so often happens fashions often emerge together in various parts of the world and are the result of the sudden availability of a new fabric, cloth, dye or technique. But we do know that the phrase denim jeans are thought to derive from several sources. No one is totally certain where the words come from. A majority of source books suggest that denim derives from the English translation of the South of France French phrase 'serge de Nîmes'. Denim fashion history is thus associated with Serge de Nimes[4].
The word "denim" comes from the name of a fabric that was first made in the city of Nîmes, France, by the André family. It was originally called serge de Nîmes but the name was soon shortened to "denim."
Denim has been used in the United States since the late 18th century. Denim was traditionally colored blue with indigo dye to make blue jeans, although "jean" formerly denoted a different, lighter, cotton fabric. The contemporary use of the word "jean" comes from the French word for Genoa, Italy (Gênes), where the first denim trousers were made.[3].
Levi Strauss and Jacob Davis supplied miners with denim pants that were made from strong material and reinforced with rivets at the places where pants tended to tear which prolonged life of pants[5].
About 1947 denim made a break-away from work clothing image, chiefly in the area of sportswear and rain wear and an occasional appearance in high fashion collections as a "different-looking" evening dress. In 1970 American youth adopted denim as their favorite fabric. Part of a "back to nature" movement that emphasized ecology and the natural denim being a fabric created from a natural fiber was a primary factor. Since 1960 the jeans business has undergone an explosive transformation, from a source of tough, cheap clothing for cowboys, blue-collar workers and penniless youth into a fashion conscious market for a widening mass of people of almost all ages[6].
By the 1990s black jeans were very popular for a while and jeans in general were seen a lot in the early 1990s. But shades of blue are always loved and sometimes the darkest shade is high fashion and sometimes the most washed out faded pairs become the hottest. Colored jeans of all shades made an appearance[4].
1.3 Flow chart of denim manufacturing process:
Today is the era of fashion industry. No one can live without adopting the fashion of denim. All over the world, hundreds of the textile industries are producing denim. In Pakistan, there are also some industries are present which are working and producing the fashion. So the question is arising that how denim is manufactured? What is the manufacturing process of denim [4]?
There is the following process of the denim manufacturing:
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| Figure 5: Denim flow chart |
First step of denim manufacturing is the yarn production. In this process opening and blending occur. Opening begins with baled cotton fiber being separated into small tufts. The next step is carding in which removing foreign matter and short fibers form the cotton into a web and convert the web into a rope-like form known as a sliver. The drawing process produces a single, uniform sliver from six card slivers[4].
There is two type of spinning occur:
I. Open end spinning
II. Ring spinning
In Open End Spinning, machines have robots on each side which automatically pieces up (repairs broken ends). On a different track, they have another robot that automatically doffs (removes full packages) and starts up a new package. The size and quality of each yarn end are monitored by the Barcoo Profile System to ensure uniformity.
In Ring Spinning, the spinning frames receive Roving via a transit system from the roving machine. Yarn is formed from cotton fibers that are twisted together after being drafted by passing between three steel rolls and three rubber rolls. The spinning frames automatically doff bobbins full of yarn and send them to package winding.
1.3.2 Ball warping:
It is the second step of denim manufacturing. Warping is transferring many yarns from a creel of single-end packages forming a parallel sheet of yarns wound onto a beam.
Ball warping is also a type of warping. Ball Warping is mainly used in manufacturing of denim fabrics. The warp yarns are wound on a ball beam in the form of a tow for indigo dyeing. After the dyeing process, the tow is separated and wound on a beam. This stage is also called long chain beaming or re-beaming[4].
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| Figure 6: Ball warping |
Dyeing is a process in which we impart color to the fabric. In dyeing the dye solution or dispersion is almost always in an aqueous medium. Dyeing is mainly depends on the type of fabric, structure of fabric and the properties of dyes.
It is the third step of denim manufacturing process. Rope dyeing is a method in which hundreds of yarns are bundled in a shape of rope and soaked in a large bath, pulled up and oxidized in air. The process is repeated 6-8 times until the color is fixed. Rope dyeing is mainly used in Denim Industry. Mainly Indigo and Sulphar Dyes are used in Rope Dyeing[7].
There are some factors which affect the rope dyeing:
- Dipping time
- Squeeze pressure
- Airing time
- Drying
- Effect of pH
- Reaction time
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| Figure 7: Rope dyeing |
- Custom designed indigo rope range for maximum flexibility with minimum waste.
- Dyes multiple yarn weights with multiple dye classes.
- Runs short or long production lots with light or heavy depths of shade.
- Mercerizing adds improved dye affinity, luster, strength & fashion effects.
- Multiple dips of indigo & oxidation time in the skier section for shade depths.
- Multiple wash boxes for rinsing & chemical application.
- Coilers lay ropes into drums in a pattern that facilitates Re-beaming operation.
It is the fourth step of denim manufacturing. Winding the dyed yarn onto the beams again from the cans is called re.beaming. Rope passed through the accumulator reverse system & back pulley to untangle them then passed through a dancer. After this, passed through the combs. Then wound onto the beam and send them for sizing if required[4].
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| Figure 8: Re-beaming |
Applying the sizing materials coating on the yarn as per requirement is called sizing. In sizing process, usually starch is used as size material[7].
Size material is used to:
- To increase the tensile strength of warp sheet.
- To increase the abrasion resistance.
- To increase the weight of yarn.
- To decrease the hairiness.
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| Figure 9: Sizing process |
It is the second last step of weaving. The process of producing a fabric by interlacing warp and weft threads is known as weaving. The machine used for weaving is known as weaving machine or loom. Weaving is an art that has been practiced for thousands of years. The earliest application of weaving dates back to the Egyptian civilization. Over the years, both the process as well as the machine has undergone phenomenal changes. As of today, there is a wide range of looms being used, right from the simplest handloom to the most sophisticated loom[4].
Denim is fabrics traditionally woven with what is known as twill weave. This is simply a weaving pattern that produces parallel diagonal ribs. The weaving process interlaces the warp, which are the length-wise indigo dyed yarn and the filling, which are the natural-colored cross-wise yarn. The warp thread is in the form of sheet. In denim, the warp-faced twill pattern calls for passing the weft yarn over one and under two (1/2), or over one and under three warp (1/3) yarns. Because there are fewer lacings in twills than in plain weaves, the yarns are freer to move when being worn resulting in a fabric that is both flexible and resilient[6].
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Figure 10: Weaving |
1.3.5 Fabric finishing:
It is the last step of denim manufacturing process “A process done to fibers, yarns and fabric causing them to change in appearance, texture and performance.”The term finishing covers all those treatments that serve to impart to the textile the desired end-use properties. These can include properties relating to visual effect, handle and special characteristics such as waterproofing and non-flammability. Finishing treatment is done to achieve the ultimate customer requirements[6].
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| Figure 11: Finishing flowchart |
1.4 Dyeing:
A process of coloring fibers, yarns, or fabrics with either natural or synthetic dyes. In other words dyeing can be defined as dyeing is a process in which we impart color into the fabric. All commercial textile dyeing processes take place by the application of a solution or a dispersion of the dyes to the textile material followed by some type of fixation process. The dye solution or dispersion is almost always in an aqueous medium[6].
Dyeing is mainly depends on the type of fabric, structure of fabric and the properties of dyes. Dyeing can be done at any stage of the manufacturing of textile- fiber, yarn, fabric or a finished textile product including garments and apparels[8].
1.4.1 Dye:
Dyes can be defined as substances that add color to textiles. They are incorporated into the fiber by chemical reaction, absorption, or dispersion[8].
Dyes are differing in
- Their resistance to sunlight, perspiration, washing, gas, alkalis and other agents.
- Their affinity for different fibers.
- Their reaction to cleaning agents and methods.
- Their solubility and method of application.
1.4.1.1 Properties of dyes:
To be of use, dyes must have the following four properties:
- Color
- Solubility in water
- Ability to be absorbed and retained by fiber substantively.
- Chemically combined with fiber (reactivity)[9].
There are several ways for classification of dyes. Each class of dye has a very unique chemistry, structure and particular way of bonding. While some dyes can react chemically with the substrates forming strong bonds in the process, others can be held by physical forces. Some of the prominent ways of classification are given below[9].
- Classification based on the source of materials.
- Classification of the Dyes- Based on the nature of their respective chromospheres.
- Classification by methods of application.
There are the following types of the dyes.
- Acid Dyes
- Natural Dyes
- Basic Dyes
- Synthetic Dyes
- Direct Dyes
- Disperse Dyes
- Sulfur Dyes
- Pigment Dyes
- Mordant Dyes
- Vat Dyes
- Reactive Dyes
- Azo Dyes
- Aniline Dyes
Vat Dyes are insoluble in their colored form. They are reduced by another chemical and converted to a soluble form. The reduced dye is applied to the fabric, and then exposed to the air which oxidizes the dye back to its colored form. Indigo dye will be used to dye a sample of cotton fabric. Indigo is the dye used to make blue jeans blue[10].
Vat dyes are mainly applied on cellulosic fibres, but some can be applied to protein fibres. They usually have outstanding color-fastness properties. Vat dyes are more expensive and difficult to apply than other classes for cellulose such as directs, sulphar, and reactive[4].
1.4.2.1 Classification of vat dyes:
Depending upon the properties, vat dyes can be classified as
- IN (indanthrene normal)
- IW (indanthrene warm)
- IK (indanthrene kalt/ cold)
IW dyes have a much higher substantivity and are dyed at 45–50°C with somewhat more caustic soda and less salt. Regenerated cellulosic fibres and mercerized cotton are dyed without salt.
IK dyes have a relatively low substantivity for cellulose and so are dyed at room temperature with a small amount of caustic soda and a high salt concentration. This group of dyes has diminished in importance[11].
1.4.2.2 Chemical constitution of vat dyes:
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| Figure 12: Vat dye and Lecue compound |
Following are the uses of vat dyes.
- Vat dyes are used in cotton dyeing where high wash & boil fastness required.
- Because of the high alkali concentration in the dye bath, pure vat dyes cannot be used on animal fibres, (wool, natural silk, & various hairs).
- Bright red is absent in vat dye range.
- Solubilized vat dyes, not requiring the presence of alkali, can be used for dyeing on animal fibres.
- Because they are dyed at low temperatures, they are used in Indonesian batik dyeing for green shades[9].
Indigo dye is an organic compound with a distinctive blue color. Historically, indigo was a natural dye extracted from plants. But today nearly all indigo dye is produced synthetically. It contains carbonyl chromospheres. The primary use for indigo is as a dye for cotton yarn, which is mainly for the production of denim cloth for blue jeans[6].
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| Figure 13: Indigo dye |
In order that indigo is able to dye the fiber, it needs to be activated (leuco-form). In other words, indigo should be converted into soluble form and the affinity to fiber should be increased. Some chemical reactions are necessary for converting indigo to leuco form. These reactions are called ‘’reduction’’. Reduction takes place in certain conditions with the presence of hydrosulfite in alkaline medium. To keep the solution alkaline (basic), caustic (NaOH) is used. After reducing and dyeing, dyed ropes have to be aerated so that the dye and fiber can be fixed together. This process is called ‘’ oxidation’’[12].
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| Figure 14: Reaction of vat dyes |
Following reaction shows that how vat dyes are reduced.
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| Figure 15: Reduction of indigo dyes |
Dyeing cotton yarn for blue jeans is an important use of Indigo. In a typical batch operation, concentrated reduced Indigo is added to a dye bath from which oxygen has been removed with little alkaline hydrous. The goods are entered and fully immersed to avoid oxidation. After about 15 min at 20–25 °C, the goods are removed and well squeezed before air oxidation. Indigo does not exhaust well because of its limited substantivity for cotton, not surprising considering its small molecular size. Deep shades must be built up by repeated dipping in the dyebath after each oxidation.
The use of too concentrated a dye bath is not effective for deep shades as it results in poor rubbing fastness. Some salt may be added to aid exhaustion. After dyeing, the goods are well soaped. The final dyed material may be aftertreated to produce a faded, worn look. Continuous methods are used for dyeing ball warps, warp beams and piece goods with Indigo. This is usually carried out in a series of 4–6 wash boxes with upper and lower rollers and nips at the exits.
The goods are threaded through each box and may be skyed at the mid-point. The first box is used to wet out the material. In subsequent boxes, the goods are immersed in the leuco Indigo solution for 10–30 s at a linear speed of about 25 m min–1, squeezed and skyed for 2 min to oxidize the leuco dye to Indigo.
The boxes are fed with a stock vat of leuco Indigo and the liquor in the boxes is circulated to maintain constant dyeing conditions. This process of several dips and oxidations is then repeated in a second series of boxes, and so on. Several rinsing and washing boxes complete the process.[4]
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| Figure 16: Denim dyeing process |
There are the following parameters on which indigo dyeing depend upon.
- Reduced indigo concentration
- Hydro concentration
- pH (the alkalinity of solution)
- Number of dye pads
- The speed of machine
- Pressure rollers
The technology which is used to modify the appearance, outlook comfort ability & fashion of the garments is called garment washing. Denim washing is known as one of the finishing treatment that has vast usage because of creating special appearance and updating clothes.[13]
There are two types of denim washing.
I. Garment Dry Process
II. Garment Wet processing
1.5.1 Garment Dry Process:
It is called Dry Process because all the processes which are listed below is done in dry condition, in the other says we don’t use any chemical including water in this process. Dry process is an important factor in Garment washing. Garments are achieved more fashionable look by applying dry process. Dry process is mainly done by hand or mechanically. The other name of this process is mechanical washing.[14]
There are following types of dry process which are done on the denim garment:
- Stone wash
- Micro-sanding
- Sand Blasting.
- Hands scraping.
- Over all wrinkles.
- Permanent wrinkle.
- Grinding &Destroy.
- Broken & tagging.
- P P Spray
- Whisker
- Scrapping
This method is most common and is used to give denim an 'old-look'. Pumice stone is one of the most important components used to abrade the surface of the fabric to obtain a surface pattern effect with color contrast and soft – handle. In this process, the fibres on the surface of the fabric are broken and removed and the inner white fibres of the warp yarn are gradually exposed. Natural patterns can be formed as the degree of abrasions varies in various parts of the garment.[2]
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| Figure 17: Stone wash |
1.5.1.2 Hand whisker:
Localized abrasion of sand paper on the garment where garment bend is called whisker. It is the first process of dry process section in garments washing. Whisker is done with the help of sharp edge emery paper rolled on fine wood stick or pasted on plastic material. Whiskers are one of the most important designs of a used look garment. The idea of whiskers is taken from the worn out lines and impression patterns generated by natural wearing on hips and front thigh area. On old jeans, a number of patterns can be finding consequential to fabric, body shape of user or sitting posture. It is also known as Cat's Whisker.[2]
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| Figure 18: Whisker |
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| Figure 19: Scrapping |
Scrapping is step which is generally being done on rigid form of garments to get distress look. Locations can be front thigh & back seat or it can be overall / global application as per Standard. Scraping can be done on inflated rubber balloons for better effect (horizontal or vertical it’s up to operator’s convenience), even it can done plain wooden board of garment size & hand pressure should be uniform in order to get better results.[15]
1.5.1.4 Tagging:
Special effect produced on the garment after wash is called tagging. It is done by nylon pins. Tagging is done by swift tag machine. Tagging or more commonly tag pinning is a very in fashion style in denim garment in these days. In this process the effect is created by swift tag machines with the help of plastic or nylon tag pins in rigid form of garment to get contrast. Most favorite areas are waistband, bottom hem, back pocket, back yoke and front pocket corners.[2]
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| Figure 20: Tagging |
This technique is based on blasting an abrasive material (mostly sand) in granular, powdered or other form through a nozzle. It is purely mechanical process. It is a water free process. Variety of distressed or abraded looks possible.[14]
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| Figure 21: Sand blasting |
Edge distressing or grinding is the process of destruction on jeans form edges of the garment. When we look at old jeans we find it destroyed from the edges of pockets, fly area, belt and bottom. Grinding is done of garments by pen type of stone tools. It can be done in mid of the wash process. To rip off warp thread from the garments with the help of emery paper (sand paper) is called destroy.[2]
1.5.2 Garment wet process:
The process which we do in the wet condition is called garment wet process. In garment wet process we use different types of garment washes and chemicals.
There are some types of garment washing processes which are given below:
- Enzyme wash
- Over dye
- Rinse wash
- Random wash
- Acid wash
- Bleach wash
- Semi bleach wash
Enzyme wash also known as “Bio-wash” which is a technique involving the use of enzyme to produce soft denim. It also has an effect on the color properties but the change is slight. The enzymes used in washing are Cellulase. Cellulase enzymes are natural proteins, which are used in denim garment processing to get stone wash look on to the denim garments without using stones or by reducing the use of pumice stone. Cellulase attacks primarily on the surface of the cellulose fibre, leaving the interior of the fibre as it is, by removing the indigo present in the surface layer of fibre. [1]
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| Figure 22: Enzyme wash |
Acid wash can be carried on Indigo & Sulphar base fabric garments. Acid wash is a chemical wash on denim which stripped the top layer of color and makes a white surface while the color remained in the lower layers of the material, giving it a faded look. This wash is being carried out by pre soaking stones in bleach and then followed by neutralization. Acid wash of denim garment normally carried out by tumbling the garments with pumice stones presoaked in a solution which contains sodium hypochlorite (5 to 10%) or potassium permanganate (3 to 6%). [14]
1.5.2.3 Bleach wash:
This in one an important step in washing denim & can be done by various bleaching agents.
- Calcium hypo chlorite
- Sodium hypo chlorite
- Hydrogen peroxide
- Potassium permanganate
Potassium Permanganate is also being used on 100% sulphur black denim fabric for bleaching/reducing agent to get unique effects. As it’s not production friendly till laundry has very expertise team to handle this program, otherwise it will result in many shades & cast. Proper Neutralizations of bleaching process is very essential in order to get rid of fabric strength, bad smell from garment, yellowing & skin irritation etc. In this process a strong oxidative bleaching agent such as sodium hypochlorite or KMnO4 is added during the washing with or without stone addition.
Discoloration produced is usually more apparent depending on strength of the bleach liquor quantity, 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 antichlor or after washed with peroxide to minimize yellowing. Materials should be carefully sorted before processing for color uniformity[7].
1.5.2.4 Over dye:
There are many variations. Blue and black can be over dyed with bright contrasting colours to obtain special effects. The most current and successful forms of over dyeing consist of dyeing washed out indigo jeans with luminous colors. In this process direct dye is applied into already Indigo dyed garment. It takes 10 pieces of garment and put into the washing machine and adds direct dye with all its auxiliaries and run it for 15 mins and checks the shade then rinse.
- Dyeing over the fabric or jeans to add another tone of color.
- Most often used is a 'yellowy' over dye to create a 'dirty' look.
- Also can be applied with spray gun or paintbrush for local coloring.
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| Figure 23: Over dye |
1.5.2.5 Tinting:
Tinting is a process where very less amount of tint is involved & mainly direct dye is being used to do this process. This is being done to change hue/cast/tone of indigo. As soon as quantity of tint color increases & it cover up indigo, reaches the level of dyeing. Tinting being used to give garments a used / vintage & muddy look. This process takes from 5 minutes to 15 minutes time for better results followed by dye fixing & cleans up of superficial dye.
Tinting is a process where very less amount of tint is involved & mainly direct dye is being used to do this process. This is being done to change hue/cast/tone of indigo. As soon as quantity of tint color increases & it cover up indigo, reaches the level of dyeing. Tinting being used to give garments a used / vintage & muddy look. This process takes from 5 minutes to 15 minutes time for better results followed by dye fixing & cleans up of superficial dye.
- The garment has been lightly colored in order to give the final denim appearance
- The techniques involve the addition of the colorant in the stone washing cycle.
- Because of this it must be insured that dyes and cellulose are compatible.
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| Figure 24: Tinting |
1.5.3 Objectives of washing process:
Following are the uses of washing process.
Following are the uses of washing process.
- To remove dirt, dust and waste materials from the garments.
- To remove size materials from the garments.
- For garments wash shrinkage occurs, so accurate measurement can be found by customers.
- Fading effect is varied here by variation of amount of detergent used, processing time and processing temperature.
- To increase brightness of garments.
- To increase smoothness of garments.
- To change the appearance of garments.
- To make garments become soft and handy.
CHAPTER 2
Experimental Work:
The research on topic “Effect of Random on Denim fabric And Study their Mechanical Properties” was initiated in Bahauddin Zakariya University College of Textile Engineering Multan was conducted at Crescent Bahumaan (LTD) Pindi Bhatian.
2.1 Materials:
In our project we required the following materials.
- Stones.
- Enzymes.
- Rags.
- KMnO4.
- NaOCl.
- Na2S2O5.
- Denim Fabric Leg tubes.
These are small pieces of knitted wool fabric. They have a very high pick up when they are dissolve in the chemicals solution. For random wash we use white color rags.
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| Figure 25: Rags |
This compound is the salt of permanganic acid, HMnO4. It is an unstable acid and exists only in solution.
Potassium permanganate forms dark purple lustrous crystals giving deep pink color in solution. Its solubility in water at 200c is only about 7%, while dissolves more at higher temperature (25% at 63oc). It is a strong oxidizing agent and oxidizes the indigo dye from denim. Its origin from China.
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| Figure 26: Potassium permanganate |
The process of acid washing jeans used chemicals, stripping off the color of the top layer, leaving the white fabric exposed. The color remained in the lower layers of the material, giving it a faded look. Acid washing could be done overall or made to look splotchy treated with potassium permanganate[16].
2.1.3 Stones:
Following are the types of stones which are mainly used in stone washing of denim.
- Pumice Stones.
- Perlite Stones.
Pumice is a type igneous, extrusive rock. The word “pumice” comes from Latin word “pumex” which means “foam”. Pumice does not get its name from its composition but from its texture. Pumice is considered a volcanic glass because the quick cooling of the viscous lava from which it is form which it is formed does not allow crystallization the result is glass. It is composed of silica, alumina, potassium oxide, soda, ferrous oxide, water, ferric oxide, magnesia and titian with different percentages. We can obtain stones from India and Australia[16].
2.1.3.2 Properties of Pumice Stone:
- When the impurities amount will be 10% of a pumice stone its density increases to 1 gm/cm3. Then the stone will not float.
- Alternative of pumice stone: SYNTHETIC STONE.
- Stone wt. /fabric wt. = 0.5 to 3 /1.
- Diameter of stone-1-7 cm.
- Moisture content-less than 5%.
- Surface properties-less than 5% fines.
- Apparent Density-0.5-0.75gm/cm3.
- Abrasion loss-35%.
- Large, hard stones last longer and may be suited for heavy weight fabrics only.
- Smaller, softer stones would be used for light weight fabrics and more delicate items.
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| Figure 27: Pumice stones |
The trend today is towards garment processing. This is because garment processing offers the processor better and more varied opportunities to add value to the garments in terms of fashionable looks as well as feel. In such a fast changing scenario, Enzymes are playing an important role[16].
2.1.4.1 Functions of Enzymes:
- Catalyze enzymes can be used to work specifically on residual peroxide as an anti-oxidant breaking it down into natural elements of water and oxygen without adversely affecting the fibres or dyes.
- Develop ‘’Bio-polishing’’ effect on denim in echo-friendly way
- Enzyme improves the ‘’Anti-pilling’’ properties.
- It attacks more the surface of the fabrics and gives a very smooth surface.
- It increases the color fastness and rubbing fastness properties.
- Achieve high-low abrasion to produce fading effect in sewing area. 2
- It just hydrolysis the cellulose, first it attacks the projecting fiber then the yarn portion inside fabric and faded affect is produced.
- It reduces GSM of the garment.
- Neutral enzyme is used for Dark shade enzyme wash because it comes fading effect slowly.
- It produces buyer loving soft feel in use.
- Acid enzyme is used for medium /light shade Enzyme wash of denim skirt because it comes enzyme effect quickly than neutral enzyme.
Sodium Meta bi-suphate is an inorganic compound composed of sodium, sulfur and oxygen. It typically comes in a white or yellowish-white crystalline powder. It easily dissolves in water, which leaves that familiar sulfur (rotten egg) smell.[16]
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| Figure 28: Sodium Meta bi- sulphate |
- Sodium Meta bi-sulphate is used as a bleaching agent in pulp and textile manufacture, as well as a reducing agent.
- Sodium Meta bi-sulphate is used in the washing plant to neutralized the garment from potassium permanganate.
- Sodium hypochlorite is generally sold in aqueous solutions containing 5 to 15% sodium hypochlorite, with 0.25 to 0.35% free alkali (usually NaOH) and 0.5 to 1.5% NaCl.
- Solutions of up to 40% sodium hypochlorite are available, but solid sodium hypochlorite is not commercially used.
- Sodium hypochlorite solutions are a clear, greenish yellow liquid with an odor of chlorine.
- Odor may not provide an adequate warning of hazardous concentrations. Sodium hypochlorite solutions can liberate dangerous amounts of chlorine or chloramine if mixed with acids or ammonia.
- Anhydrous sodium hypochlorite is very explosive.
- Hypochlorite solutions should be stored at a temperature not exceeding 20ºC (68 ºF) away from acids in well-fitted air-tight bottles away from sunlight[16].
- This is the strongest oxidative bleach.
- Hypochlorous acid is a bleaching agent having pH range 9-10.
- Sodium hypochlorite is used as a disinfectant; a water treatment agent in swimming pool water, drinking water, waste water and sewage, and pulp and paper mill process water; and as a bleaching agent for textiles.
The denim fabric selected for studies was stretchable and non-stretchable denim fabric with following specifications.
2.1.7.1 Sample No.1 Specification:
- Fabric Code ------------IHS- 1100
- Finish -------------------Flat Finished fabric.
- Warp count ------------9/1.
- Weft count -------------10/1.
- Warp density ---------- 76/1.
- Weft density ------------56/1.
- Weave ------------------3/1 Right Twill.
- G.S.M. ----------------464.6grams.
- Color --------------------- Blue.
- Raw Material -----------100% cotton.
- Slub ----------------------A264.
- T.M ---------------------4.5.
- Warp -------------------Ring Spinning.
- Weft --------------------Open End Spinning.
- Fabric Code -----------RF- 2200.
- Finish ------------------Flat Finished fabric.
- Warp count ------------ 12/1.
- Weft count ------------10/1.
- Warp density ---------80/1.
- Weft density ---------60/1.
- Weave----------------- 3/1 Right Twill.
- G.S.M. ---------------369.7grams.
- Color ----------------- Blue.
- Raw Material ------- Cotton + Lycra (0.5%).
- Slub ------------------ A220.
- T.M -------------------3.2.
- Warp ----------------- Ring Spinning.
- Weft ------------------Open End Spinning.
Leg Tube prepared in Size range 12×12 inches and were over locked from top and bottom.
2.1.8.1Sample Washing Machine Specifications:
- Machine Brand ----------Brongo.
- Model No. ---------------LX-60.
Random wash can be done through the following methods.
2.2.1 Random Wash of denim:
Random wash also called Acid wash. Through random wash we get random effects on denim garment through rags or stones which were dipped in the solution of potassium permanganate or sodium hypochlorite extracted and load in the dry washer for 10-20mints at room temperature and then neutralize the garment with sodium Meta bi-sulphate. As a result we get patchy effects on garments.
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| Figure 29: Flow Chart of Random Wash |
2.2.2 Procedure of Random Wash:
- First of all leg tube was being desized through chemicals in the washer in order to remove size material and increase the absorbency of the leg tube.
- After desizing stone wash has been applied on the leg tube to taken out slub from the leg tube.
- After stone wash leg tube has been biopolished in order to remove the protruding fibres.
- Leg tube has been rinsed in washer for 1-2 mints.
- After that leg tube has been extracted in the extractor for 1 mint.
- Dry the washer completely.
- Prepare the solution of KMnO4 or NaOCl in the tub.
- Rags have been dipped in the solution for 5 mints.
- If stones have been used then drop solution on the stones so that stone become completely wet not dipped in the solution.
- After 5 mints rags have been extracted by hands (manually).
- After that extracted rags and leg tube have been loaded in the washer for 10-15mints.
- When the required time has been completed fill the washer with water and add the neutralizer (sodium meta bi-sulphate).
- Run the machine for 5mints.
- Drain the water and fill the washer again for rinsing.
- After rinsing drain the water and extract the leg tube through extractor for 1mint.
- Dry the leg tube for 5 mints in the drier.
2.3.1 Principle:
A 100-mm (4.0-in.) wide specimen is mounted centrally in clamps of a tensile testing machine and a force applied until the specimen breaks. Values for the breaking force and the elongation of the test specimen are obtained from machine scales, dials, autographic recording charts, or a computer interfaced with the testing machine. This test method describes procedures for carrying out fabric grab tensile tests using two types of specimens and three alternative types of testing machines[17].
2.3.2 Preparation of Specimen:
- Cut specimens with their long dimensions parallel either to the warp (machine) direction or to the filling (cross) direction, or cut specimens for testing both directions if required.
- Preferably, specimens for a given fabric direction should be spaced along a diagonal of the fabric to allow for representation of different warp and filling yarns, or machine and cross direction areas, in each specimen.
- When possible, filling specimens should contain yarn from widely separated filling areas.
- Unless otherwise specified, take specimens no nearer to the selvage, or edge of the fabric, than one tenth of the width of the fabric.
- Cut each specimen 100 6 1 mm (46 0.05 in.) wide by at least 150 mm (6 in.) long with the long dimension parallel to the direction of testing and force application.
- Mount the specimen in the clamp jaws with the previously drawn parallel line adjacent to the side of the upper and lower front, or top, jaws which is nearest this edge, and with approximately the same length of fabric extending beyond the jaw at each end.
- The parallel line serves as a guide to ensure that the same lengthwise yarns of woven fabrics are gripped in both clamps and that the force application is not at an appreciable angle to the test direction of nonwoven fabrics.
- The tension on the specimen should be uniform across the clamp width.
- For high-strength fabrics where the specimen cannot be satisfactorily held in clamps, place each specimen around pins and between jaws as using jaw padding if necessary.
- Tighten the clamps to distribute the holding pressure along the clamping surface of the top (front) jaw.
- Clamps which are too tight will produce breaks at the front of the jaws; clamps which are too loose will cause slippage or breaks at the back of the jaws.
- Elongation depends on the initial specimen length which is affected by any pretension applied in mounting the specimen in the testing machine.
- If measurement of specimen elongation is required, mount the specimen in the upper clamp of the machine, and apply a uniform pretension, not to exceed 0.5 % of the full-scale load, to the bottom end of the specimen before gripping the specimen in the lower clamp.
- To achieve uniform and equal tension, attach an auxiliary clamp to the bottom of the specimen and at a point below the lower clamp of the testing machine.
- Tighten the lower clamp and remove the auxiliary clamp.
- Mark across the specimen at the front inner edge of each jaw to check for specimen slippage. When slippage occurs, the mark will move away from the jaw edge.
- Operate the machine and break the specimen.
- Read the breaking force, and elongation if required, from the mechanism provided for such purpose. Record warp and filling (machine and cross) direction results separately.
- For some testing machines, data may be obtained using an interfaced computer.
- If a specimen slips in the jaws, or breaks at the edge of or in the jaws, or if for any reason the result falls markedly below the average for the set of specimens, discard the result and take another specimen.
- Continue this until the required number of acceptable breaks has been obtained.[17]
2.4.1 Principle:
This test method covers the determination of the force required to propagate a single-rip tear starting from a cut in a fabric and using a falling-pendulum type (Elmendorf) apparatus. This test method applies to most fabrics including woven, layered blankets, napped pile, blanket, and air bag fabrics and provided the fabric does not tear in the direction crosswise to the direction of the force application during the test.
The fabrics may be untreated, heavily sized, coated, resin-treated, or otherwise treated. This method is suitable only for the warp direction tests of warp-knit fabrics. It is not suited for the course direction of warp knit fabrics or either direction of most other knitted fabrics[18].
2.4.2 Preparation of Specimen:
- Laboratory Sample for acceptance testing, take a swatch extending the width of the fabric and approximately 1 m (1 yd) along the machine direction from each roll or piece in the lot sample.
- For rolls of fabric, take a sample that will exclude fabric from the outer wrap of the roll or the inner wrap around the core of the roll of fabric.
- Test Specimens from each laboratory sampling unit, take five specimens from the machine direction and five specimens from the cross-machine direction.
- Direction of Test considers the long direction of the specimen as the direction of test.
- Cutting Test Specimens take the specimens to be used for the measurement of machine direction with the longer dimension parallel to the machine direction.
- Take the specimens to be used for the measurement of the cross-machine with the longer dimension parallel to the cross-machine direction.
- Use the cutting die. When specimens are to be tested wet, cut from areas adjacent to the dry test specimens. Label to maintain specimen identity.
- In cutting the woven fabric specimens, take care to align the yarns running in the short direction parallel with the die such that when the slit is cut, the subsequent tear will take place between these yarns and not across them.
- This precaution is most important when testing bowed fabrics.
- Cut specimens representing a broad distribution across the width and length, and preferably along the diagonal of the laboratory sample, and no nearer the edge than one-tenth its width.
- Ensure specimens are free of folds, creases, or wrinkles.
- Avoid getting oil, water, grease, etc. on the specimens when handling[18].
- Test the conditioned specimens in the standard atmosphere for testing textiles, which is 21 6 1°C (70 6 2°F) and 65 6 2 % relative humidity, unless otherwise directed in a material specification or contract order.
- Position the pendulum to the starting position and the force recording mechanism to its zero-force position.
- Place the long sides of the specimen centrally in the clamps with the bottom edge carefully set against the stops and the upper edge parallel to the top of the clamps.
- Close the clamps, securing the specimen with approximately the same tension on both clamps.
- The specimen should lie free with its upper area directed toward the pendulum to ensure a shearing action.
- Using the built-in knife blade cut a 20 mm (0.787 in.) slit in the specimen extending from the bottom edge and leaving a balance of fabric 43.0 6 0.15 mm (1.69 6 0.005 in.) remaining to be torn.
- For Die-Cut or Manually Slit Specimens If a die without a slit is used, manually cut a 20 mm (0.787 in.) long slit in the center of one edge of the long direction of the specimen. Ensure that the balance of the fabric remaining to be torn is 43 6 0.15 mm (1.69 6 0.005 in.).
- Place the parallel, unslit sides of the specimen in the clamps with the bottom edge carefully set against the stops, the upper edge parallel to the top of the clamp and the slit centrally located between the clamps.
- Close the clamps, securing the specimen with approximately the same tension on both clamps.
- The specimen should lie free with its upper area directed toward the pendulum to ensure a shearing action.
- For Wet Specimen Testing remove a specimen from the water and immediately mount it on the testing machine in the normal set-up.
- Perform the test within 2 min after removal of the specimen from the water. Otherwise, discard the specimen and replace with another one.
- Depress the pendulum stop downward to its limit and hold it until the tear is completed and the pendulum has completed its forward swing.
- Catch the pendulum just after the threshold of its backward swing and return to its locked starting position.
- When equipped, be careful not to disturb the position of the pointer.
- Record the scale reading required to completely tear the test specimen.
- The decision to discard the results of a tear shall be based on observation of the specimen during a test and upon the inherent variability of the material. In the absence of other criteria, such as in a material specification, if an unusual cause is detected, the value may be discarded and another specimen tested.
- Reject readings obtained where the specimen slips in the jaw or where the tear deviates more than 6 mm (0.25 in.) away from the projection of the original slit. Note when puckering occurs during the test.
- For microprocessor systems, follow the manufacturer’s directions for removing values from memory when the decision to discard a tear value has been made.
- Otherwise, for some test instruments manual calculation of the average is required[18].
2.5.1 Principle:
This test method covers the measurement of fabric mass per unit area (weight) and is applicable to most fabrics. Fabric mass is calculated from the mass of a specimen the length and width of which have been measured as directed in one of the procedures in Test Method D 3773 and D 3774[19].
2.5.2 Sample Preparation:
- Scale, with a capacity and sensitivity sufficient to weigh the full piece, roll, bolt, or cut units to within 60.1 % of their gross mass.
- The accuracy of the scale should be certified by a recognized authority.
- Balance, having a capacity and sensitivity to weigh within 60.1 % of the mass of the specimens being tested.
- Cutting Die, either square or round with an area of at least 13 cm2.
- Condition test specimens as directed in Practice D 1776.
- All weighing tests should be made in the standard atmosphere for testing textiles (20 6 1°C (70 6 2°F), 65 6 2 % RH), after the specimens have been conditioned in the same atmosphere.
- When the full rolls or bolts of fabric cannot be properly conditioned in a reasonable time with available facilities, perform the tests without conditioning and report the actual conditions prevailing at the time of the test.
- Such results may not correspond with the results obtained after testing adequately conditioned specimens in the standard atmosphere for testing textiles[19].
- Measure the length of the full piece, roll, bolt, or cut by the hand procedure in Test Method D 3773.
- Measure the width by the tension-free alternative by Method D 3774.
- Weigh the fabric, with shell and holder, if any, to the nearest 0.1 % of its mass.
- Weigh the holder, if any, to the nearest 0.1 % of its mass[19].
3.1 Sample preparation:
Sample #01
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4.1 Result and Discussion:
In our project we used two types of fabrics and apply random wash techniques on these fabrics. We do this for the purpose of study about GSM, Tear Strength and Tensile Strength. Calculations and readings of these tests are given below.
Sample | GSM | TEAR STRENGTH | TENSILE STRENGTH | ||
WARP | WEFT | WARP | WEFT | ||
01 | 496.1g | 6500 g | 7500 g | 116.1 kg | 77.1 kg |
02 | 370.3 g | 2600 g | 6000 g | 83.9 kg | 34.9 kg |
03 | 515.0 g | 11200 g | 10200 g | 127 kg | 71.8 kg |
04 | 368.8 g | 2500 g | 6200 g | 85.3 kg | 34.0 kg |
05 | 515.3 g | 11400 g | 11500 g | 104.3 kg | 45.4 kg |
06 | 365.7 g | 2500 g | 5600 g | 86.2 kg | 39.9 kg |
07 | 518.2 g | 1200 g | 1200 g | 135.6 kg | 77.1 kg |
08 | 370.1 g | 2600 g | 5500 g | 90.7 kg | 33.1 kg |
09 | 503.4 g | 8800 g | 11500 g | 135.6 kg | 81.6 kg |
10 | 376.3 g | 2400 g | 5100 g | 86.2 kg | 35.8 kg |
11 | 511.5 g | 11700 g | 10800 g | 135.6 kg | 89.8 kg |
12 | 380.6 g | 2700 g | 4900 g | 82.8 kg | 39.1 kg |
13 | 364.4 g | 2900 g | 7700 g | 90.7 kg | 35.8 kg |
14 | 364.8g | 2700 g | 6000g | 86.2 kg | 34 kg |
15 | 365.9 g | 2500 g | 6400 g | 82.6 kg | 37.2 kg |
16 | 378.5 g | 2800 g | 6500 g | 86.2 kg | 34 kg |
Sample 1:
In this sample we observed that fabric GSM is 496.1 grams treated with recipe 2% KMnO4 with rags shows the tear strength warp wise is 6500g and weft wise is 7500g and show tensile strength warp wise is 116.1kg and weft wise is 77.1kg.
Sample 2:
In this sample we observed that fabric GSM is 370.3 grams treated with recipe 2% KMnO4 with used stones shows the tear strength warp wise is 2600g and weft wise is 6000g and show tensile strength warp wise is 83.9kg and weft wise is 34.9kg.
Sample 3:
In this sample we observed that fabric GSM is 515.0g treated with recipe 5% KMnO4 with rags shows the tear strength warp wise is 11200g and weft wise is 10200g and show tensile strength warp wise is 127kg and weft wise is 71.8kg.
Sample 4:
In this sample we observed that fabric GSM is 368.8g treated with recipe 5% KMnO4 with used stones shows the tear strength warp wise is 2500g and weft wise is 6200g and show tensile strength warp wise is 85.3kg and weft wise is 34.0kg.
Sample 5:
In this sample we observed that fabric GSM is 515g treated with recipe 10% KMnO4 with rags shows the tear strength warp wise is 11400g and weft wise is 11500g and show tensile strength warp wise is 104.3kg and weft wise is 45.4kg.
Sample 6:
In this sample we observed rigid that fabric GSM is 365.7g treated with recipe 10% KMnO4 with used stones shows the tear strength warp wise is 2500g and weft wise is 5600g and show tensile strength warp wise is 86.2kg and weft wise is 39.9kg.
Sample 7:
In this sample we observed that fabric GSM is 518.2g treated with recipe 2% NaOCl with rags shows the tear strength warp wise is 1200g and weft wise is 1200g and show tensile strength warp wise is 135.6kg and weft wise is 77.1kg.
Sample 8:
In this sample we observed that fabric GSM is 370.1g treated with recipe 2% NaOCl with used stones shows the tear strength warp wise is 2600g and weft wise is 5500g and show tensile strength warp wise is 90.7kg and weft wise is 33.1kg.
Sample 9:
In this sample we observed that fabric GSM is 503.4g treated with recipe 5% NaOCl with rags shows the tear strength warp wise is 8600g and weft wise is 11500g and show tensile strength warp wise is 135.6kg and weft wise is 81.6kg.
Sample 10:
In this sample we observed that fabric GSM is 376.3g treated with recipe 5% NaOCl with used stones shows the tear strength warp wise is 2400g and weft wise is 5100g and show tensile strength warp wise is 86.2kg and weft wise is 35.8kg.
Sample 11:
In this sample we observed that fabric GSM is 511.5g treated with recipe 10% NaOCl with rags shows the tear strength warp wise is 11700g and weft wise is 10800g and show tensile strength warp wise is 135.6kg and weft wise is 89.8kg.
Sample 12:
In this sample we observed that fabric GSM is 380.6g treated with recipe 10% NaOCl with used stones shows the tear strength warp wise is 2700g and weft wise is 4900g and show tensile strength warp wise is 82.8kg and weft wise is 39.1kg.
Sample 13:
In this sample we observed that fabric GSM is 364.4g treated with recipe 5% NaOCl and 5% KMnO4 with rags shows the tear strength warp wise is 2900g and weft wise is 7700g and show tensile strength warp wise is 90.7kg and weft wise is 35.8kg.
Sample 14:
In this sample we observed that fabric GSM is 364.8g treated with recipe 5% NaOCl and 5% KMnO4 with used stones shows the tear strength warp wise is 2700g and weft wise is 6000g and show tensile strength warp wise is 86.2kg and weft wise is 37.2kg.
Sample 15:
In this sample we observed that fabric GSM is 365.9g treated with recipe 10% NaOCl and 10% KMnO4 with rags shows the tear strength warp wise is 2500g and weft wise is 6400g and show tensile strength warp wise is 82.6kg and weft wise is 37.2kg.
Sample 16:
In this sample we observed that fabric GSM is 378.5g treated with recipe 10% NaOCl and 10% KMnO4 with used stones shows the tear strength warp wise is 2800g and weft wise is 6500g and show tensile strength warp wise is 86.2kg and weft wise is 34kg.
4.3 Conclusion:
The simple 07 which is treated with 2% NaOCl by using rags has maximum GSM value 518.2 g and simple 14 which is treated with 5% NaOCl +5% KMnO4 by using rags has minimum GSM value 364.4 g.
The simple 11 which is treated with 10% NaOCl by using rags has maximum Tear Strength value along warp wise 11700 g and simple 05 which is treated with 10% KMnO4 by using rags has maximum Tear Strength value along weft wise 11500 g.
The simples 7, 9,11 which are treated with 2% NaOCl by using rags, 5%NaOCl by using rags, 10% NaOCl by rags respectively have maximum Tensile Strength value along warp wise 135.6 kg and simple 11 which is treated with 10% NaOCl by using rags has maximum Tensile Strength value along weft wise 89.8kg.
4.4 Future work:
In future, we will obtain more patchy structures and number of grains by using random wash with different chemicals like KMnO4 and NaOCl. It is a positive step for future work.
References:
[1] “Impact of Washing Stretchy Denim using Neutral and Acid Enzymes and Subsequent Softening Treatment on Physical , Mechanical and Sewing Properties Abstract :,” pp. 1531–1542.
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[7] “Final Year Project National Textile University,” 2010.
[8] M. J. Earle and K. R. Seddon, “Dyeing Process.” pp. 1–40, 2011.
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[10] W. H. Perkin, “Dyes and dyeing ©2003,” 2003.
[11] J. Shore, “Cellulosics Dyeing,” 1995.
[12] “Indigo Dyeing of yarn (Waleed Fida).” .
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[15] syed asim Najam, “Denim Washing.” .
[16] “washing chemicals.” .
[17] S. T. Method, “Standard Test Method for Breaking Strength and Elongation of Textile Fabrics ( Grab,” vol. 7, no. July 1995, pp. 1–8, 2001.
[18] E. Apparatus, “Standard Test Method for Tearing Strength of Fabrics by Falling-Pendulum Type,” vol. 7, 1996.
[19] S. T. Method, “Standard Test Method for Mass Per Unit Area ( Weight ) of Fabric 1.”