Textile Notes related to fiber, yarn, fabric knowledge, spinning, weaving, processing, projects, knitting, Indian Traditional Textiles and denim manufacturing
There are four main processes in the Denim washing
- Pretreatment
- Stone or Enzyme Wash- To adjust the surface effect
- Bleaching- To adjust the color
- Finishing- To adjust the handfeel of the garment
Pretreatment involves removal of impurities from the garments and desizing the garment. It also involves prevention of creases in the garment. Wetting Dispersing agent is used in desizing process. It should be able to rapidly wet the jeans so that it can prevent white lines of creases and prevents back staining. Back staining is the redeposition of indigo dyed short fibers, or loose indigo, removed during desizing, stone-washing or enzyme washing. Backstaining reduces the contrast of warp and undyed weft. It also stains pockets and labels and it is more prone ot ozone and yellowing. An anticrease agent is added to prevent crease formation during the washing process.
Enzyme in garment Industry
Enzyme is a kind of protein. They help the chemical reaction but themselves do not take part in chemical reaction. The starting molecule in a reation is called substrate and the yield molecule is called substate. Enzymes and substrate work like lock-key model so only one enzyme is useful for one type of substrate. Enzymes are better than chemical catalyst because they act in mild conditions such as room temperature. They are also biodegradable. Many enzymes are used in garment washing. An enzyme called Amylase is used in removing starch in desizing. Celullase is used in breaking and removing cellulose fibers. Laccase is used in biobleaching and catalase is used as an anti peroxide.
Stone and Enzyme Wash
Cellulase weaken the surface fibers which are then mechanically torn off during processing, taking with them indigo. However, they need mechanical action to work. Hence they are used with stones. Cellulase is also used in biopoloshing, which removes surface fibers and make the surface smooth.
Bleach
Laccase enzyme decolorises indigo without using bleach. It provides very good contrast and since it attacks only indigo dye and not the fiber so it gives excellent tensile strength.
Yellowing
The discolouration of textiles, i.e. a change of shade or loss of whiteness, giving a yellow tint, is commonly known as YELLOWING.Yellowing is due to many reasons. Cotton, yellows with age. However aging cannot make severe yellowing happen. Certain lubricants used in weaving and knitting can cause yellowing. The Anti oxidants present in these oils can cause a type of yellowing called as phenolic yellowing. The anti oxidants are also present in packaging materials and silicon softeners. Also temperature of drying and curing during processing can scorch the fibers and cause yellowing.
Indigo dyed fabrics are more prone to yellowing. Indigo when exposed to NOx or Ozone can produce yellow colored compounds. Indigo itself through simple oxidation can transform into yellow colored compounds.
There are specialised anti-yellowing softeners available. This work by either forming a protective filem, or by reacting the pollutants to form colorless compounds.
The source of these notes this presentation. This also contains images and chemical reactions. You can also view images of various denim washes here. One more resource is here.
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There is a patent document which claims that the denim fabric can be produced from waste denim yarn. In this fabric 40%-100% of waste fiber is used. To reclaim the waste fiber, the fabric is subjected to garnetting and low tension carding, before spinning it in the form of yarn and using it to weave fabric.
The only thing remains to be seen is the techno-commercial viability of such product. Garnetted fibers produce problems in carding, drawframe and posisbly in high speed weaving. Though it is claimed that such a denim will have adequate strength, it will remain a challange. It is suggested that some virgin fiber should be added in the garnetted fiber or it is subjected to some lubrication before spinning. All this will lead to increase in process cost.
Neverthless, this is a good news for your torn denim jeans which can now be recycled into a new one without damaging the environment. Just give your jeans to the local rag picker and it will eventually find itself into a new jeans. However, if you don't want to part away with your jeans, here are the instructions what you can do with them. Of course, there are 25 other ways to make use of your old jeans.
Worldwise, concerns are growing reagarding using the denim waste. A project making the use of denim shoddy is one of such cases. It is being used in myriad ways including its use in oil filters. Successful attempts have been made to make paper out of denim wastes.
Note: Garnetting is a process by which material such as threads, rags, woven cloth scraps, and the like are broken up and returned to a substantial fluffy, fibrous condition simulating the original condition of the fiber. This is done by first chopping the material to small pieces (e.g. two to six inches) and then running the pieces through a series of high speed cylinders which can be covered with wire (e.g. saw wire), steel spikes, or the like. The treatment breaks up the material into individual fibers typically having a length of one and one-eighth inches or less.
Finished Properties of Common Denim Fabrics: Understanding Weight, Yarn Count, Construction and Fastness
Denim is one of the most widely used fabrics in garments, especially for jeans, jackets, skirts, children’s wear and casual apparel. Although denim is often identified by its appearance, shade and wash effect, the real performance of denim depends on measurable fabric properties such as weight, yarn count, ends per inch, picks per inch, rubbing fastness and laundering fastness.
The original note listed finished properties for three common denim fabrics with ideal weights of 14.5 oz/sq yd, 13.75 oz/sq yd and 12.5 oz/sq yd. These values are useful because denim is often commercially discussed by weight category, but weight alone does not tell the full story. A merchandiser, fabric buyer or production person must also understand the relation between yarn count, fabric construction and finished performance.
In denim manufacturing, the fabric that comes out of weaving is not the same as the fabric finally used in garments. Denim passes through finishing operations such as singeing, desizing, washing, sanforizing, softening, skew correction and sometimes special chemical or mechanical treatments. These processes change the fabric’s handle, dimensions, shrinkage, shade appearance and apparent fabric weight.
Therefore, when we say that a denim fabric is 14.5 oz, 13.75 oz or 12.5 oz, we should be clear whether we are talking about greige weight, finished weight or washed weight. Finished properties are especially important because the garment buyer and consumer experience the fabric after finishing, not at the loom stage.
Visual 1: Denim fabric properties map showing how weight, count, construction and fastness affect final performance.
Comparative Finished Properties of Common Denim Fabrics
Property
Heavy Denim
Medium-Heavy Denim
Medium Denim
Ideal Weight
14.5 oz/sq yd
13.75 oz/sq yd
12.5 oz/sq yd
Warp Count, Washed
6.9 ± 0.6
6.9 ± 0.5
6.9 ± 0.5
Weft Count, Washed
6.0 ± 0.4
6.9 ± 0.5
9.0 ± 0.5
EPI, Unwashed
70 ± 2
70 ± 2
70 ± 2
PPI, Unwashed
43 ± 2
43 ± 2
43 ± 2
Actual Weight
14.2 oz/sq yd
13.4 oz/sq yd
12.2 oz/sq yd
Rubbing Fastness, Dry
2–3
2–3
2–3
Fastness to Laundering
2
2
2
This small table contains an important technical lesson. The three fabrics have almost the same warp count, EPI and PPI, but the weft count changes. This means that the weight difference is mainly controlled through the weft yarn, while the face character of the fabric is kept broadly similar.
Understanding Fabric Weight in Denim
Fabric weight in denim is commonly expressed in ounces per square yard. Heavier denim generally feels thicker, stronger and more rigid, while lighter denim feels softer, more flexible and easier to wear in warm conditions. A 14.5 oz denim is usually perceived as a heavy and rugged fabric, while a 12.5 oz denim is closer to a medium-weight commercial denim.
In the data, the actual finished weights are slightly lower than the ideal weights. For example, the 14.5 oz fabric shows an actual weight of 14.2 oz/sq yd, while the 12.5 oz fabric shows 12.2 oz/sq yd. Such differences can occur because of yarn variation, weaving tension, finishing loss, moisture content and process conditions.
Role of Warp and Weft Count
The warp yarn count remains nearly the same in all three fabrics, around 6.9 Ne. This suggests that the main difference between the three denim qualities is not coming from the warp yarn, but from the weft yarn. The weft count changes from 6.0 Ne in the heavier fabric to 9.0 Ne in the lighter fabric.
In the English cotton count system, a lower count number means a coarser yarn. Therefore, 6s weft is coarser than 9s weft. This explains the weight difference clearly:
\( \text{Coarser weft yarn} \Rightarrow \text{more yarn mass per unit area} \Rightarrow \text{heavier denim} \)
\( \text{Finer weft yarn} \Rightarrow \text{less yarn mass per unit area} \Rightarrow \text{lighter denim} \)
This is a useful point for merchandisers. If EPI and PPI remain almost constant, but fabric weight changes, the change is often due to yarn count, especially weft count.
Visual 2: Relationship between weft count and denim weight, showing why coarser weft gives heavier fabric.
EPI and PPI: Fabric Construction
The construction shown in all three fabrics is approximately 70 × 43. This means that the fabric has about 70 ends per inch in the warp direction and about 43 picks per inch in the weft direction. Since EPI and PPI are the same across all three fabrics, the construction density remains largely unchanged.
EPI stands for ends per inch, or the number of warp yarns in one inch of fabric width. PPI stands for picks per inch, or the number of weft yarns in one inch of fabric length. In the given case:
\( \text{EPI} = 70 \pm 2 \)
\( \text{PPI} = 43 \pm 2 \)
This is a good example of how fabric properties should be read together. Looking only at fabric weight may not explain the reason for the difference. Looking at weight, yarn count and construction together gives a much clearer technical understanding.
Why Warp Count is Similar but Weft Count Changes
In conventional denim, the warp yarn is usually indigo dyed, while the weft yarn is generally undyed or lightly coloured. The warp gives denim its characteristic blue appearance, while the weft contributes strongly to weight, handle and body.
Keeping the warp count similar helps maintain a consistent denim appearance and surface character. Changing the weft count allows the manufacturer to create different weights without drastically changing the face appearance of the fabric. This is why three fabrics can look similar at first glance but behave differently in hand feel, stiffness and garment comfort.
Rubbing Fastness and Laundering Fastness
The dry rubbing fastness given for all three fabrics is 2–3. This indicates that colour transfer during rubbing is a concern. In denim, this is especially important because indigo dye is mainly present on the surface of the yarn rather than deeply penetrating the fibre.
A dry rubbing fastness rating of 2–3 means that some colour transfer may occur when the fabric rubs against another surface. This may appear as blue staining on light-coloured shirts, shoes, bags, upholstery or inner pocketing. For the merchandiser, this means care instructions and buyer expectations should be handled carefully.
The laundering fastness is shown as 2 for all three fabrics. This means that the fabric is likely to lose shade during washing. In denim, this is not always considered a defect because fading is often part of the desired denim character. However, from a quality-control perspective, this rating must be interpreted according to the buyer’s requirement.
Relationship Between Weight, Comfort and Durability
Heavier denim usually gives better body and ruggedness, but it may feel stiff and warm. Lighter denim gives better comfort and flexibility, but may not have the same rugged appeal. Medium-weight denim often becomes the commercial balance between durability and wearability.
Fabric Weight
Advantages
Possible Limitations
Heavy denim
Strong body, rugged look, durable feel
Stiffer, warmer, slower to break in
Medium-heavy denim
Good balance of strength and comfort
May still feel firm before washing
Medium denim
Softer, easier to wear, better drape
Less rugged appearance than heavy denim
Simple Weight Calculation Concept
A simplified fabric weight relationship can be understood as:
This means that the final denim weight is influenced by both yarn size and construction. In the present example, because EPI and PPI are constant, the difference in weight is largely explained by the difference in weft count.
Practical Notes for Merchandisers
A merchandiser should not approve denim only by looking at the weight. Two denim fabrics with the same weight can behave differently if the yarn count, twist, fibre quality, weave compactness, finishing route or shrinkage control is different.
Checkpoint
Why It Matters
Finished weight
Determines body, feel and product category
Warp and weft count
Explains yarn thickness and fabric mass
EPI and PPI
Indicates fabric density and construction stability
Rubbing fastness
Shows risk of colour transfer
Laundering fastness
Shows expected wash-down behaviour
Shrinkage
Critical for garment fit
Skew and bow
Important for leg twisting in jeans
Handle and stiffness
Affects consumer comfort
Shade consistency
Critical for bulk approval
Common Mistakes in Reading Denim Specifications
One common mistake is to assume that heavier denim is always better. This is not true. Heavy denim may be unsuitable for hot climates, fashion silhouettes or comfort products. Another mistake is to compare denim fabrics only by ounce weight without checking construction.
A third mistake is ignoring rubbing fastness. Denim may pass visual inspection but still create complaints if it stains other garments or accessories. Similarly, laundering fastness must be understood according to the intended wash effect. In denim, fading can be either a defect or a design feature, depending on the product brief.
Buyer’s Interpretation of the Given Data
The data suggests that the three denim fabrics are constructed with a similar warp system and similar fabric density. The main adjustment is in the weft yarn count, which changes the fabric weight. The heaviest fabric uses the coarsest weft yarn, while the lightest fabric uses the finest weft yarn.
The fastness ratings are similar across all three fabrics, which means that changing the weight has not significantly improved or reduced rubbing and laundering fastness. This is important because fastness depends more on dyeing, washing and finishing conditions than on weight alone.
Knowledge Nugget
In denim, the blue character comes mainly from the warp, but the body of the fabric is strongly influenced by the weft. Therefore, two denim qualities can have a similar face appearance but different weight and handle because of the weft yarn.
Conclusion
The original table is small, but it contains a useful technical lesson. Denim weight is not an isolated property. It is connected with yarn count, fabric construction and finishing. In the given examples, all three fabrics have nearly the same EPI, PPI and warp count, while the weft count changes. This change in weft count explains the difference between heavier and lighter denim fabrics.
For a merchandiser, this type of specification is very valuable. It helps in understanding why a fabric feels heavier, why one denim quality may feel more rigid, and why fastness ratings must be checked even when the construction looks acceptable. A good denim evaluation should always combine measurable data with hand feel, shade behaviour, washing performance and final garment requirement.
Related Reading on Denim, Fabric Construction and Finishing
This article is intended for educational and practical understanding of textile and denim concepts. Actual fabric properties may vary depending on fibre quality, yarn type, spinning method, weaving conditions, dyeing process, finishing route, testing method and buyer specification. Readers should verify production decisions with mill technologists, testing laboratories, buyer standards and applicable textile testing methods before applying these values commercially.
In such denims, the polyester used in warp is kept low about 20-25%, because the blend is harder to dye than cotton . Polyester can be used in much higher percentage in filling. It has the advantage of being strong, durable and even in appearance.
Ball Warping: Equipment required to form the rope of yarn. It involves creeling multiple ends of yarn ( Between 350-500 ends) and collecting them into an untwisted rope for dyeing. the rope is wound onto a long cylinder called a log on a machine called as a ball warper.
Some Notes
1. Packages of yarn are preconditioned before ball warping 2. Packages are loaded into the creel ( larger lots- magine transefer creeL0 and smaller lots- swing gate or truck creel 3. Packages are placed on adapters. An adapter support the package of yarn and ensure that the package remains aligned to the tensioning devices. Wooden plug type adapter are most effective as they require least amount of exertion to remove the empty package.
Next Step is threading the tensioner located at each yarn package
1. Post and Disk tensioner. It has two posts mounted onto a flat base. two round disk are placed onto each post. The yarn is threaded between the disk and wrapped around the post. One of the parts is movable so that the angle of wrap can be varied. More tension can be added to the yarn by adding round weights onto the top disk.
Advantages are 1. Inexpnsive 2. does Marginally adequate job of maintaining yarn tension 3. Simple to thread up 4. Low maintenance requirements.
Disadvantages are 1. Yarn has a tendency to jump out from between the disks at the rear of the creel. 2. It is labour intensive- when different tension levels are required. 3. There is more frequency of cleaning up 4. It doesnt control tension well at higher speed.
2. The driven disk tensioner
It also uses twin disk arrangement, however the disks are supported from below- there are no posts. Tension is applied from above- there are weights or spring loaded. A gear under each pair of disks is matched to another gear mounted on a continuous shaft which runs the length of the vertical tension post. This shaft is connected to a 4 rpm motor which rotates the disk.
Advantage of disk rotation are 1. Thread cutting prevention 2. Dampens out variation due to ballooning action of yarn. There is mor uniform tension 4. Less effor required to change tension levels.
Disadvantages are 1. It is more difficult to thread up, there is more maintenance due to electric motor used and at high speed the tension control is not well.
The botanical name of cotton is Gossypium. It has four varieties
a. G. Arboreum, G. Herbaccum- Old world cotton, native of Asia and India- Low yield - fibers are also short and coarse.
b. G. Hirsutum, G. Barbadense- America and Carribeans- High yield- fibres long and fine
Classification of Cottons
1. Primary Parmaters- Fibre length, length uniformity, fineness, maturity and bundle strength at 0 guage and 3.2 mm guage length.
2. secondary- Trash content, honey dew content and color
1.1 Fibre length and uniformity- Most important quality parameter that decides the price of cotton-Long staple cottons are used to spin finer counts and hence fetch higher prices
Uniformity ratio= (50% span length x 100)/ 2.5% span length
1.2 Fibre fineness: Indian cotton particularly long and extra long staple varities and hybrids show low micronaire values as compared to cottons of similar staple length grown in USA, Egypt and Sudan.This is due to lower maturity levels of Indian cottons.
Poor fibre maturity results in nappiness of the yarn and also leads to problems in even dyeing of fabric. Generally, lack of moisture and nutrients and incidence of insects and pests during cotton boll developments results in low fibre maturity
1.4 Fiber Strength
In the OE rotor system, it is fibre bundle strength, that is assigned the highest importance. Fibre bundle strength is determined by using the stelometer at zero guage. and 1/8 inch (3.2mm) guage length. It is well known that fibre strength decreases when guage length is increased. Also it is observed that yarn strength is correlated well with fibre tenacity at 3.2 mm guage length. Hence the ratio of strength at zero to that of 3.2mm is known as strength uniformity ratio.
2.1 Trash including other contaminants
Cut Seeds- during ginning Trash and other extraneous matter. General carelessness in picking, sorting, handling and transportation of Kapas at all stages upto and including ginning.
2.2 Honey dew and Color of cotton.
Honey dew consists of sugar secreted by sucking insects that harbour on the cotton plants. Presence leads to roller lapping. Color is more important in USA, where cotton is picked by machines and doing so gets rubbed against plant parts and thus gets contaminated.
Assessment of Spinning Performance
FQI= LSW/F
Where L= 50% span length S= Bundle strength at 3.2 mm guage M= maturity coefficient F= Micronaire Value
FQI can be used to arrive at yarn CSP for a given count by using empirical equations.
Denim Effluent Characteristics -Dark Blue Indigo color -High Dissolved Solids ( Decomposed products of hydro) -High Chemical Oxygen Demand (COD) -High pH -Chlorides and Sulphates of Suspended matter
Effluent is characterized by “high strength low volume”, as most of the most contaminated (“high strength”) effluent come from comparatively small quantity ( “low volume”) of wash waters used for rinse after yarn dyeing with indigo. Major contaminant is Indigo.
Permissible Limits for Cotton/ Synthetic Textile Industry (India) Effluent pH= 5.5-9.0 Suspended Solids= 100 ppm Oil and Grease= 10 ppm BOD= 30 ppm COD= 100 ppm Hexavalent chromium: 0.1 ppm Total Chromium= 2.0 ppm Phenolic Compunds= 5 ppm Sodium absorption ratio= 26 Sulphides= 2.0 ppm color ( pt.Co.Scale) = 100 Bioassay test= 90% survival of fish after 9 hours in 100% effluent.
Effluent Treatment Scheme
1. Equalization Equalization tank in two compartments. Retention time of at least 7-8 hours.
2. Flash Mixing Equalisation Tank flash mixer ( to adjust pH) clarifloculator Unit ( Alum/Poly Aluminium Chloride) for coagulation/segmentation
3. flocculation ( it is a physico chemical process with 35-40% COD removal, 25-30% BOD and 70-80% color removal, also >95% color removal is possible if PAC and polymer dosage increased) overflow rate at CFU < 20 m^3/day The sludge withdrawal should not be too less or too large ( can take place in lamella unit also )
4. Aeration Effluent after CFU aeration process ( time > 18 hours) ( New recent aerators use injectors which produce very fine bubble resulting in a large air/water interface. Waste water is used as pressure water fro the operations of injection. Water +air stream are subjected at the bottom of the tower to prevent any possible sedimentation. Gas bubble rise to full height of the tower long resident time. Good utilization of oxygen upto 80% is possible.
5. Clarification Effluent from aeration clarifier ( resident time 3-4 hours) activated sludge recalculated from clarifier to aeration tank sludge thickened centrifugal decanter filtrate is then discharged to another tank.
Dissolving Oxygen Clarified Effluent deficient in dissolved oxyen (DO)( for bioassay parameters) DO make uptank ( 2 hours resident time) – the output is expected to meet the criteria.
6. Ultrafilteration Process for filtration of particles >5 n meters, from feed water made to flow at low pressure through membrane having pore size of 4-5 nm. Useful for elimination of high molecular weight organic compounds. By using this ( the original indigo concentration in rinse water is 0.05%) fully usable 5% dispersion of indigo dye is obtained. There are two types of membranes available. 1. Organic 2. Mineral – resistant to pH 0-14, resistant to mechanical and thermal conditions and are unaffected by solvents.
7. Incineration Burning of waste Major threat to possible health Destruction of resources Expensive Generate toxins
8. Sludge Disposal 85% of the waste is biodegradable. Can be used for compost. Lime sludge has agricultural value as it is free from pathogenic microorganisms Bugs convert dyes into colorless substances Microorganisms ( Geotrichum Candidum filament fungus isolated from soil) can decompose 18 different kinds of dyes in to colorless substances. Preferred pH for them is 4-7 at a temperature of 20-30 deg C. Can destroy dye in two days ( at a concentration of 12 g/lit). They can eat indigo also.
Process Control for Effluent Usually 10% of the applied indigo is washed off in rinses. Indigo fixation of yarn could be improved by: -Slightly lower pH- can reduce indigo consumption for a given visual depth of shade -Use of pre reduced indigo and indigo dyeing under nitrogen blanket. Can cut hydro consumption -Use of prereduced sulpher dye and maintain reduction potential with hydrol ( glucose + other oligomeric reducing agent) instead of sod. Sulphide.
Effluent volume can be reduced through water conservation -Washing in counter current type -Decrease size of wash tanks -Use Na2CO3 (Sod. Bicarbonate) in first rinse tank -Use Co2 for neutralization of alkali -Use as many nips as possible during washing to squeeze out alkali to maximum ( squeezed liquor should not drop back into bath) -Relying more on spray rather than immersion into the bath -Create enough stir in wash tank for best washing efficiency.
Preshrinking of Textile Fabrics- or compressive shrinkage
Shrinkage can be - Natural Wash shrinkage- When the fibres swell in the presence of water and tensions induced during Spinning, weaving and processing of fabrics - Compressive or Mechanical Shrinkage
It can be compared to the action of press. The effectiveness of ironing depends upon: Temperature of the press Amount of Moisture present in the fabrics Amount of Physical Pressure Applied Time duration of application of press.
In case of pressing, the new memory is set by drying, in compressive shrinking, it is the palmer unit which dries the fabric, thereby setting its new memory
Amount of preshrinkage left in the fabric is adjusted by varying the relative speed of the palmer to that of the rubber belt unit.
Temperature
The temperature affects in the following way the various components of the palmer/ compressive shrinkage unit
- Rubber Belt Cylinder o Lower Temperature- Fabric appearance is affected- Sharp crease o Higher temperature- rubber belt life is shortened - Palmer Cylinder o If lower temperature: No dry Stuff; Elongation of preshrunk fabric- also stretching of inspection and rolling operation. o The purpose of palmer cylinder is to dry a fabric to a level of about 4% relative humidity. If there is higher temperature, there is elongation with natural moisture regain. - Temperature of fabric as it enters rubber belt unit If properly controlled, then high production. Most fabrics will shrink more easily if heated before entering the rubber belt unit. Moisture
- 100% cotton denim may require as much as 14% moisture to permit effective pre shrinkage - Moisture must be uniform thoroughout the length, width, and depth of fabric
How to ensure moisture uniformity - Use of heated cans - Apply needed moisture of fabric vial cooling water applied to rubber belt surface. But it also depends upon the condition of the rubber belt. Freshly grinded rubber belt carry more water à water removal roll of the rubber belt unit
Penetration of moisture applied to the fabric is very important. If insufficient moistureà Innermost dry layers of yarn will act like spring and cause the fabric to elongate.
Pressure
Maximum amount of rubber belt compression should not be greater than 25% of the actual belt thickness.
More heavy the fabric, more potential, more compression will it need
d. Duration
If above three factors are maintained and we have a sufficiently large palmer unit, we can compress durably a fabric to its ‘zero’ potential.
Its important to use cooling cans at the exit of the palmer
Fabric Scray: Use of exit scray allows additional time for fabric cooling as it is impossible to roll fabrics without the use of lengthwise tension.
Guider: The function of the guider is to keep the fabric to its full width.
Skyer: It is a sort of time delay device allowing time for moisture to penetrate into the fabric without the need to increase the machine length.
Heated Can: purpose: it is to drive the surface moisture into the fabric and to preheat the fabric.
Palmer
Function
Dry the fabric and set shrinkage Adjust the shrinkage To compare incoming and outgoing fabric tension and determine fabric shrinkage
Less dense the felt, greater is the drying capacity
Exit Scary - To relax and cool; - To prevent hot stop marks. It increases the rubber belt life - To facilitate shrink environment Why Wet Finishing for Denim
- Moisture doesn’t penetrate in the core- in foam finishing - Its better to shrink fabric with a low moisture content than those which are bone dried
In integrated Machine
Padder- wetting - squeezing the moisture - application of heat
Once it is shrunk the fabric is thoroughly dried by palmer
- Hand can be adjusted in padder use of starch, lubricant - Width can be controlled by adjusting tension between the padder and dry can - Higher speed - Even ness of the moisture content- Residual moisture after leaving palmer should be 4%
Drying depends upon the pressure of the steam, m/c speed, size of palmer , construction of felt
Thicker- more grinding - cracking - more wear and tear to machine parts - energy consumption
Rubber belt: Inside circumference- 3.962m - Rubber surface width should exceed fabric width by at least 6” and preferably 8”
How to increase the life of the Rubber belt
- Nip pressure used on rubber belt should be optimum - Over tension in the rubber belt should be avoided - Belt should be run with sufficient cooling water in its interior and exterior surface - Belt should be run with lowest possible operating temperature 115 deg- 140deg - Frequency of grinding of the rubber belt should be optimum ie should be enough and at sufficient depth. - Grind when density of belt surface has varied by 10% of its original hardness - Water removal roll pressure adjustment is very important to insure max. belt life. Water acts not only to cool the rubber, but is also a lubricant - Product machine stops or “hot stops” should be avoided to the maximum extent possible. One of the best ways to eliminate is to install scrays at the entrance and exit of the shrinking machine. - Foreign objects should be avoided. Knot size for joining fabrics should be smaller. - Regular cleaning and inspection of rubber belt. - Use correct belt width - Be careful during installation and maintenance of rubber belt, avoid use of chemicals.
Function of Felt Palmer
- It is required to maintain the preshrunk fabrics in intimate uniform contact with the surface of the heated cylinder in order to ensure uniform smooth drying of the fabricà new dimensionally stable memory. - Fabric drying depends upon, palmer cylinder temperature, shrinking machine speed and permeability of the drying felt. - It helps in precise fabric shrinking adjustment. It acts as a fabric puller to precisely control tension on the fabric - Provides a pressing and calendaring effect on the preshrunk fabric
1. Vat Indigo dye 2. NaoH--> flake, lye 3. Na2SO4 4. Dispersing Agent 5. Wetting Agent 6. Potessium persulphate 7. Thin boiling Starch 8. PVA 9. Mutton Tallow- or equivalent 10. Acrylic Polymer 11. Hessian Cloth- a. 45"width, 10 oz./linear yard, b. 45"width, 14 oz. per linear yard 12. High Molecular high density polyethylene: 65" guage x 44 "width, 65" guage x 50" width 13. Spiral Built Paper a. 51mm ID x 60-60.5 mm OD x 60" long
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