Carding

Inroduction:

"Card is the heart of the spinning mill" and "Well carded is half spun" are two proverbs of the experts.
These proverbs inform the immense significance of carding in the spinning process.High production in carding
to economise the process leads to reduction in yarn quality.Higher the production, the more sensitive becomes
the carding operation and the greater danger of a negative influence on quality.The technological changes that
has taken place in the process of carding is remarkable. Latest machines achieve the production rate of
60 - 100 kgs / hr, which used to be 5 - 10 kgs / hr, upto 1970.

THE PURPOSE OF CARDING:

1. to open the flocks into individual fibres
2. cleaning or elimination of impurities
3. reduction of neps
4. elimination of dust
5. elimination of short fibres
6. fibre blending
7. fibre orientation or alignment
8. sliver formation

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TECHNOLOGICAL POINTS IN CARDING

There are two types of feeding to the cards

1. feeding material in the form of scutcher lap
2. flock feed system (flocks are transported pneumatically)

• lapfeeding
  1. linear density of the lap is very good and it is easier to maintain(uniformity)
  2. the whole installation is very flexible
  3. deviations in card output will be nil, as laps can be rejected
  4. autolevellers are not required, hence investment cost and maintenace cost is less
  5. transportation of lap needs more manual efforts( more labour)
  6. lap run out is an additional source of fault, as it should be replaced by a new lap
  7. more good fibre loss during lap change
  8. more load on the taker-in, as laps are heavily compressed
• flock feeding
  1. high performance in carding due to high degree of openness of feed web
  2. labour requirement is less due to no lap transportaion and lap change in cards
  3. flock feeding is the only solution for high prouduction cards
  4. linear density of the web fed to the card is not as good as lap
  5. installation is not felxible
  6. autoleveller is a must, hence investment cost and maintenance cost is more
  -
• Type of flock feed(chute feed)
  1. there are two basic concepts of flock feed
     1. one piece chute without an opening device
     2. two piece chute with an opening system
  2. one piece chute is simple, economical and requires little maintenance
  3. two piece chute is complex, expensive, but delivers a uniform batt.
  4. One piece chut is a closed system, i.e.excess flock returns to the distrbutor, if too much material is present,
     neps can be increased
  5. one piece chute is not flexible to run different mixings
  6. layout restrictions are more with one piece chute
• A feeding device is a must to feed the web to the Taker-in region and it should perform the following tasks
  1. to clamp the batt securely throughout its width
  2. to grip the fibres tightly without slippage during the action of taker-in
  3. to present the fibres in such a manner that opening can be carried out gently
• The divertor nose(sharp or round) and the length of the nose(guide surface) have a significant influence on
  quality and quantity of waste removed. Shart nose divertor avoids fibre slippage but the opening action is not gentle.
  If the length of the guide surface is too short, the fibres can escape the action of the taker-in. They are scraped
  off by the mote knives and are lost in the waste receiver.
• Feed roller clothed with sawtooth is always better , because it gives good batt retention. Thus the opening effect
  of the taker-in is more as it is in combing
• Rieter has devloped a "unidirectional feed system" where the two feed devices(feed roller and feed plate
  are oppositely arranged when compared with the conventional system. i.e. the cylinder is located below and
  the plate is pressed against the cylinder by spring force. Owing to the direction of feed roller, the fibre batt
  runs downwards without diversion directly into the teeth of the taker-in(licker-in) which results in gentle
  fibre treatment. This helps to reduce faults in the yarn.
• The purpose of the taker-in is to pluck finely opened flocks out of the feed batt, to lead them over the
  dirt eliminating parts like mote knives, combing segment and waste plates, and then to deliver the fibres to the
  main cylinder. In high production cards the rotational speed ranges from 700-1400
• The treatment for opening and cleaning imparted by Taker-in is very intensive, but unfortunately not very
  gentle.Remember that around 60% of the fibres fed to the main cylinder is in the form of individual fibres.
• The circumferential speed of Taker-in is around 13 to 15 m/sec and the draft is more than 1000.It clearly
  shows that fibre gets deteriorated at this opening point. Only the degree of deterioration can be controlled
  by adjusting the following
  1. the thickness of the batt
  2. the degree of openness of the rawmaterial
  3. the degree of orientation of the fibres
  4. the aggressiveness of the clothing
  5. the distance between the devices
  6. the rotational velocity of the taker-in
  7. the material throughput
  -
• Latest TRUTZSCHLER cards work with three licker-ins compared to one liker-in.The first one is constructed as
  needle roll. This results in very gentle opening and an extremely long clothing life for this roll. The other two
  rollers are with finer clothing and higher speeds, which results in feeding more %of individual fibres and
  smallest tufts compared to single lickerin, to the main cylinder. This allows the maing cylinder to go high
  in speeds and reduce the load on cylinder and flat tops. There by higher productivity is achieved with good
  quality. But the performance may vary for different materials and different waste levels.
• between the taker-in and main cylinder , the clothings are in the doffing disposition. It exerts an influence
  on the sliver quality and also on the improvement in fibres longitudinal orientation that occurs here.
  The effect depends on the draft between main cylinder and taker-in.The draft between main cylinder and taker-in
  should be slightly more than 2.0.
• The opening effect is directly proportional to the number of wire points per fibre. At the Taker-in
  perhaps 0.3 points/ fibre and at the main cylinder 10-15 points /fibre.If a given quality of yarn is required,
  a corresponding degree of opening at the card is needed. To increase production in carding, the number of points
  per unit time must also be increased. this can be achieved by
  1. more points per unit area(finer clothing)
  2. higher roller and cylinder speeds
  3. more carding surface or carding position

  speeds and wire population has reached the maximum, further increase will result in design and technological
  problems. Hence the best way is to add carding surface (stationary flats). Carding plates can be applied at

  1. under the liker-in
  2. between the licker-in and flats
  3. between flats and doffer
• Taker-in does not deliver 100% individual fibres to main cylinder. It delivers around 70% as small flocks
  to main cylinder. If carding segments are not used, the load on cylinder and flats will be very high and carding
  action also suffers. If carding segemets are used, they ensure further opening, thinning out and primarily,
  spreading out and improved distribution of the flocks over the total surface area.carding segments bring the following advantages
  1. improved dirt and dust elimination
  2. improved disentanglement of neps
  3. possibility of speed increase (production increase)
  4. preservation of the clothing
  5. possibility of using finer clothings on the flats and cylinder
  6. better yarn quality
  7. less damage to the clothing
  8. cleaner clothing
• In an indepth analysis, all operating elements of the card were therefore checked in regard to their
  influence on carding intensity. It showed that the "CYLINDER-FLATS" area is by far the most effective
  region of the card for.
  1. opening of flocks to individual fibres
  2. elimination of remaining impurities(trash particles)
  3. elimination of short fibres( neps also removed with short fibres)
  4. untangling the neps
  5. dust removal
  6. high degree of longitudinal orientation of the fibres
• The main work of the card, separation to individual fibres is done between the main cylinder and the flats
  Only by means of this fibre separation, it is possible to eliminate the fine dirt particles and dust.
  When a flat enters the working zone, it gets filled up very quickly. Once it gets filled, after few seconds,
  thereafter , hardly any further take-up of fibres occurs, only carding.Accordingly, if a fibre bundle does
  not find place at the first few flats, then it can be opened only with difficulty.It will be rolled between
  the working surfaces and usually leads to nep formation
• In princile, the flats can be moved forwards or backwards, i.e. in the same direction as or in opposition
  to the cylinder.In reverse movement, the flats come into operative relationship with the cylinder
  clothing on the doffer side. At this stage, the flats are in a clean condition. They then move towards
  the taker-in and fill up during this movement.Part of their receiving capacity is thus lost, but sufficient
  remains for elimination of dirt, since this step takes place where the material first enters the flats.
  At this position, above the taker-in, the cylinder carries the material to be cleaned into the flats. The
  latter take up the dirt but do not transport it through the whole machine as in the forward movement system.
  Instead , the dirt is immediately removed from the machine. Rieter studies show clearly that the greater part
  of the dirt is hurled into the first flats directly above the taker-in.
• Kaufmann indicates that 75% of all neps can be disentagled, and of these about 60% are in fact
  disentagled. Of the remaining 40% disentaglable nep
  1. 30-33% pas on with the sliver
  2. 5-6% are removed with the flat strips
  3. 2-4%are eliminated with the waste
  The intensity of nep separation depends on
  1. the sharpness of the clothing
  2. the space setting between the main cylinder and the flats
  3. tooth density of the clothing
  4. speed of the main cylinder
  5. speed of the flat tops
  6. direction of flats with reference to cylinder
  7. the profile of the cylinder wire
• The arrangement of the clothing between the cylinder and the doffer is not meant for stripping action,
  It is for CARDING ACTION.This is the only way to obtain a condensing action and finally to form a web. It has both
  advantages and disadvantages.The advantage is that additional carding action is obtained here and it differs
  somewhat from processsing at the flats.A disadvantage is that leading hooks and trailing hooks are formed
  in the fibres , beause the fibres remain caught at one end of the main cylinder(leading hook) and some times on
  the doffer clothing(trailing hook).
• There are two rules of carding
  1. The fibre must enter the carding machine, be efficiently carded and taken from it in as little time as possible.
  2. The fibre must be under control from entry to exit
• Carding effect is taking place between cylinder and doffer because, either the main cylinder clothing rakes
  through the fibres caught in the doffer clothing, or the doffer clothing rakes thro the fibres on the main cylinder.
  Neps can still be disentangled here, or non-separated fibre bundles can be opened a bit in this area and
  can be separated during the next passage through the flats
• A disadvantage of web-formation at the card is the formation of hooks. According to an investigation by
  morton and Yen in Manchester, it can be assumed that
  1. 50% of the fibres have trailing hooks
  2. 15% have leading hooks
  3. 15% have both ends hooked
  4. 20% without hooks
• Leading hooks must be presented to the comber and trailing hooks to the ring spinning frame.
  There must be even number of passages between card and comber and odd number between the card and ringframe.

Blow Room

Basic operations in the blowroom:

1. opening

2. cleaning

3. mixing or blending

4. microdust removal

5. uniform feed to the carding machine

6. Recycling the waste

Blow room installations consists of a sequence of different machines to carry out the above said
operations.Moreover Since the tuft size of cotton becomes smaller and smaller, the required intensities
of processing necessitates different machine configuration.

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TECHNOLOGICAL POINTS IN BLOWROOM

• Opening in blowroom means opening into small flocks.Technological operation of opening means the volume of the
  flock is increased while the number of fibres remains constant. i.e. the specific density of the material is reduced
  • The larger the dirt particle , the better they can be removed
  • Since almost every blowroom machine can shatter particles, as far as possible a lot of impurities should
    be eliminated at the start of the process.Opening should be followed immediately by cleaning, if
    possible in the same machine.
  • The higher the degree of opening, the higher the degree of cleaning. A very high cleaning effect is
    almost always purchased at the cost of a high fibre loss. Higher roller speeds give a better cleaning effect
    but also more stress on the fibre.
  • Cleaning is made more difficult if the impurities of dirty cotton are distributed through a larger
    quantity of material by mxing with clean cotton.
  • The cleaning efficiency is strongly dependent on the TRASH %. It is also affected by the size of the particle
    and stickyness of cotton. Therefore cleaning efficiency can be different for different cottons with the
    same trash %.
  • There is a new concept called CLEANING RESISTANCE. Different cottons have different cleaning resistance.
    
  • If cotton is opened well in the opening process, cleaning becomes easier because opened cotton
    has more surface area, therefore cleaning is more efficient
  • If automatic bale opener is used, the tuft size should be as small as possible and the machine stop time
    should be reduced to the minimum level possible
  • If Manual Bale openers are used, the tuft size fed to the feed lattice should be as small as possible
  • Due to machine harvesting , cotton contains more and more impurities, which furthermore are shattered
    by hard ginning. Therefore cleaning is always an important basic operation.
  • -
  • In cleaning, it is necessary to release the adhesion of the impurities to the fibres and to give hte particles
    an opportunity to separate from the stock. The former is achieved mostly by picking of flocks, the latter is
    achieved by leading the flocks over a grid.
  • Using Inclined spiked lattice for opening cotton in the intial stages is always a better way of
    opening the cotton with minimum damages. Ofcourse the production is less with such type of machines.
    But one should bear in mind that if material is recyled more in the lattice, neps may increase.
  • Traditional methods use more number of machines to open and clean natural fibres.
  • Mechanical action on fibres causes some deterioration on yarn quality, particularly in terms of neps .
    Moreover it is true that the staple length of cotton can be significantly shortened .
  • Intensive opening in the initial machines like Bale breaker and blending machines means that shorter
    overall cleaning lines are adequate.
  • In a beating operation, the flocks are subjected to a sudden strong blow. The inertia of the impurities
    accelerated to a high speed, is substantially greater than that of the opened flocks due to the low air resistance
    of the impurities. The latter are hurled against the grid and because of their small size, pass between the
    grid bars into the waste box, while the flocks continue around the periphery of the rotating beater.
  • By using a much shorter machine sequence, fibres with better elastic properties and improved
    spinnability can be produced.
  • Air streams are often used in the latest machine sequence, to separate fibres from trash particles
    by buoyancy differences rather than beating the material against a series of grid bars.
  • There are three types of feeding apparatus in the blowroom opening machines
    1. two feed rollers( clamped)
    2. feed roller and a feed table
    3. a feed roller and pedals
  • Two feed roller arrangements gives the best forwarding motion, but unfortunately results in greatest
    clamping distance between the cylinders and the beating element
  • feed roller and pedal arrangement gives secure clamping throughout the width and a small clamping
    distance, which is very critical for an opening machine
  • -
  • In a feed roller and table arrangement, the clamping distance can be made very small. This gives intensive
    opening, but clamping over the whole width is poor, because the roller presses only on the highest points
    of the web. Thin places in the web can be dragged out of hte web as a clump by the beaters
  • Honeydew(sugar) or stickiness in cotton affect the process very badly. Beacause of that production
    and quality is affected. Particles stick to metal surfaces, and it gets aggreavated with heat and pressure.
    These deposits change the surface characteristics which directly affects the quality and running behavior.
  • There are chemicals which can be sprayed to split up the sugar drops to achieve better distribution.
    But this system should use water solutions which is not recommeded due to various reasons.
  • It is better to control the climate inside the department when sticky cotton is used. Low temperature
    ( around 22 degree celcius) and low humidity (45% RH). This requires an expensive air conditioning set up.
  • The easiest way to process sticky cotton is to mix with good cotton and to process through two blending
    machines with 6 and 8 doublings and to install machines which will seggregate a heavier particles
    by buoyanccy differences.
  • General factors which affect the degree of opening , cleaning and fibre loss are,
    1. thickness of the feed web
    2. density of the feed web
    3. fibre coherence
    4. fibre alignment
    5. size of the flocks in the feed (flock size may be same but density is different)
    6. the type of opening device
    7. speed of the opening device
    8. degree of penetration
    9. type of feed (loose or clamped)
    10. distance between feed and opening device
    11. type of opening device
    12. type of clothing
    13. point density of clothing
    14. arrangement of pins, needles, teeth
    15. speeds of the opening devices
    16. throughput speed of material
    17. type of grid bars
    18. area of the grid surface
    19. grid settings
    20. airflow through the grid
    21. condition of pre-opening
    22. quantity of material processed,
    23. position of the machine in the machine sequence
    24. feeding quantity variation to the beater
    25. ambient R.H.%
    26. ambient teperature
  • Cotton contains very little dust before ginning. Dust is therefore caused by working of the material on
    the machine. New dust is being created through shattering of impurities and smashing and rubbing of fibres.
    However removal of dust is not simple. Dust particles are very light and therefore float with the cotton
    in the transport stream.Furthermore the particles adhere quite strongly to the fibres. If they are to be
    eliminated they are to be rubbed off.The main elimination points for adhering dust therefore, are those
    points in the process at which high fibre/metal friction or high fibre/fibre friction is produced.
  • Removal of finest particles of contaminants and fibre fragments can be accomplished by releasing the
    dust into the air, like by turning the material over, and then removing the dust-contaminated air.
    Release of dust into the air occurs whereever the raw material is rolled, beaten or thrown about.Accordingly
    the air at such positions is sucked away. Perforated drums, stationary perforated drums, , stationary combs etc.
    are some instruments used to remove dust

How to Do Low Water Immersion Dyeing

How to Do Low Water Immersion Dyeing
Low Water Immersion dyeing is also known as "scrunch" dyeing, "crumple" dyeing, or "crackle" dyeing. In traditional immersion dyeing, one uses a large volume of water, frequent stirring, and the use of leveling agents such as salt and, optionally, Calsolene oil, in order to make the color as smooth and featureless as possible. Low water immersion dyeing is the opposite of this approach. In low water immersion dyeing, one uses as little water as possible, crunching the fabric together for a sort of resist effect, with as little stirring as possible.
Wonderful color gradations are the hallmark of the low water technique. Where mixing opposite colors, such as red and green, result in ugly muddy effects in tie-dye, they result in gorgeous subtle shadings in low water immersion dyeing. The reason for this is that, in tie dyeing, one normally pre-soaks the fabric in the soda ash fixer, or else adds it to the dye solutions themselves; so that the dye immediately reacts with the first fiber it touches. There is no chance for the dye colors to blend before the reaction takes place. In contrast, the low water technique involves adding the fixer *last*, after allowing the colors to slowly blend and creep along the fabric, resulting in truly infinite gradations of color.
For pictures of examples, see the low water immersion section in my gallery.
Getting Started
As in other forms of hand Procion MX dyeing, study the How to Dye basic recipe first. Make sure you have all the chemicals and supplies you need for dyeing: Procion MX dyes or other fiber reactive dyes, sodium carbonate, thin rubber or plastic gloves, measuring cups and spoons, dust mask for measuring out dyes, and a small bucket, large jar, or other container for doing the dyeing in. (The container should be plastic, glass, enamel, or stainless steel, not aluminum or iron.) The container should be no wider than necessary to hold the fabric, as it is best to really cram the fabric in tightly, for maximum contrasts. Be sure to pre-wash all clothing to remove invisible finishes that can prevent the dye from getting to the fabric.


Instructions
My technique is slightly different from that described in Ann Johnston's wonderful book, Color by Accident- you should find your own techniques evolving with experience - primarily because I lost her book for a year, but had enough memory of its main points to inspire me to try, anyway. I also prefer not to work with the dye stock solutions she uses, but instead mix new colors as I need them, and I prefer not to add any fixer until after all of the dye has been added.
Applying dye. First, crumple the garment or cloth and stuff it tightly into a container. Then mix up one color of Procion MX or similar fiber reactive dye, anywhere from 1/16 to 4 teaspoons of dye per cup, total volume one to two cups (where a teaspoon is about 5 ml, and a cup is about 250 ml). Do not add urea - you want nothing but pure dye in water. It may take five or ten minutes of constant stirring to dissolve some dyess. Pour this over the garment.
Next, mix another color, in much the same manner. Try wild color combinations - I've had great success with purple plus orange, or black plus emerald green. I like to be careful to wet the entire top layer of the garment, in case air bubbles within the garment cause it to float, leaving the top regions sticking out of the dye bath. (Better, perhaps, to avoid air bubbles altogether.)
You may choose to pour a cup or two of plain water over in between adding different colors, or you may choose to put one color in the bottom of the container (having first checked the fit with the dry garment in the clean container) before adding the clothing, and pour another color over the top.
You can also use only a single color, especially if it is a mixture of dry dye colors so that the colors will tend to separate out as they creep along the fabric. Keep track of how much water you add, total, for the next step. Do not stir or mush the fabric at all in this step, unless you wish to mute the variations in the final piece.
Allowing the colors to blend and spread. After you have added enough dye and water to almost cover the garment (try weighting it down with a glass measuring cup, if it floats too much - beware of rust spots from metal objects used as weights), leave it alone for anywhere from a few minutes to an hour. This time allows the colors to creep along the fabric, creating beautiful mixtures. Pre-mixed colors will tend to separate as the constituent dyes creep along the fabric at their own individual rates. Too little time will not allow this diffusion separation to occur; too much time can actually reduce the amount of variation in the piece, however, by allowing the dyes to diffuse too thoroughly, and blend together. (How much is too much, under your chosen conditions? Only trial and error can say for sure.)
Fixing the dye. When you have left the dye to rest long enough, you can now add the fixer. This is the same sodium carbonate, or soda ash, used in the other recipes in this site. A good concentration to use is one teaspoon (5 ml) for each cup (250 ml), total volume, in the dye bath - including whatever amount of water you will be using to dissolve the soda ash in for adding it. Soda ash dissolves best in warm water, about 95°F (35°C). If you have used a total of 8 cups of water in your dye bath, then, use 9 teaspoons, or 3 tablespoons, of soda ash, dissolved in an additional cup of water. Gently pour this soda ash solution over the top of the dye bath. I add more water if the topmost bits of fabric are still sticking out of the liquid, at that point. I do not stir or agitate the mixture in any way.
Reaction Time. You must then leave the soda ash to react with the fabric and dye for a miniumum of one hour. Some prefer to "batch" the reaction for 24 to 48 hours. I have never found this added time to be necessary, though I will leave the reaction overnight when that is more convenient for me. I believe that "batching" is an attempt to make up for low temperatures in the reaction, caused by low room temperature. If your room is cold, it may be more useful to warm the reaction (*after* adding the soda ash, not before, as dye will quickly react directly with hot water, leaving none to react with the fabric) than to leave it for long periods of time. Experiment with this for yourself.
Alternatively, you may cover your container tightly (such as with plastic warp) and heat for a couple of minutes in a microwave oven, watching closely to stop the heating if enough steam accumulates to risk pushing the covering off. You don't want a blowout to mess up your microwave with dye! The amount of time required depends on your oven and your total volume, so it's better to just watch closely and stop the heating when the liquid is obviously hot. (Caution: only wet fabric may be microwaved safely; dry fabric may catch on fire.)
Salt. Some dyers prefer to add salt to their low water immersion dyeing, to increase depth of shade and/or patterning; others, including Ann Johnston, do not. Only trial and error can tell you which you prefer. You can use one teaspoon (5 ml) per cup (250 ml) of total water volume.

About the Dyes

choosing the right dye for your fiber
Your choice of dye depends directly on what kind of fabric you are using. You'll get bad results if you use a wool dye on cotton, or a cotton dye recipe on wool, or either on polyester.
Dyes for Cellulose Fibers
These are your choices if you want to dye a t-shirt. Cellulose fibers include cotton, linen, rayon, hemp, ramie, lyocell (Tencel), and bamboo.
Fiber Reactive Dyes (best choice)
Direct Dye (hot water dye, less washfast)
Vat Dyes (more complex method)
Naphthol dyes (more hazardous, less available)
All purpose Dye (hot water dye, less washfast)
Dyes for Protein Fibers
Protein fibers include all fibers made by animals: wool, angora, mohair, cashmere, as well as silk. Silk is the only non-hair animal fiber, and can be dyed like wool or like cellulose fibers, above. The high-pH recipes used for most cellulose dyes will ruin animal hair fibers.
Dyes that can be used for protein fibers include the following:
Acid dyes
Food coloring
One Shot Dyes
Reactive dyes used as acid dyes
All purpose Dye (contains acid dye)
Natural dyes (these work better on wool than on cotton)
Lanaset/Sabraset dyes
Vat Dyes Also see Dyes for Protein Fibers.
'Soy Silk' is a new plant fiber, but, because it is made from soybean protein, it should be dyed like animal fibers, instead. Like real silk, it can also be dyed with fiber reactive dyes.
Dyes for Synthetic Fibers
PolyesterPolyester requires the use of disperse dyes. See Disperse Dye for Polyester.
Nylon
Surprisingly, nylon, which is a truly synthetic fiber, happens to dye quite well with the same acid dyes that work on wool and other animal fibers, in addition to dyes that work on polyester. For more information on dyes for nylon, see Dyes for Protein Fibers. You'll want to test a swatch before committing yourself to the project, as nylons vary. Nylon can also be colored with a type of fabric paint called 'Pigment dye'.
Spandex
Spandex can be dyed with metal complex acid dyes, but it is much more common for hand-dyers to dye only the cotton portion of a cotton/spandex blend. Polyester/spandex blends cannot be dyed. See How to dye spandex.
Acetate
Acetate, also known as rayon acetate, requires the use of disperse dye. (The other type of rayon, which is a cellulose fiber, is also known as viscose rayon.)
Acrylic
Acrylic fiber can be dyed with disperse dyes or with basic dyes. See Dyeing Acrylic with Basic Dye.
Ingeo
Ingeo is the trademark for a new synthetic fiber, polylactic acid (PLA), made from corn. It is dyed like polyester, using disperse dyes, though it is evidently somewhat less washfast.
Polypropylene
Polypropylene (Herculon, Olefin) is dyed while still in liquid form, before it is extruded into a fiber. It cannot be dyed at home.
Dyeing blendsMost cotton/polyester blends are best dyed as for cotton, using fiber reactive dyes, leaving the polyester undyed. Cotton/nylon blends may be dyed with all-purpose dye, or by successive dyeing with a fiber reactive dye such as Procion MX, first with soda ash at room temperature to dye the cotton, then in hot water with vinegar to dye the nylon.

How to Tie Dye - Complete Instructions
Use fiber reactive dye for tie-dyeing. Do not use all-purpose dye!
For pictures of successful tie dyeing--essential in helping you decide what you want to create--see my Gallery and some of the many beautiful commercial tie dyeing sites on my Links to other Galleries page.
Getting Started
Study the How to Dye basic recipe first. Make sure you have all the chemicals and supplies you need....Procion MX dyes, sodium carbonate, thin rubber or plastic gloves, measuring cups and spoons, squirt bottles to put the dye solution into, rubber bands, a dust mask for measuring out dyes, and a bucket for pre-soaking the fabric in sodium carbonate solution. If you don't have everything you need, you can still tie today, and be ready to dye when you get the rest of your equipment! Be sure to pre-wash all clothing to remove invisible finishes that can prevent the dye from getting to the fabric.
Why Tie?
The whole point of tie dyeing is to prevent the dye from reaching the fabric evenly. Any place that the dye can't reach will stay white, or a lighter color, of course. The gradations of color from intense to light can be beautiful. You can accomplish this by folding the fabric, tieing it with string, using rubber bands, etc.
Another reason to tie is that it makes each garment of piece of cloth a small, neat bundle--much easier to handle if you have a lot to do. If you don't tie, but just apply the dye directly, you need more space and can do fewer garments or pieces of fabric at a time.
Ways to Tie
Fold a piece of clothing in vertical pleats, and you'll end up with horizontal stripes. Horizontal pleats result in vertical stripes (more slimming, you know). Diagonal pleats make a nice effect. Stitch a loose basting stitch in any shape you like, then pull the threads tight for another form of tie-dyeing that can have really cool results. For concentric circles, grab the cloth where you want the center to be, and pull, until you've more or less made a long tube of the garment, then apply rubber bands at intervals along the fabric. I also like the "scrunch" pattern, made by crumpling the fabric very evenly, so that ultimately it makes a nice flat disk when held with rubber bands.
For the now-traditional spiral, see the FAQ, How do you tie-dye a spiral pattern?: you lay the garment on a flat smooth surface, smooth out all the wrinkles, then make a small pleat right across where you want the center to be. Grab the very center of that pleat with a clothes pin, and begin to twist. As you twist, pleats appear farther and farther away from the center; as these pleats get too large, split the pleats with your hands, keeping each fold the same height above the table, no more than one to two inches in height.
You should not really need pictures to do the above, because it is all trial and error, anyway. You can't know what works best for you until you try it. However, if you want to see pictures of how to do the ties, check out PROchem's illustrations of tie dye folds, actual photos of a tied spiral at Real Tie Dye, and Rit®'s Virtual spiral (though you'll find the dyeing process much easier if you use fiber reactive dyes such as Procion MX, instead of "all-purpose" dye such as Rit®, which requires that you hold the disk of fabric partially submerged in boiling water for a long time). A more advanced technique for tying is illustrated at The Kind Dyes. Mike Fowler's DVD The Art of Tie-Dye (illustrated at left) shows in great detail how to tie a number of different tie-dye folds, as do True Tie Dye's Tom Rolofson's wonderful "Learn How to Tie Dye" series of DVDs (see Amazon affiliate links at right side of this page).
Color Mixing
You can make all the colors you need by mixing lemon yellow, fuchsia, and turquoise. You should probably get black, too (I prefer Dharma's New Black), as it intensifies the other colors wonderfully by contrast, and it's hard to mix yourself.
Simple rules:
a lot of fuchsia and a little yellow make red
red and yellow make orange
yellow and turquoise* make green
a lot of turquoise* plus a little fuchsia makes blue
turquoise* plus fuchsia makes purple
*(remember to double the amounts of turquoise as compared to other colors)
Color Choice
The two most obvious differences between a wonderful tie-dye and a so-so one are color choice and color saturation. You'll find that you really have to work to squirt enough dye into the folds to avoid a large amount of white on the finished garment. In choosing colors to place adjacent to each other, remember the color wheel. Do not place "opposite" colors next to each other, such as red near green, or blue near orange, or yellow near purple: the results would be a muddy mess. If you really like bright colors, as I do, avoid placing a color with red mixed *in* it, such as purple, near green.
A good basic rule is to apply two colors next to each other only if they appear next to each other in the following short list:
fuchsia...yellow...turquoise...purple...fuschia
...or, for a more detailed color scheme, choose adjacent colors from the following expanded list:
fuchsia... red... orange... yellow... green... turquoise... blue... purple...fuschia
It really does help to place fuchsia between red and purple.
For eye-popping color contrasts, you can avoid muddy mixtures of colors by adding a thickener such as sodium alginate to your dye mixtures; applying contrasting colors to the two sides of your bundled folded fabric will then result in alternating stripes.

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Mineral colors

The word ‘Mineral’ indicates that these are inorganic in nature and these colors differ from all other classes of dyes, which are organic compound. Before introduction of the coal for dyes, these mineral colors formed an important section of the dyes.
Mineral color contains metallic insoluble precipitates, which are deeply colored. These insoluble precipitates have found great application as pigment for paint. For other purposes of dyeing, the precipitates themselves are not used but they actually created in and on the fibers from the soluble substances

Examples:

Mineral colors are very limited, only about half a dozen are valuable to dyes or printers:
• Chrome yellow
• Chrome orange
• Chrome green
• Iron buff
• Prussian blue
• Manganese blue

Requirements for dyeing with mineral color
• They should be dyed under special conditions avoiding metallic contact
• They shouldn’t be wet handled
• They must be padded evenly.
• They shouldn’t have any crease before drying.
• During production of mineral khaki metal surface is used, acidity must be well controlled and pH must be adjusted to 4.

Advantages
• Very simple to apply
• Lower cost
• Easily available

Disadvantages
• Less affinity to fibers, so mechanical pressures in between the roller is required
• For commercialization some technical experience is required
• Tendering may happen due to uncontrolled pH

Mineral Khaki
A combination of iron buff and chrome green in proper proportions produces mineral khaki, which is extensively used for military uniforms. It has excellent fastness to light and wash.

Dyeing procedure
• The cotton is padded with solution containing FeSO4
• Now treated with boiling solution of Na2CO3.
• Now wash
FeSO4 + 2NaOH Fe(OH)2 + Na2SO4
Cr2(SO4)3 + 6NaOH Cr(OH)3 + 3Na2SO4
• Now the fabric is aired for the conversation of Chromium hydroxide to Chromium oxide and Ferrous hydroxide into Ferric oxide by atmospheric oxygen.
Cr(OH)3 [O] Cr2O3
Fe(OH)2 [O] Fe2O3
These oxides then combine to give khaki shade.

Recipe:
For 1% shade of khaki or Procion Yellow M4GS: 0.25%
Indanthrene yellow FSI : 0.5% Procion Blue M85GS: 0.50%
Indanthrene Black Brown NI: 0.5% Procion Brown: 0.25%
NaOH: 16 gm/L NaCl: about 35g/L
Hydrose: 5 gm/L Na2CO3: 3 gm/L
M:L = 1:5
Temp: 80 – 100°C
Time: 60- 90 min
Posted by Chariots of knowledge
Oxidation color

Some dyestuffs like aromatic amine, diamine, aminophenol etc found as intermediate compounds, which rapidly produce the final color through oxidation in the fiber substances; this class of dye is known as oxidation colors.

Oxidation colors high molecular wt., water insoluble ingrain colors. Water insoluble species is produced by oxidation reaction performed on aromatic amines and diamines.

Important Oxidation colors:
1. Aniline black
2. Diphenyl black
3. Solaniline black
4. paramine brown
5. Fuscamine brown

Why oxidation color is called ingrain dye?

Ingrain dyes are, by definition, any water insoluble colors formed in situ (on the fabric) from water soluble intermediate i.e. the dyes which are developed on fiber but they are not readymade.

The oxidation colors are formed from water soluble oxidation amines, which formed the final color on fabric through oxidation. Thus they are not readily available, but as intermediate compounds. Hence they are called ingrain dyes.

Aniline Black

Aniline black, the oxidation product is the important member of oxidation color for textile use. It is called oxidation aniline color. It is invented in 1863 with sodium chlorate and copper sulfate etc.

Aniline black dyeing and prints produce some of the most intense blacks: These colors are almost completely color stable to acids, bases and exposure to light. By far, the greatest use of aniline black is dyeing and calico printing for cotton. Silk and wool are dyed only when extensive precautions are taken against tendering.

Reagent used for dyeing

1. Soluble sat of aromatic amine: aniline or n aminophenylamine, anyline hydrochlorides
2. oxidising agents: NaClO3, KClO3, NaHCO3, KMnO4 etc.
3. Catalyst/Oxidation carrier: CuSO4, CuS, FeCl3, potassium ferricyanide
4. Hygroscopic agent: NH4Cl
5. Migration inhibitor: Na-alginate, gum etc
6. Acid liberating agent: HCl

Classification of Aniline Black:
Based on method of dyeing and chemical used:

1. Prussiate Black/Steam Aniline Black:
Oxidation catalyst: Na4[Fe(CN)6] sodium Ferro cyanide (yellow prucciated of soda, hence the name)
Oxidation by NaClO3
Color produced by steaming (> 98ºC, 5min)
2. Diphenyl Black/Copper Sulfide Aniline Black
CuS as catalyst
NaClO3 as oxidizing agent
3. Chromate Aniline
4. Aged Aniline black

Dyeing Method

Recipe:
Aniline Black 8-10%
HCl: 15%
K2Cr2O7: 10%
CuSO4: 4%
Temperature: 100C
Time 90min
M:L = depends on machine

Procedure:
• First make solution with aniline and hydrogen chloride (sometimes paste preparation). Add water to make proper solution; if necessary boil to make clear solution.
• Potassium dichromate solution is made and added to dyebath
• The material is impregnated with this solution at room temperature for 30min
• CuSO4 solution is made and is added to dyebath
• Temperature rises slowly to boiling and dyeing for 30-45min
• The substance is hot air aged with removal of the hydrogen chloride fumes. There are also emissions of volatilized amine. Temperature should not be violently fluctuated
• Oxidation occurs during drying process and the dye becomes fixed.
• Good penetration is possible since the salt of dyestuffs has no fiber affinity.

After treatment
1-2% soaping at 100°C for 10 -15min
Wash and dry

For aniline black: 5gm/L solution of dichromate or bisulfite is necessary which will not develop green tint and also molecular wt is increased by 10%.

Thus dyeing of aniline black on cellulosic fiber fabric includes four steps:
1. impregnation with the aniline liquor
2. Drying of the impregnated fabric
3. developing either by ageing or steaming
4. after treatment

Defects
1. Tendering: Presence of mineral acid causes formation of oxycellulose and hydrocellulose
2. Greeninsh color: lack of proper oxidation
Remedies - a chroming treatment with sulfuric acid
3. Bronziness: presence of excess acid causes reddish tone turn the black shade bronzy.
Remedies – treatment with a dilute solution (0.05%) of tannic acid and then dried without washing

Advantages
• Jet black dyeing on cellulose are main use
• can produce more deep color
• for some shade, vat black are 5-10% expensive by weight
• less tendering than sulfur and vat black
• Rapid color develops during steaming
• No corrosion of boiler
• almost completely color stable to acids, bases and exposure
• reduction of time

Disadvantages
• Loss of cellulosic strength due to sulfuric acid form
• effluent treatment is difficult
• more chemical may cause dyeing problem
• dye range is limited

Mordant Dyeing

The term ‘mordant’ is derived from the Latin ‘mordeo,’ which means to bite or to take hole of. Mordant dye have no affinity to textile fiber, they are attached by a mordant, which can be an organic or inorganic substances. The most commonly used mordant is inorganic chromium, so sometimes this dye is called chrome dyes. Other inorganic mordants are Al, Cu, Fe and organic mordant. Tannic acid is rarely used.

Mordant improves the fastness of the dye on the fibre such as water, light and perspiration fastness. The choice of mordant is very important as different mordants can change the final colour significantly. Most natural dyes are mordant dyes and there is therefore a large literature base describing dyeing techniques. Fiber most readily dyed with mordant dyes are the natural protein fibers, particularly wool and sometime synthetic fibers modacrylic and nylon.

It is often noted that when a mordant dye forms a lake with a metal, there is a strong colour change. This is because metals have low energy atoms. The incorporation of these low energy atoms into the delocalised electron system of the dye causes a bathochromic shift in the absorption. It is this delocalised electron system which is fundamentally responsible for colour in dyes. Since different metal atoms have differing energy levels, the colour of the lakes may also differ.

The most commonly used mordant dye is undoubtedly hematein (natural black 1), whose status as a natural product supercedes its mode of dyeing, apparently. Others are eriochrome cyanine R (mordant blue 3) and celestine blue B (mordant blue 14), both used as substitutes for alum hematoxylin but with a ferric salt as the mordant. Alizarin red S (mordant red 3) is valuable for the demonstration of calcium, particularly in embryo skeletons

Reason for so named

Some natural and synthetic dyes can be applied or fixed on wool and other textile fibers with the help of an auxiliary chemical called a mordant. These dyes are therefore called mordant dyes.

The mordant have affinity both for a fiber can be applied by using a mordant.

In wool dyeing, only chromium salts are of importance and hence mordant dyes for wool are usually called chrome dyes.

Classification

On the basis of origin

1. Natural: Alizarine

2. Synthetic: Acid chrome

1. Natural Mordant dye

Alizarine: Alizarine is an example of natural mordant dye. It is obtained from the root of the madder. Alizarine is known as polygenetic mordant dye because it develops a variety of colors on different mordants.

Mordant Color

Al Red

Sn pink

Fe Brown

Cr puce brown

Cu yellowish brown

Haematin: this is extensively used before and only one still in use found from logwood. It yield navy blue or black colors of good fastness with chromium compounds. This is used in nylon and wool.

Recipe: haematin dye: 8-10%

Acetic acid: 1cc/l [pH 4-6]

temperature: 50-90°C

Time: 2hr

As it is time consuming process, the natural mordant dyes are used in lesser extent.

2. Acid mordant dyes:

Acid color + chromium = acid chrome

Few dihydroxy azo dyes could co-ordinate so easily with chromium and they could be dyed as acid dyes and mordanted by aftertreatment with K or Na dichromate. Such dyestuffs are known as the acid mordant dyes & are used extensively for wool & also for polyamide fibers.

They have good wet fastness and most of them possess satisfactory light fastness.

Methods of dyeing:

There are three general methods of application of mordant dyes as described below:

1. Chrome mordant process: two bath process

First bath: mordanting with insoluble chromium hydrate

2^nd bath: dyeing

2. Afterchrome process: two bath/single bath process

First bath: dyeing

2^nd bath: mordanting with chromium

3. Methachrome (or chromate) process

Dye + mordant (dichromate) in same bath

Mechanism of dyeing

Fig shows an example of mordant dye and shows the formation of dye mordant complex. The chromium cation has a valency of 6 (i.e. 6 bonds) which represented by six lines toward the chromium cation.

The mordant dye is shown to the Cr cation by three of the six bonds. The other three bonds have molecules of water attached to them. It is thought that the three molecules of water are there as an intermediate step only and will gradually be water replaced by another mordant dye anion. Thus two mordant dye molecules form a complex with the Cr cation to form a lake or a dye chromium complex. The formation of these relatively large complexes results in very good wash fastness of dye.

Dyeing procedure of Alizarine dyes

· Boil cotton fabric in solution of 1 part TR oil and

10 part water for 12 hrs

· Dry at 40-60°C

· Treat again with 10°Tw acetate at 60°C for 2hrs

· Dry at 40-60°C

· Again treat with 2 part Sodium phosphate

10 part water at 30-45°C

· Dye 1-1.5% shade with calcium acetate at room temperature for 20 mins

· Wash for 30 min at 70°C

· Soap wash, dry

Dyeing of wool with synthetic mordant:

Dyeing recipe

Dye 1-5%

Acetic acid (80%): 2-5% [pH 4-5]

Glauber salt: 10-25%

H₂SO₄: 1%

L:R= 1:20

Time 45-60 min

Mordanting recipe:

K dichromate: 2%

Temperature: 80-100°C

Time 45 min

M:L = 1:20

Dyeing procedure

· Prepare the dye bath with acetic acid and glauber salt.

· Temperature of the bath is raised to 50-60°C and the goods are entered

· The liquor is brought to boil for 30 min

· H₂SO₄ is now added to complete exhaustion and boiling is continued for another 30 mins

· When dye bath is exhausted and boiling has been continued for long enough for the color to be level, the temperature is allowed to drop and Potassium dichromate is added

· Chroming is continued at boil for 30 min

It is extremely important to make certain that goods are dyed uniformly before the dichromate is added because there will be no further migration afterward. The dye liquor must also be virtually exhausted before mordanting, because of dye remains in solution it will be precipitated on the surface of the fibers in form of its insoluble lake and cause poor rubbing fastness.

Disadvantages:

· Color matching is difficult as the process of mordanting means that the color builds up gradually

· Length periods of applications are both detrimental to protein and polyamide fibers and rather costly.

· Dichromate salts become pollutants once they are discharged into sewerage.

Posted by Chariots of knowledge

Latest News [PM Unveiled BGMEA web Portal]

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Honorable Prime Minister Sheikh Hasina unveiled B2B web portal for Ready Made Garment Sector on The three-day Bangladesh Apparel and Textile Exposition (BATEXPO) in Pan Pacific Sonargong Hotel, Dhaka. Finance Minister Abul Maal A. Muhith, LGRD Minister Syed Ashraful Islam and Commerce Minister Faruk Khan, BGMEA President Abdus Salam Murshedy, 1st Vice President Nasir Uddin Chowdhury, 2nd Vice President Md. Shafiul Islam (Mohiuddin) , Vice President Faruque Hassan, Vice President (Finance) Md. Siddiqur Rahman, Chief Co-ordinator BATEXPO - 09 Mohsin Uddin Ahmed Niru, BGMEA directors were with the prime minister.

Rayon Fiber (Viscose)

Rayon Staple Fiber
Rayon Textile Filament Fiber
Rayon Industrial Filament Fiber

First U.S. Commercial Rayon Fiber Production: 1910, Avtex Fibers Inc. (Formerly FMC Corporation and American Viscose)

Current U.S Rayon Fiber Producers: None currently

Federal Trade Commission Definition for Rayon Fiber: A manufactured fiber composed of regenerated cellulose, in which substituents have replaced not more than 15% of the hydrogens of the hydroxyl groups. (Complete FTC Fiber Rules here.)

Basic Principles of Rayon Fiber Production — In the production of rayon, purified cellulose is chemically converted into a soluble compound. A solution of this compound is passed through the spinneret to form soft filaments that are then converted or “regenerated” into almost pure cellulose. Because of the reconversion of the soluble compound to cellulose, rayon is referred to as a regenerated cellulose fiber.

There are several types of rayon fibers in commercial use today, named according to the process by which the cellulose is converted to the soluble form and then regenerated. Rayon fibers are wet spun, which means that the filaments emerging from the spinneret pass directly into chemical baths for solidifying or regeneration.

Viscose rayon is made by converting purified cellulose to xanthate, dissolving the xanthate in dilute caustic soda and then regenerating the cellulose from the product as it emerges from the spinneret. Most rayon is made by the viscose process.

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Viscose Process
Most commercial rayon manufacturing today utilizes the viscose process. This process dates to the early 1900s, with most of the growth in production occurring between 1925 and 1955. In the early period, production was mainly textile filament, although the first staple was produced in 1916. High performance rayons, such as tire cord, did not appear until the late 1930s, with the advent of hot-stretching and addition of larger amounts of zinc to the spin bath. Invention of modifiers in 1947 brought on super tire cords and marked the beginning of the high-performance rayon fibers.

All of the early viscose production involved batch processing. In more recent times, processes have been modified to allow some semi-continuous production. For easier understanding, the viscose process is a batch operation. Click on each process step for a brief explanation.

Cellulose
Purified cellulose for rayon production usually comes from specially processed wood pulp. It is sometimes referred to as “dissolving cellulose” or “dissolving pulp” to distinguish it from lower grade pulps used for papermaking and other purposes. Dissolving cellulose is characterized by a high a -cellulose content, i.e., it is composed of long-chain molecules, relatively free from lignin and hemicelluloses, or other short-chain carbohydrates.

Steeping
The cellulose sheets are saturated with a solution of caustic soda (or sodium hydroxide) and allowed to steep for enough time for the caustic solution to penetrate the cellulose and convert some of it into “soda cellulose”, the sodium salt of cellulose. This is necessary to facilitate controlled oxidation of the cellulose chains and the ensuing reaction to form cellulose xanthate.

Pressing
The soda cellulose is squeezed mechanically to remove excess caustic soda solution.

Shredding
The soda cellulose is mechanically shredded to increase surface area and make the cellulose easier to process. This shredded cellulose is often referred to as “white crumb”.

Aging
The white crumb is allowed to stand in contact with the oxygen of the ambient air. Because of the high alkalinity of white crumb, the cellulose is partially oxidized and degraded to lower molecular weights. This degradation must be carefully controlled to produce chain lengths short enough to give manageable viscosities in the spinning solution, but still long enough to impart good physical properties to the fiber product.

Xanthation
The properly aged white crumb is placed into a churn, or other mixing vessel, and treated with gaseous carbon disulfide. The soda cellulose reacts with the CS₂ to form xanthate ester groups. The carbon disulfide also reacts with the alkaline medium to form inorganic impurities which give the cellulose mixture a characteristic yellow color – and this material is referred to as “yellow crumb”. Because accessibility to the CS₂ is greatly restricted in the crystalline regions of the soda cellulose, the yellow crumb is essentially a block copolymer of cellulose and cellulose xanthate.

Dissolving
The yellow crumb is dissolved in aqueous caustic solution. The large xanthate substituents on the cellulose force the chains apart, reducing the interchain hydrogen bonds and allowing water molecules to solvate and separate the chains, leading to solution of the otherwise insoluble cellulose. Because of the blocks of un-xanthated cellulose in the crystalline regions, the yellow crumb is not completely soluble at this stage. Because the cellulose xanthate solution (or more accurately, suspension) has a very high viscosity, it has been termed “viscose”.

Ripening
The viscose is allowed to stand for a period of time to “ripen”. Two important process occur during ripening: Redistribution and loss of xanthate groups. The reversible xanthation reaction allows some of the xanthate groups to revert to cellulosic hydroxyls and free CS₂. This free CS₂ can then escape or react with other hydroxyl on other portions of the cellulose chain. In this way, the ordered, or crystalline, regions are gradually broken down and more complete solution is achieved. The CS₂ that is lost reduces the solubility of the cellulose and facilitates regeneration of the cellulose after it is formed into a filament.

Filtering
The viscose is filtered to remove undissolved materials that might disrupt the spinning process or cause defects in the rayon filament.

Degassing
Bubbles of air entrapped in the viscose must be removed prior to extrusion or they would cause voids, or weak spots, in the fine rayon filaments.

Spinning - (Wet Spinning)
The viscose is forced through a spinneret, a device resembling a shower head with many small holes. Each hole produces a fine filament of viscose. As the viscose exits the spinneret, it comes in contact with a solution of sulfuric acid, sodium sulfate and, usually, Zn⁺⁺ ions. Several processes occur at this point which cause the cellulose to be regenerated and precipitate from solution. Water diffuses out from the extruded viscose to increase the concentration in the filament beyond the limit of solubility. The xanthate groups form complexes with the Zn⁺⁺ which draw the cellulose chains together. The acidic spin bath converts the xanthate functions into unstable xantheic acid groups, which spontaneously lose CS₂ and regenerate the free hydroxyls of cellulose. (This is similar to the well-known reaction of carbonate salts with acid to form unstable carbonic acid, which loses CO₂). The result is the formation of fine filaments of cellulose, or rayon.

Drawing
The rayon filaments are stretched while the cellulose chains are still relatively mobile. This causes the chains to stretch out and orient along the fiber axis. As the chains become more parallel, interchain hydrogen bonds form, giving the filaments the properties necessary for use as textile fibers.

Washing
The freshly regenerated rayon contains many salts and other water soluble impurities which need to be removed. Several different washing techniques may be used.

Cutting
If the rayon is to be used as staple (i.e., discreet lengths of fiber), the group of filaments (termed “tow”) is passed through a rotary cutter to provide a fiber which can be processed in much the same way as cotton.

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Other forms of regenerated cellulose fibers that are classified by the Commission as rayon without separate, distinctive names include high wet modulus rayon, cuprammonium rayon and saponified rayon.

High wet modulus rayon is highly modified viscose rayon that has greater dimensional stability in washing.

Cuprammonium rayon is made by converting the cellulose into a soluble compound by combining it with copper and ammonia. The solution of this material in caustic soda is passed through the spinneret and the cellulose is regenerated in the hardening baths that remove the copper and ammonia and neutralize the caustic soda. Cuprammonium rayon is usually made in fine filaments that are used in lightweight summer dresses and blouses, sometimes in Combination with cotton to make textured fabrics with clubbed, uneven surfaces.

When extruded filaments of cellulose acetate are reconverted to cellulose, they are described as saponified rayon, which dyes like rayon instead of acetate.

Rayon Fiber Characteristics

• Highly absorbent
• Soft and comfortable
• Easy to dye
• Drapes well

The drawing process applied in spinning may be adjusted to produce rayon fibers of extra strength and reduced elongation. Such fibers are designated as high tenacity rayons, which have about twice the strength and two-thirds of the stretch of regular rayon. An intermediate grade, known as medium tenacity rayon, is also made. Its strength and stretch characteristics fall midway between those of high tenacity and regular rayon.

Some Major Rayon Fiber Uses

• Apparel: Accessories, blouses, dresses, jackets, lingerie, linings, millinery, slacks, sportshirts, sportswear, suits, ties, work clothes
• Home Furnishings: Bedspreads, blankets, curtains, draperies, sheets, slipcovers, tablecloths, upholstery
• Industrial Uses: Industrial products, medical surgical products, nonwoven products, tire cord
• Other Uses: Feminine hygiene products

General Rayon Fiber Care Tips — Most rayon fabrics should be dry-cleaned, but some types of fabric and garment construction are such that they can be hand or machine washed. For washable items, use the following as a guide:

• Fabrics containing rayon can be bleached; some finishes, however, are sensitive to chlorine bleach.
• Use mild lukewarm or cool suds. Gently squeeze suds through fabric and rinse in lukewarm water. Do not wring or twist the article.
• Smooth or shake out article and place on a non-rust hanger to dry. Rayon sweaters should be dried flat.
• Press the article while damp on the wrong side with the iron at a moderate setting. If finishing on the right side is required, a press cloth should be used.
• Between wearings, rayon articles may be pressed with a cool iron. (For specific instructions, refer to garment's sewn-in care label.)