Polyester Microfibers:- Dyeing and Wet Processing

Microfiber

A synthetic fiber that is extremely soft, lightweight, breathable, durable and ultrafine. In fact, microfibers are two times finer than silk and one hundred times finer than a human hair. Microfiber is currently manufactured from acrylic, nylon, polyester and rayon.Ultra-microfibers on the market are even finer – some having thickness of just 1/200th the thickness of human hair!

Microfibres refer to staple fibres, or individual filaments within yarns, which have fineness less than 1 decitex ( 1 grams per 10,000 meters) and For any fiber to be classified as microfibre yarn, the weight per 10,000 metres of yarn (dtex) is divided by the number of filaments (f), the result must be below 1.
All about microfibers

Microfibers: Functional Beauty

Properties of Polyester Microfibers

1. Lightweight and flexible
2. 
   
   Good stability and shape retention
3. 
   
   Anti-wrinkle property
4. 
   
   Have a wicking ability that permits perspiration
5. 
   
   Comfortable to wear as they are more spongy
6. 
   
   Doesn't water stain - superior water repellency is available
7. 
   
   Woven or knitted into a very high quality fabric construction
8. 
   
   Formerly commenced as a polyester microfiber, today you can find nylon, rayon and acrylic microfibers too.
9. 
   
   Strong and durable, water repellent and wind resistant -so tightly woven, that the fabric can't be penetrated by wind, rain or cold
10. 
    
    Lightweight, resilient or resist wrinkling, have a comfortable array, preserve shape and resist pilling
11. 
    
    The positively charged microfibers draw dust; the tiny fibers are capable to enter the microscopic surface voids most materials
12. 
    
    Washable, dries quickly and also washable in at the water temperatures up to 200 degrees and their characteristics will remain intact.
13. 
    
    Electrostatic effect - Hair, lint and other dust particles are attracted and grabbed by the microfibers without lifting dust.
14. 
    
    The density of the material allowable it to grip six to eight times its weight in water hence high absorbing power capacity
15. 
    
    The attraction capability of the microfibers is so sound, even absorbs bacteria and germs - hence can be use as germ or bacteria free purpose
16. 
    
    The fabric consists of millions of small tiny conduits that carry oil and grease too.
17. 
    
    Benefits of microfibers
18. 
    
    Comfortable - very soft, texture like silk, lightweight
19. 
    
    Due to its fineness and superior fiber surface area making deep, rich and bright colors achievable
20. 
    
    Less "sweaty" in warm weather than usual synthetics
21. 
    
    Quickly cleanable - clean just with water
22. 
    
    Highly intense and shrink-resistant
23. 
    
    Presents insulation and breathability
24. 
    
    Change without help - to establish lovely drape
25. 
    
    Very fine - finer than the most precise silk
26. 
    
    More reusable for cleaning alternative - compared to other mops more efficient and long life

Dyeing of polyester Microfibers
Due to their fineness, the total surface area of microfibre yarn or fabric is far greater than ordinary fibres. Threfore

1.Due to its special structure ,micro fibers has much larger quantity of size ,oil agents and wax on warp yarns.

2.Since microfibres have very small interstitces, with consequent difficulties of size accessibility and duffusibility, desizing becomes quite difficult and costly.

3.Microfibres have greater absorption area resulting in a dyeing rate four times higher than that of normal, which can cause unlevelness in dyeing.

4.They also require more dyestuff than standard fibres to obtain the same depth of shade.
5.Larger external surface means an increase in number of threads exposed to light which, on destruction of dye, is expressed as lower light fastness rating.
6. Wash fastness and color fastness to rubbing is also poor.
7.Staple microfibres offer difficulty in carding.

The problems in wet processing of microfibers can be overcome by

1.Better knowledge about the size applied and optimum parameters during desizing operation.

To achieve satisfactory dyeing effects ,desizing and refining process must be done before dyeing and after desizing and refining , there should be no impurities left such as electrolyte, antistatic finishing agent , spin finishes and blot.

2.Pre-setting

Suitable pre setting conditions ( time ,temperature and tension) helps not only in stable dimensional stability ,softness but also better dyeing results.

3.Alkali weight reduction

Alkali weight reduction s to treat the fabric with concentrated alkali at high temperature.fber molecule hydrolyse under this condition and lose some weight with change in properties, thus space occurs between crossing points and rubbing resistance relative to slippage among yarns becomes small.Alkali weight reduction makes fabric soft, liveliness, limber and improved absorption.

2.Careful selection of the dyes.

Proper dye selection which are
1.Compatible
2.Having same exhaustion rates
3.Having high wash fastness properties.
4.Good migration and levelling properties
 eliminates problems regarding build-up and fastness properties.
Disperse dyes for polyester microfibers

3.Optimizing the dyebath conditions and dyeing cycle.


Optimised dyeing cycles can be worked out by controlling the temperature to account for the high rate of dyeing and to eliminate the risk of uneven dyeing.Chemicals and dyes to be added at, at least 10-20 deg.C lower temperature than normal polyester fiber dyeing. The additions of dyes must be progressive or devided at least into 4 parts. The heating rate must be slow from 40 deg C to 100 deg C. 10-20 min more holding time required at 130 deg C as compared to normal PES.


4.Proper selection of  Dyeing machinery.

The dyeing machine must have the required automation to fufil the requirements of microfiber dyeing such as microprocessor controlled dosing , proper and accurate heating rate control etc.


5.Proper selection of dyebath additives
such as
Levelling agents :- A strong levelling agent which shall start working at lower temperatures.
Dispersing agents :- Higher quantities of dispersing agents are needed because amount of dyes required are more to produce the desired depth.
Chelating agents:-
Anticreasing agents,Dyebath softners/Lubricants :- Because microfiber textiles are prone to creasing , therefore use off dyebath lubricants is must.

6.Proper aftertreatment of dyed goods.
Soaping :- In order to obtain satisfactory color effect , fabric should be soaped after dyeing .Soaping is the key process to achieve satisfactory dyeing results on polyester especially polyester / nylon microdenier fabric.


Reduction clear :-Good reduction clear process is needed to achieve satisfactory washing , rubbing and light fastness properties.
Washing :-Is required for neutralising and removing alkali after reduction clear treatment.
Softening, anti soil and antistatic treatment :-Because microdenier fiber easily stains and produces static charges, a hydrophilic ,antistatic and antisoil treatment besides softening is highly recommended to ensure fabric softness and comfortability.

Recommended Dyeing Cycle for polyester Microfibers

Dianix PLUS( Dystar) or Longsheng  is a new range of five compatible, level-dyeing dyes for reliable dyeing of medium and heavy shades, especially on microfiber and weight-reduced polyester, whether applied under mild alkaline conditions to control trimer, or under conventional acid conditions.
Dianix E-PLUS" for Pale Shades on Polyester Fabrics
Fashion application of polyester

Application of polyester Microfibres

Microfibers are most commonly found in polyester and nylon. Some rayon and acrylic micros are in production and available to consumers. Micros can be used alone or blended with conventional denier man-made fibers as well as with natural fibers such as cotton, wool, and silk.

In textiles

Microfibers are used in a variety of fabrics, but most commonly in dress and blouse weight garments. Suit jackets and bottom weights are becoming available. Look for micros in lingerie, rainwear, outdoor fleece and wind-resistant sportswear, as well as tents, sleeping bags, track and jogging suits. The strength of microfibers make them particularly adaptable to sueded or sandwashed finishes because of their extensive fiber surface area and the use of strong fibers like polyester and nylon. As a result, many microfibers simulate the appearance of sandwashed silk.

Other Main products for which microfiber are ideally suited:

• Microfiber Glass Cloth

• Duster/Multi-purpose Microfiber Cleaning Cloth

• Microfiber Scrubber

• Microfiber Kitchen Cloth

• Microfiber Optical & CD Cloth

• Microfiber Mops

• Microfiber Cleaning Sponge

• Microfiber Cleaning Cloths – Terry Cloths, Suede Cloths, Waffle-Weave Cloths

Microfiber Makes the Grade
http://www.tex.in/education/nextiles/fib/mic/mic.html
http://ygmfranchise.blogspot.com/2007/07/cleaning-tips-microfiber.html
http://www.microfibergreen.com/is-microfiber-green-product.html
http://www.norwexnow.com/microfiber%20science.html

 

Fabric Dyeing Machines

Open width dyeing Machines
Batch dyeing
Batchwise dyeing of woven cellulose fabrics
Semicontinuous dyeing
Continuous Dyeing
A Project Report on Continuous Dyeing
Rope Dyeing Machines
Watch Videos:-
Fabric Dyeing-1
Fabric Dyeing-2
Multiflux HT Fabric Dyeing machine
Fabric dyeing
Rapid and efficient dyeing: A literature survey with emphasis on jet dyeing, 1970-78 (Shirley Institute publication)
Cotton Dyeing and Finishing : A Technical Guide
Chemistry for Textile Students; A Manual Suitable for Technical Students in the Textile and Dyeing Industries

Textile Wet Processing

An Introduction to textile Wet Processing

Fibers ,Yarns , threads ,Woven and knit textiles goods cannot be processed into apparel and other finished textile products until they have passed through several water-intensive wet processing stages. Wet processing enhances the appearance, durability, and serviceability of textiles by converting undyed and unfinished goods, known as gray or greige goods, into finished consumers’goods. Also collectively known as  dyeing and fmishing, wet processing has been broken down into four stages:

1.Fabric or yarn  preparation
To ensure that the textile has the right physical and chemical properties to enable it to be coloured or finished.
EXAMPLE:
Desizing, Singeing, Scouring, Bleaching etc.
2.Coloration or dyeing
To provide the textile with colour either for aesthetic reasons or for some functional purpose determined by the end-use of the product.
EXAMPLE:
Yarn Dyeing ,Fabric Dyeing
3.Printing
Textile printing is the process of applying colour to fabric in definite patterns or designs.
EXAMPLE
Roller printing, cylinder printing, or machine printing ,Stencil printing ,Screen-printing ,Digital textile printing 4.Finishing.
To provide the textile with the properties that the end-use demands and which have not already been provided by any earlier processes.
EXAMPLE:
Crease resistance, dimensional stability, stain resistant ,Water Repellency, Flame Repellency, Antisoiling finish etc.
These stages, involve treating gray goods with chemical baths and often require additional washing,rinsing, and drying steps. Note that some of these steps may be optional or repeated depending on the style-quality- type  of textile items being manufactured.

Read More
Water and textile Wet Processing -1
Historical notes on the wet-processing industry
AATCC Garment Wet Processing Technical Manual
A workbook for pollution prevention by source reduction in textile wet processing
Trainer's Workbook on Cleaner Production in Textile Wet Processing

Winch Dyeing Machines

Winch dyeing

A dyeing machine consisting essentially of a dye vessel fitted with a driven winch ( usually above the liquor level) which rotates and draws a length of fabric, normally joined end to end, through the liquor.

Winch dyeing machines are a low cost design that is simple to operate and maintain, yet versatile in application proving invaluable for preparation, washing or after treatments as well as the dyeing stage itself. In all winch dyeing machines a series of fabric ropes of equal length are immersed in the dye bath but part of each rope is taken over two reels or the winch itself. The rope of fabric is circulated through the dye bath being hauled up and over the winch throughout the course of the dyeing operation. Dyestuff and auxiliaries may be dosed manually or automatically in accordance with the recipe method.

Description  and Dyeing Method on Winch Dyeing Machine

The basic principle of all winch dyeing machines is to have a number of loops or ropes of the fabric in the dye bath, these ropes are of equal length , which are mostly immersed in the liquor in the bath. The upper part of each rope runs over two reels which are mounted over dyebath. At the front of the machine , above the top of the dye liquor , is a smaller reel, which is called jockey or fly roller. The fly roller remain free wheeling along with fabric rope. At the back of winch tank is the winch wheel, which pulls the fabric rope from the dye bath over the jockey reel for dropping in the dye bath for immersion. From the dropped location , the fabric rope travels back . to be lifted and fed to winch wheel.

The dyeing process on winch dyeing machines is based on higher M:L as compared with other dyeing machines. The process is conducted with very little tension . The total dyeing time is lengthier as compared to other machines.

Advantages of Winch Dyeing
a. Construction and operation of winch are very simple.
b. The winch dyeing machines are suitable for types of wet processing operations from desizing to softening.
c.The winch dyeing machine is suitable for practically all types of fabrics ,which can withstand creasing in rope form processing.
d. Thr tension exerted on winch is less than jigger,the material thus dyed is with fuller hand.
e. The appearance of the dyed goods is clean and smooth on winch dyeing machines.

Limitations Of Winch Dyeing
a. Batch dyeing operations needs trimming, sewing, opening out the rope , loading and unloading for individual lots separately.
b. Since several lengths of fabric are run over the winch reel into the liquor and sewn end to end,Continuous length processing is not possible in a single batch.
c. Fabric is processed in rope form which may lead to crease marks , particularly in heavy , woven , thin and light synthetics.
d. Most of the machine work under atmospheric conditions.
More Information On Winch Dyeing Clik Here
Winch Dyeing Machines
Fabric dyeing Machines

Pad Dyeing Machines

Padding Mangles


The pad dyeing machines overcome the deficiency of winch and jigger dyeing machines of smaller batch size and discontinuity in dyeing. Padding mangle offer continuous process of the fabric in concerned liquor , such as pretreatment, dyeing or finishing.
Application of dyestuffs is conducted in the pad dyeing machines with single or multiple dipping in solution .During padding, the fabric passes into a solution of chemicals, under a submerged roller and out of the bath. It is then squeezed to remove excess solution .The objective of this process is to mechanically impregnate the fabric with the solution or dispersion of chemicals Pad impregnation is common for the dyeing of fabric and for the application of finishing chemicals.

A Practical Introduction to the Continuous Dyeing of Woven Fabrics

Machine Description

Main parts of a padding mangle

The main frame

The frames are usually fabricated construction , to withstand vibrations and heavy workloads.

Tension elements

While the cloth passes on to the padding machine no slackness should occur in fabric either in weft or warp directions and the weft threads of cloth should remain parallel to the nip at the squeezing point.

The padding mangle bowls

The nip rollers (often called bowls) are the key to successful pad dyeing. In general, two-bowl nips are preferred for lightweight or standard fabrics running at moderate speeds, whereas three-bowl arrangements are intended for heavier or more densely woven qualities that may be more difficult to wet out and thus require a double-dip and double-nip treatment.

Cloth Guiding arrangement

Are provided so that machine should have a universal feeding and delivery system at a uniform tension .

Pressure generation and application

It is either pneumatic or hydraulic.

The dye trough

The pad trough is usually a deep U-shaped vessel with a single roller attached to the base of a displacement block that leaves a narrow passage to accommodate the moving fabric.
A cost study of thermosol and continuous solvent dyeing

Dyeing Method

The padding operation itself consists of two essential steps: thorough impregnation by immersion of the absorbent fabric in a dye solution containing a wetting agent, followed by squeezing of the wet fabric between rollers to expel air and replace it with dye liquor, as well as expressing surplus liquor back down the sloping fabric surface to the pad trough.

The cloth to be padded is taken up by either from the folded form or from the batched condition and fed to the padding machine over a set of guide rollers. The fabric is straighten in warp as well as weft directions .It is necessary to attach and end piece on both the sides of batch.

The fabric to be padded should be padded should be pretreated , free from loose fly ,waste ,oily matter , flat , crease free and with opened-out selvedges.

To obtain consistency of shade it is most important that the fabric running speed and the length of immersion of fabric in the dye liquor remain constant throughout the padding run. The three main types of automatic level control are:

1. Float switches: these are reliable and are unaffected by foam but they are relatively bulky

2. Conductivity probes: these are small and neat but foaming of the pad liquor adversely affects their performance

3. Differential pressure detectors: those with a hollow tube projecting downwards from the liquor surface are difficult to clean and the preferred type is that with a closed diaphragm set in the base of the vessel.

4. The control of pad liquor temperature is highly desirable to achieve consistent results.

Further Readings
 Jet or pad/wet steam dyeing of tublualr knitted cotton fabrics with reactives: Which costs less? : a summary report (Hatra research report)
Pad-batch Dyeing of Plant Fibres (Rural Technology Guide)

Jigger Dyeing Machines

About Jigger
Jigg or jigger dyeing machine is one of the oldest dyeing machine used for cloth dyeing operations. Jigger machine is suitable for dyeing of woven fabrics, up to boiling temperature without any creasing . Jigs exert considerable lengthwise tension on the fabric and are more suitable for the dyeing of woven than knitted fabrics. Since the fabric is handled in open-width, a jig is very suitable for fabrics which crease when dyed in rope form.
Some wovens are conveniently dyed on jigger are ,
a. Taffettas
b.Plain wovens
c.Satins
d.Poplins
e.Ducks
f.Suiting and Shirting material.
g.Sheetings etc.
but have limited application on fabrics which are tension sensitive such as crepes , flat crepes , knits , net fabrics and elastomeric warps etc.
Machine Description
The jigger machines have two main rollers which revolve on smooth bearings and are attached to with a suitable driving mechanism , which can be reversed when required. The fabric is wound on one of the main rollers and fed from the other. The fabric move from one roller to the other through the dye liquor trough located at the lower part of the machine . There are various arrangement of guide rollers at the bottom of liquor trough ,and during each passage the cloth passes around these guide rollers .
The concentrated dye liquor is usually introduced directly into the dyebath in two equal portions, which are added just before commencing the first and second ends. The liquor is agitated by the movement of the fabric through the dyebath. Several horizontal spray pipes are fitted across the full width of the trough in order to expedite fabric rinsing.
Live steam injected into the bottom of the trough through a perforated pipe across the width of the jig heats the liquor. Some modern jigs also have heat exchangers for indirect heating.
Covering the top of the jig minimizes the heat loss to the atmosphere, keeps the temperature uniform on all parts of the fabric and minimizes exposure of the liquor and the cloth to air. Minimizing exposure to air is important when using sulphur or vat dyes since these dyes can be oxidized by atmospheric oxygen.
A few meters of leading fabric, similar in construction to the cloth under process, is stitched to each end of the cloth batch , to allow the entire length of the fabric to pass through the dye bath during the dyeing process. When jig processing is completed, the fabric is run onto an A-frame via a nip or suction device to remove extraneous water during unloading.
Modern machines such as automatic and jumbo jiggers have full automation in drive , tension regulation and control , fabric speed and metering, smooth and jerk less stop and start , counters for number of turns , gradual and noiseless reversal, automatic temperature regulation and control etc.

Dyeing process on Jigger

The dyeing process on jigger is regarded as a series of intermittent padding operation followed by dwelling periods on the main roller , during which the dyeing action and diffusion takes place. The factors controlling the rate of dye absorption are:

1.The amount of interstitial dye liquor retained in the interstices of the fabric weave.

2.The exhaustion of the interstitial liquor in the dwell period between successive immersions.

3.The degree of interchange of liquor during one immersion (interchange factor).

In the dyeing on jigger machines the cloth revolves on two main rollers , The open-width fabric passes from one roller through the dyebath at the bottom of the machine and then onto a driven take-up roller on the other side. When all the fabric has passed through the bath, the direction is reversed . Each passage is called an end. Dyeing always involves an even number of ends. The dye bath has one or more guide rollers , around which the cloth travels , and during this immersion achieves the desired contact with the dye liquor. During this passage the fabric picks up adequate quantity of dye liquor , excess of which is drained out but still a good quantity is held in the fabric . During rotation of rollers this dye penetrates and diffuse into the fabric. The real dyeing takes place not in the dye liquor but when the cloth is on the rollers, since only a very small length of fabric is in the dyebath and major part is on the rollers . Therefore the speed of cloth during immersion in dye liquor has a very little effect on percentage of shade produced.

see video click here

Some critical problems related to the conventional jigger dyeing machines ( which are minimized in the modern day machines) The major problems are side-to-centre color variations, called listing, and lengthways color variations, called ending.

Other problems are

• Temperature control from side-to-side and end-to-end of the roll

• Tension control from end-to-end

• Constant speed control from end-to-end

• Prevention of creases

• Prevention of air

Limitations of jigger Dyeing

1.Jigs exert considerable lengthwise tension on the fabric and are more suitable for the dyeing of woven than knitted fabrics.

2.In textile preparation due to the swelling and dissolution of size, which makes the fabric slippery and unstable in roll form.

3The low liquor ratio makes washing-off difficult.

4.There is little mechanical action in a jig machine and it is less suitable where vigorous scouring is required before dyeing.

5.Moiré effects or water marks may arise on some acetate and nylon fabrics because of pressure flattening the structure of the rolled fabric.

New Developments in this Field

Click here

Read More About Jigger Dyeing
Jig Dyeing Machine
Click here 1
Dyeing

Jet Dyeing

Jet Dyeing Machine

A machine used for dyeing of fabric in rope form.Jet dyeing machines came into existence with a purpose to minimise or eliminate the drawbacks of earlier machines like winch , jigger and beam dyeing units.

Principle of the Technology

Jet dyeing is a process that can be used for batch dyeing operations such as dyeing, bleaching, washing and rinsing. In this process, dyeing is accomplished in a closed tubular system, basically composed of an impeller pump and a shallow dye bath. The fabric to be dyed is loosely collapsed in a form of a rope, and tied into a loop. The impeller pump supplies a jet of dye solution, propelled by water and/or air, whch transport the fabric within the dyeing system ,surrounded by dye liquor , under optimum conditions. Turbulence created by the jet aids in dye penetration and prevents the fabric from touching the walls of the tube, thus minimizing mechanical impact on the fabric.

see video jet dyeing machine 

Special Features and Applications

1.Jet dyeing machines can be operated even at high temperatures and pressures. Jet dyeing systems are fitted with cooling systems with the potential for reuse of the warmed water on the next dyeing cycle.

2.Jet dyeing systems operate at a low liquor ratio, or the ratio of the mass of the dye bath to the mass of the fabric in the dyeing machine. Compared to conventional dyeing, typically with a liquor ratio of 1:15 to 1:25, jet dyeing can be operated at a liquor ratio from as low as 1:3 up to 1:6. Consequently, the dyeing operation consumes less water and chemicals, and generates less effluent.
3.Since the dyeing process depends on dye concentration, the lower liquor ratio increases the dyeing rate and dye fixation.
4.Increased dyeing rate results to quicker machine drains and fills, and more rapid heating and cooling. The latter decreases energy requirements for heating the dye bath, which then leads to reduced steam and boiler use, reduced fuel consumption, and fewer emissions to the atmosphere from combustion.
5.The lengthwise tension is less , widthwise tension is absent and fabric achieves better fullness and handle.
6.The frequent movement of fabric round the jet through the machine reduces the tenedncy of crease formation.
Limitations of Jet Dyeing machines
1.High Initial investments and maintenance cost.
2.Limited accessibility during the dyeing process.
3.Foam forming substances are to be avoided.
4.Any roughness of the  inside surface cause damage to cloth.
5.In case of cloth breakage , rethreading is complicated.
Types of Jet Dyeing Machines
After incestifating the dyeing results under different conditions such as development of new fiber blends , different construction fabrics,interaction position of jet,quantity of the dyeliquor to be  present in around the fabric and the type of impact of the dyeliquor on the fabric in the jet area, the following type of jet dyeing machines were developed,
1.Fully flooded jet dyeing machines click here
2.Soft flow Jet dyeing machines Click here for details
3.Low liqour ratio . reel jet dyeing machines. Click here for details .

Watch animated working principle  of jet dyeing  machine.

Beam Dyeing Machines

Beam dyeing machine

A machine for dyeing yarns or fabrics  that have been wound onto a special beam that has evenly perforated holes along its barrel. The dye is forced through the barrel into the yarn/fabric from inside to outside and vice versa. The beam dyeing machines may be capable of dyeing a single beam or to dye multiple beams. The fabric or yarn have better dyeing results because of there is no dimensional changes as well as there is no mechanical force applied to it. The high performance pumps circulate the dye liquor in efficient manner to achieve even dyeing results.
The working principle is same as that of HTHP yarn dyeing machines. The process of beam dyeing is as follows,
1. The fabric or yarn in open width is rolled on to a perforated beam.
2.The beam then subsequently inserted  into a dyeing vessel.
3.The machine is closed and pressurized.
4.The dye liquor is circulated in to out and out to in directions , under pressure and temperature is employed as per the process requirement.
5.The chemicals and auxiliary are injected  as per requirement of the process.

A Thies Beam Dyeing machine

A Thies Beam Winding Machine

Sizing and Desizing

Sizing

Before threads can be woven into fabric, they must be "sized," a process that adds a strengthening and smoothing coating to the thread.Sizing of the warp yarn is essential to reduce breakage of the yarn and thus production stops on the weaving machine. On the weaving machine, the warp yarns are subjected to several types of actions i.e. cyclic strain, flexing, abrasion at various loom parts and inter yarn friction.

Sizing -- the dipping-in-a-hot-chemical-bath stage of the traditional textile process -- allows threads to withstand all the friction and stretching and straining of weaving. The size that soaks into the threads during this process is a solution of starch or PVA (polyvinyl alcohol) -- compounds that coat the threads for lubrication, smooth down any stray fibers, and strengthen the threads.

The sizing of spun yarns: With special reference to the specification, preparation and use of size mixings
Sizing agents
Different types of water soluble polymers called textile sizing agents/chemicals such as modified starch, polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC), acrylates are used to protect the yarn. Also wax is added to reduce the abrasiveness of the warp yarns. The sizing agents may be classified into two categories,
1.Natural Sizing agents such as starch and its derivatives , cellulose and its derivatives and protein based sizing agents.
2.Synthetic Sizing Agents such as polyacrylates ,modified polyesters ,poly vinyl alcohol based and styrol/maleic acid copolymers.

Sizing Process
Warp sizing
Sizing: Materials, methods & machines
On sizing machines, warp thread material is supplied either from a warp beam or from several thread beams with simultaneous take-off. The warp threads may be pre-wetted and impregnated with sizing liquor in a second immersion bath. The threads then pass through combs that separate them and prevent them from gluing together. The parallel threads are then dried on cylinders, rewound and fed to the loom or knitting machine in this form.
Basic requirements for any sizing operation is an even size application over the entire warp. But also the perfect thread tension and the right degree of drying of the warp have a direct impact in the quality of the fabric.


The materials used in sizing: Their chemical and physical properties, and simple methods for their technical analysis and valuation; a course of lectures ... at he Manchester School of Technology
Desizing
The purpose of a desizing process is to remove sizes that have been attached to warp yarns during a weaving process. Prior to the desizing process, therefore, the size analysis should be performed in order to set desizing conditions suitable for the sizes.

Desizing Methods

Different methods of desizing are: A desizing method is selected on the basis of analysis of size , type of fabric , eco friendliness , ease of removal , cost of desizing and effluent treatment.

• 
  
  Enzymatic desizing
  
  
• 
  
  Oxidative desizing  Read about : What are oxidative desizing agents?
  
  
• 
  
  Acid steeping
  
  
• 
  
  Rot steeping
  
  
• 
  
  Desizing with hot caustic soda treatment,
  
  
• Hot washing with detergents

Eliminating the use of water in preparation of textile yarn for weaving and fabric desizing (WRRI bulletin)
Desizing:- process and parameters
Desizing :-Plasma treatment in Desizing Research paper
A presentation on Sizing and Desizing
Common problems in Sizing and desizing
Cotton sizing and desizing in brief

Desizing Efficiency test
Enzymes used as natural and cost effective biocatalysts
Enzymatic Desizing of fabricsWater, energy and chemical recovery from Desizing
Eco friendly wet processing Slide show

Singeing

Also called gassing,Singeing is a part of pretreatment process of fabric and usually a first step after weaving. Singeing is a process applied to both yarns and fabrics to produce an even surface by burning off projecting fibres, yarn ends, and fuzz. This is accomplished by passing the fibre or yarn over a gas flame or heated copper plates at a speed sufficient to burn away the protruding material without scorching or burning the yarn or fabric.
Singeing is a finishing method for smoothing surfaces of fabrics by burning. A gas-singeing machine is normally employed. The gas-singeing machine is typically equipped with four burners, and is capable of singeing one or both surfaces of the fabrics. A water-cooled roller is provided at a location opposite to the burners, thereby enabling singeing to be performed without undermining the strength of even thin fabrics. It is important to set a drain temperature of the water-cooled roller in a range of 50 to 55 C. Cautions are required because a dew-point is generated when the water-cooled roller is cooled down too much, and results in increased amount of remaining fuzz or adhered carbon. The fabric feed speed is preferably set at around 100 to 150m/minute.
Yarn singeing and singeing machines
Common problems in singeing and solution
Singeing Fundamentals