Determination of Abrasion Resistance of Fabric

Determination of Abrasion Resistance of Fabrics

Plain Abrasion Resistance

Apparatus - Universal Wear Tester

Prior to test, the fabric should be Conditioned to moisture equilibrium from the dry side, in the standard atmosphere of 65+-2% relative humidity and 27+-2 deg C temperature. The test should be carried under standard atmospheric conditions.

Method for determination of plane Abrasion Resistance

1. Cut five circular test specimens of 112 mm in diameter, taking care to take specimens from areas containin the same wales or courses in knitted fabric or the same warp or weft yarn in woven fabric.

2. Set the instrument for inflated diaphram test.

3. Place the specimen over the rubber diaphram in smooth condition and clamp the specimen in place without disturbing it.

4. Place the abrasive paper on the abradent plate under sufficient tension to be held smooth and in such a position that the contact pin, reaching through a hole in the abradent is even with the surface of the abradent. In the absence of any specific material specification , zero emery polishing paper should be used as the abradent.

5. Set the air pressure under the diaphram and load on the abradent plate. In the absence of any specific material specifications, the air pressure should be 0.3kg/sq.cm (4 p.s.i.) and the load on the abradent should be 454 gm. Ensure that the air pressure control and contact between the inflated specimen and loaded abradent is in a state of equilibrium before abrasion is started. To ensure consistent inflation of the diaphragm, inflate to a higher air pressure ( 25 per cent) and then reduce the testing pressure.

6. If the unidirectional abrasion is desired, disengage the rotation mechanism of the specimen clamp and bring the specimen into the direction by turning and setting the clamp after the diaphragm has been inflated.

7. In the event that multi-directional abrasion is required, or if no specific indication as to the abrasion direction is given in the fabric specification, engage rotation mechanism of the specimen clamp.

8. Remove pills of matted fibres interfering with proper contact between specimen and abradent during the test if they cause a marked vibration of the abradent plate.

9. If the specimen slips in the clamp or the air pressure does not remain constant during the test or anomalous wear pattern is obtained, discard such individual measurements and test an additional specimen..

10. One of the following methods is selected for determination of end point as per test specifications:

a. Breakage of Thread: Abrade the specimen until all fibres in the centre of the abraded area are worn off so that the diaphragm and abradent head come into contact and the instrument automatically stops.

b. Removing a predetermined thickness of the material. Abrade the specimen using the electrical depth micrometer to determine the automatic end-point for removing a predetermined thickness of the material from the specimen.

11. Unless the continuous changing abrasion head is used, abradent paper is changed after every 300 cycles.

12. Report shall include the following information :

a. Type of abradent
b. Type of abrasion ( unidirectional or multi directional)
c. No. of cycles to reach the end point as determined by electrical contact.

Related Links

Testing Abrasion Resistance For Socks

Properties of Polyester

Tenacity (gpd)	High Tenacity	Normal Tenacity	Staple
Dry	6-7	4.5-5.5	3.5-4
Wet	6-7	4.5-5.5	3.5-4
Elongation (%)
Dry	12.5-7.5	25-15	40-25
Wet	12.5-7.5	25-15	40-25
Density	1.38	1.38	1.38

Moisture Regain

At 65% RH and 70 deg F--> 0.4%

Because of low moisture regain, it develops static charge. Garments of polyester fibres get soiled easily during wear.

Thermal Properties

Polyester fibres are most thermally stable of all synthetic fibres. As with all thermoplastic fibres, its tenacity decreases and elongation increases with rise in temperature. When ignited, polyester fibre burns with difficulty.

Shrinkage

Polyester shrinks approx 7% when immersed in an unrestrained state in boiling water. Like other textile fibres, polyester fibres undergo degradation when exposed to sunlight.

Its biological resistance is good as it is not a nutrient for microorganisms.

Swelling and Dissolving

The fibre swells in 2% solution of benzoic acid, salycylic acid and phenol.

Alcohols, Ketones, soaps, detergents and drycleaning solvents have no chemical action on polyester fibres.

Chemical Resistance

Polyester fibres have a high resistance to organic and mineral acids. Weak acids do not harm even at boil. Similarly strong acids including hydrofluoric acids do not attack the fibres appreciably in the cold.

Uses of Polyester

1. Woven and Knitted Fabrics, especially blends.
2. Conveyor belts, tyre cords, tarpaulines etc.
3. For filling pillows
4. For paper making machine
5. Insulating tapes
6. Hose pipe with rubber or PVC
7. Ropes, fish netting and sail cloth.

Manufacturing Process of Polyester

Manufacture of Polyester

These fibres are also known as Terylene, Terene, Dacron etc.

These fibres are synthetic textile fibres of high polymers which are obtained by esterification of dicarboxylic acids, with glycols or by ester exchange reactions between dicarboxylic acid esters and glycols.

Thus Terylene is made by polymerising using ester exchange reation between dimethyl teraphthlate and ethylene glycol.

Raw Materials

The main raw materials required for the manufacture of Terylene polyester fibres are p-xylene ethylene glycol and methanol.

or Dacron ( Du Pont ) is produced by polycondensation reaction using Teraphthaleic Acid (TPA) and Ethylene Glocol

Manufacture of TPA

P-xylene-- Air, nitric Acid-->P-Toluic Acid--> Teraphthaleic Acid

Manufacture of DMT

p-xylene--Air 200 degC, co-toluate--> Toluic Acid--Ch3OH--> Monomethyl toluate--oxidation--> Monomethyl teraphthalate--CH3OH--> DMT

The use of Dimethyl Teraphthalate is preferred instead of Teraphthalic acid as the purity of the reacting chemicals is essential and it is easier to purify DMT than teraphthalic acid.

Manufacture of Ethylene Glycol

Ethylene--Oxidation with air-->Ethylene Oxide--Hydrolysis-->Ethylene Glycol
or
Ethylene--Hypochlorous Acid HOCl--> Ethylene Chlorohydrin--Alkaline Hydrolysis--> Ethylene Glycol

Production


The polymer is made by heating teraphthalic acid with excess of ethylene glycol ( Both of high priority) in an atmosphere of nitrogen initially at atmospheric pressure. A catalyst like hydrochloric acid speeds up the reaction.

The resulting low molecular weight ethylene glycol teraphthalate is then heated at 280 deg C for 30 minutes at atmospheric pressure and then for 10 hours under vacuum. The excess of ethylene glycol is distilled off. the ester can polymerise now to form a product of high molecular weight. The resulting polymer is hard and almost white substance, melting at 256 deg C and has a molecular weight of 8000-10000. Filaments are prepared from this.

Spinning of Polyester Fibres

The polymer is extruded in the form of a ribbon. This ribbon is then converted into chips.

The wet chips are dried and fed through a hopper, ready for melting. This molten polymer is then extruded under high pressure through spinnerettes down to cylinder.

Each spinnerette contains 24 or so holes. A spinning finish is applied at this stage as a lubricant and an antistatic agent. The undrawn yarn is then wound onto cylinders.

This yarn goes to the drawing zone, where draw twist machines draw it to about four times their original length. This is hot drawn in contrast to cold drawing of nylon filaments.

For the production of staple fibres, the filaments are first brought together to from a thick tow. These are distributed in large cans. The tow is drawn to get correct strength. Then it is passed through a crimping machines, the crimps being stabilized by heating in ovens. It is then cut into specified lengths and baled ready for despatch.

Properties of Nylon 6

Properties of Nylon 6

Nylon 6 has certain advantages over Nylon 6,6,. Firstly the systheisi fo caprolectum is easier than that of Hexamethylene Diamine and Adipic Acid. Therefore it is cheaper to make Nylon 6 than Nylon6,6. Secondly Nylon 6 has greater affinity for acid dyes than Nylon6,6,

Mechanical Properties

Density: 1.14 g/cc
Tenacity: Dry= 4.2-5.8 gpd, Wet=4.0-5.3 gpd
Elongation at Break--> Dry = 24-40, Wet=28-43
Elastic Recovery at 4% extension= 100%
Moisture Regain= 4%
Because of low MR, wet nylon dries quickly.
Melting Point= 215 deg C ( Nylon 66-250 deg C)
It is weakened by prolonged exposure to sunlight.

Chemical Properties

1. It is resistant to most organic acids such as benzene, chloroform, acetone, esters ethers etc.

2. It dissolves in phenol, cresol and strong mineral acids.

3. good resistant towards alkalies.

4. Resistant to inorganic acids

These fibres are cylinderical in shape, with smooth surfaces and without having any markings. The fibres are unifrom in diameter and appear round in cross section.

Uses


a. Tyre Cord Manufacturing
b. Fishing Lines
c. Luxury Yachts
d. Stockings with good fit, sheerness, quick washing and drying properties.

Manufacturing Process of Nylon 6

Manufacturing Process of Nylon 6

Nylon Manufactured in India at present is of this type. This is made from Caprolactum which is made by a series of reactions using products obtained from coal tar

Coal Tar--> Benzene--Chlorine--> Chlorobenzene--> Sodium Phenate--HCL--> Phenol--H2 (Nickel)-->Cyclohexanol--Oxidation Air Fe, Zn Catalyst--> Cyclohexanone--> Cyclohexanone Oxime--H2SO4--> Caprolectum

Polymerisation

Caprolectum is a white flaky solid, melting at 68 deg C and is soluble in water. the polymerisation is carried out in stainless steel cylinders.

Hot Caprolectum is mixed with a suspension of pigment, acid promotor and acid chain stopper. The extent of polymerisation depends upon the temperature of polymerisation. The purpose of acid chain stopper is to stop furthur polymerisation so that a desired density of molten polymer may be obtained.

The molten polymer is extruded into ribbons and cut into chips. These chips are used for the production of continuous filaments.

Melt Spinning

Continuous filaments are made by melt spinning. Dry polymer chips are fed to a melt spinning apparatus, wherein one section of the chips fall, into a melting region where they are heated electrically to 250-260 deg C. The molten polymer flows into a conical section to form a pool, which feeds a spinning pump and spinnerette. The pool is kept under an atmosphere of nitrogen to prevent decomposition by air.

The molten polymer leaving the pump is filtered before entering the spinnerette which is a stainless steel disc having a number of holes, the number and diameter of which determine the type of yarn formed. Before reaching the machine in which cheese is build up, the filaments are moistened with water to ensure dimensional stability of the final packages.

The yarn thus formed is not strong enough and has a very high extensibility. the yarn contains a large number of macro molecules which are unoriented and these must be oriented so as to lie parallel to the length of the fibre to develop full strength. This is done by stretching the yarn to 3-4 times its original length.

Properties of Nylon 6,6

Properties of Nylon 6,6

Strength

The most outstanding property of nylon is its strength and elasticity. The tenacity varies from 8.8-4.3 gpd while corresponding elongation at break varies from 18-45%. The wet strength of nylon is 80-90% of its dry strength and the elongation at break increases by 5-30% on wetting.

Density: 1.14 g/cc

Elastic Recovery

When nylon yarn is stretched 1,2 and 4% with a load of 0.25 gpd for 30 seconds and then released the recovery after 60 seconds is 38, 63 and 73% respectively.

Moisture Regain

Nylon has a moisture regain of about 4% at 65% RH and 70 deg F.

Action of Light

Like other fibres, nylon undergoes degradation and weakens when exposed to lights.

Appearance

Nylon is dull and semi opaque before cold drawing, but on orientation its lustre is greatly incresed. Delustering is done by adding TiO2 in the polymerisation mixture.

Action of Heat

Nylon melts at 262 deg C in an atmosphere of Nitrogen and at 250 deg C in air. When a very hot iron is used for ironing nylon garments, sticking or even fusion may take place. Therefore ironing should not be done above 180 deg C. Permanent set may be applied to Nylon by heat setting with 25 psi pressure with saturated steam. The pleats thus set remian on wearing and washing even in hot water.

Chemical Properties

Nylon is extremely stable chemically. For example dry cleaning solvents, alcohols, aldehydes, ketones, ethers, hydrocarbons, chlorinated hydrocarbons, soaps and synthetic detergents and water including sea water do not affect Nylon.

Also it has got a remarkable stability towards alkali.

Biological Properties

Nylon is not a nutrient for Mildew or bacteria and is not eaten up by moth larvae. But they bite their way up when imprisoned in nylon cloth. It is harmless to human skin.

Manufacturing Process of Nylon 6,6

Manufacturing Process of Nylon 6,6

Nylon 6,6 is made from Hexamethylene diamine and adipic acid as shown in the figure below.



Spinning of Nylon 6,6



The chips of nylon polymer are fed through a hopper A, into a spinning vessel B, on an electrically heated grid ( perforated plate) C. The perforations are so small that the chips do not pass through, but when melted, the liquid can pass.

The molten nylon collects as a pool D, at the bottom of the vessel. This liquid should not come into contact with oxygen or air and hence nitrogen is introduced into the vessel. The molten polymer is kept at a temperature of about 288 deg C and sucked by a pump F, into a spinnerette E. The molten polymer solidifies as soon as it emerges out of the spinnerette. The filament thus formed pass through a colloing zone, in which cold air G circulates directed towards the filaments. The filaments are then passed through a steam chamber H, to wet them before winding on the bobbin L.

Drawing

Nylon filaments as obtained are not very strong. They have to tbe drawn 4-7 times their original length. This is done by cold drawing. The yarn in pulled off from bobbin L through guides M and N, between a pair of rollers O. The speed of rotation of these rollers determines the initial speed. The yarn then goes over a deflector P, and two to three times around roller Q, running at five times the speed than that of O. The yarn subsequently courses through another guide R, and wound on another bobbin which rotates at very high speed, to impart twist in the yarn before being wound.

Properties of Acetate Rayon

Properties of Acetate Rayon

55/20/3s means 55 denier yarn, 20 filament and 3 TPI S side.

Moisture content of sec. Cellulose acetate is 6.5% at 70 deg F and 65% RH.
( Moisture Content= Wt of water in a material /Total wt of material) ( Moisture Regain= wt of water in a material/ oven dry wt of material)
( RH= actual humidity/ humidity of air saturated in water).

Tenacity of Acetate rayon is 1.4 gpd at dry state and 0.9 gpd at wet state.

Elongation at break is 25% in dry state and 35% in wet state

Acetate Rayon is more sensitive to heat. It begins to weaken at 93 deg C. At 175 deg C it becomes sticky and melts at 260 deg C. Like nylon and polyester it is thermoplastic. Thus permanent crimp, pleats and creases can be imparted to the garment under carefully controlled conditions.

Acetate rayon is soluble in acetone, methyl ethyle ketone etc.

Some degeneration takes place when this fiber is exposed to light but not very serious.

It is stable to hot water.

It can also withstand treatment with soap or alkali solution having a pH of not more than 9.5 at temp upto 100 deg C. Therefore it can undergo normal scouring and dyeing operations without affecting the lustre.

It is unaffected by dilute solutions of weak acids but attacked by strong acids. Concentrated organic acids cause swelling

It is resistant to attack by bacteria and fungi. Its low moisture content contributes to resistance to mildew.

It is non toxic and non irritating to skin

Only a few striations ( 2-3) are present in the fibre as can be seen from the longitudinal view. The cross section of the fiber have individual lobes and are round and smooth. It is the smaller number of lobes or serrations of acetate fibres that distinguish the fibre from more numerous serrations of viscose rayon.

Manufacturing Process of Acetate Rayon

Acetate Rayon

We know that

Alcohol + Acid --> Ester

If the cellulose is treated with acetic acid under certain conditions the free hydroxyl groups of cellulose are converted into ester groups.

Manfacture of cellulose acetate

Unlike inthe case of viscose rayon and cuprammonium rayon, where cellulose is dissolved and regenerated, cellulose acetate is manufactured by converting cellulose into a chemical compound of cellulose ( or chem modified cellulose) which is then dissolved in a suitable solvent ( chloroform or acetone) and spun by evaporating the solvent. Thus while viscose and cuprammonium rayons are regenerated fibres, acetate rayon is regenerated modified fibre.

Raw Material

Cotton linters and wood pulp are the most common employed raw materials for the manufacture of acetate rayon

Acetylation Process



The pretreated purified cotton linters are fed into an acetylator ( closed vessel) containing a mixture of acetic anhydride, glacial acetic acid and a small amount of concentrated sulphuric acid. For every 100 kg of cotton linters, 300 kg of glacial acetic acid, 500 kg of acetic anhydride and 8-10 kg of concentrated su;phuric acid may be used. The acetylator consists of a metal tank having a circular door at the top. The door is sealed after adding the mixture of chemicals and cotton linters. A stirrer having many blades rotates in the acetylator to mix the ingredients thoroughly. The acetylation reaction is an exotherimic reation. Heat is removed by circulating cold water through a jacket fitted to the acetylator. The acetylation reation is completed in 7-8 hours at 25-30 deg c. Triacetate is formed at this stage and it is in the form of a suspension in the acetylation mixture called the acid dope.

Hydrolysis ( Partial Deacetylation)

The acid dope from the above process is stored in jars for ageing. Acetic acid, water and sulphuric acid are added and allowed to stand for 10-20 hours. During this period, called ripening period, partial conversion of acetate groups to hydroxy groups takes place. The mixture is then diluted with water and stirred continuously when white flakes of acetate rayon get precipated. The flakes are placed in a centrifuge and the excess water is forced out of the cage through perforations. The flakes are then dried.

Spinning Solution or Dope

Acetate rayon is manufactured by dry spinning. It is dissovled in a volatile solvent (Acetone) to form the spinning solution or dope. This solution is forced through a spinnerette into a chamber in which hot air is circulated. The solvent evaporates leaving filaments of acetate rayon.

The details are as follows. Dried acetate flakes are mixed with three times the weight of acetone in enclosed tanks which are provided with powerful stirrers. The acetate dissolves slowly in the solvent. It takes about 24 hours for the complete dissolution to give a thick clear liquid called dope. The solution is filtered and deareated.

Spinning Process



The dope is spun into acetate rayon filaments on the dry spinning process. The dope is fed from a spinning tank into spinning cabinets. The dope coming out of the spinnerette travels a distance of 2-5 meters vertically downwards to a feed roller, from where it is guided on to a bobbin at a much greater speed than the speed of spinning. This imparts twist to the filaments.

Some Online Resources in Silk: A Practical Guide to Silk Types and Market Terms

Silk is one of those fibres where the same word can mean different things to different people. A weaver may speak in terms of Korea silk, China silk, Desi silk, Katiya, Matka or Ghicha, while a textbook may classify silk into Mulberry, Tasar, Eri and Muga. A merchandiser, therefore, needs both languages: the scientific classification and the market vocabulary.

This note began as a search for useful online resources on silk, especially for terms that are frequently heard in Indian textile markets but are not always clearly explained in standard textile books. The most important lesson is simple: when somebody says “silk”, we must immediately ask: which silk, which yarn route, which cocoon source, and which fabric construction?

India is especially important in this discussion because it produces all four commercially known natural silks: Mulberry, Tasar, Eri and Muga. Tasar, Eri and Muga are generally grouped as Vanya silks, or non-mulberry silks. For a buyer or student, this classification is only the beginning. The real understanding comes when we connect the fibre source with yarn preparation, weaving practice, finishing and market terminology.

Table of Contents

• Why Silk Terms Are Confusing
• The Four Major Natural Silks
• Mulberry Silk
• Tasar or Tussar Silk
• Eri Silk
• Muga Silk
• Important Indian Market Terms in Silk
• Reeled, Spun and Waste-Based Silk
• Buyer’s Checklist Before Approving Silk Fabric
• Care of Silk Fabric
• Related Reading
• General Disclaimer

Visual 1: Silk understanding map showing fibre source, yarn route, fabric character and market terminology.

Why Silk Terms Are Confusing

Silk terminology is confusing because it comes from several worlds at the same time. Some terms come from biology, such as Mulberry, Tasar, Eri and Muga. Some come from yarn preparation, such as reeled silk, spun silk, noil silk and filature silk. Some come from market usage, such as Korea silk, China silk and Desi silk. Some come from Indian craft practice, such as Matka, Ghicha, Katiya, Balkal, Gajji and Mashru.

The problem starts when we treat all these terms as if they belong to the same classification system. They do not. For example, Mulberry is a silk type based on the silkworm and feed source. Matka is better understood as a spun silk yarn or fabric character. Dupion is related to double cocoons and slubbed yarn. Gajji is a fabric construction and market term, not a biological silk category.

A useful way to reduce confusion is to ask four questions. First, what is the fibre source? Second, is the yarn reeled, spun, drawn or waste-based? Third, what is the fabric construction? Fourth, how is the term used in the market? Once these questions are asked, silk becomes much easier to understand.

The Four Major Natural Silks

The four important natural silks in the Indian context are Mulberry, Tasar, Eri and Muga. Mulberry silk is generally associated with smoothness, fineness and lustre. Tasar silk is associated with natural texture, subdued lustre and earthy character. Eri silk is associated with softness, warmth and spun yarn character. Muga silk is associated with Assam, natural golden colour and cultural value.

Silk Type	General Source	Typical Character	Common Practical Use
Mulberry Silk	Bombyx mori silkworm feeding mainly on mulberry leaves	Smooth, lustrous, fine and regular	Sarees, scarves, dress materials, luxury fabrics
Tasar or Tussar Silk	Wild or semi-wild silkworms, often from the Antheraea group	Textured, earthy, slightly coarse and naturally rich	Sarees, dupattas, stoles, furnishing, dress materials
Eri Silk	Eri silkworm, often associated with castor leaves	Soft, warm, woolly and spun-silk-like	Shawls, stoles, winter textiles, comfort fabrics
Muga Silk	Associated strongly with Assam	Natural golden colour, lustrous and durable	Traditional garments, sarees, ceremonial textiles

Mulberry Silk

Mulberry silk is the best-known and most widely used type of silk. It is produced by the silkworm Bombyx mori, which feeds mainly on mulberry leaves. In general trade language, when people simply say “silk”, they often mean mulberry silk unless specified otherwise.

Mulberry silk is valued for its smooth handle, lustre, softness and drape. It is used in sarees, dress materials, scarves, furnishing fabrics, carpets and many traditional Indian textiles. From a merchandiser’s point of view, mulberry silk is usually associated with finer and more regular yarns compared to many wild silks.

However, final fabric quality depends not only on the fibre. It also depends on yarn denier, twist, degumming, weaving, finishing, dyeing and the skill of production. In simple terms, a fabric can be made from mulberry silk and still vary greatly in handle, lustre, strength, transparency and price.

Tasar or Tussar Silk

Tasar silk, also written as Tussar or Tussah, is a non-mulberry silk. In India, tasar is strongly associated with traditional and craft-based fabrics. It is often described as having a slightly coarse, textured, natural and earthy character.

Tasar does not try to imitate the smooth perfection of fine mulberry silk. Its beauty lies in its natural irregularity, subdued lustre and organic texture. Many tasar fabrics have beige, honey, coppery or dull-gold tones depending on source, processing and dyeing.

For merchandisers, Tasar is important because it frequently appears in sarees, dupattas, stoles and dress materials. The buyer should check whether the fabric uses reeled tasar, spun tasar, Ghicha, Katiya or other waste-based yarns, because each of these gives a different fabric character.

Eri Silk

Eri silk is another non-mulberry silk. The name is linked with the castor plant, as castor leaves are one of the important food sources of the Eri silkworm. Eri silk is often called a “peace silk” in popular language because, traditionally, the moth may emerge from the cocoon before the fibre is spun.

Unlike mulberry silk, Eri is generally spun rather than reeled. This is because the cocoon structure does not easily provide one long continuous filament in the same way as mulberry silk. The resulting yarn has a warm, soft, woolly and cottony handle rather than the slick smoothness of filament silk.

This makes Eri particularly interesting for shawls, stoles, winter textiles and fabrics where comfort and softness are more important than high lustre. A buyer should not reject Eri because it lacks the shine of filament silk. Its value lies in a different kind of silk experience.

Muga Silk

Muga silk is one of India’s most distinctive silks. It is associated with Assam and is famous for its natural golden colour, lustre and durability. Muga is not just another silk variety. It carries geographical, cultural and heritage value.

Among Indian silks, Muga has a special identity because it is closely tied to Assam’s textile culture. Its golden tone is natural, and the fabric is often prized for ceremonial and traditional garments. Because genuine Muga is rare and expensive, authenticity becomes very important.

In the market, one may hear expressions such as “Muga look”, “Muga finish” or “Muga colour”. These should not be confused with genuine Muga silk. A merchandiser must check whether the term refers to actual Muga fibre or merely to a colour and surface effect inspired by Muga.

Visual 2: Comparison of Mulberry, Tasar, Eri and Muga silk by source, handle, lustre and typical product use.

Important Indian Market Terms in Silk

Indian silk markets use many words that are extremely useful but not always standardized. Terms such as Katiya, Balkal, Matka, Ghicha, Dupion, Gajji, Mashru, Korea silk, China silk and Desi silk should be understood carefully. Some terms indicate yarn origin, some indicate cocoon condition, some indicate waste utilization, and some indicate fabric construction.

Katiya Silk

Katiya is an important trade term, especially in the tasar silk chain. It may be understood as yarn made from the portion of tasar cocoons left after the reelable silk has been removed. In many tasar production systems, the cocoon does not yield one continuous high-grade filament throughout.

The better reelable portion is taken first. The remaining portion, waste or partially reelable material may then be processed into spun or irregular yarn. Katiya usually implies more irregularity, more texture and a different price-quality position compared to fine reeled silk.

Balkal Silk

Balkal is another term connected with tasar. It is generally associated with the peduncle or anchoring portion of the cocoon. This portion is weaker and less suitable for fine reeling, but it can still be converted into useful yarn.

Balkal belongs to the family of yarns where silk waste or lower-grade cocoon portions are converted into fabric value. Such yarns may show unevenness, slubs, thickness variation and rustic appearance. These are not necessarily defects if the fabric is designed for that look.

Spun Silk

Spun silk is made from short lengths of silk fibre obtained from silk waste, pierced cocoons, floss or other non-reelable material. This distinction is important because not all silk yarn is filament yarn. Some silk yarn is produced in a spinning system, somewhat comparable in principle to cotton or wool spinning.

Spun silk may have less brilliance than continuous filament silk, but it can have a beautiful soft handle. It is useful where a slightly textured, less slippery and more fabric-like surface is desired.

Noil Silk

Noil silk is made from the shorter fibres removed during combing in the spun silk process. It is usually more matte, less lustrous and more textured than regular spun silk. It may resemble cotton or wool in surface character while still retaining the identity of silk fibre.

Silk Form	General Character
Reeled filament silk	Smooth, lustrous and made from continuous filament
Spun silk	Made from shorter silk fibres, softer and more textured
Noil silk	Made from very short fibres, more matte and irregular

Dupion Silk

Dupion silk is reeled from double cocoons, where two silkworms spin together and their filaments become interlocked. Because the filaments cannot be reeled as smoothly as regular cocoons, the yarn develops irregularities, slubs and thick-thin effects.

Dupion is an excellent example of a textile principle: what is technically irregular can become aesthetically valuable. The slubs and cross-lines in Dupion are often the very reason designers like it. It is used in sarees, lehengas, jackets, home textiles and occasion wear.

Filature Silk

Filature silk refers to raw silk reeled by machine, as distinct from silk prepared by hand in cottage or traditional settings. In practical buying, filature silk suggests more controlled reeling, better regularity and more standardized yarn quality.

However, the word “filature” should not be treated as a complete quality guarantee. One must still examine denier, evenness, cleanliness, twist, strength, gum content, dyeing behaviour and fabric performance.

Matka Silk

Matka silk is one of the most important trade terms in Indian silk fabrics. It is generally associated with textured silk yarn made from pierced or waste cocoons. Matka fabrics are usually thicker, textured and somewhat linen-like in appearance.

Matka is not meant to look perfectly smooth. Its charm is in the unevenness. It often carries a handspun quality and rustic elegance. In current trade, however, the term may be used broadly, and the exact production method should be verified with the supplier.

Mashru

Mashru is not always a pure silk fabric, but it is very important in the study of Indian traditional textiles. It is usually understood as a satin weave fabric with a glossy surface, traditionally involving silk or rayon in the warp and cotton in the weft.

Historically, Mashru is associated with a fascinating cultural logic: the fabric gives a silk-like appearance on the outside while keeping cotton in contact with the body. In modern markets, Mashru may be made with rayon, viscose, cotton, silk or blends depending on price and production context.

Gajji Silk

Gajji is commonly associated with a heavy satin weave silk fabric, especially used in Bandhani and tie-dye sarees and dupattas from Gujarat and Rajasthan. Gajji has a dense, smooth and lustrous surface.

It accepts tie-dye effects beautifully because the satin surface reflects colour strongly. In the market, “Gajji silk” may sometimes be loosely used, so the buyer must confirm whether the fabric is pure silk, art silk, viscose or a blend.

Korea Silk, China Silk and Desi Silk

Korea silk, China silk and Desi silk are useful market terms, but they must be handled carefully. They are not the same as the scientific classification of silk into Mulberry, Tasar, Eri and Muga. They may refer to yarn origin, denier range, texture, evenness or local trade convention.

For example, when a supplier says Korea × China, it may mean one type of yarn in the warp and another in the weft. But this should always be confirmed because trade language can vary by region and supplier. A merchandiser should convert such expressions into a technical specification before approving production.

Reeled, Spun and Waste-Based Silk

Many confusions in silk can be reduced if we separate silk into three broad routes: reeled silk, spun silk and waste-based silk. This classification is very useful because it explains why two fabrics can both be called silk but behave very differently.

One fabric may be smooth, lustrous and slippery. Another may be matte, thick, textured and almost linen-like. Both can be silk, but their yarn route and fabric construction are different.

Route	Meaning	Examples
Reeled silk	Continuous filament unwound from cocoon	Mulberry filament, filature silk, some tasar
Spun silk	Short fibres spun into yarn	Eri, spun silk, Matka
Waste-based or leftover silk	Made from pierced cocoons, peduncles, noil or cocoon waste	Katiya, Balkal, noil, some Matka and Ghicha-type yarns

A simple textile equation can be remembered as:

\( \text{Silk Fabric Character} = \text{Fibre Source} + \text{Yarn Route} + \text{Fabric Construction} + \text{Finishing} \)

This equation is not a mathematical formula in the strict scientific sense. It is a practical reminder that fabric character is never decided by the fibre name alone. A silk fabric becomes what it is because of the entire chain from cocoon to yarn to fabric to finishing.

Visual 3: Flow chart showing how cocoon quality and processing route lead to reeled silk, spun silk, noil, Matka, Katiya and Balkal.

Buyer’s Checklist Before Approving Silk Fabric

Before approving any silk fabric, a buyer should not rely only on the name given by the supplier. The name may be useful, but it is only the starting point. The buyer must convert the name into fibre content, yarn route, construction and performance expectations.

1. Is it pure silk, blended silk, art silk, viscose or polyester?
2. Is the yarn reeled, spun, handspun, drawn or waste-based?
3. Is the silk type Mulberry, Tasar, Eri, Muga or a trade-quality term?
4. What is the yarn count or denier?
5. What is the warp yarn and what is the weft yarn?
6. Is the fabric degummed, semi-degummed or gum-retaining?
7. What weave is used: plain, twill, satin, crepe or jacquard?
8. Is the irregularity intentional, as in Dupion or Matka, or is it a defect?
9. Is the colour natural, dyed, printed or finished?
10. What care method is recommended?

These questions help prevent one of the most common buying mistakes: comparing two silk fabrics only by price without understanding fibre source, yarn route, construction and finishing. In silk, a lower price may mean a different raw material, different yarn route, different fabric density or different authenticity level.

Care of Silk Fabric

Silk care depends on the type of silk, dyeing, finishing, embellishment and fabric construction. However, some general precautions are useful. Silk should usually be protected from harsh sunlight, strong alkalis, chlorine bleach, aggressive rubbing and high heat.

Many silk fabrics are best dry-cleaned, especially if they are expensive, heavily dyed, embroidered, printed or embellished. Washing should be done only when the care label or supplier confirms that the fabric is washable.

Risk	Why It Matters
Sunlight	Can weaken silk and fade colours
Alkali	Silk is a protein fibre and may be damaged by strong alkalis
Perspiration	Can affect colour and handle if not cleaned properly
Perfume	May stain or affect dyes and finishes
Rough rubbing	Can cause abrasion, fibrillation or surface damage
High heat	Can affect lustre, handle and dimensional stability

Quick Glossary for Merchandisers

Term	Simple Explanation
Mulberry silk	Silk from Bombyx mori fed mainly on mulberry leaves
Tasar or Tussar	Wild or non-mulberry silk, often textured and earthy
Eri	Spun non-mulberry silk, soft and warm
Muga	Golden silk associated with Assam
Katiya	Yarn from leftover tasar cocoon material after reelable portion
Balkal	Yarn from peduncle or anchoring portion of tasar cocoon
Matka	Textured silk yarn or fabric often made from pierced or waste cocoons
Noil	Short fibres removed during spun silk processing
Dupion	Slubbed silk associated with double cocoons
Filature silk	Machine-reeled raw silk
Gajji	Heavy satin silk fabric often used in tie-dye traditions
Mashru	Satin fabric traditionally with silk or rayon face and cotton back

A Small Note on Authenticity

Silk terminology in the market is not always standardized. Some names are scientific, some are regional, some are trade terms and some are marketing expressions. Therefore, a merchandiser should avoid accepting a fabric name at face value.

A better approach is to combine three forms of knowledge. First, understand the scientific classification: Mulberry, Tasar, Eri and Muga. Second, understand the production route: reeled, spun, handspun, waste-based, filature or cottage-made. Third, understand the market vocabulary: Korea, China, Desi, Matka, Gajji, Katiya, Balkal and Dupion.

When these three layers are combined, silk becomes much easier to understand. The buyer is then able to ask better questions, compare fabrics more fairly and avoid being misled by attractive but vague market names.

Related Reading on Silk Fabrics and Indian Textile Terms

• Silk Fabric Terms Explained — Part 1: A Practical Map for Understanding Silk Fabrics
• Silk Fabric Terms Explained — Part 2: Understanding Silk Yarns
• Silk Fabric Terms Explained — Part 5: Indian Silk Terms — Bafta, Kora, Ghicha and Matka
• How to Know Whether a Fabric is Pure Silk, Blended Silk or Part Silk
• Degummed Silk Yarn: How Raw Silk Becomes Soft and Lustrous

General Disclaimer

This article is intended for textile education, merchandising awareness and general understanding of silk terminology. Silk trade terms may vary by region, supplier and market practice. For commercial buying, quality approval, labelling, export documentation or legal claims, the fibre content, yarn route, construction, processing and care instructions should be verified through supplier declarations, laboratory testing and relevant standards wherever required.

Properties of Cuprammonium Rayon

Properties of Cuprammonium Rayon

Cuprammonium rayon is a regenerated cellulose fibre known especially for its fine filament structure and soft, silk-like handle. Like viscose rayon, it is made from cellulose, but the method of manufacture gives it certain distinctive characteristics, particularly in fineness, appearance, swelling behaviour, and dye absorption.

The following points summarise the important properties of cuprammonium rayon. Some numerical values and older technical descriptions should be verified from standard textile fibre references before academic citation.

1. Extreme Fineness of Filaments

One of the most important characteristics of cuprammonium rayon is the extreme fineness of its filaments. Filaments as fine as about 1.33 denier have been reported as being regularly produced, whereas viscose rayon has often been described in older textile literature as having a usual denier of around 2.5 denier.

This increased fineness is generally associated with the stretching or drawing applied to the filaments during spinning. Finer filaments give the fibre a softer feel and a more delicate drape.

Needs source verification: The specific denier values of 1.33 for cuprammonium rayon and 2.5 for viscose rayon should be checked against a standard textile fibre textbook or manufacturer data.

2. Soft and Silk-like Handle

Because of its fineness, cuprammonium rayon produces a soft, smooth, and silk-like handle. This makes it suitable for lightweight fabrics where softness, fluid drape, and a refined appearance are desired.

In fabric form, this property can be especially useful for dress materials, linings, saree-like drapable fabrics, scarves, and other products where a soft touch is valued.

3. Similarity to Cotton, but with Greater Swelling

Cuprammonium rayon is a regenerated cellulose fibre and therefore has many properties similar to cotton. However, it differs from cotton in some important structural aspects.

The average degree of polymerisation, often written as DP, is lower than that of cotton. Also, a larger portion of the fibre structure is occupied by amorphous regions. Because of this, cuprammonium rayon swells more readily than cotton.

Technical Note:
In textile science, degree of polymerisation refers to the average length of cellulose polymer chains. A lower DP generally indicates shorter cellulose chains. Amorphous regions are less ordered parts of the fibre structure, and these regions are usually more accessible to water, dyes, and chemicals.

As a result of greater swelling and higher accessibility, chemical reactions may take place faster in rayon than in cotton. This is important in wet processing, dyeing, finishing, and chemical treatment.

4. Behaviour on Burning and Exposure to Sunlight

Like viscose rayon, cuprammonium rayon burns rapidly. Older textile sources state that it chars at around 180°C. It is also reported to be degraded and weakened by exposure to sunlight in the presence of oxygen and moisture.

On ignition, cuprammonium rayon may leave behind ash containing traces of copper, due to the copper-based solvent system used in its manufacture.

Needs source verification: The charring temperature of 180°C and the statement regarding copper-containing ash should be checked from authoritative textile testing or fibre chemistry references.

5. Tensile Strength

The average tensile strength of cuprammonium rayon has been reported as approximately 1.7–2.3 in the dry state and 0.9–2.5 in the wet state.

These values appear to come from older fibre-property references. The unit is not mentioned in the original note and should therefore be verified before use in formal academic writing.

Needs source verification: Confirm the tensile strength values and their units. In textile references, fibre tenacity may be expressed in g/denier, cN/tex, or other units.

6. Elongation at Break

Cuprammonium rayon has been reported to show an elongation at break of about 10–17% in the dry state.

This means that the fibre can stretch to some extent before breaking. In practical fabric behaviour, elongation influences comfort, drape, crease recovery, and handling during processing.

Needs source verification: The stated elongation range should be verified from standard fibre-property tables.

7. Moisture Regain

At 70°F and 65% relative humidity, the moisture content of cuprammonium rayon is reported to be about 11%, similar to viscose rayon.

This relatively high moisture regain contributes to comfort in wear, because regenerated cellulose fibres can absorb moisture better than many synthetic fibres such as polyester or nylon.

Needs source verification: The 11% moisture content figure should be checked against standard textile fibre regain tables.

8. Dye Absorption

Cuprammonium rayon has good dye absorption. Its absorption power for direct dyes has been reported to be greater than that of viscose rayon, resulting in deeper shades under comparable dyeing conditions.

This behaviour can be related to the fibre’s accessible cellulose structure and swelling tendency. In practical dyeing, this may affect shade depth, dye uptake, and process control.

Needs source verification: The comparison of direct dye absorption between cuprammonium rayon and viscose rayon should be checked from dyeing or fibre chemistry references.

9. Microscopic Appearance

Under microscopic examination, cuprammonium rayon filaments appear uniform in longitudinal view. Their surfaces generally show no prominent markings.

In cross-section, the filaments are usually round and smooth, though they may occasionally appear slightly oval.

Practical Note:
Microscopic appearance is useful in fibre identification. Cotton shows natural twists or convolutions, while viscose rayon often shows striations. Cuprammonium rayon is generally smoother and more uniform in appearance.

Summary Table: Key Properties of Cuprammonium Rayon

Property	Description	Practical Significance
Fineness	Very fine filaments; older sources mention about 1.33 denier	Soft handle, smooth surface, good drape
Handle	Soft and silk-like	Useful for lightweight, elegant fabrics
Structure	Lower DP than cotton; more amorphous regions	Greater swelling and chemical accessibility
Burning behaviour	Burns rapidly like viscose rayon	Important for fibre identification and safety understanding
Strength	Moderate tensile strength; reported values need unit verification	Affects processing and fabric durability
Elongation	About 10–17% dry elongation reported	Influences flexibility and fabric behaviour
Moisture content	About 11% at 70°F and 65% RH reported	Contributes to comfort and absorbency
Dye absorption	Good absorption of direct dyes; deeper shades reported than viscose rayon	Relevant for dyeing depth and shade control
Microscopic appearance	Smooth longitudinal view; round or slightly oval cross-section	Useful for fibre identification

Conclusion

Cuprammonium rayon is valued mainly for its fine filament structure, soft silk-like handle, good moisture absorption, and attractive dyeing behaviour. Although it shares many properties with cotton and viscose rayon because all are cellulose-based fibres, its greater fineness and smoother microscopic appearance give it a distinctive character.

For students and textile professionals, cuprammonium rayon is a useful example of how manufacturing method, fibre structure, and end-use performance are closely connected. However, some numerical values commonly found in older notes should be verified from reliable textile references before being used in academic or technical documentation.

Suggested References / Sources to Check

The following references may be useful:

1. Textile Fibres: Their Physical, Microscopical and Chemical Properties — J. Merritt Matthews
2. Textile Fibers, Dyes, Finishes, and Processes — Howard L. Needles
3. Physical Properties of Textile Fibres — W. E. Morton and J. W. S. Hearle
4. Manufactured Fibre Technology — V. B. Gupta and V. K. Kothari
5. Identification of Textile Materials — The Textile Institute
6. Textile Science — E. P. G. Gohl and L. D. Vilensky
7. Handbook of Textile Fibres: Man-Made Fibres — J. Gordon Cook
8. BIS, ASTM, or Textile Institute standards on fibre identification and moisture regain
9. Manufacturer technical data sheets for cupro / cuprammonium rayon
10. Academic papers or technical notes on regenerated cellulose fibres and cupro fibre properties

Manufacturing Process of Cuprammonium Rayon

Cuprammonium Rayon


Like Viscose Rayon, cuprammonium rayon is also a regenerated cellulose fibre. Cotton linters are used as the source of cellulose for this rayon.

Ammonical copper oxide solution is also known as cuprammonium hydroxide solution. Cuprammonium hydroxide solution is a solvent for cellulose. When a solution of cellulose in cuprammonium hydroxide is diluted with water or treated with dilute sulphuric acid, the cellulose is regenerated or reprecipitated. By using a spinnerette, filaments of this regenerated cellulose can be produced.

Manufacture of Cuprammonium Rayon

The source of cellulose for this rayon is cotton linters, the purification of cotton linters is carried out in two stages:

a. Mechanical Treatment
b. Chemical Treatment

Mechanical Treatment

The cotton linters are transported in bales in highly compressed state and the object of the mechanical treatment is to loosen them and to remove mechanically admixed and loosly bound impurities such as dust sand, seed residues etc.

Chemical Tratment

The mechanically opened and purified cotton linters are boiled under pressure for several hours with dilute sod ash ( Na2Co3) solution (2%) to which a little amount of caustic soda may be added. The natural fatty matter present in the cotton is converted into soluble substance by the action of soda ash and thus removed from cotton linters.

Dissolution of Cellulose

In this, a solution of hydrated copper sulphate in 300-400 liters of water is introduced in a vessel at ordinary temperature with stirring. Some sugar is also added followed by caustic soda solution to form copper hydroxide.

Ground linters suspended in water are added to the above mixture to form copper cellulose.

The copper cellulose is filtered to remove the liquid, well ground and dissolved in a solution of ammonia in water.

Spinning Solution

By adding certain compounds to the cuprammonium cellulose solution, the solution is made more suitable for spinning. These compounds include glycerine, glucose, tartaric acid, citric acid, oxalic acid, can sugar etc.

Stretch Spinning

In the spinning process, the cuprammonium cellulose solution is discharged through nozzles ( spinnerette) into a solution of sulphuric acid in the form of relatively thick threads which are subsequently pulled( stretched ) to very fine filaments.

Properties of Viscose Rayon

Properties of Viscose Rayon

Moisture Absorption

It absorbs more moisture than cotton. Moisture Content of Coton is 6% at 70 deg F and 65% RH, and for Viscose Rayon it is 13% under the same conditions.

Tensile Strength

The Tensile Strength of the fibre is less when the fibre is wet than when dry. It is 1.5-2.4 gpd in the dry state and 0.7-1.2 gpd in the wet state. For high tenacity variety the values are 3-4.6 gpd and 1.9 to 3.0 gpd.

Elasticity

The elasticity of Viscose Rayon is less than 2-3%. This is very important in handling viscose yarns during weaving, stentering etc when sudden tensions are applied.

Elongation at Break

Ordinary Viscose rayon has 15-30% elongation at break, whule high tenacity rayon has only 9-17% elongation at break.

Density

The density of Viscose rayon is 1.53 g/cc. Rayon filaments are available in three densities: 1.5, 3.0 and 4.5

Action of Heat and Light

At 300 deg F or more, VR loses its strength and begins to decompose at 350-400 deg F. Prolonged exposure to sunlight also weakens the fibre due to moisture and ultraviolet light of the sunlight.

Chemical Properties

Viscose rayon consists of cellulose of lower DP than cotton cellulose. Also amorphous region of Viscose rayon is present to a greater extent, therefore, Viscose rayon reacts faster than cotton with chemicals. Acids like H2SO4 HCL breaks the cellulose to hydrocellulose. Oxidising agents like Na(OCl)2, Bleaching powder, K2Cr2O7, KMnO4- form oxycellulose. Cold acid solutions for a short time do not attack viscose rayon.

Action of Solvents

Textile solvents can be used on Viscose rayon without any deteriorating effect. Viscose rayon dissolves in cuprammonium hydroxide solution.

Effect of Iron

Contact with iron in the form of ferrous hydroxide weakens viscose rayon yarns. Therefore staining, marking or touching of rayon to iron or iron surface should be avoided.

Action of Microorganisms

Microorganisms ( moulds, mildew, fungus, bacteria) affect the colour, strength, dyeing properties and lustre of rayon. Clean and dry viscose rayon is rarely attacked by moulds and mildew.

Longitudinal View

The longitudinal view of these fibres show many striations running parallel to the long axis of the fibre. The cross section of viscose has striated periphery, having many sharp indentations, and cross sectional contours vary from circular and oval to ribbon-like forms.

Some Common Indian Fabrics

Here is a site which gives some details about the fabrics sold in Indian markets ( although the language is a bit colloquial)

Khadi Cotton
Bandani Cotton
Linen
Poplin
Vial Cotton
Teri Rubia
2x2 Rubia Cotton
Lizzy Bizzy Cotton:50% cotton 50% Polyster
Polyester
Bafta Cotton
Lining cotton
Floral cotton
Small Pleads cotton
Medium Pleads cotton
Cotton Silk
Khadi Silk
Bandani Silk
Raw Silk
Pure Silk
Crepe Silk
Polyester Silk
Satin Silk
Crepe Back Satin
Chikan kari
Chiffon:
Georgette
Artificial Silk Sari fabric
Silk Sari fabric
Sari Border
Curtain Fabric
Crepe
Net Fabric
Tissue
Wool

Manufacturing Process of Viscose Rayon

Viscose Rayon

It is a regenerated cellulosic fibre and cellulose is the raw material for producing this man made fibre.

The raw material is obtained from a special variety of wood called spruce.

Manufacturing Process

a. Purification of Cellulose:

The manufacture of viscose rayon starts with the purification of cellulose. Spruce trees are cut into timber. Their barks are removed and cut into pieces measuring 7/8" x 1/2" x 1/4". These pieces are treated with a solution of calcium bisulphite and cooked with steam under pressure for about 14 hours.
The cellulosic component of the wood is unaffected by this treatment, but the cementing material called lignin, which is present in the wood, is converted into its sulphonated compound which is soluble in water. This can be washed off, thereby purifying the remaining cellulose. This cellulose is treated with excess of water. After this it is treated with a bleaching agent (sod hypochlorite) and finally converted into paper boards or sheets. This is called wood pulp, which is normally purchased by the manufacturers of viscose rayon.

b. Conditioning of Wood Pulp:
The pulp sheets are cut by a guillotine to the required dimension and are kept in a special room. Air moves freely among the divisors by means of ventilatorys, the temperature is maintained at 30 deg celcius. In this way the desired moisture content can be had.

c. Steeping Process:
The conditioned wood pulp sheets are treated with caustic soda solution ( about 17.5%). It is called mercerising or steeping. The high DP cellulose (1000) is converted into soda cellulose. The sheets are allowed to soak (steep0 until they become dark brown in colour. This takes about 1-14 hours. The caustic soda solution is drained off and sheets are pressed to squeeze out excess caustic soda solution. 100 kg of sulphite pulp gives about 310 kg of soda cellulose.

4. Shredding or cutting process:
The wet, soft sheets of soda cellulose are passed through a shredding machine which cuts them into small bits. In 2-3 hours the sheets are broken into fine crumbs.

5. Ageing Process:
To obtain almost ideal solution of cellulose, the soda cellulose is stored in small galvanised drums for about 48 hours at 28 deg C. This process is called ageing process.The ageing process is essential. During This process, the DP od soda cellulose is decreased from 1000 to about 300 by oxygen present in the air, contained in the drum.

6. Churning Process or Xanthation:
After ageing, the crumbs of soda cellulose are transferred to rotating, air tight, hexagonal churners or mixers. Carbon disulphide ( 10% of the weight of the crumbs) is added to the mixer and churned together for 3 hours by rotating the mixers at a slow speed of 2 rev per minutes. Sodium cellulose xanthate is formed during this process and the colors of the product changes from white to reddish orange.

7. Mixing or dissolving Process:
The orange product i.e. sod.cell.xanthate is in the form of small balls. These fall into a mixer called dissover which is provided with a stirrer. A dilute solution of caustic soda is added, and the contents are stirred for 4-5 hours and at the same time, the dissovler is cooled. The sod.cell.xan. dissovles to give a clear brown thick liquor, similar to honey. This is called 'viscose' and it contains about 6.5% caustic soda and 7.5% cellulose.

8. Ripening Process:
This viscose solution requires to be ripened to give a solution having best spinning qualities. Ripening is carried by storing the viscose solution for 4-5 days at 10 to 18 deg. The viscosity of the solution first decreases and then rises to its original value. The ripened solutoin is filtered carefully and is now ready for spinning to produce viscose rayon filaments.

9. Spinning Process:

The viscose solution is forced through a spinnerette, having many fine holes ( 0.05-0.1mm) diameter. The spinnerette is submerged into a solution containing the following chemicals.
10% --> sulphuric acid, 18%- Sod sulphate, 1% - Zinc sulphate, 2% glucose, 69% water.

The spinning solution is kept at 40-45 deg celcius.

Sodium sulphate precipitates the dissoved sod. cell.xanthate. Sulphuric Acid converts xanthate into cellulose, carbon disulphide and sod. sulphate. the glucose is supposed to give softness and pliability to the filaments whereas zinc sulphate gives added strength.

The quality of viscose rayon filament formed depends upon:

1. The temperature of the spinning bath
2. The composition of the spinning bath.
3. The speed of coagulation
4. The period of immersion of the filament in the spinning bath.
5. The speed of spinning.
6. The stretch imparted to the filaments.

As a number of filaments emerge from the spinnerette, they are taken together to an eye at the surface of the spinning bath and then guided to two rollers from where they are wound on to a spindle.

Common Yarn Faults in Manmade Fibres

Common Yarn Faults in manmade fibres

1. Slubs:

Slub like thick faults seriously mar the appearance of fabrics made from manmade fibres. The following measures can be taken

A. In Blends with cotton

a. properly select the cotton component
b. ensure proper grinding of wirepoints at cards
c. regularly check the ringframe drafting system.

B. In 100% manmade fibres

a. Ensure adequate number of doublings
b. avoid too wide a roller setting and inadequate weighting on rollers.
c. Select correctly the fibres in regard to their compatibility in length.

2. Crackers

This defect is characterised by the cracking sound produced when the yarn is pulled. The sound is produced due to sudden rupture of fibres curled around the yarn.

- Crackers are caused mainly by the presence of very long fibres due to improper cutting of the two.

- They can also be caused due to high vairability in the elongation of the constituent fibres in the blend.

- Ensure wider roller setting in the back zone, adequate roller weighting and avoid too narrow a spacing between the aprons.

- It is helpful to have low roving twist and higher spinning tension through the use of heavier traveller.

3. Neps

This can also mar the appearance of a fabric

- In man made fibres longer and finer fibres tend to produce more neps.
- Other reasons of neps are
- Excessing beating of fibres in the blow room
- Loading of licker-in or cylinder at card
- Blunt wire points on various carding elements
- excessive lap weight

4. Fluffy Yarn

In general presence of short fibres and proneness to static accumulation tend to produce this defect.

The fault can be corrected by maintaining proper atmospheric conditions and reducing the fluff on roving.

5. Smoky Yarn

- The yarn containing synthetic fibres get smoky through long exposure of the running bobbin in a dirty atmosphere in the ring spinning system.

- Installation of smoke filters in H-plant can correct the problem

- Use of roving build can check this defect.