1. INTRODUCTION TO TEXTILES

Food, shelter, and clothing are the basic necessities for the survival of human civilization. Textiles play important role in making of clothing and making the shelters more comfortable and attractive. They are also used in the production or processing of many items used in day-to-day living, such as food and manufactured goods. An ideal starting place to gain an understanding for textiles is given by definitions of several basic terms.

1.      Fiber

-          A unit of matter characterized by flexibility, fineness and a high length to width ratio.

-          It is defined as thin, fine and hair like substance, natural or manufactured, with a high length to width ratio and with appropriate properties for being processed into a fabric.

2.      Yarn

-          An assemblage of fibers twisted or laid together so as to form a continuous strand that can be made into textile fabrics.

-          It is defined as a linear form of fibers, twisted as a continuous strand that can be made into a fabric.

3.      Fabric

-          A piece of material that have been twisted together to form strands that are suitable for garment construction.

-          A fabric is produced from a yarn by performing mechanical operations as interlacing or interloping or intermeshing process. At this stage the fabric is referred as a grey cloth.

4.      Dying

-          It is a coloration of textile substrates for the purpose of improving the aesthetic features. It is a chemical process of applying color to textile substrates like fiber, yarn, fabric or garment by using natural or synthetic dyes.

5.      Printing

-           It is a chemical process of applying design to the fabrics for further enhancement of aesthetic features by using various techniques.

6.      Filament

-          A fiber of indefinite length

7.      Staple fibers

-          Short fibers or fibers of discrete length

8.      Filament fibers

-          long fibers or fibers of indefinite length  

         Importance of studying textiles to a fashion Designer

·         Acts as a professional career

·         Helps designers to make a sensible choice of choosing fabrics that complement their design

·         Enables designers to make different type of fabrics under fabric construction methods

·         Designers acquire knowledge on how to care for different textile products

·         Designers are able to improve the aesthetic value of different fabrics

2. Classification of textile fibers

Textile fibers are classified into two main classes

i.                    Natural fibers

ii.                  Manmade fibers

NATURAL FIBERS

They occur naturally and are extracted from natural resources/raw materials. They are further grouped into three classes;

i.                    Vegetable/plant / cellulosic

Plant fibers are composed of cellulose i.e. the structural material that gives strength to plants and therefore are classified as natural cellulosic fibers. Vegetable fibers are obtained from the following

a.       Leaves – sisal, manila, abaca

b.      Seeds – cotton, kapok

c.       Stem bast – flax, hemp, jute

d.      Fruits – coir

e.       Husk – coconut

The strands of cellulose fibers in the plants are associated with other natural materials such as lignin, wax, gum and pectin.

The cellulose fibers therefore have to be separated from other materials for it to be useful raw materials for textiles.

ii.                  Animal / protein fibers

Natural protein fibers are obtained from animal sources like hair and other secretion. Fibers include

a.       Covering from such animals as sheep, mohair goat, Cashmere goat, horse, rabbit and camel.

b.       Secretions are obtained from the larva, or worm stage, of the silkworm, which spins the cocoon from which silk fibers are obtained and from the spider which spins fine fibers in making its web.

There are some properties of hair fibers and secretions which are quite similar and on the other hand there are properties which are totally different.

There are two types of animal fibers

a.       Filament length – a continuous length from silk worm

b.      Stable length – short length e.g. Wool & hair obtained from the process of sheering

iii.                Mineral fibers

Fibers obtained from minerals e.g. Asbestos, they are of little significance but are used in specialized materials e.g. fine resistance fabrics.

MAN-MADE FIBERS / MACHINE MADE FIBERS

This are fibers that are made by chemical reactions. Classified into two groups;

i.                    Synthetic

These are textile fibers that are wholly produced from chemical substances. Synthesis (to build up). They are made by combining a chain of smaller molecule to five a larger molecule.

The large molecule is known as polymer and the process is known as polymerization e.g.

AIR + WATER + COAL + PETROLEUM = POLYMER

Example of synthetic fibers; polyester, nylon, acrylic, mod acrylic

ii.                  Regenerated fibers

This are reborn fibers gotten from natural materials, treated with chemicals to give filament fibers e.g. cotton linters & wood pulp treated with chemicals.

Examples of regenerated fibers.

a.       Viscos rayon

b.      Acetate rayon

c.       Tri-acetate

3. GENERAL PROPERTIES OF FIBERS

i.                    Tenacity

They must possess sufficient strength to be worked on and processed by machine.

ii.                  Abrasion resistance

Ability of a fiber to withstand the rubbing in everyday use

iii.                Flexibility /Pliability

ü  Ability of the fibers to bend without breaking.

ü  Fibers must be pliable in order to form yarns, fabrics that can be creased and have quality of draperbility and ability to move with the body.

iv.                Elastic recovery

Ability of fibers to recover from strain, coming back to its original shape i.e. Ability of the fiber to return to original length after tension that produced elongation and after the fiber has been released.

v.                  Elongation

 The ability to be stretched or lengthened.

Benefits of stretch in fabric during wear

-          Comfort

-          Greater freedom of motion

-          Ductility i.e. material can change shape without breaking

-          Durability

-          Stretch fabrics give best fit

vi.                Stiffness / rigidity

Opposite of flexibility is the resistance to bending or creasing.

vii.              Cohesiveness/Spinning quality

Ability of the fiber to stick together in the yarn    manufacturing processes

viii.            Uniformity

The fibers must be similar in length and width in the spinning quality and flexibility

ix.                Lustre

Refer to the gloss / shine, that fiber possess

Determines the fiber’s brightness/dullness

x.                  Color

ü  Natural color of fibers varies from pure white to grey and black

ü  Natural fibers exhibit the greatest color differences

ü  Man-made fibers are usually white or off- white as they are manufactured

xi.                Moisture regain and absorption

This is the ability of a fiber to take in moisture from air given the standard condition or temperature and moisture. Sometimes called hydrophilic or hygroscopic. 

ü  Fibers have a certain amount of water as an integral part of their structure

ü  Fibers with good moisture regain will accept dyes and finishes more readily than those with low moisture regain

xii.              Dye ability

Ability of fibers to readily accept dyes.

xiii.            Resiliency

Ability of a fiber to return to shape following compression, bending or similar deformation

xiv.            Flammability and thermal reactions

The burning characteristics of fibers are important in determining care and use of textile products.

xv.              Thermo-plasticity

Ability of fibers to soften and be molded under application of heat.

xvi.            Versatility

Ability of a fiber to produce a wide range of products.

ASSIGNMENT 1: Learners to draw the classification table of fibers

                            Differences between Natural and Man-Made Fibers

4. PROCESSING OF NATURAL FIBERS-natural fibers

This majorly consist of Cotton, Linen, Silk, wool and jute

                                                     COTTON

ORIGIN

The word cotton is derived from the Arabic word qoton or qutun, which means a plant found in conquered land. Cotton is fiber that grows from the surrounding surface of seeds in the pods, or balls of a bushy mallow plant. It is composed basically of a substance called cellulose.

Cotton is still the fiber used mostly in the world. People around the world mostly use cotton as the main fiber. They prefer garment made from cotton than any other fibers. More over cotton is one of the best fiber suitable for our climate. The main raw material used for cotton fabric is cotton pod. Ancient records shows that garments made out of cotton were used by Indians also.

Greek Philosophers refers that Indians were best in growing, spinning and weaving pure cotton fabric between 3000 BC-1500AD. Marco Polo on his voyage to our country states that the world’s finest cotton fabrics were made from India. Cotton fabrics from India, are fine and of outstanding quality. Archeological findings at Mohenjo-Daro suggest that the cotton plant was already domesticated and being used for making textiles over 5000 years ago.

Growth of cotton

·         Cotton is planted in the spring, when temperatures reach around 60 degrees, and grows best in fertile, well-drained soil.

·         The most favorable conditions for cotton belt are North America, Egypt, India, china and United States

·         Cotton grows on bushes of 3-4 feet height

·         It takes about six to eight weeks, depending on the weather, after planting for the bloom or flowers to appear and fall off

·         When the blossom falls off the ball begins its growth

·         Inside the ball are seeds from which the cotton fibers grow. They are also called seed hair

·         When the ball is ripe i.e. reach maturity stage, it splits open and the fluffy white cotton stands out from the ball

·         The cotton is picked up with the help of machine or by hand

·         After harvesting the cotton fibers must be separated from seeds and this is done by large machines known as Gins. This process helps to remove unwanted impurities such as leaves, twigs and stalks. Ginning machine are of two different types:

i.                    Saw gin – the teeth of the rotating saw pass through a metal grating slits which are too narrow to allow passage of other larger mater.

ii.                  Roller gin – used for longer type of cotton consisting of roller covered with leather to reach the fiber and cling as the roller revolves a knife set to its surface scrapes away and removes the seed and large impurities.

Cotton bales are then picked in bales weighing about 200kg-250kg, cotton has to be graded readily for scale and this assessment is made by skilled inspectors who consider the staple color and the number of impurities.

The quality of cotton varies according to:

-           Variety of plants

-          Growing conditions in the area

NOTE: The fluffy white mass of cotton or seed hair which is in the seed is known as Lint. A few days a second shorter and darker growth forms and sticks to the seed, this second growth is known as Linters.

There are two types of picking machines:  

i.                    The picker – pulls the fibers from the balls.

ii.                  The stripper – pulls the entire ball from the plant.

GROUPS OF COMMERCIAL COTTON

There are three types of cotton classified in their length of fineness

i.                    Long fine cotton – fibers are 3.3cm-6.4cm long, these are the top quality longer staple cotton and are well known types such as Egyptian and Sea Island. They are not easy to grow, are expensive and used for fine cotton fabrics.

ii.                  Standard cotton – fibers have staple length of 2cm-3.3cm, this forms bulk of cotton and include American upland cotton. Are used for standard fabrics such as poplin.

iii.                Coarse cotton – are fibers with staple length of less than 2cm they form the coarse grade cotton which includes Asiatic and Indian fiber. Are used for low quality fibers sometimes blended with wool for blankets and carpets.

Manufacture/production of cotton

Cotton fibers undergo the following processes before used in clothing construction:

1.      Ginning

·         The seeds are removed and fibers are pressed into bales

·         The process is carried out by a machine

·         The seeds removed are used for production of oil, soap and cosmetics

·         The fiber at this stage is called LINT

2.      Bailing

·         Cotton is pressed/compressed into bales

·         The bales are wrapped with jute cocking

·         The bales are supplied to mills

3.      Opening and breaking/picking/bale breaking

·         The bales are opened and loosened together, the cotton is beaten to remove impurities.

·         Fluffing of fibers which was tightly packed into bales is also carried out

·         Layers of fibers from several bales are fed into an opener and emerge like a fluffy mass of 10-15 times as bulky as compared to the bale

·         The picking machine continues the loosening and cleaning of the fibers and a thick white sheet is formed which is called  A LAP

·         Blending and mixing is also done at this point i.e. fibers from different bales are mixed promotional in the blow room.

4.      Carding

·         Carding machines that have wire-like comps further remove impurities e.g. seeds, stocks, leaves etc.

·         While this is happening cotton is drawn into a lap which passes between two cylinders covered with clothing, the clothing is heavy fabric with many specialties bent wires.

·         Individual fibers are straightened and made parallel

·         Cotton is thoroughly cleaned off all dirt and foreign matter

·         There is sorting of long and short fibers and the fibers emerges from the carding rolls as a thin sheet.

Objectives of the carding process

i.                    To remove impurities and fiber entanglements.

ii.                  To separate fibers from others in its original toughs.

iii.                To mix fibers together to provide uniform distribution.

iv.                To form a bulky silver of overlapping, piecing aligned fibers.

v.                  To remove short fibers in naps (small entangled knotted fibers) forming a compact.

vi.                Ball which is not likely to be dis-entangled by drafting.

5.      Combing

·         It is a continuation of the carding process. If cotton is to be used for making fine materials it’s combed at this stage by fine needled. It removes the short and keeps the rest of the fibers nearly parallel and fluffy.

·         The fibers are long staple, fine, uniform strong and of good quality

6.      Drawing

·         Means bringing together many card silvers which are then fed into two pairs of rollers which further stretch the silvers to decrease diameter. The slivers are fed into drawing rolls at the same time, this is a continuation of blending which began in the opening process.

·         The drawing frame consists of four sets of cells with each travelling at a faster speed than the previous set.

·         The difference in the speed causes elongation of the sliver and reduction in the diameter.

7.      Roving

·         This is similar to drawing but the diameter of the sliver reduces further and slight twist is given and wounded on the bobbins that are fed into the spindle. It’s done on a speed frame the silver is now called roving.

8.      Spinning &weaving

·         More twist is added to the yarns to make it strong and fine, can be doubled at this stage. In factories cotton is spun into yarns on large spinning machines it is fed to the spools which are sent for weaving to the weaving mills.

There are six methods of spinning.

i.                    Ring spinning

ii.                  Mule spinning

iii.                Cap spinning

iv.                Open end spinning

v.                  Foyer spinning

9.      Beaming / winding

The last stage where yarns are wound onto various yarn holders i.e. the spools, bobbins and warp beams in preparation for weaving.

10.  Dyeing &finishing

·         The woven fabric is dyed with different colors

·         Finishing is given to the fabric to improve its appearance

·         The bobbins are placed in the spinning frame where they are passed through several sets of rollers running at successively more speed and finally drawn out to yarn of desired sizes.

                              COTTON IDENTIFICATION

a.      Microscopic test

i.        Under a microscope, the longitudinal view of cotton fibers look like a twisted ribbon or a collapsed and twisted tube with a rough surface

ii.      Under the cross-sectional view cotton fibers are flat, kidney or bean shaped with lumen parallel to the larger direction.

b.      Mercerization is carried out where fibers are put in caustic soda to open the lumen and twist the convolutions, this causes swelling of fibers which improves dye intake. Cotton does not have a natural twist. The finishing process makes them swollen straight, smooth and round with a shining surface

Cross sectional view of mercerized is circular with no or less lumen.

Cross sectional view/morphology                     longitudinal view/morphology.

c.       Burning test.

·         Cotton ignites and burns quickly, it flares up with a yellow flame, smoke is white or light colored and smells like burnt paper or leave and it leaves a small amount of fluffy grey ash.

NOTE: The test does not apply when cotton is mixed or blended with another fiber because other fibers react differently to burning.

   Physical properties

1)      Color - Natural cotton is off-white when harvested but can be bleached white, dyed or printed to any color of choice.

2)      Lustre -Natural cotton is dull due to the twisted nature of the fiber but it can be modified through mercerization. Mercerization is a process that makes cotton take dye better and increases its Lustre

3)      Elongation and elastic recovery- It has poor elongation and elastic recovery properties but is better than linen. Poor elastic recovery contributes to the creasing property of cotton Stability/strength

4)      Cotton shrinks after the first wash but doesn’t do so with subsequent washes. Unless it has been pre shrinked during manufacture, it is advisable to shrink them by clumping or immersing them in water before making them. Mercerized cotton is more dimensionally stable than un-mercerized cotton.

5)      Resiliency-Has poor resiliency and creases badly without recovery, unless treated with resin to be crease resistant.

6)      Absorbency- Cotton is absorbent and regains moisture from the atmosphere.

                    - It’s water absorbency property contributes to;

a)      Lack of static build-up

b)      High water-based dye affinity

c)      Comfort in wear

d)     Longer drying duration

7)      Cotton is strong - It’s stronger when wet than when dry and becomes heavier when wet. It is stronger when wet because extra hydrogen bonds are formed, the fiber can hence withstand all stresses of production i.e. weaving, processing, garment construction etc.

8)      Warmth - Cotton is warm to the wear as it holds air around the skin of the wearer which acts as an insulator from the cold weather elements.

9)      Hygroscopic moisture: Cotton does not hold moisture so well as wool or silk but absorbs it and so feels damp much more quickly and spreads rapidly throughout the material.

Thermal properties

·         Cotton fibers have the ability to conduct heat energy, minimizing any destructive heat accumulation hence suitable for night dresses.

·         Cotton fibers can withstand high temperatures i.e. hot ironing it’s a good conductor of heat.

·         Excessive application of heat energy causes it to scotch and burn i.e. long exposure to sunlight.

Chemical properties

1)      Effects on Acids

·         Strong acids will destroy the fibers immediately e.g.  Hot dilute acids or cold concentrated acids

·         Dilute inorganic acids will weaken the fiber and if left dry will rot it.

·         After treatment with acidic solutions cotton articles should be thoroughly rinsed in water.

2)      Effects on Alkalis

·         Cotton has an excellent resistance to alkalis

·         It swells in caustic alkalis (NaOH) but does not damage it

·         It can be washed repeatedly in soap solution without a problem

3)      Effects on organic solvents

·         Cotton has high resistance to normal cleaning solvents

·         Cotton is dissolved by the copper complexes e.g. cup ammonium hydroxide

4)      Effect of bleaching: These have no effects until used in uncontrolled conditions with heat.

5)      Effect of sunlight and weather: Ultraviolet rays of sunlight affect the strength of fiber and change the color to yellow when exposed to prolonged period.

6)      Affinity to dyes: Cotton takes in dyes better than linen but not as readily as silk and wool.

Biological properties

·         Cotton acts as food for micro-organisms which feed on the cloth and damage it, mildew and bacteria damages cotton.

·         Resistance to insects: Moths and beetles will not affect or damage the cotton. But the sliver fish eats the cotton cellulose.

Advantages of cotton

i.                    They are natural fibers free from chemicals

ii.                  It does not irritate the skin i.e. comfortable

iii.                They are a great option for hot weather

iv.                Dyes and prints well

v.                  Drapes well

vi.                Strong hence durable

vii.              Easy to handle and sew.

Disadvantages of cotton

i.                    Its flammable (burns easily)

ii.                  Has low resilience creases badly.

iii.                Dump clothes tend to develop mildew, requires airing for storage.

iv.                High degree of shrinkage.

v.                  Weakened by perspiration and the sun

vi.                It saturates so quickly and it’s not water proof.

                                           COTTON FABRICS

1.      Flannelette and flannel -A soft napped cotton fabric which is warm to wear due to the fact that the nap traps a layer of air between the body and the cold outside

2.      Organdie- It is a thin light fabric in plain weave with a very stiff finish. It is made from good quality combed yarn.

3.      Muslin- It is cotton made of plain weave. It is made in a wide range of weights from delicate sheers to coarse sheeting

4.      Ginger- A clothing fabric usually of yarn-dyed cotton in plain weave

5.      Poplin-Has a rib weave and it’s used for night wear, underwear, blouses and babies cloth

6.      Gingham-Used for shirts, blouses etc.

7.      Terry cloth-Used for toweling i.e. making bath towels, baby napkins, night’s gowns and bed covers

8.      Laces –Many are still made from cotton dresses

9.      Lawn – has higher count very fine for lining clothes, underwear, blouses, handkerchiefs and petticoats.

10.  Percale – are also higher counts used in sheeting fabrics

11.  Broad cloth – has finer and closer ribs.

12.  Dimitri – has twill weave

13.  Jeans

14.  Damask – has large woven designs mainly used for table clothes and dresses

15.  Cotton jersey – netted cotton fabrics are mainly for men underwear, t-shirts and vests

16.  Corduroy – lorded velveteen cloths whereby the weft ply forms the cords or ribs

17.  Calico – medium weight fabric used for sheets, aprons, overalls, cushion covers, pillow cases etc.

    FINISHES FOR COTTON FABRICS

A fabric finish is applied to a fabric once it has been made to improve its appearance, feel or other properties

Fabric finishes are classified into 2 categories:

Chemical finishes-Chemicals are used followed by curing or drying. It’s also known as wet finish

Mechanical finishes-They usually involve specific physical treatment to a fabric surface to cause a change in fabric appearance. It’s also known as dry finish

The finishes applied may be Temporary, Permanent or Renewable.

Chemical finishes applied to grey

Special finishing techniques are done to improve function and properties of cotton. Example

·         Mercerizing - Cotton fibers are treated with a solution of sodium hydroxide, making them stronger, softer and more lustrous

·         Crease resistance - Resin-based finish is used to reduce how much the fabric creases

·         Stain resistance - A silicone-based spray is used to prevent grease and dirt clinging to the fibers

·         Flame resistance – It’s used to slow down the rate of burning of fibers in case of fire

·         Water repellency - Silicones are applied to the fabric’s surface to temporarily prevent water being absorbed by the fabrics. PVC can be used to coat the fabric to make it permanently water proof but doesn’t allow the skin to breathe

Mechanical finishes

·         Calendaring – It’s used to make one or both surfaces of the fabric smooth and shiny

·         Sulfurizing or Pre-shrinking- Prevents a fabric and the produced from shrinking after production

·         Napping –Used to make the fabrics soft, warm, and absorbent

·         Singeing – It’s designed to burn off the surface fibers from the fabric to produce smoothness.

·         Embossing – Used to add decoration on cotton fabrics

                                    Cotton blends

Among the various types of blends available in market today are polyester, cotton terycotton, silk, linen cotton, viscose rayon and cotton- nylon

Reasons of blending are:

·         To facilitate processing.

·         To improve properties like dimensional stability.

·         To produce better performance.

·         To improve texture, hand or feel appearance of fabrics.

·         To produce multi-color fabrics.

·         To reduce cost.

Characteristics of cotton fibers and products

·         Comfortable to wear

·         Resists build up static electricity

·         Wrinkles easily

·         Can withstand heat, detergents and bleach

·         Can be damaged by mildew

·         Can be damaged by prolong exposure to sunlight

 Uses of cotton fibers and fabrics

·         Used in hospitals  for bandages, gloves, surgical purposes

·         Cotton is used to make varieties of sewing threads

·         Used to make household products like mops and wipes

·         For making furnishing e.g. carpets

·         Garments are also made from cotton for men, children and women.

-          Children wear since they are warm and dry fast

-          Uniforms and dresses since they are strong.

-          Underwear because they dry rapidly, absorbent and warm.

·         The inside seed is used as cooking oil

·         For making furnishings e.g. carpets

Care of cotton fabrics

·         Wash by friction method (rubbing &squeezing) using soapy water unless loosey colored or given a special finish that will be damaged by heat.

·         Sterilize the fabric by boiling in hot water

·         Rinse in cold water to freshen the fabric

·         Drip dry to minimize creasing

·         Iron with hot iron

LINEN FIBERS

Growth / cultivation

Flax is a bast fiber obtained from the stems or stalks of the flax plants. Flax is an annual plant that is grown for its fiber, seeds or both. Flax is the oldest fiber on record, first grown by the Egyptians having along the banks of the Nile. Other sources lay claim to the earliest usage of flax to be in the Stone Age. The term “linen” is often misused, being applied to fabrics that simply look like linen, or being used as a general term for sheets, towels, and tablecloths.

Linen is a natural yarn or fabric which comes from the fibers of the stalk of the flax plant ("most useful linen"). Flax plant requires a temperate climate and adequate rainfall. It has a single slender stem, with no branches apart from those bearing its flowers. The plant is sown in April, produces delicate blue flowers in June and is harvested in August. The violet blue flax flower is a sign of the finest fibers

Other varieties of flax have a pinkish white blossom and produce poorer fibers and yarns. There are three degrees in the ripening of the flax grown to produce linen: green, yellow and brown

·         Flax that is pulled too early is green in color - Produces very fine but weak fibers.

·         Overripe flax is brown - The stems are strong but brittle but produce too high proportion of undesirable short fibers ("'tow").

·         When the flax is yellow, the fibers are long and supple, and therefore ideal for further processing

The growing season takes about 85-100 days. When the flowers are ready the plants are pulled up by the roots. The fibers then have to be separated from the other tissues in the stem and this is carried out by a fermentation process called Retting.

Major producers are USSR, Portland Belgium, France, Holland, Romania, Northern Island and Netherlands.

Manufacture /production/processing of Linen (Flax)

1)      Pulling and rippling

This as a process aimed at removing the seeds and seed pods from the plants i.e. the stalks are combed by spikes called Ripples to remove the leaves and seeds.

Fibers may be pulled by hand or use of mechanical pullers, roots are pulled intact as the fibers extend below the ground, after drying the plant is ripped i.e. it’s pulled through special thrashing machine that removes the seed pods on force. This is done by thrashing where by whereby hand thrashing is employed in small scale farm.

2)      Retting process

Sun, dew and rain help detach the fibrous skin from the central wood, the stems take on a beautiful russet hue.

To obtain the fibers from the stalk the outer wood portion must be rotted away. It’s known as Retting. It’s the process that softens and separates the fibrous core of the plant from the outer layer which is composed of woody matter

·         Retting is carried out in the following ways:

                                                        i.            Dew retting

                                                      ii.            Pool retting

                                                    iii.            Tank retting

                                                    iv.            Stream retting

                                                      v.            Chemical retting

i)                    Dew retting

It involves spreading of flax on the ground where it’s exposed to the action of dew and rain to bring about fermentation and provides favorable conditions for bacteria activities

This natural process gives uneven results but provides the strongest and durable linen, it requires 4-6 weeks

ii)                  Pool / dam/ river retting

It is a process whereby flax is packed in shelves and immersed in a pool of stagnant water and bacteria in the water rot away the outer stalk covering. Time required is 2-4 weeks for the woody cork to soften. Produces good quality fibers

iii)                Tank retting

It utilizes large tanks in which the flax is stacked and the tank is filled with water under controlled temperatures of 22-33 degrees Celsius which increases the speed of bacteria action. It requires 4-5 days.

Its uniform in strength and light in color, it gives very lustrous fibers

iv)                Stream retting

The flax is stacked along banks of slow moving streams, it’s a slow retting process but reduces the unpleasant smell associated with dew and pool retting. Produces good quality flax

v)                  Chemical retting

Special Chemicals e.g. dilute sulphuric acid are put in banks and stalks are submerged/immersed in a few hours, it is done used to loosen the flax from the stalks. It is usually limited to experiments because chemicals weaken the fibers.

3)      Breaking and scutching process

After retting is complete, the fibers are rinsed and dried, Stalks are bundled together and passed between fluted rollers in a breaking machine that brake the outer woody covering into fragments without damaging the fibers running through the stem.

The fibers are then scutched to separate outer covering into usable fibers. Scutching is the process of dressing flax.

Scutching involves scrapping a small wooden knife down the length of the fibers as they hang vertically, pulling the broken woody bits away from the fibers

Breaking flax fibers                                             scutching process

4)      Hackling

It is a combing process to straighten and parallelize the fibers. This separates short fibers called TOW found in table linen and dish cloths, from the long fibers known as LINE used in the fine table clothes, handkerchiefs etc. and parallel fibers called SLIVERS.

It uses a hackle which is a bed of pins which are usually used to comb the fibers for drawing and aligning purposes

                                      Hackling process

5)      Spinning process

The flax fibers are drawn into required thickness of yarns and twist is impacted for extra strength. The twisted yarns are then wounded onto bobbins or spool to be used in fabric construction processes.

Flax fibers are span either wet or dry, wet spinning is considered to give the best results.

6)      Weaving

Linen yarn is generally woven into sheets. This is a process of interlacing the wefts and warps at right angle to form fabric in a loom

                                    LINEN/FLAX IDENTIFICATION

1)      Microscopic property

Under a microscope linen looks like having sided cylindrical filaments with fine pointed edges. The filament show nodes at intervals, it looks like bamboo stick having joints that result into a little unevenness. The central canal/Lumen casts a shadow giving a slightly darker effect down the Centre

Cross-sectional view clearly show lumen and the thick outer wall of a polygon shape. The immature fibers may be oval and have larger lumen than mature fibers.

            Longitudinal  view                                             Cross –sectional view  Linen fibers

2)      Burning test

Linen takes longer to ignite, produces ashes that are very brittle, smells like burning grass

Linen is easily extinguished by blowing on it as you would a candle.

Physical Properties

·         Lustre-Flax fibers have a high nature lustre with a high shin

·         Tenacity –flax fibers are durable and easy to maintain because of their high fiber strength

·         Pliability/flexibility-flax has low flexibility and this may reduce serviceability where frequent bending is required in use

·         Elastic recovery and elongation-It has very little elacisity

·         Color –flax fibers are yellowish to grey in color

·         Resiliency –They have low resiliency,they are stiff and posses little resiliency however finishes can be applied to offset this disadvantage

·         Moisture regain-flax has a standard moisture regain of 12%

3)      Thermal properties

·         Flax is highly resistant to decomposition by dry heat and withstand temperatures of upto 150 degrees celcius

·         Prolong exposure above 150 degrees celcius  will result to gradual discoloration

·         However fabrics may be ironed safely with temp.of 260 degrees celcius

4)      Chemical properties

·         Effects of Acids-linen is damaged by highly densified acids but low dense acids does not affect it if it is washed instantly after aplication

·         Effects of Alkalis-Linen has an excellent resistance to alkalis.that is,it is not affected by the strong alkalis

·         Effects of Bleaching Agents-Cool chlorine and hypo-chlorine bleaching agents does not affect the Linen fiber properties

·         Effects of organic solvents-linen has high resistance to normal organic solvents

·         Dyes –it is not suitable to dye but can be dyed by direct and vat dyes

5)      Biological properties

·         Effects of micro organism-linen is attacked by fungi and bacteria

      - Mildew feed on linen hence rotting and weakening the materials

·         Effects  of insects-linen is not attacked by moth grubs or beetles

                                    LINEN FABRICS

1)      Damask – It usually comes in one color and is often used for linen napkins, linen tablecloths, linen table runners and other home textiles

2)      Toweling –This are all types of Linen that are used to produce towels and comes in different sizes.

3)      Sheeting linen- It is a heavy fabric made wide so that it can be used to manufacture sheets. It is also a lovely fabric for suits, dresses and other linen clothing.

4)      Loosely woven linen- The fabrics are designed to be highly absorbent. They are commonly used for diapers and sanitary towels

5)      Glass toweling- This type of linen fabric has a loose weave that makes it more absorbent and better suited for cleaning purposes, but also slightly less durable

6)      Linen suiting-comes in twill weave,used mostly for drapery

             Finishes  applied to linen/flax

The ultimate step in fabric processing, finishing includes treatments designed to change the appearance of the yarn or linen fabrics and giving them the values sought by consumers in terms of comfort, aesthetics and functionality. Four categories are distinguished: bleaching, dyeing, printing and finishing.

·         Beetling

-          A mechanical treatment that uses  beetlers/fallers to give fabrics a flattened effect

-          Its also used to add flexibity and smoothness

·         Calendering –Used to impact different degree of lustre to the fabric

·         Mercerizing –Used to add lustre and smoothness of linen fibers

·         Sizing   

-          A solution of starch or resin is used to fill up spaces between yarns

-          Applied to increase weight,body and luster

Advantages of linen fabric:

• Excellent strength gains strength when wet
• Hydrophilic: absorbs water and dries quickly
• Cool in warm weather
• Washable
• Withstands very high temperatures when washing and ironing
• No static, pilling, or lint problems
• Unique texture from the thick-and-thin pattern of the fibers

Disadvantages of linen fabric:

• Like cotton it wrinkles very easily
• Fair abrasion, low durability
• Poor drape and elasticity
• Expensive

             Characteristics of linen products

·         Linen is affected by mildew  when exposed to moisture

·         Withstand very high temperatures therefore hot iron can be used to iron Linen item

·         Its resistance to alkalis but strong acids affect linen

·         Has natural stifffeness and becomes crisp when it’s dry

·         It lacks pliability and therefore cracks easily if folded on the same place many times

·         Its absorbent and water spreads quickly over the surface of the fabric.

·         Its lustrous

·         Linen resists soiling

·         They are resistance to moths

·         No resiliency

·         Its stronger when wet than when dry

                Uses of linen fabrics

·         They are used for wears e.g dresses and suits

·         Used for household uses such as table clothes, napkins, runners, pillow cases, drapes and curtains.

·         Used in hospitals for patients clothing

·         Industrial uses linen for lace, sewing threads, leather items, shoes and boots.

·         Linen comes from the stalk of flax plant which is a plant fiber used especially for making ropes

·         Linen can be easily dyed and the color does not fade when washed

·         Linen seed produces linseed oil for food, explosives, petrolium, medicine.

ASSIGNMENT :Discuss FIVE (5) ways of caring and storing of Linen/flax products

OTHER PLANT FIBERS

1.      Coir (from Malayalam kayar, cord) is a coarse fiber extracted from the hairy outer shell of a coconut. There are two sorts. White coir, harvested from unripe coconuts, is spun to yarn that is used in mats or rope. Brown coir, from fully ripened coconuts, is thicker and stronger than white coir. It is used in mats, brushes, and sacking. Pads of brown coir sprayed with latex (rubberized coir) are used as upholstery padding in cars. The coir fiber is relatively waterproof and is one of the few natural fibers resistant to damage by salt water.

2.      Hemp comes from the weed Cannabis sativa. The hemp fibers, like those of flax, are freed from the stalk by a retting process. The properties of hemp resemble those of cotton. It is used for rope and coarse fabric, and is a potential reinforcement for natural fiber–reinforced composites.

3.      Jute is a long, soft, shiny vegetable fiber made from the stems of plants in the genus Corchorus, family Malvaceae. It is one of the cheapest of the natural fibers and is second only to cotton in the amount produced and variety of uses. It is spun into coarse, strong threads and woven to make sack-cloth, hessian, or burlap. There is interest in using jute as a reinforcement in composites, replacing glass.

4.      Kenaf (Hibiscus cannabinus) is a fast growing stem-fiber used to make industrial textiles, ropes, and twines. Emerging uses of kenaf fiber include engineered wood, insulation, and clothing-grade cloth, and as a reinforcement in polymer-matrix composites.

5.      Palmyra palm (Borassus) is a genus of fan palms, native to tropical regions of Africa, Asia, Sand New Guinea. Palm fiber (sometimes called vegetable horsehair) is derived from its leaves. The fibers are springy and strong, making it good for stuffing furniture and mattresses.

6.      Ramie (Boehmeria nivea) comes from the stem of a flowering plant in the nettle family. It is one of the strongest natural fibers. It is used for cordage and thread and is woven into fabrics for household furnishings (upholstery, canvas) and clothing, frequently in blends with other textile fibers.

7.      Sisal fibers

With the botanical name Agave sisalana, is a species of flowering plant native to southern Mexico but widely cultivated and naturalized in many other countries. It is valued for cordage because of its strength, durability, ability to stretch, affinity for certain dyestuffs, and, like coir, it is resistant to deterioration in saltwater. The higher-grade fiber is converted into yarns for the carpet industry. Sisal is now also used as a reinforcement in polymer-matrix composites.

It yields a stiff fiber used in making rope and various other products. The term sisal may refer either to the plant's common name or the fiber, depending on the context. The sisal fiber is traditionally used for rope and twine, and has many other uses, including paper, cloth, footwear, hats, bags, carpets, geotextiles, and dartboards. It is also used as fiber reinforcements for composite fiber-glass, rubber and cement products.

8.      Kapok fiber

(Ceiba pentandra), also called Java cotton, ceiba, or Java kapok, seed-hair fiber obtained from the fruit of the kapok tree or the kapok tree itself. The kapok is a gigantic tree of the tropical forest canopy and emergent layer.

Common throughout the tropics, the kapok is native to the New World and to Africa and was transported to Asia, where it is cultivated for its fiber, or floss. The kapok’s huge buttressed trunk tapers upward to an almost horizontal, spreading crown where large, compound leaves are made up of five to eight long, narrow leaflets. In full sun, the kapok can grow up to 4 metres (13 feet) per year, eventually reaching a height of 50 metres (164 feet).

The kapok is deciduous, dropping its foliage after seasonal rainy periods. Flowering occurs when the tree is leafless, thereby improving access for the bats that feed on the sugar-laden nectar of kapok blossoms. In doing so, the bats unwittingly pollinate the tree’s flowers. The flowers open at night and have five petals that are white or pink on the outside. Only a few flowers on a given branch will open on any particular night during the two or three weeks that the tree blooms.

·         Kapoks do not bloom every year, and some may go 5–10 years without flowering. When the tree does bloom, however, it is prolific, producing up to 4,000 fruits measuring up to 15 cm (6 inches) long. Eventually these pods open on the tree, exposing the pale kapok fibers to the wind for dispersal. The fibers, in which over 200 seeds are loosely embedded, is sometimes referred to as silk cotton and is yellowish brown, lightweight, and lustrous.

·         In harvesting kapok fiber, the pods are either cut down or gathered when they fall, then broken open with mallets. The seed and fiber, removed from the pods by hand, are stirred in a basket; the seeds fall to the bottom, leaving the fibers free. The seeds may be processed to obtain oil for making soap, and the residue is used as fertilizer and cattle feed.

SILK FIBERS

Introduction

Silk is a natural  protein fiber produced by the larvae of a moth to form cocoons. It’s the only natural fiber that is produced in filament form. It’s also referred to as “queen of fibers” due to its luxurious appearance

Sericulture or silk farming is the rearing of silkworms for the production of raw silk. Silk farming began in China in 2640BC, and later spread to Korea and Japan, Westward to India and Persia then to Spain, France and Italy. Today’s major producers of silk are China, India, and Japan

There are two types of silk namely:

1)      Mulberry /cultivated silk- It’s creamy white or yellowish white in color

2)      Wild silk-It’s color range from brownish to golden yellow in color

Bombyx mori silkworms are used for producing cultivated silk and are typically grown in a controlled environment.

·         Tussah, Eri, and Muga are wild silk varieties. Wild silk production varies by species and cultural practices in which the larvae are allowed to feed in their natural habitat and are then collected to spin cocoons in controlled environment.

·         Silk such as peace silk and ahimsa silk (produced without killing the silkworm) are marketed as eco-friendly fibers. This type of silk is produced using wild and cultivated silk cocoons from which the moth has emerged. Fabrics produced with cultivated and wild silk fibers are available in a variety of fabric weights and constructions, and are used for apparel and home interiors.

Rearing of silk

-          The silk moth lays eggs

-          The eggs hatch and the larvae feed on mulberry leaves

-          When the silkworms are about 10,000 times more heavily than when they hatched then they become ready for spinning a silk cocoon

-          The silk is produced in two glands i.e. in the silkworms head and then forced out in liquid form through openings called spinnerets

-          The larvae extrude two strands of silk fiber that are held together by a natural gum.

-          The filaments are made of a protein known as fibroin, and the gum is a protein known as sericin. Silk products from which sericin has not been removed are known as raw silk

                    Examples of silkworm life cycle

  Production/Manufacture/Processing of silk

Involves the following steps:

1)      Sorting

Cocoons for breeding are separated from those to be used for spinning.

2)      Reeling

It’s the process of unwinding the filament from the cocoon, the operation prevents defects in the raw silk.

As the filament of single cocoon is too fine for commercial use, three to ten strands are usually reeled at a time to produce the desired diameter of raw silk thread. Several cocoons are placed in hot water to soften the gum and the surfaces are brushed lightly to find the ends of the filaments then collected, threaded through a guide and wound on to a wheel called ‘reel’.

3)       Throwing

The process of twisting strands of different thickness in order to increase their strength or hold them together to form a ‘Thrown silk’.

This yarn later goes to weaving or knitting industry based on the type of yarn produced. The silk looks dull and it is harsh to touch because it still contains the gum. It is therefore called Raw silk.

4)      Spinning

The Short ends of silk fibers from the outer and inner edges of the cocoons and those from broken cocoons are spun into yarns forming the spun silk

5)      Degumming

Raw silk is boiled in soap and water until the gum is removed. This process is known as De-gumming. Sericin or gum is not usually removed until after the cloth is woven because it serves as warp sizing that protects the yarns from mechanical injury during weaving.

Sericin remains on the fiber during reeling, throwing and before finishing processes are applied. The presence of gum or Sericin increases the tendency for the silk to water spot on the fabrics during ironing. The gum is removed by boiling the fabric in soap and water.

6)      Finishing

Silk fabrics require very few finishes because they have natural luster, softness and drape ability. They are woven then they are either printed or dyed.

7)      Weighting of silk

This is the addition of solutions or metallic salts or tin compounds to the silk fiber in controlled environments to replace the weight lost during the de-gumming process.

When silk is boiled to remove the excess of natural gum or sericin, it loses weight. This loss of weight is replaced through treatment by metals like tin, aluminum in water solutions which are not removed by washing. Weighted silk is not durable because sunlight and perspiration weakens fibers. Heavy weighting causes silk to crack.

                        VARIOUS TYPES OF SILK

There are three types of silk yarns

1.      Reeled silk

There are five types of silk that are classified under reeled silk, they are;

        i.            Thrown yarn – this is a single yarn made of several strands or reeled silk spun together.

      ii.            Organzine yarn – these yarns re used for making warp threads where strength is required e.g. fabrics for draperies, upholstery and sheeting.

    iii.            Tram yarn – used for making fabrics with high tensile strength. It is a ply yarn where final twist of the single yarn lie in the same direction. It is mostly used for making weft threads.

    iv.            Duppion yarn – this is double silk made from knotted cocoons. This gives a textured effect to the yarn. It is used to make fancy fabrics e.g. shantung and duppion.

      v.            Tussah yarn / wild silk – this is made from uncultivated silk got from wild silk worms that feed on the leaves of oak trees. It is brown in color, more uneven and coarser.

2.      Raw silk

Silk that has not had any degumming.

3.      Spun silk

Yarns made from short fibers of broken cocoons or short ends of reeled silk. It requires more twisting and is less expensive than reeled silk.

4.      Waste / Noil silk

These are got from the waste of spun silk, they are dull, rough and lifeless used for making artillery bags. This are bags used by army men when they go out to fight. They are sometimes called waste silk.

                                  SILK IDENTIFICATION

1)      Microscopic structure /Test

a)      Longitudinal view

ü  Silk fibers are straight and smooth.

ü  Raw silk looks like irregular elliptical ribbons with transparent rod like structures

ü  Wild silk/Tussah has a flattened, coarse, thick and broader fiber having fine wavy lines all across its surface.

ü  Cultivated silk is narrower with no marks on it

b)     Cross-sectional view

ü  It is triangular with rounded corners

ü  It is composed of fibroin, consisting of two filaments called brin which is held together by Sericin

2)      Burning Test

ü  Silk burns slowly and will have trouble staying lit and produces an orange flame

ü  It produces smoke and smell of a burning hair/feather and leaves black residue and small balls that are brittle on the edges.

Physical properties

i)                     Strength

-          Silk is the strongest natural fiber hence reduces the problem of wear from abrasion. The strength of the spun silk yarns depends on the length of silk staple.

-          It is weaker when wet than when dry.

ii)                  Cleanliness and wash ability

-          Silk is a hygienic material because its smooth surface does not attract dirt. It can also be easily cleaned by mild soaps and dry cleaning

iii)                Color

Easily dyed therefore available in different colors. The color of the silk is dependent primarily on the species of silkworm and its diet prior to spinning its cocoon. Cultivated silk is off-white, whereas the color of wild silk ranges from off-white to dark brown.

iv)                Resilience

-          Silk retains their shape and have moderate resistance to wrinkling

v)                  Drape ability

-          Silk has a pliability and suppleness’ that aided by its elasticity and resilience gives it excellent drape ability

vi)                Luster

-          Silk fibers, especially cultivated silk, are lustrous hence quite prestigious and attractive. Silk Noil is dull.

vii)              Absorbency

-          The good absorptive property of silk also contributes to it being used in warmer atmosphere

viii)            Quite elastic – therefore its crease resistant

Chemical properties

i)                    Reaction to Alkalis

-          Silk can be damaged if the concentration and temperature is high. A mild soap or detergent in lukewarm water is advisable

ii)                  Reaction to Acid

-          Concentrated mineral acids will dissolve silk faster than wool

-          Organic acids do not harm silk

iii)                Affinity for dyes

-          Silk has good absorbency and thus has good affinity for dyes

iv)                Resistance to perspiration

-          Perspiration weakens and yellows silk fabric

v)                  Reaction to bleach

-          Strong bleaches contain sodium hypochlorite will deteriorate silk. Mild bleaches like sodium carbonate and hydrogen peroxide may be used with normal caution

Thermal properties

·         Heat conductivity: Since silk is a protein fiber. It is a non-conductor of heat like wool. Hence it is used for winter apparel

·         Effect of light: Continuous exposure to light weakens silk faster than wool.

·         Silk ignite and continue burning when there is a source of flame

·         After removal from flame it will scatter and eventually extinguish itself

·         Gives a crisp brittle ash and gives off oduor like that of burning hair/feather

Biological properties

·         Resistance to mildew: silk will not be affected by mildew unless left for some time in damp state

·         Resistance to insects: silk may be attacked by the larvae, clothe moth or carpet beetles     

                        SILK FABRICS                  

a.       Chiffon-This is a shear fabric which drapes beautifully and it’s warm and light in weight

b.      Foulard –it’s a twill woven fabric used for scarves and dresses

c.       Net –used for bridal wear as it drapes well

d.      Poult –This is rather a stiff silk fabric

e.       Velvet –Has a beautiful sheen and always very light.

a.      FINISHES APPLIED TO SILK

Finishing processes that enhance the appearance of fabrics and add their serviceability are given to silk fabrics. They include:

        i.            Singeing – used to add smoothness to the fabric

      ii.            Bleaching – very little is required when silk is completely degummed

    iii.            Steaming – used to form pile weaves

    iv.            Pressing – Removing wrinkles from finished fabric by passing it through rollers

         CHARACTERISTICS OF SILK FABRIC

·         It’s lustrous

·         Silk is absorbent

·         It’s expensive

·         Damaged by chemical exposure

·         Loses strength when wet

·         Good dye ability with rich colors

·         Has a good drape

Favourable Properties: Silk has rich subdued Lustre, is porous, which allows the skin to breathe, provides warmth without the weight or itch of wool. It is one of the strongest natural fiber but loses strength when wet.

Unfavourable Properties: Silk is sensitive to heat. A warm iron should be used. The fiber has poor resistance to prolonged exposure to sun light and can be attacked by moth. Curtains and draperies should be protected from direct light as silk weakens faster than cotton or wool. Silk is damaged by alkalis but resistant to acids.

                         USES OF SILK

1.      Silk is an expensive luxury fabric e.g. evening wear, wedding dresses and other garments for special occasions.

2.      Apparel e.g. shirt, blouses, jersey, stockings, underwear, ties and dresses

3.      Lace and other trimmings or decorations used on garments and furnishings.

4.      Silk is used primarily in apparel and home furnishing items because of its appearance and cost.

5.      Silk is extremely versatile and can be used to create a variety of fabrics from sheer chiffons to heavy beautiful brocades and velvets.

6.      Due to its absorbency it is appropriate for warm weather wear.

7.      Because of its low conductivity it is used for cold weather wear, also in furnishing

8.      Silk is often blended with other fibers to add soft luster for furnishing fabric.

9.      Expensive hands made rugs are made from silk.

ASSIGNMENT Determine FIVE (5) ways of caring for silk fabrics.

                                        WOOL

             Introduction

It’s a protein fiber and most common of animal hair fibers. Its composed of a protein called Keratin which contains Sulphur as well as Carbon hydrogen and Nitrogen present in every protein. Most of the wool used for textiles comes from sheep

Other sources are alpaca goat,Rabbit and any fury animal

          GROWTH AND PRODUCTION

The best type of wool is referred to as Merino wool which is soft,fine and comes from Merino sheep. Wool can be sheared from living animal or pulled from the hide that has been slaughtered for meat.

Sheard wool is called clip/fleece wool and is considered quality/superior. Slipe wool is inferior in quality to fleece wool hence lacks elasticity and lustre

Sheering is done with power sheer onces a year. Sheered wool has clean cut ends and primarily wool grading is done while they are still in pieces because it becomes important in determining the cost.After grading the pieces are shipped to the mill/factory to be processed in yarn and fabrics

Producers of wool are Australia,South Africa,United States of America and Agentina

The quality of wool fibers is determined by:

1. Breed
2. Climate
3. Food
4. General care
5. Sheep health

Cold weather produces a harder and heavier fiber

Exclusive moisture dries out the natural grease

Insufficient or poor food retards growth.

  WOOL PROCESSING

1)      Sorting

·         Its done by hand

·         Wool is graded according to finest of individual fibers and also according to their length and color

2)      Scouring/washing  

·         Wool fibers contain grease,dirt and other substances which must be washed or scoured

·         Its carried out in hot soapy water to remove natural grease and sweat

3)      Rinsing

·         The fiber is rinsed thoroughly until all traces of soap are removed and dryed thoroughly

4)      Carbonizing

·         Its emersing wool in dilute sulphuric acid to enable vegetable matter such as the seeds and leaves to become dry and powdery to be crushed in later stages

5)      Oiling

·         Wool is unmanageable after scouring and therefore is treated with various oils including animal,vegetable and minerals or blended to keep it from becoming brittle

·         This is also done to lubricate it for spinning operation.

·         Wool may be spun into two types of yarns and the processes vary as follows

v  Woollen processes/system

v  Worsted processes/system

                                      Wollen process/System

6)      Carding

·         The wool is passed via the machine rollers covered with sharp steel wires.

·         The wires disentangle with sharp separate malted fibers(i.e fibers that have clinged together) and mixing them.

·         The process help in removing persisting impurities e.g. dirt and short fibers are removed.

·         Fibers are straightened and parallelized i.e fibers are arranged in an uniform manner to form a sliver

7)      Spinning

·         The mass of carded wool(sliver) is drawn out and twisted/span into wollen yarns as soft and fluffy.

·         The yarn spun are soft,thick and fluffy made of short fibers and are suitable for knitting and production of bulky material

·         The bulky  materials undergo via a process of milling/Folling which is a pre-shrinking process for wollen materials

·         The pre-shrinking process make the material stable,firm,non stretching & non-shrinking

                     Worsted process/system

10)  Carding  

·         The fleece is passed through combs that strengthens and aligns the fibers

·         It strengthens the wool fibers an aligns them in one direction

11)  Combing

·         This process involves passing wool fleeces through combs which strengthens fibers further.

·         Shorter fibers are removed from the fibers and the strengthened ones are straightened to make them parallel

·         Any unwanted material are removed

·         Short fibers are called NOILS while the long fibers are called TOPS

12)  Drawing /Drafting

·         In drawing the slivers are doubled and redoubled,drafted or drawn into a roving

·         The sliver is made more compact and thin

13)  Roving

·         After the fibers are taken to the roving process where slight twist is imparted

14)   Spinning

·         The Tops are span to yarn or threads by twisting

·         The yarns are usually smoother,stronger,longer,lustrous and firmer

·         They are used for weaving fine suitings and dress materials

·         In worsted yarns,fabers are more organised and lie closely together along the direction which is more and highly twisted.

                       Differences between woollen and worsted yarns

 CLASSIFICATION OF WOOL

1)      Type of wool

i.                    Merino wool

 Merino sheep produce the best quality wool which is originated from Spain. The fiber grow from 5cm – 10cm long, are fine, soft and full of crimp therefore they make warm fabrics (shorter and finer the fiber, the better the quality)

They are not very strong compared to the other types of wool fibers. They are used for making top quality fabrics where softness and warmness are valued.

iii.    Crossbred wool

This is got from British breeds that are crossbred with Merino sheep. They are reared for both meat and wool production. This fibers range from 8cm – 20cm long but thicker than that of Merino sheep. The fiber is not as soft and crimp as merino but are stronger, more resilient and more lustrous, they are ideal for making apparel.

2)      Type of woolen yarn

i.                    Worsted wool

·         Made from long fibers which run parallel to each other

·         They are highly twisted to give them added strength

·         They produce firm, smooth and strong yarns which are lustrous

ii.                  Woolen

·         They are made of short fibers

·         They are softer, fluffier, warm and less twisted than worsted wool

3)       Classification by fleece

                 i.            Lamb’s wool: The first fleece sheared from lamb about six to eight months old. This is fine in quality and soft texture.

               ii.            Hogget wool: Wool obtained from sheep of 12 to 14 months old that has not been previously shorn.

             iii.            Pulled wool: Pulling woolen from slaughtered sheep for the meat to be eaten

             iv.            Cottee wool: Very poor grade of wool.

               v.            Weather wool: Any fleece clipped after the first shearing is called wether wool.

                                          WOOL IDENTIFICATION

1)      Microscopic structure

a)      Longitudinal view-Under microscopic view wool has a rough and fluffy surface with cross markings due to the overlapping scales.

b)     Cross-sectional view-Wool is oval to circular shape with variation in diameter

Longitudinal structure of wool                                                Cross-sectional structure of wool

The cross-section of wool shows 3 layers called the epidermis/cuticle which is composed of scales

The major is the cortex which is composed of cortex cells and in the middle is the medulla.

Physical structure of wool

Four distinct regions of wool

The Outer Sheath or Epicuticle: This is the outer most layers, and is a thin, water-repellent membrane. It is the only non-protein part of the fiber, and it protects the fiber like a covering of wax. The membrane repels water, and in this sense acts as a water proof coating on the fiber. Wool fabrics will repel the water that falls on them during a short rain shower.

The scale cell layer:  beneath the epicuticle there is a layer of flat, scale-like cells, which overlap like the shingles on a roof or fish scales. The free ends of the scales point towards the tip of the fiber.

Cuticle

·         It’s the outermost layer of wool fiber

·         Has a membrane over scale cells

·         It plays an important part in wool shrinkage

·         There is also a thin watery repellant membrane which gives protection and repels water

·         However, they are mainly small and microscopic pores in that epi-cuticle through which water vapor may pass in wool

Cortex 

·         It makes up the bulk of the wool fibers

·         It forms the main body of the wool fiber

·         It consists of millions of long spindle shaped cells held together by a strong binding material

·         It’s the basic arrangement on the material composing the cortex give strength and elasticity

·         It consists of intermediate cells that hold color pigment.

Medulla

·         It is the inner most layer of wool

·         It consist of large spiral shape air fitted cells

·         Wool fibers have characteristics of elasticity to wool

·         Fibers to hold together when twisted into yarns

·         This waviness gives characteristics of elasticity to wool

·         Fibers which can be stretched out and then relax to crimp form like spring

2)      Burning Test

·         Wool burns with an irregular flicker, extinguishing itself quickly when the flame is removed, it smells of burning feathers and leaves a black crushable ball.

·         The odor given off may be compared to the smell of burning hair/feather

3)      Chemical test

It dissolves in boiling sodium hydroxide (NaOH) solution and hardened by water.

Physical properties

1.      Luster-wool has medium luster

2.      Color –it varies from off white, brown to green depending on the breed of the sheep

3.      Tenacity –wool is weak however if yarns and fabrics of optimum weight and time is produced the end product wears well and retains shape

4.      Elastic recovery and elongation-wool has excellent elasticity and extensibility as it may extend more than 70% when wet however recovery is superior

5.      Resiliency –It’s exceptionally good and it readily springs back to shape after crushing and rinsing

6.      Moisture regains-The ability to absorb makes it comfortable in humid and cold atmosphere.

7.      Length –wool fibers range from 2.5-1.5 cm  long for staple fibers then 15-30 cm for long fibers

Chemical properties

1.      Effects of acids-It’s resistant to acids however higher concentration of acids may decompose wool

2.      Effects of alkalis-Wool is sensitive in alkali and it will dissolve in dilute caustic soda solution

3.      Effects of oxidizing agent-It’s affected by oxidizing agent as hypo chloride bleaches which damage protein fiber

4.      Organic solvents-Most of organic solvents used in cleaning and stain removal are safe and don’t damage wool fibers.

5.      Effects of sunlight-Ultra-violet rays of the sun cause fiber degradation and if exposure is prolonged it causes discoloration on the fibers

6.      Static charges-wool builds up static charges within wool yarns and fabrics.

Biological properties

·         They are damaged by moths unless they are given moth-proof finish

·         They are resistant to bacteria

·         It’s affected by mild

Wool fabrics

·         Gabardine-worsted closely twill woven fabrics used for coats, suits and rain coats

·         Knitted jersey-Used for dresses and suits

·         Tweed –used for jackets and coats

·         Tartan – A checked, twill-weave, medium-weight woolen fabric that comes in a wide variety of color schemes

·         Flannel – Medium-weight, strong wool fabric with a plain or twill weave. It has a napped finish on one or both sides so is soft and cozy to the touch. Often used for suits, jackets, skirts and trousers.

·         Cashmere – a very soft, fine fabric that’s comfortable and warm to wear. It’s made from the fleece of the Kashmir goat, and is often used for scarves

Treatments given to wool fabrics

a)      Perching –Examining cloth for defects while it is run over two rollers

b)      Burling –Removing loose threads and knots

c)      Mending –Darning flaws and defects if there are any

d)     Shearing –Cutting and shaving for a uniform surface

e)      Singeing and steaming-Used for hard finish of worsted fabrics

Characteristics of wool products

Disadvantages

a.       Stretches out of proportion when wet

b.      Picks dirt fast

c.       It’s fed on by moths and carpet beetles

d.      It’s weakened by strong exposure to sunlight

e.       Harmed by strong alkalis, such as strong detergents and hence it is best to dry clean or wash with mild soaps with a very gentle action, otherwise shrinkage or loss of shape may occur.

f.       It shrinks badly

  Advantages

a.      Wool fiber is warm

b.      It is absorbent thus absorbs moisture

c.       It’s resistant to bacteria

d.      It drapes well due to its liability

e.       It’s resistant to acids

f.       It’s durable due to their elastic strength

g.      Wool fiber burns slowly with spluttering and once removed from flame it is self-extinguishing.

Uses of wool

·         Used for making all types of apparel e.g. dresses, coats, jersey, knitted fabrics, boots and shoes.

·         Blankets

·         Upholstery e.g. Carpets, seat covers.

NOTE: Due to high demand and insufficient supply of new wool. Wool is usually recycled or reused. This is done by undoing garments made of wool. Shoddy wool is got from loosely woven or knitted fabrics that don’t suffer much damage when being undone. Mungo wool is got from heavily milled, felted or closely woven clothing. More damage is usually caused by reprocessing, therefore, reprocessed wool is poorer quality but is normally blended with new wool for making cheaper fabrics.

Care for wool fabrics

·         It can be dry cleaned and pressed easily but laundering is difficult unless the fabrics have been treated to be washable but care must be taken

·         It requires warm water and hot water and the temperatures should remain constant throughout washing

·         Agitation should be minimal to reduce the effect of felting

·         If bleaching is necessary use hydrogen peroxides.

ASSIGNMENT:  learners to research and write notes on JUTE as a natural fiber (30 marks)

ASBESTOS (A MINERAL FIBER)

Origin

Asbestos is a naturally occurring rock, made from several different minerals. The unique feature is the fact that rocks are formed when the minerals crystallize in the form of fibers, instead of in the normal way. Much of the asbestos today is obtained from Canadian rocks which are crashed in order to extract the fibrous crystals.

It is a minor fiber. This means it is produced in small quantities. It is produced from mineral rocks found in Canada, Italy and South Africa.

PROCESSING OF ASBESTOS

ü  Once the rock is mined, it is crushed and screened so as to separate the asbestos from rest of the rock.

ü  The fibers extracted during the screening are cleaned and graded by length.

ü  The purified asbestos fiber is carded and collected as a narrow ribbon or roving. These roving can be spun into yarns on convectional machinery.

ü  The fibers may be blended with 5% to 20% of cotton or rayon.

Properties of asbestos

i.        It is quite fine and lustrous, and maybe either soft or stiff

ii.       It has a high tensile strength and excellent dimensional stability; that is it does not shrink or stretch.

iii.                It accepts dye readily, but has poor color fastness and poor absorbency.

iv.                It has excellent fire resistance as it does not burn even in the fiercest flame.

v.                  It is also resistance to chemicals and sunlight.

vi.                Highly resistant to acids and alkalis.

USES OF ASBESTOS

i.                    Its ability to resist burning therefore Used for firefighting clothes and equipment i.e. fire proof protective clothing.

ii.                  Theatre curtains

iii.                Conveyor belts for hot materials

iv.                Electric insulation

Note: the asbestos yarn has little strength     

4.1. more info on processing of natural fibers

Man-made fibers can be modified at any stage during the production process (with additives such as pigments) or immediately afterwards (by drawing, crimping or the application of finishes) to suit the end product. The fibers can be created to match the requirements of the textile. Once engineered to fit a given application, fiber characteristics are identical from batch to batch. Alternatively if a desired result cannot be achieved by modifying one type of man-made fiber, different types can be modified to give the required performance.

GENERAL PRINCIPLES

All man-made fibers are produced from polymers. These substances are solids at normal temperatures. The polymers which are the starting products for man-made fibers may well be in form of chips, small particles of perhaps one to two millimetres in diameter and two to three millimetres in length.

In order to make filaments from these polymers, their physical shape must be altered, and the polymer chips must be converted to a liquid form. This is necessary as the polymer needs to be forced or extruded through fine holes to form filaments.

The process of producing a man-made fiber is often termed ‘spinning’.  This leads to confusion with the purely mechanical process of assembling staple fibers into a yarn, which is called ‘spinning’. The process of producing a man-made fiber will therefore be described as ‘extrusion’.

There are three methods of extruding fibers: Melt extrusion, Solvent-dry extrusion and Wet extrusion. The method used for each fiber depends upon the ease of conversion of the polymer from solid to liquid state.

·         If the polymer can be converted to a liquid form easily just by heating, then melt extrusion can be used.

·         If polymer is chemically damaged by heating but can be dissolved in a suitable solvent which will later evaporate, then dry extrusion is used.

·         If polymer cannot be heated or dissolved in an evaporative solvent, wet extrusion must be used.

The molecules in the extruded filaments are likely to be randomly orientated within the fiber. For the fiber to have good tenacity and a reasonable low extension at break, the molecules need to be lined up along the fiber axis. In order to do this, a further process known as stretching or drawing is needed.   This increases the tenacity and decreases the extension-at-break.

The production of manmade fibers usually includes the following processes:

        i.            Preparation of polymer (polymerization, chemical modification, etc.)

      ii.            Preparation of the spinning fluid (polymer melt or solution)

    iii.            Spinning (extrusion, solidification, and deformation of the spinning line or filament)

    iv.            Drawing (due to a higher linear speed at the take-up roll relative to that at the die; drawing is used to increase the degree of molecular orientation and improve the tensile strength, modulus of elasticity and elongation of the fibers)

      v.            Heat treatment

    vi.            Textile processing (twisting, oiling, dyeing, etc.).

Three processes for man-made fiber production

1.      Melt extrusion

This is the simplest fiber production processes. It is used for the production of Polyester, Polyamides, Propylene and Polymers such as nylon, polyethylene, polyvinyl chloride, cellulose triacetate

The polymer is melted and extruded through the fine holes of a spinneret (metal plate with small holes drilled through it). The number of holes in the spinneret determines the size of the yarn, as the emerging fibers are brought together to form a single strand. The molten polymer passes through the holes in the spinneret plate and emerges into a steam of cool air which causes it to solidify. The solidified bundle of filaments is passed around a rotating roller and then forwarded to a collecting device.

The melt extrusion process can therefore be split into three stages heating, extrusion and cooling.

Drawing

The fibers is not yet suitable for use because the polymer molecules are not highly oriented along the fiber axis. To orient them, the fiber is drawn forming areas of crystalline order. In this process the fiber is in a plastic rather than a molten state.

2.      Solvent-dry extrusion

If a polymer will not meet the conditions for melt extrusion, an alternative method of converting the solid polymer to a liquid state must be used. If it is possible to use a volatile solvent, that is a solvent which is highly reactive, then the polymer can be extruded into warm air to evaporate the solvent away. This is known as solvent-dry extrusion and is the least used for major fiber production techniques.

The polymer solution is extruded through a spinneret into heated gas so that the solvent is rapidly evaporated from the filaments. The filaments drop through the hot gas steam for five to six metres to a rotating roller and are then fed to the wind-up device.

Cellulose acetate, cellulose triacetate, acrylic, modacrylic, aromatic nylon, and polyvinyl chloride are made by dry spinning.

After treatments

Filaments must be washed to remove any remaining solvent from the extrusion stage. Drawing can also be carried out at this stage, in either air or liquid.

3.      Wet extrusion

1.      If the polymer does not melt without decomposition and will not dissolve in a volatile solvent, it must be dissolved in a non-volatile solvent to change it from solid to liquid state. There are two steps in wet extrusion: physical process and chemical regeneration. In this the polymer solution (i.e., polymer dissolved in a solvent as in dry spinning) is spun into a coagulating solution to precipitate the polymer (solidify them). This process has been used with acrylic, modacrylic, aromatic nylon, and polyvinyl chloride fibers.

AFTER TREATMENTS

As for solvent-dry spinning, the filaments of viscose must be washed to rid them of any chemicals from the coagulating bath. The filaments are dried then suitable spin finishes are applied.

SYNTHETIC FIBERS

Introduction

They are made up of substances which do not normally form fibers but are synthesized. To synthesize is to build new molecular structures by adding small molecules to give a large, long molecule. This process is known as polymerization. And the large molecule formed is known as polymer.

Made fibers from synthetic polymers are created using polymerization of various chemical inputs to create polymers.  Polymerization is the process of combining many small molecules into a large molecule – a polymer.    Polymers are simply large molecules composed of repeating structural units.  Polymers used for synthetic fibers are produced from intermediates (which in turn have been produced from crude oil) and applying a catalyst. Polymers are the building blocks of synthetic fibers

NYLON (A POLYAMIDE)

ü  Is the oldest synthetic fiber, It belongs to the polyamide group polyamides are formed with a recurrent amide group (-CO-NH-) as part of the polymer chain. There are different types of nylons distinguished by the chemical structure of the individual polymer.

ü  The original form of nylon is known as 6.6 because it has six carbon atoms.

o   Examples of nylon fabrics:

·         Brocade                            

·         Damask

·         Gabardine

·         Lace net

·         Satin

·         Knitted fabrics (jersey)

It is produced in USA and UK in both filament and staple form

PRODUCTION OF NYLON

It is produced in the following ways:

1.      POLYMERIZATION

ü  The raw materials are heated , causing the short chain molecules to combine to make long molecules until fibers are formed

ü  These fibers are cooled whereby they solidify into a hard ribbon like from.

ü  They are then cut into chips ready for spinning.

2.      SPINNING

ü  The polymer chips are heated to a molten mass.

ü  They are passed through tiny holes in a spinneret, cooled and solidified into filament form.

ü  They are then twisted together to form a yarn.

3.      DRAWING

ü  The yarn is stretched or drawn so as to reduce the thickness and lengthen the filaments. This increases the strength and changes the appearance of the fiber from dull and opaque to shiny and clear.

ü  If staple fibers are needed the filament fibers are cut and a crimp is added.

   Properties of nylon

1.      Has a cool, clammy feel when in filament form, however this feel can be altered by creating filaments which are three-sided. In nature to give a smoother and softer fabric. 

2.      It is lustrous, transparent and has high tensile strength.

3.      It is very strong and durable, both wet and when dry.

4.      It has high resistance to abrasion and is very elastic, meaning it easily comes back to its original form after any stretching, pull or bending. For this reason it needs little or no ironing.

5.      It is also mildews, moth and flame resistance and has low resistance to sunlight.

6.      It has good resistance to alkalis but is disintegrated by strong acids.

7.      It has very low absorbency i.e. hydrophobic for this reason it dries quickly however, it also makes it build up electrostatic electricity making it very uncomfortable to wear as it clings on the body.

8.      It is thermoplastic, this means it is sensitive to heat. This quality is exploited to permanently set pleats in garments.

9.      It is easy to wash and doesn’t burn readily, it is one of the safest textile fibers.

10.  It is very versatile, it’s produced into various types of yarns from very sheer to very stout.

11.  It blend well with cotton, wool, rayon and silk giving them added strength.

12.  It also dyes well and has good color fastness however, this quality makes it pick up color or grease from other garments when laundering

NOTE: A distinct disadvantage of nylon made from spun yarns is that it pills badly. Pilling is the formation of a small balls of fiber on the fabric on the fabric due to friction.

Spun yarns are the staple fibers that are cut from the filament fibers in order to produce short fibers.

Advantages of nylon

a.       Lightweight

b.      Strong and durable

c.       Abrasion resistance

d.      Easy to wash and dries easily

e.       Resist shrinkage and wrinkles

f.       Insulating properties

Limitations of nylon

a.       Builds up electrostatic electricity making it very uncomfortable to wear as t clings on the body

b.      Poor resistance to sunlight

c.       Picks up oils and dyes in wash

d.      Thermoplastic i.e. sensitive to heat

Identification test for nylon

1.      BURNING TES

·         Nylon draws away from the flame before igniting.

·         It drips and melts in flame producing white smoke.

·         It forms a hard bead and smells of fresh celery, chemical or acid.

·         It is self-extinguishing.

2.      CHEMICAL TEST

 It is soluble in formic acid and carbolic acid (90% phenol).

3.      MICROSCOPIC TEST

The longitudinal view shows long, smooth filaments

Cross-sectional view shows circular, spotted structures.

Fiber structure may be varied to give different fiber properties e.g. a triobal filament maybe created to produce fabric with more glitter.

USES OF NYLON

1. Used in general apparel, which is sportswear, stockings, foundation garments, overalls, rainwear, lingerie, blouses, skirts and shirts.

2. Used for trimmings such as ribbons and lace.

3. Used in making furnishing such as carpets, bed-sheets, curtains and upholstery.

4. It is also quite useful for industrial uses in making industrial making tires, ropes, tarpaulins and conveyor belts.

5. Widely used in hosiery and household furnishings.

6. Mainly used for outer wear and swim wear fabrics, ski pants and active sportswear.

7. Used for lining material in coats, jackets because of excellent durability however it is expensive

TERYLENE (A POLYESTER)

Terylene is one of the polyesters in the market today. Polyesters are derived from petroleum by products namely; ethylene, glycol and terephalic acid.

Polyester fiber are produced in filament, staple and low lengths.

Other types of polyesters are: Dacron, kodel and vycron.

PRODUCTION OF TERYLENE

Its production is similar to that of Nylon.

Properties of Terylene

1.      Shrink resistance and extremely strong, It is popular for apparel fabrics

2.      It is cool to wear and quite resilient.

3.      It is also crease resistance therefore it needs little or no ironing and is good for travelling.

4.      It has a high abrasion resistance.

ACRYLIC (A POLYACRILONITRILE)

Acrylic is produced from acrylonitrile; which is got from either petroleum or natural gas.

True acrylics have over 85% of acrylonitrile while mod acrylics have between 35% - 85%

PRODUCTION OF ACRYLIC

Are production in a similar manner to other synthetics?

Orlon is dry spun and produced in both filament and staple forms, whereas acrilan and courtelle are wet spun and produced in staple form only.

Properties of acrylic

i.                    Lustrous and has a warm, soft handle

ii.                  Does not irritate the skin

iii.                Light  weight, strong and durable

iv.                Crease, shrink and stretch resistant.

v.                  Moth and mildew resistant

vi.                It is Thermoplastic

vii.              Damaged by alkalis but resist acids.

viii.            It is not damaged by sunlight or abrasion

ix.                Has low moisture absorbency, therefore Dries quickly

x.                  It builds up electricity and may even produce sparks for this reason it is used in an operating room as it can ignite ether a gas that is used to make patients sleep so that they do not feel pain during operation.

Identification test

1.      Burning test

·         Melts in flame, rolls, twists and forms droplets of hot, molten plastic.

·         May or may not continue to burn after the flame is removed.

·         Produces an acid or chemical oduor

·         Forms a hard, thick, black beaded edge.

2.      Chemical test

Dissolves in 80% sulphuric acid.

3.      Microscopic test

Longitudinal view – shows a fiber which looks look like fine glass rods

Cross-sectional view – shows circular structures

Uses of acrylics

1.      Used in making of general apparel such as coats, suits, dresses, blouses and underwear.

2.      Used to make carpets, blankets and bed spreads, lining fabrics and limited fabrics

                                   MODACRYLICS

They are modified acrylics. They contain between 35-85% acrylonitrile. Their characteristics are similar to those of acrylics but they are fire resistant, self-extinguishing, do not drip and are easier to dye.

Examples of mod acrylics include Dynel, teklan and kanekalon.

Uses of mod acrylics

Because of their fire resistant characteristic, mod acrylics are widely used for making children’s nightwear, racing drivers, overalls, fireside rugs, electrical insulations, furnishings, public buildings, wigs and hair pieces.

                      POLYOLEFIN FIBERS       

These are fibers that are made from 85% ethylene or propane gas. They are produced by melt spinning and are used for household and industrial purpose due to their low moisture absorbency.

Examples of polyolefin are polypropylene and polythene

Properties of polythene

1.      Polyolefin are rot proof

2.      Color fast in sunlight

3.      Light weight

4.      Very strong

5.      Relatively cheap

6.      Have low moisture absorbency

7.      They are not affected by either alkalis or acids but are affected by sunlight.

Uses of polyolefin

·         Used for making deck chair covers, ropes, packing papers, fishing nets, filter cloths and carpet backing.

ACTIVITY: why do you think polythene is not popular for making apparel fabrics?

Let us now learn about some fibers that are used minimally in the textile industry, they have much lower production rate but are important all the same. They are referred to as minor fibers.

                                 MINOR FIBERS

SPANDEX (AN ELASTOMERIC FIBER)

Elastomeric fibers are got from polyurethane which is derived from petroleum by products. They have a high elasticity power of between 450%-700% and have complete and instant recovery.

They are often blended with other fibers so as to give them the preferred texture and appearance e.g. spandex, Lycra (UK & USA) and spanzelle (USA).

Properties of spandex

1.      Spandex fibers can stretch up to 500%-800% of their length before breaking.

2.      They high recovery rate once released therefore, they are used for sportswear such as swim suits.

3.      Superior dye ability with brilliant colors.

4.      Very good resilience and highly flexibility; Very good abrasion resistance. Good dimensional stability in wet condition; however some types shrink with the exposure to the high temperature.

5.      They resist perspiration, this makes them ideal for sportswear and underwear

6.      Good resistance to household bleaches and most acids but are damaged by hot alkalis as it causes rapid deterioration. It is resistant to dry cleaning solvents;

7.      They dry quickly, easy to launder and blend well with nylon and Terylene.

Spandex in Consumer Use

i.                    Lycra in swimwear, innerwear and active sportswear means providing fitting clothes with comfort and freedom of movement.

ii.                  It also improves the quality of Knitted / Woven fabrics as it prevents bagging and accelerates wrinkle recovery.

iii.                Lycra in swimwear, innerwear and active sportswear means providing fitting clothes with comfort and freedom of movement.

iv.                Make home furnishings such as bed sheets, curtains and seat covers.

v.                  It also improves the quality of Knitted / Woven fabrics as it prevents bagging and accelerates wrinkle recovery.

POLYVINYL CHLORIDE FIBERS (P.V.C)

These fibers are not used for clothing purposes because they are very sensitive to heat and therefore, cannot be ironed. However, they may be used to bond some needle constructed fabrics.

Properties of P.V.Cs

1.      P.V.C are moth, mildew, and chemical and flame resistant but sensitive to heat.

2.      They are non-absorbent

Uses of P.V.Cs

a.       Are used for industrial purposes such as protective clothing, tarpaulins (lorry covers) and filter cloths

b.      They are used for home furnishing such as seat covers, desk chairs and carpets.

MAN-MADE OR REGENERATED FIBERS

We have looked at fibers that occur in either animals or plants as well as fibers that are processed from chemicals that is synthetic fibers. Although synthetic fibers are man-made the “the man-made” refers to all fibers that are processed from both natural raw materials and chemicals. They are produced by the chemical treatment of certain raw material, the main raw materials are wood pulp, cotton linters, petroleum extracts and by products of coal. Other fibers are made from proteins like milk, soya beans as well from maize meal and a natural rubber base.

They can be divided into two main groups namely viscose rayons and acetate or triacetate rayons

VISCOSE RAYONS

It’s the first man-made fiber formally called artificial silk. It was developed by scientists who tried to copy the silk worm by producing a liquid secretion which can solidify into filament. It is mainly produced from cellulose of spruce and eucalyptus trees as well as cotton linters, petroleum extracts and by products of coal e.g. are crepe, damask, flannel, gabardine, jersey, satin, taffeta and velvet

Processing of viscose rayon

It’s processed in the following steps

i.                    Source

The eucalyptus and spruce trees are felled and the bark is removed. This is done in pulp mills, the cellulose is extracted, pressed and cut into sheets.

ii.                  Steeping

The cellulose is steeped into caustic soda, which converts it into alkali cellulose which is then shredded into crumbs and left to oxidize.

iii.                Xanthation

The alkali cellulose is treated with carbon disulphide to give sodium cellulose xanthate

iv.                Dissolving

The sodium cellulose xanthate is dissolved in caustic soda (NaOH) to form the spinning solution known as viscose which is left to ripen or to ferment.

v.                  Filtration

Any undissolved particles are removed by filtration

vi.                Wet spinning and extrusion

The viscose is forced through fine holes in a jet (a spinner) into a coagulating bath of sulphuric acid and salts. This process produces the original cellulose in filament form.

If fine staple fibers are required the filaments from several jets are drawn together and the low is cut into fibers of desired length.

vii.              Washing

The yarns are washed to remove all traces of chemicals then they are dried 

viii.            Twisting and winding

The yarns are given a twist and wound on to bobbins

Properties of viscos rayon

i.                    Rayon is smooth, absorbent and cool to wear as it is a good conductor of heat for this it is quite comfortable to wear.

ii.                  It is fairly strong but is weaker when wet

iii.                It dyes and is highly color fast when spun dyed

iv.                It drapes well

v.                  It burns readily

vi.                It is affected by static electricity

vii.              Its damaged by acids and alkalis and especially by acetone for this care should be taken during laundry-work and especially when removing stains

viii.            It is also damage by friction, twisting and wringing therefore, it should be washed by kneading and squeezing method and should not be tumbled dried.

ix.                It may also shrink or stretch unless its specially treated

Identification test for viscose rayon

i.                    Burning test

Viscose rayon burns easily, flaming, smells of burning paper (like cotton) and leaves grey ash.

ii.                  Chemical test

It dissolves in acetone (nail vanish remover)

iii.                Microscopic test

Longitudinal view shows long smooth fibers

Cross sectional view shows deep striations

                 Uses of viscose rayon

1.      It’s quite versatile and therefore it may be used for all wearing apparel and industrial clothing

2.      Household furnishing such as  table linen, curtains, carpets, blankets and bedspreads

ACETATE RAYON

It is produced from cotton linters and wood pulp treated with acetic acid. It is the nearest substitute to silk e.g. are satin, taffeta, brocade and knitted fabrics used for making lingerie.

Processing of acetate rayon

i.                    Source

Cellulose is got from wood pulp and cotton linters, it is treated with acetic acid to make the polymer more active.

ii.                  Acetylation

More acetic acid is used to replace the hydrogen atoms of the hydroxyl group by the acetyl group to form cellulose acetate, some of the acetyl groups are removed.

iii.                Ripening

The cellulose acetate solution is allowed to ripen until acetylation is complete

iv.                Precipitation

The cellulose acetate is precipitated by adding water

v.                  Drying

It is washed, dried and made into white flakes

vi.                Spinning

The spinning solution is made by dissolving the flakes in acetone with the addition of a little water.

vii.              Filtration

The solution is filtered and pumped through a spinneret, the filaments are solidified by a current of warm air this is known as dry spinning.

Filament and staple yarns can both be produced this way

NB: Acetate can be spun dyed whereby the dye stuffs are added to the acetate solution before it is spun. This ensures the color is inside the fiber thus giving greater color.

Properties of acetate rayon

i.                    It has an attractive rich appearance

ii.                  It has very good draping quality

iii.                It is absorbent, soft and smooth, it dyes well and blends well with other fibers

iv.                Resistant to moth and mildew

v.                  Thermoplastic heat set pleats are permanent

vi.                Shrink and crease resistant

vii.              It is slightly weaker when wet

viii.            Builds up static electricity when ironing

ix.                It also fades color due to sunlight exposure

x.                  Weakened by long exposure to acids, alkalis and sunlight

xi.                Dissolves in acetone

Identification test for acetate rayon

i.                    Burning test

It melts, rolls and twist to form a thick, black beaded edge. It has low melting point and produces a chemical acidic odour.

ii.                  Chemical test

It dissolves in acetone

iii.                Microscopic test

Longitudinal view shows long smooth fibers like striated rods while the cross-sectional view shows bulb like structures.

Uses of Acetate Rayon

i.                    Quite versatile and attractive for this they are used for all wearing apparel including lingerie (underwear) and children wear

ii.                  Furnishing and draperies

iii.                Hand knitting yarns as well as cigarette filter tips.

TRIACETATE RAYON

It’s made from wood pulp and oil treated with acetic acid and acetic anhydride. It’s a similar composition to that of acetate rayon but triacetate rayon has not less than 92% acetated hydroxyl group ions e.g. are tricel and arnel.

Processing of Triacetate Rayon

It’s similar to that of Acetate Rayon only the flacking is done the flakes are dissolved in methylene chloride plus alcohol.

The yarn is dry spun but it must be given an anti-static treatment before it is wound on to a package. It is produced in both filament and staple yarns.

Properties of Triacetate Rayon

i.                    Burning test – the edge melts, rolls, twists and forms droplets of molten plastic. It may or may not continue burning once flame is removed.

It produces a chemical or acidic odour and forms a hard black mass.

ii.                  Chemical test – it gets swollen by acetone

It dissolves in methylene chloride.

Uses of Triacetate Rayon fabrics

a.       Used to make general apparel such as blouses, dresses, scarves, suits, ties, slacks and lingerie

b.      Make rainwear

c.       Make ribbons and interlining for quilts

METALIC FIBERS

They are made from metal, metal coated with strong polyester, clear plastic or cellulose acetate, a core completely covered by metal. They are produced by slitting very thin sheets of the metal into narrow ribbons since they are quite weak and soft they are used as a wrapping around a strong fiber.

The color is put in the adhesives, which stick the plastic to the metal. Different colored yarns of aluminium are often used because gold and silver tend to discolor. Polyester may be used as a coating for Aluminium fiber.

Metallic fibers are used to add richness, luxury or glitter to fabrics. Latex is an example of a metallic fiber.

Larex metallic fiber

 Latex

Properties of Metallic fibers

1.      Metallic fibers are quite expensive

2.      Weak and soft

3.      Quite durable, light and smooth

4.      Washable and dry cleanable

5.      They crease easily

6.      Fairly good elasticity and elongation

Uses of metallic fibers

1.      Metallic fibers are used for making apparel

2.      Making furnishing fabrics such as those used in car upholstery, theater curtains, spectacle frames as well as radio and television sets.

GLASS FIBERS

This is ordinary glass made into yarns, glass is made up of silica (sand) and limestone. The fibers lack elasticity and flexibility necessary for general clothing, therefore they are used for industrial and household purposes only

Properties of Glass fibers

i.                    Glass fibers are strong but non absorbent

ii.                  They do not stretch but are easy to wash

iii.                They are flame and wrinkle resistant

iv.                They withstand sunlight

v.                  They resist mildew and cold acids but they are damaged by alkalis.

vi.                They break easily

vii.              They produce sharp ends on the fabric for this reason they are unsuitable for clothing.

Uses of Glass fibers

i.                    Glass fibers are useful because of their fire resistant ability hence used to make curtains, firefighting clothes, insulating electrical equipment, fire screen spectacles as well as in fabrics for making restaurant table cloths

ii.                  In industries plastics are reinforced with glass to make fabrics that are stronger than steel

Reinforced plastic

4.2. processing of sisal

5. MAN-MADE FIBERS

MAN MADE FIBER PRODUCTION

Man-made fibers can be modified at any stage during the production process (with additives such as pigments) or immediately afterwards (by drawing, crimping or the application of finishes) to suit the end product. The fibers can be created to match the requirements of the textile. Once engineered to fit a given application, fiber characteristics are identical from batch to batch. Alternatively if a desired result cannot be achieved by modifying one type of man-made fiber, different types can be modified to give the required performance.

GENERAL PRINCIPLES

All man-made fibers are produced from polymers. These substances are solids at normal temperatures. The polymers which are the starting products for man-made fibers may well be in form of chips, small particles of perhaps one to two millimetres in diameter and two to three millimetres in length.

In order to make filaments from these polymers, their physical shape must be altered, and the polymer chips must be converted to a liquid form. This is necessary as the polymer needs to be forced or extruded through fine holes to form filaments.

The process of producing a man-made fiber is often termed ‘spinning’.  This leads to confusion with the purely mechanical process of assembling staple fibers into a yarn, which is called ‘spinning’. The process of producing a man-made fiber will therefore be described as ‘extrusion’.

There are three methods of extruding fibers: Melt extrusion, Solvent-dry extrusion and Wet extrusion. The method used for each fiber depends upon the ease of conversion of the polymer from solid to liquid state.

·         If the polymer can be converted to a liquid form easily just by heating, then melt extrusion can be used.

·         If polymer is chemically damaged by heating but can be dissolved in a suitable solvent which will later evaporate, then dry extrusion is used.

·         If polymer cannot be heated or dissolved in an evaporative solvent, wet extrusion must be used.

The molecules in the extruded filaments are likely to be randomly orientated within the fiber. For the fiber to have good tenacity and a reasonable low extension at break, the molecules need to be lined up along the fiber axis. In order to do this, a further process known as stretching or drawing is needed.   This increases the tenacity and decreases the extension-at-break.

The production of manmade fibers usually includes the following processes:

        i.            Preparation of polymer (polymerization, chemical modification, etc.)

      ii.            Preparation of the spinning fluid (polymer melt or solution)

    iii.            Spinning (extrusion, solidification, and deformation of the spinning line or filament)

    iv.            Drawing (due to a higher linear speed at the take-up roll relative to that at the die; drawing is used to increase the degree of molecular orientation and improve the tensile strength, modulus of elasticity and elongation of the fibers)

      v.            Heat treatment

    vi.            Textile processing (twisting, oiling, dyeing, etc.).

Three processes for man-made fiber production

1.      Melt extrusion

This is the simplest fiber production processes. It is used for the production of Polyester, Polyamides, Propylene and Polymers such as nylon, polyethylene, polyvinyl chloride, cellulose triacetate

The polymer is melted and extruded through the fine holes of a spinneret (metal plate with small holes drilled through it). The number of holes in the spinneret determines the size of the yarn, as the emerging fibers are brought together to form a single strand. The molten polymer passes through the holes in the spinneret plate and emerges into a steam of cool air which causes it to solidify. The solidified bundle of filaments is passed around a rotating roller and then forwarded to a collecting device.

The melt extrusion process can therefore be split into three stages heating, extrusion and cooling.

Drawing

The fibers is not yet suitable for use because the polymer molecules are not highly oriented along the fiber axis. To orient them, the fiber is drawn forming areas of crystalline order. In this process the fiber is in a plastic rather than a molten state.

2.      Solvent-dry extrusion

If a polymer will not meet the conditions for melt extrusion, an alternative method of converting the solid polymer to a liquid state must be used. If it is possible to use a volatile solvent, that is a solvent which is highly reactive, then the polymer can be extruded into warm air to evaporate the solvent away. This is known as solvent-dry extrusion and is the least used for major fiber production techniques.

The polymer solution is extruded through a spinneret into heated gas so that the solvent is rapidly evaporated from the filaments. The filaments drop through the hot gas steam for five to six metres to a rotating roller and are then fed to the wind-up device.

Cellulose acetate, cellulose triacetate, acrylic, modacrylic, aromatic nylon, and polyvinyl chloride are made by dry spinning.

After treatments

Filaments must be washed to remove any remaining solvent from the extrusion stage. Drawing can also be carried out at this stage, in either air or liquid.

3.      Wet extrusion

1.      If the polymer does not melt without decomposition and will not dissolve in a volatile solvent, it must be dissolved in a non-volatile solvent to change it from solid to liquid state. There are two steps in wet extrusion: physical process and chemical regeneration. In this the polymer solution (i.e., polymer dissolved in a solvent as in dry spinning) is spun into a coagulating solution to precipitate the polymer (solidify them). This process has been used with acrylic, modacrylic, aromatic nylon, and polyvinyl chloride fibers.

AFTER TREATMENTS

As for solvent-dry spinning, the filaments of viscose must be washed to rid them of any chemicals from the coagulating bath. The filaments are dried then suitable spin finishes are applied.

SYNTHETIC FIBERS

Introduction

They are made up of substances which do not normally form fibers but are synthesized. To synthesize is to build new molecular structures by adding small molecules to give a large, long molecule. This process is known as polymerization. And the large molecule formed is known as polymer.

Made fibers from synthetic polymers are created using polymerization of various chemical inputs to create polymers.  Polymerization is the process of combining many small molecules into a large molecule – a polymer.    Polymers are simply large molecules composed of repeating structural units.  Polymers used for synthetic fibers are produced from intermediates (which in turn have been produced from crude oil) and applying a catalyst. Polymers are the building blocks of synthetic fibers

NYLON (A POLYAMIDE)

ü  Is the oldest synthetic fiber, It belongs to the polyamide group polyamides are formed with a recurrent amide group (-CO-NH-) as part of the polymer chain. There are different types of nylons distinguished by the chemical structure of the individual polymer.

ü  The original form of nylon is known as 6.6 because it has six carbon atoms.

o   Examples of nylon fabrics:

·         Brocade                            

·         Damask

·         Gabardine

·         Lace net

·         Satin

·         Knitted fabrics (jersey)

It is produced in USA and UK in both filament and staple form

PRODUCTION OF NYLON

It is produced in the following ways:

1.      POLYMERIZATION

ü  The raw materials are heated , causing the short chain molecules to combine to make long molecules until fibers are formed

ü  These fibers are cooled whereby they solidify into a hard ribbon like from.

ü  They are then cut into chips ready for spinning.

2.      SPINNING

ü  The polymer chips are heated to a molten mass.

ü  They are passed through tiny holes in a spinneret, cooled and solidified into filament form.

ü  They are then twisted together to form a yarn.

3.      DRAWING

ü  The yarn is stretched or drawn so as to reduce the thickness and lengthen the filaments. This increases the strength and changes the appearance of the fiber from dull and opaque to shiny and clear.

ü  If staple fibers are needed the filament fibers are cut and a crimp is added.

   Properties of nylon

1.      Has a cool, clammy feel when in filament form, however this feel can be altered by creating filaments which are three-sided. In nature to give a smoother and softer fabric. 

2.      It is lustrous, transparent and has high tensile strength.

3.      It is very strong and durable, both wet and when dry.

4.      It has high resistance to abrasion and is very elastic, meaning it easily comes back to its original form after any stretching, pull or bending. For this reason it needs little or no ironing.

5.      It is also mildews, moth and flame resistance and has low resistance to sunlight.

6.      It has good resistance to alkalis but is disintegrated by strong acids.

7.      It has very low absorbency i.e. hydrophobic for this reason it dries quickly however, it also makes it build up electrostatic electricity making it very uncomfortable to wear as it clings on the body.

8.      It is thermoplastic, this means it is sensitive to heat. This quality is exploited to permanently set pleats in garments.

9.      It is easy to wash and doesn’t burn readily, it is one of the safest textile fibers.

10.  It is very versatile, it’s produced into various types of yarns from very sheer to very stout.

11.  It blend well with cotton, wool, rayon and silk giving them added strength.

12.  It also dyes well and has good color fastness however, this quality makes it pick up color or grease from other garments when laundering

NOTE: A distinct disadvantage of nylon made from spun yarns is that it pills badly. Pilling is the formation of a small balls of fiber on the fabric on the fabric due to friction.

Spun yarns are the staple fibers that are cut from the filament fibers in order to produce short fibers.

Advantages of nylon

a.       Lightweight

b.      Strong and durable

c.       Abrasion resistance

d.      Easy to wash and dries easily

e.       Resist shrinkage and wrinkles

f.       Insulating properties

Limitations of nylon

a.       Builds up electrostatic electricity making it very uncomfortable to wear as t clings on the body

b.      Poor resistance to sunlight

c.       Picks up oils and dyes in wash

d.      Thermoplastic i.e. sensitive to heat

Identification test for nylon

1.      BURNING TES

·         Nylon draws away from the flame before igniting.

·         It drips and melts in flame producing white smoke.

·         It forms a hard bead and smells of fresh celery, chemical or acid.

·         It is self-extinguishing.

2.      CHEMICAL TEST

 It is soluble in formic acid and carbolic acid (90% phenol).

3.      MICROSCOPIC TEST

The longitudinal view shows long, smooth filaments

Cross-sectional view shows circular, spotted structures.

Fiber structure may be varied to give different fiber properties e.g. a triobal filament maybe created to produce fabric with more glitter.

USES OF NYLON

1. Used in general apparel, which is sportswear, stockings, foundation garments, overalls, rainwear, lingerie, blouses, skirts and shirts.

2. Used for trimmings such as ribbons and lace.

3. Used in making furnishing such as carpets, bed-sheets, curtains and upholstery.

4. It is also quite useful for industrial uses in making industrial making tires, ropes, tarpaulins and conveyor belts.

5. Widely used in hosiery and household furnishings.

6. Mainly used for outer wear and swim wear fabrics, ski pants and active sportswear.

7. Used for lining material in coats, jackets because of excellent durability however it is expensive

TERYLENE (A POLYESTER)

Terylene is one of the polyesters in the market today. Polyesters are derived from petroleum by products namely; ethylene, glycol and terephalic acid.

Polyester fiber are produced in filament, staple and low lengths.

Other types of polyesters are: Dacron, kodel and vycron.

PRODUCTION OF TERYLENE

Its production is similar to that of Nylon.

Properties of Terylene

1.      Shrink resistance and extremely strong, It is popular for apparel fabrics

2.      It is cool to wear and quite resilient.

3.      It is also crease resistance therefore it needs little or no ironing and is good for travelling.

4.      It has a high abrasion resistance.

ACRYLIC (A POLYACRILONITRILE)

Acrylic is produced from acrylonitrile; which is got from either petroleum or natural gas.

True acrylics have over 85% of acrylonitrile while mod acrylics have between 35% - 85%

PRODUCTION OF ACRYLIC

Are production in a similar manner to other synthetics?

Orlon is dry spun and produced in both filament and staple forms, whereas acrilan and courtelle are wet spun and produced in staple form only.

Properties of acrylic

i.                    Lustrous and has a warm, soft handle

ii.                  Does not irritate the skin

iii.                Light  weight, strong and durable

iv.                Crease, shrink and stretch resistant.

v.                  Moth and mildew resistant

vi.                It is Thermoplastic

vii.              Damaged by alkalis but resist acids.

viii.            It is not damaged by sunlight or abrasion

ix.                Has low moisture absorbency, therefore Dries quickly

x.                  It builds up electricity and may even produce sparks for this reason it is used in an operating room as it can ignite ether a gas that is used to make patients sleep so that they do not feel pain during operation.

Identification test

1.      Burning test

·         Melts in flame, rolls, twists and forms droplets of hot, molten plastic.

·         May or may not continue to burn after the flame is removed.

·         Produces an acid or chemical oduor

·         Forms a hard, thick, black beaded edge.

2.      Chemical test

Dissolves in 80% sulphuric acid.

3.      Microscopic test

Longitudinal view – shows a fiber which looks look like fine glass rods

Cross-sectional view – shows circular structures

Uses of acrylics

1.      Used in making of general apparel such as coats, suits, dresses, blouses and underwear.

2.      Used to make carpets, blankets and bed spreads, lining fabrics and limited fabrics

                                   MODACRYLICS

They are modified acrylics. They contain between 35-85% acrylonitrile. Their characteristics are similar to those of acrylics but they are fire resistant, self-extinguishing, do not drip and are easier to dye.

Examples of mod acrylics include Dynel, teklan and kanekalon.

Uses of mod acrylics

Because of their fire resistant characteristic, mod acrylics are widely used for making children’s nightwear, racing drivers, overalls, fireside rugs, electrical insulations, furnishings, public buildings, wigs and hair pieces.

                      POLYOLEFIN FIBERS       

These are fibers that are made from 85% ethylene or propane gas. They are produced by melt spinning and are used for household and industrial purpose due to their low moisture absorbency.

Examples of polyolefin are polypropylene and polythene

Properties of polythene

1.      Polyolefin are rot proof

2.      Color fast in sunlight

3.      Light weight

4.      Very strong

5.      Relatively cheap

6.      Have low moisture absorbency

7.      They are not affected by either alkalis or acids but are affected by sunlight.

Uses of polyolefin

·         Used for making deck chair covers, ropes, packing papers, fishing nets, filter cloths and carpet backing.

ACTIVITY: why do you think polythene is not popular for making apparel fabrics?

Let us now learn about some fibers that are used minimally in the textile industry, they have much lower production rate but are important all the same. They are referred to as minor fibers.

                                 MINOR FIBERS

SPANDEX (AN ELASTOMERIC FIBER)

Elastomeric fibers are got from polyurethane which is derived from petroleum by products. They have a high elasticity power of between 450%-700% and have complete and instant recovery.

They are often blended with other fibers so as to give them the preferred texture and appearance e.g. spandex, Lycra (UK & USA) and spanzelle (USA).

Properties of spandex

1.      Spandex fibers can stretch up to 500%-800% of their length before breaking.

2.      They high recovery rate once released therefore, they are used for sportswear such as swim suits.

3.      Superior dye ability with brilliant colors.

4.      Very good resilience and highly flexibility; Very good abrasion resistance. Good dimensional stability in wet condition; however some types shrink with the exposure to the high temperature.

5.      They resist perspiration, this makes them ideal for sportswear and underwear

6.      Good resistance to household bleaches and most acids but are damaged by hot alkalis as it causes rapid deterioration. It is resistant to dry cleaning solvents;

7.      They dry quickly, easy to launder and blend well with nylon and Terylene.

Spandex in Consumer Use

i.                    Lycra in swimwear, innerwear and active sportswear means providing fitting clothes with comfort and freedom of movement.

ii.                  It also improves the quality of Knitted / Woven fabrics as it prevents bagging and accelerates wrinkle recovery.

iii.                Lycra in swimwear, innerwear and active sportswear means providing fitting clothes with comfort and freedom of movement.

iv.                Make home furnishings such as bed sheets, curtains and seat covers.

v.                  It also improves the quality of Knitted / Woven fabrics as it prevents bagging and accelerates wrinkle recovery.

POLYVINYL CHLORIDE FIBERS (P.V.C)

These fibers are not used for clothing purposes because they are very sensitive to heat and therefore, cannot be ironed. However, they may be used to bond some needle constructed fabrics.

Properties of P.V.Cs

1.      P.V.C are moth, mildew, and chemical and flame resistant but sensitive to heat.

2.      They are non-absorbent

Uses of P.V.Cs

a.       Are used for industrial purposes such as protective clothing, tarpaulins (lorry covers) and filter cloths

b.      They are used for home furnishing such as seat covers, desk chairs and carpets.

MAN-MADE OR REGENERATED FIBERS

We have looked at fibers that occur in either animals or plants as well as fibers that are processed from chemicals that is synthetic fibers. Although synthetic fibers are man-made the “the man-made” refers to all fibers that are processed from both natural raw materials and chemicals. They are produced by the chemical treatment of certain raw material, the main raw materials are wood pulp, cotton linters, petroleum extracts and by products of coal. Other fibers are made from proteins like milk, soya beans as well from maize meal and a natural rubber base.

They can be divided into two main groups namely viscose rayons and acetate or triacetate rayons

VISCOSE RAYONS

It’s the first man-made fiber formally called artificial silk. It was developed by scientists who tried to copy the silk worm by producing a liquid secretion which can solidify into filament. It is mainly produced from cellulose of spruce and eucalyptus trees as well as cotton linters, petroleum extracts and by products of coal e.g. are crepe, damask, flannel, gabardine, jersey, satin, taffeta and velvet

Processing of viscose rayon

It’s processed in the following steps

i.                    Source

The eucalyptus and spruce trees are felled and the bark is removed. This is done in pulp mills, the cellulose is extracted, pressed and cut into sheets.

ii.                  Steeping

The cellulose is steeped into caustic soda, which converts it into alkali cellulose which is then shredded into crumbs and left to oxidize.

iii.                Xanthation

The alkali cellulose is treated with carbon disulphide to give sodium cellulose xanthate

iv.                Dissolving

The sodium cellulose xanthate is dissolved in caustic soda (NaOH) to form the spinning solution known as viscose which is left to ripen or to ferment.

v.                  Filtration

Any undissolved particles are removed by filtration

vi.                Wet spinning and extrusion

The viscose is forced through fine holes in a jet (a spinner) into a coagulating bath of sulphuric acid and salts. This process produces the original cellulose in filament form.

If fine staple fibers are required the filaments from several jets are drawn together and the low is cut into fibers of desired length.

vii.              Washing

The yarns are washed to remove all traces of chemicals then they are dried 

viii.            Twisting and winding

The yarns are given a twist and wound on to bobbins

Properties of viscos rayon

i.                    Rayon is smooth, absorbent and cool to wear as it is a good conductor of heat for this it is quite comfortable to wear.

ii.                  It is fairly strong but is weaker when wet

iii.                It dyes and is highly color fast when spun dyed

iv.                It drapes well

v.                  It burns readily

vi.                It is affected by static electricity

vii.              Its damaged by acids and alkalis and especially by acetone for this care should be taken during laundry-work and especially when removing stains

viii.            It is also damage by friction, twisting and wringing therefore, it should be washed by kneading and squeezing method and should not be tumbled dried.

ix.                It may also shrink or stretch unless its specially treated

Identification test for viscose rayon

i.                    Burning test

Viscose rayon burns easily, flaming, smells of burning paper (like cotton) and leaves grey ash.

ii.                  Chemical test