bast fibre

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BastBastFibres

Bast Fibers

• Fibres are obtained from the Bast or Stem• Fibres are obtained from the Bast or Stemof the plants.

• They are also called as Stem fibres or Bark fibres.

• Bast fibres are constructed with long and thick walled cells that overlap with each other.

• These fibres are cemented with each other and with the inner stem of the plant by means of natural non-cellulosic binding agents (glue).

• The fibres glued to each other form a continuous type of strand that may run through out the length of the stem.

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• Fibres are released from the inner stem of the plant by a natural decomposition process called as retting or rotting.

• They can be used in both continuous strand andseparated individual form.

• There are so many different types of bast fibres, but the most important fibres in this category are:but the most important fibres in this category are:– Flax– Jute– Hemp– Ramie

Fla /Flax / Linen

Flax Is an Ancient Crop

• Flax has been grown since the beginnings of civilization, and people all over the world have celebrated its usefulness throughout thehave celebrated its usefulness throughout the ages.

• Cultivated flax, L. usitatissimum, is of 2 types: – grown for the seed and

f fi i– for fibre production.

• In North America, it is primarily the oilseed varieties which are produced commercially.

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• Historians weave the magic of flax into ancient history and records show that the human race has eaten this seed since early times.

• About 3 000 B C• About 3,000 B.C.– Flax is cultivated in Babylon. – Burial chambers depict flax cultivation and

clothing from flax fibres.

• About 650 B.C.– Hippocrates writes about using flax for the relief

of abdominal pains. – In the same era, Theophrastus recommends the

use of flax mucilage as a cough remedy.

• About 1st Century A.D.– Tacitus praises the virtues of flax.

• About 8th Century A D• About 8th Century A.D.– Charlemagne considered flax so important

for the health of his subjects that he passed laws and regulations requiring its consumption.

• About 15th Century A.D.– Hildegard von Bingen used flax meal in

hot compresses for the treatment of both external and internal ailments

• Flax, in addition to cotton, is also one of the earliest fibre used by man.

• Flax fibre is obtained from a special type of plant called as Linum Usitatissimum.

• Which grows in most cold to moderate temperature regions through out the worldtemperature regions through out the world.

• The outer layer of stem of this plant is – hard & – unsuitable for textile purposes

• The inner layer of the stem contains – soft, long & thick walled fibres in a strand

form that are used as textile fibres.

• The major producers of flax are Argentina,Canada, France, Russia, Switzerland, UK, & USA

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Growth

• Flax plant is an annual plant - grows once a year. y

• A full mature flax plant has a height of 3 to 4 feet.

• This plant has a single long stem with very few side branches in it.

Flax Plant

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• Branches are only present in the area where the plant bears flowers.

• When flowers appear and the seeds begin to ripe, at this point, the harvesting of this plant takes place.

Harvesting Flax Plant

• Harvesting is done – Manually or – Automatic mechanical pullers can be used

• After Harvesting, – Roots & branches are removed from the plant– Only the stem is obtained.

• These stems are then tied in bundle forms.

• About one fourth part of the stem of flax plant contains useful fibres.

Processing

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Retting• The process of separating the fibre from the wood.

• This is done either chemically or biologically• This is done either chemically or biologically

• It is a natural decomposition process of fermentation by means of which the fibre strand can be removed from its woody inner stem.

• The most commonly used method are :-– Dam Retting– Dew Retting– Tank Retting– Chemical Retting

Dam Retting

• Dams or ponds are dug up into the ground.

• Bundled stems are immersed for 10 days.

• This is an ancient method of retting

• It is no longer used because many impurities are also added to the fibre.

Dew Retting• Stem of plants is spread on the ground for several

weeks.

• Dew during the night & rain encourages this process.

• This method is applied in areas facing water shortage

• The main drawback is that it makes the fibre grey / blackish in colour.blackish in colour.

• This technique is mostly used in Europe.

• Dew retting is cost effective as less labour is required & no water goes wasted by this method.

Tank Retting• Most suitable retting method that gives the most uniform and

good quality of fibres.

Th b dl f t t i t t t k• The bundles of stem are put into a water tank.

• The water is heated to a temperature of 30° Celsius.

• Sometimes the water is circulated to accelerate the process.

• This process takes about three days.

• Best quality fibres are obtained by double tank retting: – the fibres are partially retted once and then they are dried – after drying second stage of retting is carried out.

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Chemical Retting• Using chemicals like caustic soda, sodium carbonate, soaps and

dilute mineral acids can also do the retting

• This process proves more costly than natural retting as well as the quality of fibres produced is similar.

• Only advantage is the speed of operation, done within few hours.

• A special type of chemical retting - cottonization, also possible.

• In cottonization, retting is carried out up to an extent where very fine fibres can be obtained.

• These fibres resemble the cotton fibres that can also be spun on normal cotton spinning machinery.

Breaking• After the fibres are separated from its inner

woody core by retting,

• In this process, the fibres are passed through a pair of fluted roller of the breaking machine.

• The woody core is broken down into small fragments without damaging the fibres.

Scutching (Beating Out)• Process of separating the fragments of woody

matter from the fibres.

• Done by beating or striking the straws with metal or wooden blades.

• The wood separated by this process is called as shive, which can be used as a fuel.

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Hackling• Fibres are combed / hackled by passing them through

series of combs.

• Each successive comb used is finer than the previousEach successive comb used is finer than the previous

• This helps to separate the coarse fibres from the fine ones in order to make the fibres parallel and aligned to each other.

• The short and coarse fibres obtained are called as Tow• The short and coarse fibres obtained are called as Tow& are used for low grade yarns

• The long and fine fibres are called as Line & are spun into high quality yarn

Spinning• Spinning can be carried out in

– Dry form for coarse fibres &W t f f fi fib– Wet form for fine fibres.

• In wet form, the fibres are converted into a roving and then passed through a boiling water bath.

• This softens the gummy material between the fibres making it easier for drafting and aligning as the roving is spun into a yarn.

Properties ofProperties of Flax Fibres

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Structure & Appearance• The flax fibre has a yellowish white appearance.

• Its appearance depends upon the type of retting• Its appearance depends upon the type of retting

• It has a smooth, uniform and lustrous appearance.

• Its lustre improves when impurities are removed by scouring and bleaching.

• The length of flax fibre in a strand form -few inches to 3 feet.

A erage length of fibre strand 8 to 24• Average length of fibre strand = 8 to 24 inches.

• Because of breaking and scutching, max length of the fibre strand is up to 16 inches.

• Flax can either be used in – strand form or in – individual fibre form.

Fine Structure• As an individual fibre:

– length of the ranges from ¾ inches to 3 inches M di t f b t 20 i (0 02 )– Mean diameter of about 20 microns (0.02 mm).

• Microscopic examination: – transparent cylindrical structure with

smooth or sometimes slight crimped surface.

• The diameter of the fibre varies at different points.

• The fibre also has a lumen or canal running through its centre.

• The lumen is regular and well defined which tapers to a point at both ends of the fibre.

• The cross-section of the flax fibre is circular having a polygonal structurehaving a polygonal structure.

• However the immature fibres have more oval cross-section with wider lumen.

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• Tensile Strength 5.8 gms / decitex

• Elongation inextensible 1.8%D - 2.2%W

• Elastic Properties highly elastic p g y

• Specific Gravity 1.54

• Moisture 12% - 20%, Gains strength

• Thermal Properties Highly resistant 120° C

• Sunlight strength decreases

• Insects highly resistant

Uses of Flax• Fabrics that are exposed to moisture like sail

fabric, tent, fishing line, etc.

• Ability to absorb moisture is useful in towels.

• High quality linen fabrics for dress purposes.

• Linen bed sheets, bed spreads

• Linen fabric used as a glass cleaning cloth.

• Waste of linen fibres are used in making bank notes, cigarette paper and writing paper.

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Seeds & Yarns

Jute

• 2nd most important bast fibre

• Used since prehistoric time

• Inner bark of a plant - Genus Corchorus

• widely grown in hot and humid regions of• widely grown in hot and humid regions of Asia - Bangladesh, India, Thailand & Pakistan

• Used in sacking, baggage cloth, ropes, cords, etc

• Rarely used for dressing purposes

• Nineteenth C - upto late 1970s - a value fibre

• Alternative - better quality products based on man-made fibres

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Growth• Annual plant p

• Height - 15 feet

• Stem Diameter - ¾ inchStem Diameter ¾ inch

• Upon maturing - harvested by cutting off lower part of the stem by means of blades

• Harvesting is generally carried out by hand

• After harvesting, leaves & branches are d d f l t ti d iremoved and useful stems are tied in

bundle form

Processing

– Dam type retting is preferred - 5 to 7 days to complete,

h fib d f h i b k– Then fibres are separated from the inner bark without scutching and breaking processes.

– After separation - washed thoroughly and dried in sunlight

– Dried fibres compressed into a bale form for spinning purpose.

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Spinning

• Jute fibres cannot be spun in dry state

• During spinning, necessary to add a small amount of mineral oil to the fibres

• Normal quality yarns have about 5% of mineral oil

• Fibres = finer - better quality yarns having oil up to 1% can also be produced

Bleaching & Dyeing• Jute fibres generally converted into cheap

goods like sacks, bags, etc. g , g ,

• So process of bleaching & dyeing are avoided

• Yarns used for carpets have to be dyed in p yvarious colours – thus bleached and dyed

• These yarns are specially used for ropes, cords, carpet backing yarns, etc

D ed ith cheap d es like direct and basic d es• Dyed with cheap dyes like direct and basic dyes

• Very less fastness - used where fabric is not subjected to lot of moisture and washing

• Better quality jute yarns, costly dyes like azo-free, vat & reactive dyes

Properties

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Structure & Appearance• Colour - yellow to brown & sometimes grey

• Appearance - Natural silky and lustrous

• Feel - rough and harsh.

• Continuous strand form

• Bound by non-cellulosic gummy material

J t fib t i 20% li i• Jute fibre contains 20% lignin.

• Length of jute in strand form can go up to 7 feet

• Retting sometimes destroys the cells giving a hairy appearance to it

• But retting does not separate individual fibre from each other

• Individual fibre length - very short i.e. about 0.1 inch.

• Mean diameter of individual jute fibre – 22 Microns - 0.022 mm.

Cross-Section• Polygonal structure - five or six sides

• Oval shaped thick walled lumen runs through the inner part of the fibre.

• Contrary to flax, the lumen of jute is y , jirregular in thickness.

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• Tensile Strength 3.5 gms / decitex

• Elongation inextensible 1.7%

• Elastic Properties poorp p

• Specific Gravity 1.5

• Moisture 13.75% - 23%, Decrease strength 15%

• Thermal Properties Good Insulator

• Sunlight strength decreases

• Insects highly resistant

Uses of Jute• sacks and bags.

• storage and transportation of agricultural goods

• backing fabric for carpets and rugs.

• Fine jute fabrics are used in curtains and furnishing fabrics.

• Rarely, jute is used for cheap dress fabric.