Bast Fibre (Flax):

Flax (also known as common flax or linseed), with the binomial name: Linum usitatissimum is a member of the genus Linum in the family Linaceae. It is a food and fibre crop that is grown in cooler regions of the world. The species is native to the region extending from the eastern Mediterranean, through Western Asia and the Middle East, to India.

Textile classification- 

·        The flax fiber is classified, as natural, cellulose, bast, multi-cellular fiber.

·        It is considered to be a heavy fiber, for this reason that most linen textile materials are of light construction.

·        Thick linen textile materials would be uncomfortably heavy to wear.

 Description

Flax, Linum usitatissimum, is an upright annual plant growing to 1.2 m (3 ft 11 in) tall, with slender stems. The leaves are glaucous green, slender lanceolate, 20–40 mm long and 3 mm broad.

The flowers are pure pale blue, 15–25 mm diameter, with five petals; they can also be bright red. The fruit is a round, dry capsule 5–9 mm diameter, containing several glossy brown seeds shaped like an apple pip, 4–7 mm long.

In addition to referring to the plant itself, the word "flax" may refer to the unspun fibers of the flax plant. New Zealand flax is not related to flax but was named after it, as both plants are used to produce fibers.

History

The earliest evidence of humans using wild flax as a textile comes from the present day Republic of Georgia, where spun, dyed, and knotted wild flax fibers were found in Dzudzuana Cave and dated to the Upper Paleolithic, 30,000 years ago.^[2][3][4] Flax was first domesticated in the Fertile Crescent region during the Neolithic Revolution and is one of the oldest fiber crops in the world.^[5] There is evidence of a domesticated flax by at least 7,000 years ago (5,000 BCE) in northern Iraq, and use of the crop steadily spread, reaching places as far as Switzerland and Germany by 5,000 years ago (3,000 BCE).^[6] In China and India flax was domesticated by at least 5,000 years ago (3,000 BCE).^[7]

Flax was extensively cultivated in ancient Egypt, where temple walls had paintings of flowering flax and mummies were entombed in linen.^[8] Egyptian priests only wore linen, as flax was considered a symbol of purity.^[9] Phoenicians traded Egyptian linen throughout the Mediterranean, and the Romans loved to use it for their sails.^[10] As the Roman Empire declined, so did flax production, but Charlemagne revived the crop in the 8th Century CE with laws that meant to promote the hygiene of linen textiles and the health of linseed oil.^[11] Eventually Flanders became the major center of the linen industry in the European Middle Ages.^[11] In North America, flax was introduced by the colonists and it flourished there.^[12] But by the early 20th Century cheap cotton and rising farm wages had caused production of flax to become concentrated in northern Russia, which came to provide 90% of the world's output. Since then flax has lost its importance as a commercial crop, due to the ease of more durable fibers.^[13]

Flax Fiber morphology

·        The flax fiber is a thick, regular fiber with a subdued luster.  It ranges in length from about 10cm to 100 cm, averaging about 50cm in length.  As the flax fiber is a strand of cells, it thickness depends upon the number of these cells, about 3-6 cells constitute a fiber cross section.  The flax cells are about 25mm long and 10µm to— 20µm thick. This would be given an average fiber thickness ranging from about 40µm to 80µm.

•  Its fiber length to breadth ratio is 15000:1 for the longest and the best flax and 1500:1 for Short flax fibers.  The color of flax varies from light blond to grey blond, the particular shade resulting from the agricultural and climatic conditions under which it was grown and the quality of retting.  The subdued luster of flax is due to its long regular fiber surface, which is coated with a film wax. This enables a significant amount of the incident light to be reflected, resulting in the
•  There may be up to 80 nodes in a single flax fiber cell. The length of the node indicates the width or thickness of the fiber cell.  Where ever a node occurs, it indicates a change in the spiral direction of the fibrils which constitute the cell walls.  Such spiraling imparts strength to the cell and, hence, to the flax fiber

·         The micro-structure of flax- The flax fiber cell is covered with a wax film.  The cell walls of flax are constructed of spiraling fibrils composed of cellulose polymers.  On the whole, the flax cell is more sturdily constructed then the cotton cell, as indicated by the former’s thicker cell walls.  This explains, in part, the greater tenacity of flax compared with cotton.

·         The flax polymer and its polymer system- it has a degree of polymerization of about 18000.  This means the flax polymer is about 18000nm long, and about 0.8nm thick.  The polymer system of flax is more crystalline, because of its longer polymers, spirals about each other at approximately 6° to the fiber axis, thereby contributing towards the tenacity and durability of fiber.  The greater crystallinity of flax fibers is demonstrated by the fact that they are stronger, crisper and stiffer to handle, and textile materials wrinkle more readily.

  

Physical properties of Flax:

1.     Tenacity-

  Flax is a very strong fiber because it’s very crystalline polymer system permits its extremely long polymers to form more hydrogen bonds than cotton polymers.  Elastic-plastic nature- The very inelastic nature is due to very crystalline polymer system.  It tends to lock its polymers into position with the aid of the countless hydrogen bonds which form between the polymers.  Flax will resist being flexed or bent,. When these are bent or flexed, their polymers are liable to break leading to fractures in the polymer system.

2.      Hygroscopic nature-

Flax fiber is very absorbent, Owing to the countless polar –OH groups in its polymers; these attract water molecules, which are also polar.  Aqueous swelling of the flax fiber is due to a separation or forcing apart of polymers by the water molecules in the amorphous regions only.  The polarity of the water molecules, attracted to the hydroxyl groups on the polymers, dissipate any static charge which might develop.

3.      Thermal properties- 

Flax has the best heat resistance and conductivity of all the commonly used textile fibers. No satisfactory explanation can be offered for this.  Excessive application of heat energy causes the flax fiber to scouch, char and burn, this is an indication that flax is not thermoplastic, which may be attributed to the extremely long fiber polymers and the countless hydrogen bonds they form.

Chemical properties of Flax

Flax is a natural cellulosic fiber and it has some chemical properties. Chemical properties of the Flax fiber are given below:

1.     Effect of Acids: Flax fiber is damaged by highly densified acids but low dense acids does not affect if it is wash instantly after application of acids.

2.     Effects of Alkalis: Flax has an excellent resistance to alkalis. It does not affected by the strong alkalis.

3.     Effects of Bleaching Agents: Cool chlorine and hypo-chlorine bleaching agent does not affect the Flax fiber properties.

4.     Effect of Organic Solvent: Flax fiber has high resistance to normal cleaning solvents.

5.     Effect of Micro Organism: Flax fiber is attacked by fungi and bacteria. Mildews will feed on Flax fabric, rotting and weakling the materials. Mildews and bacteria will flourish on Flax under hot and humid condition. They can be protected by impregnation with certain types of chemicals. Copper Nepthenate is one of the chemical.

6.     Effects of Insects: Flax fiber does not attacked by moth-grubs or beetles.

7.     Dyes: It is not suitable to dye. But it can be dye by direct and vat dyes

 Harvesting

Flax is harvested for fiber production after approximately 100 days or a month after the plant flowers and two weeks after the seed capsules form. The base of the plant will begin to turn yellow. If the plant is still green the seed will not be useful, and the fiber will be underdeveloped. The fiber degrades once the plant is brown.

Methods: There are two ways to harvest flax, one involving mechanized equipment (combines), and a second method, more manual and targeted towards maximizing the fiber length.

Mechanical

The mature plant is cut with mowing equipment, similar to hay harvesting, and raked into windrows. When dried sufficiently, a combine then harvests the seeds similar to wheat or oat harvesting. The amount of weeds in the straw affects its marketability, and this coupled with market prices determined whether the farmer chose to harvest the flax straw. If the flax was not harvested, it was typically burned, since the straw stalk is quite tough and decomposes slowly (i.e., not in a single season), and still being somewhat in a windrow from the harvesting process, the straw would often clog up tillage and planting equipment. It was common, in the flax growing regions of western Minnesota, to see the harvested flax straw (square) bale stacks start appearing every July, the size of some stacks being estimated at 10-15 yards wide by 50 or more yards long, and as tall as a two-story house.^{[citation needed]}

Manual

The mature plant is pulled up with the roots (not cut), so as to maximize the fiber length. After this, the flax is allowed to dry, the seeds are removed, and is then retted. Dependent upon climatic conditions, characteristics of the sown flax and fields, the flax remains on the ground between two weeks and two months for retting. As a result of alternating rain and the sun, an enzymatic action degrades the pectins which bind fibers to the straw. The farmers turn over the straw during retting to evenly rett the stalks. When the straw is retted and sufficiently dry, it is rolled up. It will then be stored by farmers before scutching to extract fibers.

Flax grown for seed is allowed to mature until the seed capsules are yellow and just starting to split; it is then harvested by combine harvester and dried to extract the seed.

Process Flow of Flax Cultivation:

Flax fiber is cultivated in the hot region of the world. Like all of the fiber cultivation process, it has a cultivating flow chart. Here, I have presented a process flow of flax cultivation.

Land preparation

↓

Seed sown

↓

Plant grows

↓

Harvesting

↓

Retting

↓

Breaking

↓

Scutching

↓

Hacking

↓

Flax fibers (line and tow)

Manufacturing process of Flax

1. Collection of plants- when the stems of the plant turns yellow at the seeds turn green to pale brown. The plants are pulled out by the roots. These are tied into bunches.

2. Drying and rippling- after pulling the Flax, plant is tied in bundles and left to dry for few days. The leaves and seeds are removed from the stems by a process called Rippling. For this, the head of the stem is passed through coarse comb. After the removal of leaves and seeds, the stems are again tied up in bundles. Seeds are used for the production of Linseed oil.

3. Retting- this is an important process. The fleshy part of the stem is rotted by contact with water. Retting is a ferment process where the Pectin Overrun (Pectin eater) bacteria eat the gum (pectin) which binds the fiber to the stem.

There are 5 method of retting-

A.   Dew retting- 

Stems are spread out in fields and are exposed to rain, sun and dew for several weeks, until; the stalk begins to separate from the fiber. It takes around 15-30 days. Because of long exposure to the sun and other natural conditions, causes to discoloration of the fiber.

B. Water retting-

 The bundle of the stems are kept in running or segmented water for about 2 weeks . Swift running of water carries away the bacteria and thus slow down the fermentation. The stem bundles are covered with straw and stones are put on the straw to give extra weight. After 2 weeks the stalks (upper portion of stem) separates out from the fiber

C. Wooden vat retting-

 The stems are steeped in water at the controlled temperatur75°-90° in a Vat or in a container until the stems get soft. This is a fast process and the easiest method of retting and the quality of the fibers are good from this process.

  D. Chemical retting

In this process the stems are treated with mild/dilute conc. Acid and alkalis then the fibers are easily removed from the stems.

  E. Enzyme retting

Enzyme retting is the safest and fastest process of retting, in this process the fibers can be taken out from the stems.

4. Breaking and scutching-

 When the stems are completely dry linen fiber are separated from these stems when the decomposed woody tissue is dry. It is crushable by passing through iron Rollers. The breaking operation breaks the outer stalk. It reduces the stalk to small pieces of bark called slivers. Scutching is done with the help of scutching machine which removes the broken slivers by means of rotating wooden peddles, thus releasing the flax fiber from the stem or it separates the fibers from woody stalk

 5. Hackling or combing and spinning

During this process series of iron combs are used, ranging from course to fine. Fibers are pulled through the teeth of combs, beginning with the coarse one. The short fibers break off used for inferior quality Lenin called Tow linen. Then the spinning process is carried out- Tow-lines long staple or line Carding Carding Card Card Slivering Slivering Sliver Sliver Spinning Drawints Raning Coarse yarn (linen) Rove Spinning fine yarn (linen)

6. Weaving, finishing & dyeing

 Bleaching is given to the yarn and later on dyeing is done. The reason being the Linen yarn is in natural color i.e. grey or yellowish grey. Dyeing can not be done directly because it is not white in color. That is why bleaching is done before dyeing.

Advantages of Flax fibre:

Some of the positives of using linen-clothing are that it adds to charm and trendiness to any attire. Being a stylish fabric, you can buy nicely printed pattern clothing and look extremely fashionable. Many designers now display linen clothing that is well-liked by the people around. Pattern clothing has a natural luster.

Linen-clothing can last longer because of its characteristics; such as high strength and durability. Texture clothing is made from strong flax fibres which mean that it is available in a variety of textures.
Linen-clothing can be worn in any kind of weather. It can even be worn in a hot and humid weather, because it is highly absorbent. Pattern clothing makes you feel fresh because it is not sticky and removes skin perspirations. Linen clothing can be tailored without any trouble.

Linen clothing can be washed and dried easily. It can even be hand-washed. In fact, washing makes linen clothing softer, however, make sure you use soft water. It does not stretch or elongate but keeps in shape even after routine washes, hanging and ironing. Linen clothing can be printed, finished and designed easily.

Disadvantages of Flax fibre:

With a number of advantages linen fabric comes with various disadvantages as well, however, they are not many in number. Linen clothing can lose its charm if washed with hard water. Therefore, you need to be extra careful while washing texture clothing with chemicals and detergents. Texture clothing is restricted to a small range of colours, providing not much variety.

It wrinkles and creases easily which can make you look untidy. It is best not to fold linen clothing for storage, you should hang it. Another disadvantage is that pattern clothing is a little more expensive than cotton; making cotton products more desirable.

 Applications of Flax Fiber

• Table wear 
• Suiting 
• Clothing apparel 
• Surgical thread 
• Sewing thread 
• Decorative fabrics 
• Bed linen 
• Kitchen towels 
• High quality papers 
• Handkerchief linen 
• Shirting 
• Upholstery 
• Draperies 
• Wall coverings 
• Artist’s canvases 
• Luggage fabrics 
• Paneling 
• Insulation 
• Filtration 
• Fabrics for light aviation use 
• Automotive end uses 
• Reinforce plastics and composite materials. 
• Flax could conceivably be mixed with excess grass seed straw or softwood fiber in composite boards 

End uses of Flax fibre:

Industrial Uses:

Flax is still produced for its oil rich seed. Linseed oil has been used as a drying agent for paints, varnishes, lacquer, and printing ink. Unfortunately these markets have eroded somewhat over the years with the production of synthetic resins and latex. One bright spot in the market has been the use of linseed oil as an anti-spalling treatment for concrete where freezing and thawing effects have created problems on streets and sidewalks. Occasionally the straw is harvested and used to produce some paper products. 

Livestock Feed:

Linseed oil meal is an excellent protein source for livestock containing about 35% crude protein. Flax straw on the other hand, makes a very poor quality forage because of its high cellulose and lignin content. 

Human Food:

Recently there has been some interest in seed flax as a health food because of its high amount of polyunsaturated fatty acids in the oil.