- 1 History of Linen
- 2 Definition Of Linen
- 3 Production & Sources Of Linen
- 4 Features of Flax Fibres
- 5 Manufacturing Process Of Linen
- 6 Linen Finishing Process
- 7 Processing Into Yarn
- 8 Appearance & Structure
History of Linen
Linen has been known in civilized societies for thousands of years. Flax was already being cultivated systematically by ancient Egyptians, Babylonians, Phoenicians, and other civilizations between 5000 and 4000 BC. Mummies from the pyramids of Egypt are wrapped in linen; cotton was unknown in Ancient Egypt until about 400 BC. The Romans laid down precise procedures for processing flax fibres which were hardly different, in principle, from that used today. Linen was especially popular in the middle Ages. It remains to this day a highly valued natural product.
Definition Of Linen
Textile made up of the flax plant is Linen. Linen requires continuous process to manufacture, the fibre is known for its coolness and freshness in hot seasons. Fibre is very absorbent.
There are many products that are made from linen such as – bags, towels,aprons, bed linens, men, and women’s wear.
The word linen has been originated from West Germany and cognate to the latin name for the flax pant – linum.
Production & Sources Of Linen
World production of flax has been almost constant for the last 25 years at between 600 000 and 700 000 tones. This represents less than 1.5% of world fibre production.
Features of Flax Fibres
In comparison to cotton, flax is also a renewable, biodegradable raw material, but it is more environmentally friendly because it requires minimal pesticide, herbicide, fertilizer, and irrigation. The flax fibre yield per acre is from 2 to 3.5 times higher than that for cotton, depending on the region and conditions. Flax has outstanding health, hygienic, and comfort properties: it is hypoallergenic, antiseptic, protective against UV radiation, naturally insect repellent, highly absorbent, electrostatic free, and thermo-regulating.
Technical flax fibre consists of many individual fibre cells whose physical properties are similar to those of cotton: length between 0.6 cm and 6.5 cm and means thickness of about 0.02 mm. This similarity of cotton and flax individual fibre cells (ultimate fibre) has revived interest in converting technical flax fibres into cotton-like fibres in order to process them on cotton spinning equipment. The reduction of the flax fibre length and thickness is called cottonisation and can be done by mechanical, chemical, ultrasound and enzymatic treatments. Cottonised flax can be processed in blends with cotton on cotton spinning equipment for a more diverse range of applications.
It is also the strongest of all the vegetable fibres being two to three times stronger than cotton. Natural flax colors range from shades of ivory, tan and gray. White or pure white is only achieved through various bleaching processes.
Flax is a renewable resource and has the potential to be much more eco-friendly than cotton. It requires far less use of pesticides and artificial fertilizers. It grows best under traditional farming methods where the crops are rotated and fields are allowed to lay fallow; it also benefits from a longer lifespan.
With crop rotation, it is not necessary to use chemical fertilizers and pesticides when growing flax. Even when these are used flax requires only one fifth of the pesticides and artificial fertilizers that are required for commercially grown cotton. Additionally, linen is up to twelve times stronger than the equivalent cotton product, which dramatically increases its life spun and therefore does not need to be replaced so often.
Linen absorbs dye well, especially natural dyes and does not require chemical treatments. It can be sun bleached to avoid the use of artificial agents. Flax processing is, however labor intensive, requiring skilled workers. It also produces minimum wastage, as there are several by-products. These include linseed oil for linoleum, soap, fuel and cattle feed.
Flax has grown for thousands of years, and always with great respect for the environment. Flax is a plant that grows naturally with very little chemicals used (much less than other crops). No irrigation is needed for growing flax. The flax plant is gentle on the land and flax is easy to incorporate into modern crop rotation cycles. The processing of flax needs very little energy and does not harm nature.
Water retting process has been replaced by the environmentally friendly dew retting on the field. Flax has some inherent ecological characteristics as all parts of the plant are used (there is no waste) and are 100% biodegradable or recyclable.
Desirable properties are that the fibre length should not be shorter than 6-12mm and that the fibre length should be several hundred times the width to give a high L/D ratio. These two conditions are important. The absence of either would not allow the fibre to hold together which would not allow fibres to be twisted together to form a yarn.
The fineness of the fibre which is dependent on the width of fibre enables the determination of how fine a yarn can be produced. There is a large variation in fibre dimension as it is an inherited characteristic that can be greatly influenced by soil and weather.
|Dimensions||Length||Width ,mm||Fineness, um||L/D|
Flax fibres are extracted from the stalks of the flax plant, which may be grown either for its fibres or for its seed. For fibre extraction, tall varieties with white to light blue flowers and a height of 80 to 120 cm are grown.
The shorter types are grown for linseed oil.Flax is an annual plant; it must be re-seeded every year. It thrives in temperate climates. Regions with a maritime climate grow the best flax qualities. Planting is in March and April, and growth takes 90 to 120 days.
The plant has side branches only at the top of the stem, from which the flowers grow. After flowering, the mature plant develops seed capsules the size of peas. The seeds are about 2 mm long and are very rich in oil. Harvesting is in July and August.
Construction of Flax Fibres
The cross-section of a flax stalk is composed of several layers which have to be removed in order to release the fibre bundles. The fibre bundles extend all the way to the plant roots.
They are made up from individual fibres (ultimate’s) of about 25 to 40 mm in length which is cemented together by a mixture of lignin’s, pectins and hemicelluloses. This cement comprises about 30% of the dry weight of flax, with the remainder being mainly cellulose. Flax fibres are relatively stiff, and have a smooth surface, without crimp or convolutions.
Unlike cotton, flax fibres are multi-cell technical fibres obtained from the stem of the annual plant Linum usitatissimum.
The length of flax fibres in a scutched state varies from a few centimeters (tow fibres) up to 100 cm, while the linear density of technical flax fibres ranges from 1.25 tex to 2.5 tex. Comparing to the cotton spinning system, the traditional flax spinning system is more labor intensive, less efficient and less economical.
- Natural fibres of vegetable origin are constituted of cellulose with varying amount of other natural substances such as lignin, pectin, hemicelluloses, waxes, and gums. Flax is lignocelluloses fibre where cell wall is mainly made up of cellulose, hemicelluloses, and lignin. Cotton is a non-cellulosic fibre that does not contain lignin. Cellulose is a basic structural component of plant fibres and has a molecular weight > 10*6 g/mole. It is the most important organic compound produced by plants. Cellulose molecules run parallel to one another and form the spiral that is highly parallel to one another in vegetable fibres. Flax contains a low percent of cellulose than cotton and the spiral angle of cellulose is lower than that of cotton. A lower helix angle increases the stiffness of the fibre, accounts for low extensibility and makes the fibre brittle.
- Hemicelluloses are also found in all plant fibres. Hemicelluloses are polysaccharides bonded together in relatively short, branching chains. They are intimately associated with the cellulose microfibrils, embedding the cellulose in a matrix. Hemicelluloses are very hydrophilic.
- Lignin, the Latin word for wood, which gives rigidity to the plant.
- Yarns are built up by twisting together the long, thin flexible but strong things called fibres, therefore, the properties of the yarn depends very largely on the properties of the fibres from which it is made.Strength is needed to enable the fibres to withstand the spinning process and to provide the strength in the final yarn. Flexibility permits the fibres to be spun. Flax is a stronger fibre than cotton. It is particularly inextensible fibre and it stretches only slightly as tension increases. It has a high degree of rigidity and resists bending.
|Fiber||Density(g/m3)||Ultimate strain at break|
|Tensile strength (g/dtex)||Moisture absorption|
Manufacturing Process Of Linen
Extraction Of The Fibre Bundles
Removing the seeds and other extraneous material from the stems.
Traditionally, the plant was harvested whole, including the roots, in order to preserve the full length of the fibres. Nowadays harvesting machinery is available either for pulling or, more often, for cutting.
Drying & Breaking –
Usually, the stalks will be stacked in bundles in the field (stoking) and left to dry out, but drying ovens can also be used.
The stalk becomes partially separated from the fibre when the wet plants are placed in the fields to dry. When the decomposed woody tissue is dry, it is crushed by being passed through fluted iron rollers. This breaking operation reduces the stalk to small pieces of bark called shives.
Degrading the woody part of the stems so that the fibres are loosened. Retting can be natural, in the field or pond (dew retting), or can be accelerated by using tanks of warm water, with or without extra chemicals.
The scutching machine removes the broken shives by means of rotating wooden paddles, thus finally releasing the flax fibre from the stalk. This operation can be done by hand as well as by machinery.
After loosening the fibres from the wood by retting, the flax straw is broken and the woody parts are removed by scutching. The products are line fibre, with a length of 45 to 90 cm, and scutcher tow, with a length of 10 to 25 cm.
The simple coming process known as hackling straightens the flax fibres, separates the short from the long staple, and leaves the longer fibres in parallel formation. For very fine linen, hackling is done by hand. For faster and more efficient combing, hackling is done by machine.
The short-staple flax fibres, called the tow, are used for the spinning of irregular linen yarns. Tow is put through a carding operation, similar to the carding of a cotton staple, which straightens the fibres and forms them into a sliver ready for spinning into yarn.
The long-staple fibres are used sometimes dressed flax. Line fibres are from 12 to 20 inches in length. They are put through machines, called spreaders, which combine fibres of the same length, laying them parallel so that the ends overlap. The sliver thus formed passes through sets of rollers, making a rove for the final spinning process, which inserts the necessary twist.
The standard measure of flax yarn is the cut. If 1 pound of flax fibre is drawn out to make 300 yards, the yarn is known as Ne 1. When drawn out to make twice 300 yards, it is labeled Ne 2. The higher the yarn count, the finer the yarn. Exceptionally fine linen yarns for fine laces have been spun as high as 600s.
Although flax is one of the strongest fibres, it is inelastic and requires a carefully controlled, warm, moist atmosphere for both methods of spinning.
Dry spinning does not moisture. It produces rough, uneven yarns, which are not especially strong. These yarns are used for making coarse, heavy, and inexpensive linen fabrics.
This method requires a temperature of 120F (50C), which is conductive to the production of soft, fine, even yarns. By passing the roving through hot water, the gummy substance on the fibre is dissolved, permitting drawing out the roving into a fine yarn of high yarn count.
Linen Finishing Process
Linen is generally scoured before it is given a finish, and the finish used depends upon the intended purpose and use of the fabric. The most common treatment given to linen is bleaching.
Linen is usually bleached in the piece except when it is to be used for such purposes as yarn-dyed fabrics and dress linen. The two methods used are grass bleaching and chemical bleaching.
Grass bleaching produces the finest results. It is accomplished by spreading the linen out in the fields so that it is gradually bleached in the sun. This process is time-consuming but less injurious to the linen; it is therefore considered more desirable.
Although chemical bleaching is the method chiefly used, it may adversely affect the durability of the finished fabric owing to the weakening effects of the chemicals. The process requires boiling the linen in a lime solution for eight to ten hours to remove such impurities as wax, then rinsing it in water, bleaching it with hydrochloric acid, washing the fabric again, and then, finally, treating it with caustic soda to neutralize any acid that still remains.
Bleaching produces four grades in the finished product: fully bleached, three-quarters bleached, half or silver bleached, and quarter bleached. Unbleached linen makes the fifth grade. A fully bleached linen fabric is less enduring than any other grade.
Unbleached linen is the strongest because the natural strength of the fibre has not been weakened by the bleach. It is sometimes called gray linen or brown linen.
Other Linen Processes
The natural characteristics of linen are enhanced by the following processes.
- Beetling: For flexibility and uniform thickness.
- Calendaring: for luster and smoothness.
- Mercerizing: for luster.
- Sizing: for added body.
- Wrinkle-resisting: for resilience and easier care.
Linen is never napped. The fibre does not lend itself to this process, nor would napping be desirable for long-staple yarns of hard surface. Where some crease resistance is obtained by reducing the yarn to short staple, the strength of the linen, which is its chief attribute, is sacrificed.
Thus, any fuzziness in a linen fabric indicates the use of short staple or the presence of another fibre.
Dyeing of Linen
Linen is seldom yarn-dyed. The surface of the natural flax fibre is hard and nonporous and is, therefore, impenetrable to dyes. The cells of the fibre are held together with tissue that can be broken down only in a severe bleaching process.
Highly colored linens, therefore, will not give lasting service because they must have been fully bleached to absorb the dye. The colors are therefore usually pastel or dark but dull shades.
Processing Into Yarn
LINE FLAX: The longer fibres of the line tow are spun into relatively smooth, strong, uniform linen yarns using the linen (wet spinning) process.
TOW FLAX: The shorter fibres of the hackle tow are spun into coarser, irregular yarns or may be used for blending with other fibres.
AFINE, COTTONISED FLAX: The shortest tow fibres may also be chemically and mechanically reduced further – even to their ultimate’s – so that they are short and fine enough to be blended with cotton.
Appearance & Structure
- The surface structure of fibre is most important in that it controls the behavior of the fibres in the yarn. The cross-sectional shape of a fibre has an important influence on its behavior in a yarn. Cotton has a flat ribbon-like cross section. The cotton fibre appears to be twisted frequently along the entire length with the direction of the twist reversing occasionally. Twists are referred to as convolutions and it is believed that they are important in spinning because they contribute in the natural interlocking of the fibres in a yarn, enabling the fibres to grip to one another when spun.
- Flax is polygonal in cross-section. The fibre cell shows up as long cylindrical tubes which may be smooth or striated lengthwise. They do not have convolutions which are characteristic of cotton. The width of the fibre may vary several times along its length. There are swellings or ‘nodes’ at many points and the fibre show characteristic cross-marking.
- Sustainability and Eco-friendliness:
- The farming of cotton requires the use of large volumes of agrochemicals to provide protection against pests and also large volumes of irrigation water to maximize fibre yield. Both these requirements have damaging effects on the environment. Flax has considerably fewer requirements for intensive agricultural intervention and almost zero requirements for fertilizers and pesticides. Flax is also useful break crop being beneficial in crop rotation and is sustainable. And biomass production of these plants recycles CO2, cleaning the atmosphere.