Today, studies on flax and many other stem fibers have increased. Because linen is a raw material for oil and composites as well as textile products. In addition, technical textiles and some special textile products are advantageous both because of their high added value and because they increase the competitiveness of the manufacturer.
Linen and other stem fibers can easily be used in such products. Apart from that, they do not cause environmental problems since they are natural. However, in order for them to be used, they must be cleaned and undergo many processes. Since flax is a stem fiber, it is usually obtained from the outer parts of the stem between the bark and the inner tissue and becomes usable by the pooling process. Pooling is the biochemical separation of fibers from non-fiber tissues. With the enzymatic pooling method and raw pooling, the disadvantages of other currently valid pooling methods are eliminated, and high and repeatable quality fiber with modified properties for special applications can be obtained.
Bast fibers such as jute, ramie, hemp, kenaf and flax are obtained from the cortical region of the plant stem. Flax (Linum usitatissimum L) is the oldest known stem fiber, as well as an agricultural product used as food and fuel. The place of linen in the industry goes back to ancient times and was especially appreciated and used in the Renaissance period.
The use of flax in America is much more than in other western countries. While traditional linen consists of long straight fibers in Europe, many industrial analyzes indicate that general use in America consists of short staple fibers mixed with cotton or other fibres. Linen is the raw material of both oil and textile and composite industries. In addition to the use of linen products in textiles, the use of nonwovens and composite products is increasing significantly. Flax fiber strengthens bio-based composites and reduces the amount of non-biodegradable products. The stem of flax grown for fiber is longer than that grown for seed and has less branching.
TFlax grown for seed is often considered coarser than required for textiles and is an option for composites (technical grade fiber production). Flax, which is grown in large quantities for seed, remains as a by-product after the seeds are taken and creates significant environmental problems. Therefore, the use of the fibers of plants grown for seed in composites provides advantages in product development both in terms of fiber properties and thickness, and also helps to solve the environmental problem.
Harvest of flax
The roots are left to one side and the stems are left to dry in the field in bunches.
After the leaves on it are dried and shed, they are tied with their own stems and made into bundles. Obtaining the fiber from the dried plant takes place in three stages. These are refutation, forging and carding.
POOLING THE LINEN
The purpose of the pooling process is to release the cellulose fibers by separating them from the surrounding tissues. This is done either by microorganisms penetrating into the plant body or by enzymatic processes by converting pectinase, which binds fiber bundles together, into simple water-soluble compounds. Pooling can be done in dew, stagnant water, stream, hot water, chemically or enzymatically. Although pooling in water, which is based on fermentation with anaerobic bacteria, gives high fiber quality, it has been abandoned years ago in western countries because it causes unacceptable environmental waste. Raw pooling is done by keeping them in the open area with aerobic fungi. This method is preferred in western countries and many flax fibers are produced in this way. However, pooling in dew;
1-dependence on certain geographical regions with suitable humidity and temperature for pooling
2- Obtaining coarser and lower quality fibers compared to pooling in water
Decreased consistency in 3-fiber properties
4- Pooling is still a big problem for the production of flax fiber due to its disadvantages such as keeping the agricultural fields busy for weeks.
In the 1980s, various studies were started in Europe for the development of enzymatic pooling to replace raw pooling. As a result of these researches, commercial enzyme mixture Flaxzyme and various enzymes were produced by Nova Nordisk (Denmark). In 1987 Sharma used a mixture of enzymes to remove non-cellulosic fractions from raw pooled fibers. Van Sumere and Sharma determined in 1991 that the fineness, strength, color and waxiness of the fibers obtained from pooling using Flaxzyme were comparable to those of flax fibers best pooled in water.
Despite all the developments, dew pooling is still the most used in Europe. One of the most important reasons preventing the commercial development of enzymatic pooling is the price. In the United States, the US Department of Agriculture's Agricultural Research Service has worked to re-develop the flax fiber industry for use in textiles and composites, and has developed an enzymatic pooling process. Whichever method is used, effective pooling separates the fiber bundles from the epidermis/cuticle and core. In addition, fiber bundles break down into smaller bundles and individual fibers. The fibers are separated from the non-fiber compounds and the middle lamella is disrupted to form independent fibers.
After pooling, the amount of pectin, arabinose, xylose decreases, while the amount of glucose, mannose and galactose increases. In a study by Akin et al., enzymes containing high amounts of pectinase were studied. The separation of the fibers from the body was evaluated by scanning electron microscopy, light microscopy and Fried test. The commercial enzyme mixtures used have high pectinolytic activity as well as xylenase and cellulase activity. As a result of the experiments, it was determined that cultures with high pectinase activity but unstable xinelase and cellulase activity had a high effect on flax pooling. Scanning electron microscopy showed that when the vegetative areas were exposed to enzymes unprotected, Ultrazym and Flaxzyme were effective in separating the fibers, but did not pool effectively when the stems were still intact. In addition, increasing temperature changed the cell wall-destructive activity of enzymes. An effect at 40 and 50°C is 22 times faster than an effect at 2°C. As mentioned earlier, the enzyme price required for effective pooling is a major disadvantage of enzymatic pooling. Therefore, methods that reduce the amount of enzyme used are commercially necessary.
Polysaccharide degrading enzymes are different in 3 types of pooling. For example, pectinase and hemicellulases released by fungal colonies in dew pooling slowly pool over a period of 5-8 weeks. In contrast, aquatic and enzymatic pooling ends in 3-7 days. There are significant structural differences in the resulting products, especially in water docking. In a complex way, the quality of flax is related to the ratio of residual pectin, hemicellulose, lignin and lipid in the pooled fiber.
OBTAINING LINEN FIBER-DIETTING METHOD-FATTING
After the rot process is finished, the bunches are arranged vertically and dried in the open air or in the sunless place. The dried stems are first hammered with a mallet. Then they are broken in manganese. Manganese is just a blunt blade made for this job. The stem parts where woody cells are found in manganese are broken down and shed.
OBTAINING LINEN FIBER-DIETTING METHOD-CARDING
The flax fibers are first whipped to remove the woody particles remaining on it. Cleaning the woody structure broken in manganese is also cleaned with combs consisting of nailed structure. It is then combed to separate the long and short fibers from each other and smooth the fibers. What remains is the fiber bundle. It is brought into the form of bundles, baled and put on the market.
Low quality fibers are catalyzed using acid, base or soap solutions. Catalyzed fibers are often used mixed with cotton.
OBTAINING LINEN FIBER-DIETTING METHOD
In order to distinguish the flax fibers from the other tissues to which they are attached, the digestion process is performed. The decay process is carried out by three different methods. These; dew-rot, hydro-rot and chemical digestion.
Decay with Dew
In regions with high humidity, flax stalks are laid on the meadows and released into moist air. Rotting of flax stalks occurs with the help of microorganisms. Microorganisms that reproduce with the effect of moisture dissolve the pectin substance, which serves to bind the fiber bundles to the woody cells during this reproduction, and the fibers are separated from each other. This process is completed in 1–1,5 months. With this method, very soft fibers are obtained.
Digestion with Water
In arid regions, flax stalks are made in streams or ponds. Since microorganisms reproduce quickly in hot water, the process takes a short time. In rivers, the process is completed in 1-5 weeks. In stagnant waters, in the pool or in private pools in the factory, the digestion process is completed in 4-6 days, as the water heats up more and in a short time.
The point to be considered in the digestion process is to keep pooling and temperature under control. Otherwise, microorganisms, after breaking down the outer pectin, begin to dissolve the inner pectin, break the fiber bundle and separate into individual cells. This is called cottonization or cottonization of flax. In this case, it reduces the quality of the linen.
Flax stalks are kept in pools with 3% HCl for 2-3 days. It is then washed and neutralized. Faster but lower quality fibers are obtained than other digestion methods.
PHYSICAL AND CHEMICAL STRUCTURE OF LINEN
When the flax body is cross-sectioned, it is seen that it contains different layers. An epidermis layer surrounds the fiber piles. These are strong stem fibers and extend from the root upwards along the stem length. The piles of fibers are surrounded by a hard inner body containing woody cells called shives. There is an empty space in the center of the trunk. Each fiber stack consists of 10-40 single fibers. Their lengths range from 14 μ to 70 mm. Average fiber length is 20-35 ml. The fiber fibrils are composed of microfibrils brought to the median by the elementary fibrils. The first wall of the cells contains pectin with traces of lignin, while the secondary wall is mainly cellulose. Cambial cells separate the fibers from the splinter area.
In the structure of flax, there are many substances besides cellulose. Chemical analyzes were performed by liquid gas chromatography as described by Morrison. Glucose amounts are significantly higher than pectin and/or hemi-cellulose. Glucose, the indicator of cellulose, shows that this tissue fiber contains a lot of structural polysaccharide. Flax fibers contain high levels of cellulose, as well as unique sugars. Pectinasic and hemi-cellulosic sugars are removed during pooling. When the pooled flax sample is evaluated, the amounts of glucose, mannose, and galactose in the remainder decrease by 50%, 27%, and 8%, respectively. The galactan chains and arabinoglactan proteins in the secondary wall give flax a significant strength. Carbohydrates predominate in stem tissue, with minor amounts of aromatics, waxes, and cutin.
Physical Properties of Flax Fiber
1-Fiber thickness is between 0,014–0,025 mm.
2-The length of the fiber bundle is between 30–90 cm. The length of the single fiber is between 7-8 cm.
3-Flax is yellowish white in color, slightly bluish.
4-Long and thin flax is preferred.
5- Elongation at break; It is 1,8% when dry and 2,2% when wet. Its durability is 20% higher when wet.
6- Its specific gravity is 1,5 g/cm³.
Chemical Properties of Flax Fiber
Linen fibers show the properties of cotton fiber against chemical reagents.
1-It is not affected by boiling water, sun and detergent.
2-Moisture absorption is better than cotton. For this reason, maximum 18% humidity is accepted in trade. It feels dry even though it carries moisture.
3-It deteriorates at temperatures above 120 ºC.
4-When exposed to sunlight for a long time, its durability decreases.
USAGE AREAS OF LINEN FIBER
It is generally used in summer outerwear to keep it cool. Shirts, jackets, trousers etc. in home textiles; tableware, ornaments, bedding etc. used in construction. It is also used as a fiber in water installations, rope making and quality paper making.
FEATURES OF LINEN FABRICS
Linen fabric is a natural fiber.
It is much more durable than other fabric types, especially cotton fabric.
This type of fabric, which has a glossy structure, has less flexibility.
Linen fabric has a high moisture absorption feature, so it is frequently used in bathroom products.
One of the most well-known features of this fabric is that it creases quickly, so the use of linen clothes is not comfortable.
The reason why it is more preferred in hot weather is that it allows the body to breathe and stay cool with its large porous structure.
Linen fabric, which has a smooth and hairless structure, is preferred because it does not get dirty quickly.
It needs frequent ironing.
It should be cleaned by hand with cold water or dry cleaned. It is not suitable for machine washing.
When used on walls, it contributes to heat and sound insulation.
Its durability, not attracting dust and not leaving itself allows it to be used frequently as upholstery.
Thanks to its reflective feature, it minimizes complaints such as color fading in the sun.