Flax structure

There are three types of flax:

• longweed, which has a stem that is weakly branched only at the apex and is used mainly for producing textile fiber;
• curly, cultivated for seeds (oil flax), has a bunch of branching stems, is low-growing, grows in the southern regions;
• mezheumok, which occupies an intermediate position in its structure, has a branching stem, its fiber can be used for the production of coarse fabrics and twine.

Flax plant:
a – types of flax;
b – flower;
c – seed head

We will consider fiber flax. The length of its stem is 80–120 cm, diameter 1–3 mm. The color of the stem changes during the growing season: first it is green, then milky-waxy and finally yellow. Narrow (15–3 mm) long (5–25 mm) leaves grow along the stem at a distance of 35 cm. After flowering, the leaves fall off as they mature. At the top of the stem several branches are formed, which can also branch. At the ends of the branches grows an odorless blue, sometimes white or pink flower, which has five petals and five stamens. After self-pollination, the flower develops into a seed head.

On a cross section of the stem, one can observe the outer layer-skin (epidermis) 1 with a surface covered with a film impregnated with waxy substances (cuticle) 2. The skin consists of dense vascular cells with thickened walls. Bark 3 is located directly under the skin. Its cells are partially filled with chlorophyll. Lubofibrous bundles 4 lie in the tissues of the cortex. They consist of groups of elementary fibers with thick cellulose walls, glued together by middle plates of pectin and other adhesives. The shape of the elementary fibers is faceted and gluing occurs along planes – the edges of the fibers. Conducting tissue 5 consists of thin-walled elongated cells. Educational tissue (cambium) 6 in the form of a one- or two-layer ring lies on the border with wood 7. The core 8 lines the inside of the stem. Cavity 9 is not filled with tissue. Approximately one-third of the cross-section of the stem (excluding the cavity and core) is occupied by fibrous and surrounding tissues. Two thirds are filled with wood. By weight it is 25–45% bast and 75–55% wood. Elementary fibers with a length of 2,5 to 120 mm are oriented along the stem, have a pointed shape at both ends and a channel closed on all sides inside. Elementary fibers glued along the edges form bundles of technical fibers. The elementary fibers are shifted along the bundle and their thinned ends seem to be wedged between neighboring ones. In some places, fibrous bundles (technical fibers) are glued together, forming a mesh structure (anastomosis).


Structure of flax stem (cut)
1 – skin (epidermis)
2 – cuticle
5 – bark
4 – bast fiber bundles
5 – conductive fabric
6 – educational fabric
7 – wood
5 – core
9 – cavity

Through the process of crumpling and fraying, the fibers take on the appearance of long strands, the length of which is approximately equal to the length of the stem. Some of the fibers break off or break off, become tangled and end up in the scuffing waste. Destroyed wood from the stem (fire) also ends up in the scraping waste. “Industrial fiber” is a term that defines the condition of the fiber entering processing and does not strictly reflect either botanical or structural characteristics. Technical fibers can be long or short, tangled or straightened. The high degree of polymerization of cellulose fiber provides it with high strength characteristics and high resistance to light, washing, and wear. A number of flax cellulose satellites give it biostability, high hygroscopicity and moisture capacity, and ensure a complete absence of static electrical charges. Flax fiber is straightened and cellulose is highly oriented, so flax fiber elongates very little when loaded.

Chemical composition of flax and cotton fiber, %

Physico-mechanical properties of flax and cotton fiber

Tensile strength can be characterized by various parameters:

• breaking stress – load leading to rupture, related to the cross-sectional area, N/mm2;
• breaking length – the length of the fiber (conventionally long), which leads to its breaking under the influence of its own weight, km;
• breaking load related to fiber fineness in tex, cN/tex.

For example, the breaking length of an elementary fiber with a distance of 3 mm between the dynamometer clamps is 60 km, while its strength is only 15 g. When flax fibers are moistened, their strength increases to 40%. This phenomenal quality of flax distinguishes it from all known textile fibers.

Elasticity – a property of flax fiber or thread that determines its performance under mechanical stress. In practice, it is characterized by elongation at break. The relative elongation of the elementary flax fiber is very small and equal to 2,8%. Based on the shape of the load-elongation curve, the elastic modulus can be determined. This module corresponds to the tangent of the slope of the curve at its beginning. For flax this module is 14,3 g/(cm * tex).

Chemical composition of flax fiber and its accompanying elements (satellites). Elementary fibers are 98% cellulose, which in turn consists of 44,4% carbon, 42,4% oxygen, 6,2% hydrogen.

The cellulose macromolecule consists of 2500–3500 glucose molecules. Each pair of glucose molecules contains a water molecule (H20).
Cellulose chains can be arranged differently, depending on which the cellulose is amorphous or, as in the case of flax, oriented along the fiber axis.
X-ray diffraction analysis shows that flax cellulose is highly crystalline and therefore very resistant to chemical and physical influences. During spinning processes, elementary fibers are combined with a certain amount of cellulose satellites found in industrial fibers.

Green flax bast contains: cellulose 52-58%, water-soluble substances 8-10%, hemicellulose 12-16%, lignin 2-4%, pectin 3-5%, wax 1-2%, water 14%.

Linen fire – the wood of the stem consists of cellulose, hemicelluloses, lignin, and also a small amount of short fibers.
Flax seeds. The weight of 1000 fiber flax seeds is approximately 5 g, and oil flax up to 14 g. 30–35% of the oil is extracted from fiber flax seeds, and more than 40% from oil flax seeds. The use of flaxseeds has as long a history as the use of flax fiber. The quality of linseed oil cannot be compared with other natural and synthetic oils. Chemists have not yet been able to obtain a complete substitute for it. Flaxseed oil is superior to other oils in its desiccant properties - the property of rapid drying with the formation of a durable film that protects against moisture and corrosion. This explains the fact that the canvases of the great artists of the Renaissance, painted, by the way, on linen and with paints prepared in linseed oil, have been preserved for more than 5 centuries without fading.
The desiccant properties of flaxseed oil are explained by the presence of unsaturated fatty acids with one or many bonds between carbon atoms. Oxygen from the air is fixed on these ethylene bonds, forming an oxyethylene group, known in chemistry as a strength stabilizer, which turns into a thin layer of varnish.
Flaxseed oil is widely used in the food industry and pharmaceuticals to reduce cholesterol in the blood and for the preparation of anti-oncological drugs.