Development of the technology of preliminary processing of flax plant, long and short fiber extraction in the territory of Fergana region

Аннотация

Contemporary researchers have specified that natural flax fiber is comparable with synthetic fibers due to its unique physical and mechanical characteristics which have been recognized for decades. Flax fiber-reinforced composites have the potential for wide usage in sport and maritime industries, and as automotive accessories. In addition, this composite is in the development stages for future applications in the aeronautical industry. However, designing the flax composite parts is a challenging task due to the great variability in fiber properties. This is caused by many factors, including the plant origin and growth conditions, plant age, location in the stem, fibers extraction method, and the fact that there is often a non-uniform cross section of the fibers. Furthermore, the water and moisture absorption tendency of the flax fibers and their composites and the consequent detrimental effects on their mechanical performance are also major drawbacks. Fibers may soften and swell with absorbed water molecules, which could affect the performance of this bio- composite. Flax fibers’ moisture absorption propensity may lead to a deterioration of the fiber–matrix interface, weakening the interfacial strength and ultimately degrading the quality of the composite. This review represents a brief summary of the main findings of research into flax fiber reinforced composites, focusing on the challenges of its water and moisture absorption behavior on their performance. Keywords: Flax fiber composites, moisture absorption, mechanical properties, interfacial strength, water diffusion Structure and composition of flax fiber. A flax stem has the constituents of bark, phloem, xylem, and a void at the center. The fibers are located as fiber bundles in the outer surface of the plant stem as shown in Figure 2. The flax plants can grow to heights of 80 to 150 cm in less than 110 days since the plants are fast-growing by nature. The bundles (technical fibers) are between 60 and 140 cm long and their diam- eter ranges from 40 to 80 lm. A flax stem contains 20–50 bundles in its cross section. Each bundle consists of 424 “JOURNAL OF SCIENCE-INNOVATIVE RESEARCH IN UZBEKISTAN” JURNALI VOLUME 03, ISSUE 06, 2025. JUNE ResearchBib Impact Factor: 9.654/2024 ISSN 2992-8869 10–40 spindle-shaped single (elementary) fibers 1–12 cm long and 15–30 lm in diameter. Charlet et al reported that the elementary fiber diameters are different if taken from the bottom, the middle, and the top part of the flax stems. The mean fiber diam- eter was found to decrease from the bottom to the top of the stems. The elementary fiber (Figure 3) denotes a single cell in the flax plant. Each elementary fiber is composed of concentric cell walls that are different from each other in terms of thickness and the arrangement of their con- stituents. Each cell wall consists of what is known as a primary (outer) and a secondary cell wall. These are concentric cylinders with a small open channel in the middle called a lumen. The primary cell wall can be up to 0.2 mm thick and the lumen can be as small as 1.5% of the fiber cross section. The secondary cell wall con- tains three sub-layers S , S , S .The single flax fibers have been shown to possess different 1 2 3 shapes within cross sections along the fiber axis, which some researchers approximated to hexagonal or pentagonal cross sections. However, the fibers vary in their non- uniform geometrical shapes along the axis. Owing to these irregularities in the thickness of the cell walls, the fibers vary greatly in strength. The main constituents of flax fibers are cellulose, hemicellulose, lignin, and pectin. A small percentage of wax, oil, and structural water are also found.Both primary and secondary cell walls are composed of cellulosic materials. Cellulose fibrils (diameter between 0.1 lm and 0.3 lm) are surrounded by con- centric lamella, composed of about 2% pectin and 15% hemicellulose, which contribute to the thermal degra- dation and water uptake behavior of the fibers.The secondary cell wall is the major part of the fiber diam- eter and S layer is its dominating 2 constituent. This layer consists of highly crystalline cellulose microfibrils bounded by lignin and hemicellulose. The microfibrils in the S layer follow a spiral pattern 2 at an angle of 5–10◦ along the fiber axis, which explains the stiffness and strength of the fiber in the axial direction. The middle lamella is considered to be the matrix which bonds the cell together described the technical fibers, which are extracted by partially separating the fiber bundles in the flax plant and can be as long as the stem length (approximately 1 m). The technical fibers (i.e. the bundles of elementary fibers) consist of 10–40 elementary fibers in the cross section. The elementary fibers overlap for a considerable length and are glued 425 “JOURNAL OF SCIENCE-INNOVATIVE RESEARCH IN UZBEKISTAN” JURNALI VOLUME 03, ISSUE 06, 2025. JUNE ResearchBib Impact Factor: 9.65