Fiber, which sometimes makes up more than 80% and mostly 100% of nonwoven products, is the most important material for these products and the properties desired from the final product are directly dependent on this structure.
Cotton: Especially in medical textiles and transfer belts.
Viscous: In the field of rubber and industrial weaving.
Acrylic-Modacrylic: In guard uniforms, in wigs.
Polypropylene: Cord and rope, covering fabrics, filter elements, geotextiles, medical textiles, fishing.
Polyamide: Rope and similar applications, safety belts, parachute fabrics, fishing, welding suits, sports equipment manufacturing as composite material, cargo and marine, tire manufacturing, transmission belts and military applications.
Polyester: It is used in tire manufacturing, rope making, sailor suits, filter fabrics, felt manufacturing, medical textiles, and fire clothing.
High Performance Glass Fiber: In the aerospace industry, construction sites, generators, steam turbines, communication technology and tire manufacturing. High Performance Polyethylene: In the manufacture of workwear, rope and cable construction, protective clothing, composite construction, fishing, medical equipment.
Carbon Fiber: In the aerospace industry.
Ceramic Fiber: It is used as insulation material.
Natural Fiber Structured Non-Woven Surfaces: They are structures made of fibers such as cotton, wool, jute.
Artificial Fiber Made Nonwovens: Rayon, polyester, polypropylene, nylon, viscose, acrylic, kevlar, nomex, carbon, glass etc. They are structures that contain many high performance fibers.
Nonwovens with Harmonic Fiber Structure: They are nonwoven surfaces consisting of a mixture of two or more fibers. These structures can be natural/artificial or artificial/artificial fiber blends. Mixtures are generally made to increase strength properties. On some nonwovens, one of the blended fibers acts as a binder.
In general, the properties of fibers that are effective on nonwovens are as follows:
• Fiber denier or size
• Moisture retention
• Section shape
• Flexibility
• Surface properties
• Strength
• Crimp, crimp features
• Elongation
• the finishing material it contains
• Module
As can be seen, there are many parameters in the selection of suitable fibers for nonwovens. In addition, fiber prices play a very important role in raw material determination. Not only the initial cost is important, but also the cumulative cost of a bale of fiber until it becomes a finished nonwoven ball.
The machines to be used in production also change according to the use of staple and filament fiber. Wool type carding machine is used to make the staple fibers into the cheesecloth surface. Needling machine, which is a mechanical method at the tissue binding stage, when it is desired to produce high unit weight fabrics. is preferred.
Since fabric is produced directly from fibers without using yarn in the Nonwoven Industry, maximum use of fibers is made and the production of fibers in nonwoven production is higher than in other technologies.
COTTON FIBER
Cotton fiber, which is one of the most used and important fibers in our country, is preferred because of its high production, strength and water absorption properties.
Although cotton fiber is creamy white in color, it can also vary according to climate, growing conditions and plant type. Its height is between 4 cm and 7,5 cm. The diameter of cotton fiber is 6-25 mm. Its density is between 1,50 and 1,55.
The cotton fiber of a thin-walled plant cell filled with protoplasmic fluid is covered and the part that is torn from the seed is open. There is a thin layer of oil and wax called the cuticle at the outermost part of the cell. Just below this layer is the primary cell wall consisting of fibrils made of cellulose. The fibrils of this wall are arranged spirally. Toward the center is the secondary cell wall, which forms the entire mass of the fiber and is also made of cellulose.
This wall consists of three regions.
- In the outermost layer, the fibrils show a spiral structure with an angle of 20-30 degrees to the axis.
- The fibrils in the second region are located at the same angles, but in the opposite direction of the other region.
- In the third region of its secondary wall, it surrounds the channel called the lumen, which is filled with protoplasmic fluid.
This liquid contains proteins, sugars and minerals. Cotton easily absorbs moisture from the air. Although it adsorbs 20% moisture under standard conditions (at 65 temperature and 8,5% relative humidity), it may feel dry when held by hand. The maximum humidity allowed in trade is 8,5%. At 100% relative humidity, the cotton material adsorbs 25-27 water. The elongation amount of the fiber is 7-8% on average. It has no elastic properties. When cotton is wetted, it absorbs water up to 70% of its weight, shortens in length and thinness due to swelling in the fiber that absorbs water, and increases in durability.
Cotton fiber decomposes in concentrated and strong acids in hot and cold temperatures. It is completely soluble in concentrated sulfuric acid. It decomposes and rots with dilute acids to yield hydrocellulose on heat. When burned, it leaves a black, crushable ash that smells like burning paper. Polymers degrade in cotton that is exposed to UV rays in sunlight, air oxygen, humidity and polluted air conditions. Since cotton fiber is a fiber with a high moisture-holding ability, blood, urine, etc., leaving the body. It can easily absorb liquids and is biodegradable due to its natural nature. Besides absorbing the liquid, it also allows air passage. Cotton fibers show good strength when wet and can be easily sterilized. Since it is heat resistant, it retains heat well. In addition, it is preferred in the production of non-woven surfaces due to its non-allergic and softness properties.
WOOL FIBER
Animal-based wool fiber, which is one of the natural fibers, is a fiber with properties such as fineness, length, elasticity and curl, which are not found to the same extent in most other fibers, as well as features such as good heat retention, low wettability and felting.
When the cross-section of the wool fiber is examined;
- outermost epidermis
- cortex in the middle
- And the medula layer is seen inside.
The epidermis layer, also called the cuticle, is the outer surface of the fiber. This layer is the surface of the fiber visible under the microscope. It consists of flake-shaped cells that close on each other. These cells are hard and horny in structure. It looks like fish scales or roof tiles. This layer helps protect the interior of the fiber and gives it some stiffness.
Wool fiber is more resistant to acids than bases. Wool treated with solutions of dilute inorganic acids absorbs some acid due to the amtopheric property of keratin. Wool dissolves easily in base solutions. Bases affect cystine bridges, not just salt bonds in wool; In addition to the mechanical properties of wool, it also reduces the amount of sulfur in the structure of keratin and dissolves some keratin depending on the concentration of the base.
Wool fiber that is exposed to light for a long time becomes brittle and loose. Its affinity for dyestuffs decreases. There is yellowing in color. This is because UV rays affect peptide and disulfide bonds. Wool fiber is suitable for the production of non-woven textiles due to its moisture absorption, heat retention and felting properties. The production of cheesecloth from wool fiber is made by dry (carding, air-laid) or wet processing as it is in the form of short fibers. Among the fixing processes, chemical or mechanical bonding methods are used. The structure of the wool fiber and its production methods create the final product that absorbs moisture, retains heat (insulation), has bulky and semi-soft properties.
POLYESTER FIBER
Polyester, a synthetic fiber used extensively in the textile industry; It is obtained by drawing the Polyethylenetephthalate (PET) polymer obtained by the condensation of ethylene glycol and organic acids, terephthalic acid or dimethyl terephthalate, from the melt. Polyester fiber has many uses with its hydrophobicity, high strength and non-crease. With these features, polyester fiber is an important fiber type that plays a role in improving the usage properties in cotton, viscose and wool blends.
The longitudinal section of the polyester fiber has a smooth rod-like appearance. Its cross section is mostly round. There are also different sections according to the flat form. When they are first produced, they are in the form of endless filaments. Then, they can be cut to desired lengths. 3-5 cm in cotton type, 6-15 cm in wool type. Fineness in synthetic fiber is as desired during production. Densities; Dacron 1.38 gr/cm³, Kodel 1.22 gr/cm³, Vikron 1.37 gr/cm³. Colors are white in production. If desired, colored fibers can be obtained by adding pigment colorants to the fiber drawing solution. It is brilliant in production. If desired, the fiber can be dulled by adding matting agents to the spinning melt or by various subsequent processes.
The polymer material obtained in the production of polyester fiber is cut into approximately 4 mm dimensions and converted into a shape called granule. The granules obtained are converted into filaments by the soft spinning method.
In the soft spinning method; The polymer pieces obtained by chemical means are melted and turned into liquid by being heated to a temperature above the melting point in the melting unit consisting of a heated grid or extruder. The molten polymer is sprayed to the rooms with cold air flow from the nozzles under constant pressure with the help of a pump. Finishing is applied to the fibers that solidify with the help of cold air flow, and then the fibers are wound into bobbins by providing fiber orientation by stretching-drawing process. According to the place of use; For staple fiber production, the fibers are cut to the desired length and baled.
One of the most important features of polyester fiber is its high elasticity. With this feature, it is the most superior fiber among synthetic fibers. Its dehumidification feature is very low. It is around 0.4%. It can be described as completely hydrophobic. Heat resistance Softening and adhesion temperature is 230ºC. They have extremely good stability when fixed. Its melting points are 260ºC. It burns slowly. It drips when it is free and open. It has a static electricity problem due to its low moisture absorbency. The highest degree of pilling among textile fibers is seen in polyester. Polyester fiber shows a very high performance against water and chemicals. It is an extremely hydrophobic fiber to water. It can absorb 100% water even at 1% relative humidity. Under normal conditions, it has 0,4% hygroscopic humidity.
Polyester fiber is resistant to weak acids at boiling temperatures of acids. Although it has good resistance to strong acids at room temperature, it has poor resistance to strong bases. It maintains its whiteness as it has good resistance to sunlight behind the glass.
Polyester fibers, which are preferred in the production of nonwovens due to their properties such as high strength, high resistance to chemicals and heat, and bulky structure, can be used alone in the products in the aforementioned industry, as well as mixed with fibers with different properties. Generally; It is used in the production of artificial leather, geotextile, sanitary pads, wet wipes, filtration materials, on the base of laminated and coated fabrics.
VISCOSE FIBER
It is a staple fiber type produced artificially by chemical processes of cellulose obtained from trees with high cellulose content such as red pine, beech, spruce, and poplar.
It can be produced in the desired cross-section shape according to the shape of the holes of the arrangement used in its production, and it has an indented cross-section, which is generally referred to as the shape of popcorn. When viewed longitudinally, there are lines running along the fiber. It is brighter in color compared to other cellulose-based fibers and its density is 1.49-1.53g/cm3.
The trees in question in viscose production; After the bark parts are removed, they are divided into small pieces called sawdust. As a result of the treatment of sawdust with chemicals such as NaOH (Sodium hydroxide) or Ca(HS03)2 (Calcium hydrogen sulfide) at high temperature and pressure, other substances (such as lignin, hemicellulose, pectin) present in the structure are removed. The pure cellulose obtained is melted by keeping it in a 17,5%-18% NaOH solution at 18–20°C, and it is divided into smaller pieces to form a homogeneous mixture. Then after treatment with CS2 (carbon sulfide), An orange colored and thick solution called viscous is obtained..This solution is converted into filament by wet spinning (spinning) method, and the resulting filament is called viscose silk..
In wet spinning method; The viscose solution is conveyed with constant pressure to the production head called the duvet, which is in a coagulation bath and has multiple holes on it, and the resulting filaments solidify even though they come out of the coagulation bath thanks to the solution in the coagulation bath. Then, the filaments formed for the proper placement of the molecules in the fiber on the fiber axis are subjected to stretching-drawing, washed in order to remove the remaining materials from the coagulation bath, treated with various chemicals and wound into bobbins. Viscose fiber, which is a staple fiber, is obtained by cutting viscose silk in the form of filaments to the desired length.
Wet strength of viscose fiber; l. 2-1,7 g/denier, dry strength; 2,3-3,0 g/denier. In case the force applied to the viscose fiber is within the elastic limit; It has been determined that it elongates 15-30% as dry and 20-35% as wet.
The fineness of viscose fiber is expressed in denier. Viscose fiber is generally produced as 1,5-2,5 and 3.75 denier. Viscose fiber has high moisture absorption due to its structure. Fiber takes a significant amount of moisture from the air. Commercially, the moisture value of viscose is 13%. The ash value in viscose varies according to the production method. The ash content of the fiber depends on the type of water in the caustic used for suppression. The less minerals in the water, the lower the ash content. In dry viscose, this amount is about 0.15-0.25%. The influence of light is significant. The moisture content of viscose increases the effect of light and the value of its strength decreases. If viscose is exposed to drying, its strength decreases and color fading occurs.
The effect of acid against viscose depends on the applied time and temperature. Organic acids do not affect 1-3% viscose. Time and temperature are important in inorganic acids. In both cases, the applied acid must be removed. Aviation gives the viscose fiber an antistatic property. Excessive spin will cause the fibers to slip over each other. This also affects negatively. The optimum spin finish applied to viscose is around 2.0%.
Viscose, which is a preferred fiber type in the nonwoven industry in terms of its widespread availability, low cost and ability to be processed with all kinds of nonwoven surface production methods; especially in combination with the ability to absorb. It is used as wet wipes, cleaning cloth and non-woven fabrics in the fields of health and hygiene.
POLYPROPYLENE FIBER
Polypropylene, a petroleum product, is polymerized under suitable conditions and turned into a polymer material that can be drawn into chemical fibers. Fiber spinning from polypylene, which was first polymerized in Italy in 1952, was only realized in 1954. Today, polypropylene fibers are obtained according to the soft spinning or irregular spinning method. Their cost is very low, they are generally used as plastic materials.
The cross-sections of polypropylene fibers are generally round, and their longitudinal appearance is cylindrical. However, fibers with different cross-sections are obtained according to the shape of the nozzle hole used in the drafting method. The cross-section of the fibers obtained according to the irregular drawing method is flat, and their longitudinal appearance is strip-like. Polypropylene fiber has a smooth and waxy appearance under the microscope. They are obtained colorless, but can be given in the desired color by dyeing the polymer liquid during production.
The fineness of polypropylene fibers produced as mono filament, multi filament, staple or tow varies depending on the usage area. The average strength of a PP fiber is 65cN/tex. The elongation ability is considered good. Elongation at break is 17-20%. Flexibility is very high. Its specific gravity is 0,91 g/cm3. It is the lightest of the fibers used in textiles. In practice, it does not absorb any moisture, it is less than 0,05%. Its strength and elongation are the same in wet and dry conditions. Like all hydrophobic fibers, it has a static electricity problem. Heat conduction is not good. That's why it's considered a warm fiber. It melts at 160-170C. It is resistant to cold.
Polypropylene fiber is suitable for the production of nonwovens due to its high strength, resistance to wind and light, lightness, moisture-proof and low melting point. The production of cheesecloth from polypropylene fiber can be done by dry (carding, air-laid) or wet processes, as well as by endless fiber process as it is a continuous fiber in filament form. Among the fixing processes, chemical, heat and mechanical (needling, resting) bonding methods are used.
