Useful Information


al. Nylon(n), Fr. Nylon (m), Eng. nylon Polyamides formed by the polymerization of dicarboxylic acids and diamines, the first synthetic yarn. Nylon was first made in 1938 and was used to make nylon stockings.

A nylon thread consists of linear giant molecules arranged in parallel. Each of these giant molecules belongs to the group of super polyamides. A polyamide is a long chain polymer produced by the reaction of a diamine with a diacid. Starting from different amines and acids, different nylons are obtained. The three main types of nylon yarn are identified by numbers. Nylon 66 is the first nylon to be developed and has the highest melting temperature and tensile strength. Nylon 6 is similar but softer. Nylon 610 is a heavier material and is used in tooth and hair brushes, fishing nets, surgical wound sutures, etc. used. Nylon 610 is more resistant to water than others. These three types of nylon are now mainly used in parachutes instead of silk, in fabric weaving, nets, rugs, tulle curtains, typewriter tapes, water and airtight curtains, insulating wires, in the chemical industry, and in filters. Hard and solid nylon is used (by molding the powder material) in the production of items such as combs and dinnerware.

Production: Nylon 66, the most well-known of the nylons, is obtained from hexa methylene diamine with adipic acid. Adipic acid is represented by the formulas HOOC-(CH2)4-COOH, and hexamethylene diamine by the formulas H2N-(CH2)6NH2. The polymerized product is formed by the successive separation of water molecules between a large number of adipic acid molecules and an equal number of hexamethylene diamine molecules. In the polymer…NH-(CH2)6-NH-CO-(CH2)4-CO… ring is repeated cyclically. The raw nylon coming out of the polymerizer is cut into chips. Nylon melts when heated. Melting is done in an argon atmosphere. Because it can be affected by the weather.

While molten nylon is in liquid form, it is sprayed with pressure through fine holes. As the nylon threads cool, they solidify. These threads are then extended by being drawn in the cold. Thus, very flexible and strong yarns are obtained. These yarns are very resistant to air and factors that degrade organic materials. However, it melts towards 230°C. The thickness of nylon strands is measured in denier. If 9000 m of yarn is drawn from 15 grams of nylon, this yarn is 15 denier. Such threads are used instead of silk in the manufacture of women's hosiery. Moreover, nylon threads are more flexible than silk threads, more durable, more resistant to small creatures and chemical factors, hold less moisture and oil, and can be dyed better.

Diamine and diacids, which are the primitive materials of nylon, are obtained synthetically in industry from the primitive materials of coal, air, water and petroleum. Since these primitive materials are very abundant and cheap, the final product nylon is also cheap.


1. Ring Twist Method
The elasticity of the yarns produced on normal false twisting machines is reduced with the help of the heater placed in the twisting machine. During this process, 40-150 T/m twist is given to the yarn. Here, too, the output rollers rotate 20 - 25% faster than the input rollers. This method, which is very slow and costly, is used for Nylon 6, Nylon 66 and polyester yarns with 45 - 270 denier fineness.

2. Double Thread Twist Method
The elasticity of yarns textured according to the false twist method can be reduced in double yarn twisting machines. For this, 40 - 150 T/m twist is given to the yarns passing through the heaters as in the twisting machine. The best part of this process is that the twisting takes place during the yarn flow, the homogeneity of the heat treatment and the ready-to-sale bobbins are obtained at the end of the heat treatment. In this process, it can be applied to Nylon 6, Nylon 66 and polyester yarns with a thickness of 40 - 280 dtex (45 - 70 denier).

3. Folding Twisting Machine Method
Heat treatment is applied to elastic yarns and 60-100 T/m twist is given at the same time in the sheathed Ratti machine developed by the Italian Ratti company. The elongated yarns obtained by this method are fluffier and softer than the set yarns obtained by previous methods.

4. Coil Winding Machine Method
The elastic yarn obtained by the false twist method is subjected to heat treatment in the winding machine. The heating apparatus added to the coil transfer machine works according to the following method and its length is 160 cm. The theoretical speed of the machine is 450 rpm, and after the heat treatment, the yarns are wound into crossed bobbins. It can be applied to Nylon 6, Nylon 66 and polyester with a thickness of 50-280 tex, as stated in previous methods, in the process of decreasing elasticity by coil transfer method.

5. Finishing Method of Woven and Knitted Fabrics
The yarns obtained by the false twist method are woven or knitted by using them in weft and warp, or only weft or only warp. Then, during the finishing process, these fabrics are stretched into frames and subjected to heat treatments. Thus, the desired level of elongation is obtained. Although the yarns obtained have good dyeing abilities, they have a high tendency to spin.


Air-jet texturing method is the most useful and versatile method among the texturing methods known so far. Most texturing methods involve a mechanical deformation during the heat treatment of thermoplastic endless yarns. Unlike these other texturing methods, air-jet texturing is a purely mechanical method. In this method, voluminous and low-resilience yarns with loops on the surface are produced by means of a cold air flow, and these yarns are very similar to spun natural short fiber yarns such as cotton or wool yarn in terms of appearance and physical properties. Although the bulkiness of stretchable texturized yarns produced by other textured methods decreases with the magnitude of the tension that can be applied to them, the geometric shape of the air-jet texturized yarns remains unchanged under the forces corresponding to the tensions encountered during weaving and wearing.

This is due to the entangled and loopy structure that the air-jet texturing method brings to the yarn. The yarn surface is covered with interlocked small loops that are well connected to the core of the yarn. Since these loops cause the creation of an insulating air layer between the fabrics, they play the same role as the hairs on the surface of spun natural fiber yarns.

Air-Jet Texturing
The process includes the principle of overfeeding. Overfeeding means that the multi-filament endless feed yarn taken from a bobbin is fed to the jet at a certain speed and taken from the jet at a lower speed than this speed. To achieve this overfeed, the yarn first passes through the feed rollers W 1.1 and W 1.2. The feed rollers spin faster than the W2 take-up roller. Overfed filaments are passed through the jet and ejected from the texturized tip. Here, the filaments are converted into textured yarn by the effect of the compressed air flow produced by a compressor.

The region between the feed rollers and the jet is called the feed zone. The region between the jet and the exit rollers is known as the exit region. It increases the stability of the textured yarn by passing between the take-out rollers and the receiving rollers. This area is called the fixation zone. Before the feed yarn enters the jet, it is wetted either by passing it through a water bath or by means of a wetting unit, texturing the yarn by wetting is an important factor that increases the yarn quality.

The textured jets are usually in a box. Thanks to this box, both the noise of the air jet is reduced and the used water and oils flowing from the surface of the filaments during texturing are collected in the box. The yarns textured with the air-jet technique have a completely different structure. The structures of these yarns are very similar to yarns spun with staple natural fibres.

Although the bulkiness of the drainable yarns decreases under the influence of the load applied to them, the bulkiness of the air-jet texturized yarns remains virtually unchanged even under very high loads. The loads under its influence can be as high as those encountered during weaving and clothing. This feature is the protruding loops of air-jet textured yarns. These look like hairs on the surface of yarns spun with natural fibers. These fibers allow the formation of a stagnant air layer between two fabrics and provide thermal insulation. Air-jet texturing provides wide possibilities for obtaining different yarns. So much so that the method can even be done blending filaments during the process. This versatility opens up workspaces for the texturizer that other texturing yarns cannot. In addition, the feeding threads do not have to be thermoplastic. Although polyester and polyamide are by far the most processed materials, other filaments such as polypropylene, glass, viscose and acetate aisles are used for special purposes. Woven fabrics for sports and casual wear are produced from air-jet textured yarns to replace spun yarns.

When the knotted structure produced by some jets is exaggerated, it can be imitated with the properties of both cotton and linen yarn. Thin filament yarns are more suitable for doing this. Due to the loops protruding from the surface of the yarn, it is quite appropriate to make bed linens and ski suits from air-jet textured yarns. Because high friction properties are required from both products. Fabrics woven from these yarns are used for PVC coating in the industrial area. The reason for this is that the surface loops allow good adhesion. Most of the automobile manufacturers in Europe use fabrics made from air-jet-textured yarns for seat covers. Because these fabrics are highly resistant to overcrowding and structurally stable.

Various Textured Jets

Air-jet texturing of synthetic yarns has a history of approximately 30 years. During this time many advances were made in the process and a wide variety of jets were designed. The heart of the air-jet texturing method is the texturing jet. Jets may differ in design details, but the basic principles are exactly the same.

Another variant of this jet uses a cylindrical impactor. All these jets use a contracting and expanding geometry called "venturi" for texturing. As you can see, the basic principles are the same in all texturing jets, there are only minor design differences. However, all basic textured jets are grouped into two classes according to their structure. Continuing advances in jet design since the 1950s, combined with the development of more convenient feed yarns, have resulted in the following material advances.

1. Increased texturing speed up to 600 m/min.
2. Reduction in compressed air consumption up to 6 m/h at 10 bar (absolute) pressure for fine yarns
3. Elimination of the need to use pre-twisted feed thread
4. Improvement in textured yarn quality.

Properties of Air-Jet Textured Yarns

Textured yarn quality varies depending on many variables. Its % stretching is lower than other yarns. The heart of the air texturing machine is the texturing jet. The amount of air consumed by this jet and the texturing speed it allows affect the economy of the method. Different texturing jets can be used in the machine. In the texturing jet, the yarn is overfed at a rate of approximately 20-25%. The higher this value, the more bulky the textured yarn will be. However, as the feed rate increases, the stability of the yarn decreases.

Factors Affecting Yarn Quality

  • Thread Speed

  • Overfeed in Air Jets

  • Amount of Water Spent

  • Type of Yarn

  • Yarn Fineness

  • Number of Filaments in Yarn

  • Air Pressure

  • Fixing Temperature

  • Withdrawal Amount in the Stabilized Zone

    Measurements made for quality determination of textured yarns;
    • Boil shortening
    • Stability
    • Uster unevenness
    • Fineness determination
    • Tensile strength and elongation at break
    • Knitting and dyeing
    Based on experience, polyester yarn (167 dtex f68,du-pont) used in DU-Pont texturing jet
    Boiling temperature shortening 7.9%
    Hot air shortening 13.9%
    Strength 4.1 cN/dtex
    Elongation 29.3%
    Oil content 1-0.3%

    Air Flow and Its Effect on Flaments

    Axial velocities of the air stream (without filament in the jet) were measured using a dynamic model of the standard Hema jet at 4x magnification, and these processes showed that the air stream reaches ultrasonic velocities at the jet exit under the working pressures used in texturing. It shows a typical velocity distribution recorded at the exit of the jet at an absolute pressure of 7 bar, and the shape of the outlet is thought to cause this unevenness in the velocity distribution.

    The filaments that were not rotated at right angles after the jet were released, and Bock and Lünenshioss showed that the filaments were opened and dispersed in the jet by the effect of turbulence and ultrasonic current. In addition, research has shown that when the filaments are released in the air stream, they will move faster than the normal texturing speed. This also applies to filaments with excess length that can move freely in the air stream due to overfeeding. Acar et al. suggested that filaments dispersed in the flow undergo different drag attenuation in different regions, which is proportional to the square of the local air velocity. At any given moment, these different forces cause some different filaments to move faster than other filaments. It is quite possible that these filaments form loops, since the position of the filaments is constantly changed due to the turbulent flow during the process, the drag forces acting on each filament can also change, and loops can be formed along the yarn at random intervals in this filament.

    Effect of Flament Section and Number

    Each filament is subject to fluid forces in the flow. These forces cause the filaments to bend and twist. All filaments make a 90° turn at the exit of the jet, as they are pulled down as a result of the tension in the yarn that occurs as a result of loop formation and shortening of the filaments. This bending and torsion created by fluid forces is countered by the stiffness of the filaments. It has been suggested that thin filaments with round cross-sections are more suitable than thick filaments for air-jet texturing. Because such filaments have less bending, torsion and inertia resistance. Therefore, smaller drag forces will be required to blow these filaments out of the jet and will be easier to bend and twist during loop formation.

    Filaments that are not round in cross section. For example, an elliptical cross-section filament may be more suitable for air-jet texturing. This type of filament has a larger surface area to volume ratio and therefore experiences greater frictional drag force. Since the filaments that are not round cross-section will be bent around the main diameter, the projection areas in the exit direction will be larger, and therefore the pressure and friction forces acting on these filaments will be higher.

    Effects of wetting the yarn during processing:
    Wetting the yarn during processing is an industrially accepted and widely used method. Thus, the efficiency of a texturing is increased and higher quality yarns are obtained. Various studies have shown that very small amounts of water produce the desired effects.

    Fluid velocities, which are the main factor in determining the forces acting on the filaments, are only slightly affected by the intrusion of small amounts of water into this flow. This insignificant effect will adversely affect the texture. Because water in the air reduces the air flow rate.

    The friction between the filaments themselves and between the filaments and the outer surfaces such as the yarn guides and the inner walls of the jet plays a very important role during texturing. As a result, wetting of the filaments between air-jet and texturing has a lubricating effect, reducing the friction that exists between the filaments themselves and between the filaments and other surfaces. This leads to an increase in the net drag forces acting on the lubricating filaments, resulting in better texture and better yarns.

    A similar reduction in friction can also be achieved by rearranging the feed roller, wetting unit and jet. In addition, as the friction between the filaments decreases, wetting allows the filaments to shift more relative to each other, thus facilitating the formation of loops, resulting in high quality yarn production.