How to ensure that the strength and elongation of the yarn meet the standards in the winding of polyester hot melt yarn

How to ensure that the strength and elongation of the yarn meet the standards in the winding of polyester hot melt yarn
In the production process of polyester hot melt yarn, it is crucial to ensure that the strength and elongation of the yarn meet the standards. This not only affects the quality and performance of the product, but also directly affects the application effect and market competitiveness of the final product. This article will introduce in detail how to ensure the strength and elongation of the yarn meet the standards by controlling each link in the winding process of polyester hot melt yarn.

1. Basic characteristics of polyester hot melt yarn
Polyester hot melt yarn is a functional fiber with the characteristics of low melting point, high adhesion, high strength and good stability. Its melting point is usually between 110-180°C, and it can melt quickly at high temperature and bond to other materials, forming a stable bond after cooling. These characteristics make polyester hot melt yarn widely used in various scenarios that require strong bonding, such as 3D uppers, curtains, chenille yarn, woven collars, ribbons, etc.

2. Factors affecting the strength and elongation of the yarn
1. Raw material quality
The quality of raw materials is the basic factor affecting the strength and elongation of the yarn. High-quality polyester raw materials can ensure the uniformity and consistency of the fiber, thereby improving the strength and elongation of the final product. Therefore, choosing high-quality polyester raw materials is the first step to ensure product quality.

2. Spinning process
The spinning process is a key link in the production of polyester hot melt yarn, which directly affects the strength and elongation of the yarn. The main process parameters include spinning speed, stretching multiple, stretching temperature and setting temperature.

2.1 Spinning speed
The spinning speed affects the tensile elongation and stretching multiple of the winding yarn. The higher the spinning speed, the lower the tensile elongation of the winding yarn and the smaller the stretching multiple. Therefore, the spinning speed should be adjusted appropriately according to the quality of the winding yarn and equipment conditions.

2.2 Stretch multiple
The stretch multiple directly affects the strength and elongation of the finished yarn. The higher the stretch multiple, the higher the strength, lower the elongation and lower the linear density of the finished yarn. However, if the stretch multiple is too high, the yarn will break, resulting in hairy yarn and broken ends. If the stretching ratio is too low, the stretching will be uneven, and “rubber band” yarns will appear. Usually, the stretching ratio should be selected between 3.5 and 4.2.

2.3 Stretching temperature
The stretching temperature affects the activity of the molecular chain. Normal stretching can only be performed when the temperature is higher than the glass transition temperature (Tg). The Tg of polyester winding yarn is 69°C, so the stretching temperature is generally selected between 80 and 90°C. Within this temperature range, the change in temperature has no obvious effect on the strength of the stretched yarn, but with the increase in temperature, the stretching ratio can be appropriately increased, the boiling water shrinkage of the finished yarn is reduced, and the crystallinity is increased.

2.4 Setting temperature
The setting temperature affects the elimination of internal stress of the yarn and the strengthening of physical properties. The temperature of the hot plate is generally selected at around 180°C, because the crystallization time of polyester between 160 and 190°C is the shortest. As the temperature of the hot plate increases, the boiling water shrinkage of the stretched yarn decreases and the dyeing rate decreases. However, if the temperature of the hot plate is too high, the macromolecules will relax, the tensile stress will decrease, and deorientation will occur, resulting in reduced strength of the wire.

3. Winding technology
The winding technology also has an important influence on the strength and elongation of the wire. During the winding process, the tension and winding density of the wire need to be strictly controlled to ensure the uniformity and stability of the wire.

3.1 Winding device
The design and performance of the winding device directly affect the winding quality. For example, an improved winding device includes a winding roller, a collection tank, a fan and a blower, which can effectively remove impurities on the hot melt wire and prevent impurities from being wound into the material roll, thereby improving the winding quality.

3.2 Wire dropping device
The design of the wire dropping device is also crucial. A new type of wire dropping device can keep the distance of the monofilament moving up and down consistent with the length of the I-shaped barrel, so as to ensure that the monofilament can be evenly wound on I-shaped barrels of different lengths.

III. Quality control method
1. Standard test method
In order to ensure that the strength and elongation of the wire meet the standards, standard test methods can be used for quality control. Commonly used test methods include ASTM D5035-11 and ASTM D4964.

1.1 ASTM D5035-11
ASTM D5035-11 is a standard test method for breaking force and elongation of fabrics (peeling method), which is suitable for determining the breaking force and elongation of most textile fabrics. This method includes loose strip and cut strip test procedures, which are applicable to woven fabrics, nonwoven fabrics, felt fabrics, and impregnated or coated fabrics.

1.2 ASTM D4964
ASTM D4964 is a standard test method for tension and elongation of elastic fabrics (constant rate of extension tensile testing machine), which is applicable to the measurement of tension and elongation of wide or narrow elastic fabrics made of natural or artificial fibers. This method is to load and release tension at a predetermined speed by mounting a ring specimen on a CRE type tensile testing machine, draw a tension recovery curve, and calculate the elongation under the specified ring tension.

2. Real-time monitoring and adjustment
During the production process, real-time monitoring and adjustment are the key to ensuring that the strength and elongation of the thread strip meet the standards. By installing sensors and automatic control systems, parameters such as spinning speed, stretching multiple, stretching temperature and shaping temperature can be monitored in real time, and real-time adjustments can be made based on the monitoring results. For example, the use of advanced control systems and sensors can ensure that the temperature and tension during the stretching process remain within the optimal range, thereby improving the strength and elongation of the yarn.

IV. Practical application cases
1. High modulus, low shrinkage polyester industrial yarn
In the production of high modulus, low shrinkage (HMLS) polyester industrial yarn, the strength and elongation of the yarn can be effectively regulated by heat treatment at 150°C for 5 minutes under different pre-tension conditions (0~0.10 cN/dtex). The results show that with the decrease of pre-tension, the breaking strength of HMLS polyester industrial yarn decreases slightly, the initial modulus and the breaking strength under 5% deformation decrease significantly, and the elongation at break increases significantly. By applying a certain pre-tension, the shrinkage stress of HMLS polyester industrial yarn when heated during post-processing can be effectively offset, thereby reducing the mobility of the molecular chains in the amorphous region, and reducing the amplitude of changes in mechanical properties and amorphous region structure.

2. Polyester low-elastic yarn
After adopting low-temperature drying technology, the elongation at break of polyester low-elastic yarn increased by 5%, and the anti-pilling performance increased by 10%. This shows that by optimizing the drying process, the strength and elongation of the yarn can be significantly improved.

V. Conclusion
In the winding process of polyester hot-melt yarn, ensuring that the strength and elongation of the yarn meet the standards is the key to improving product quality and market competitiveness. The strength and elongation of the yarn can be effectively improved by controlling the quality of raw materials, optimizing the spinning process, improving the winding technology, and implementing strict quality control methods. Specific measures include selecting high-quality raw materials, adjusting the spinning speed, controlling the stretching multiple and temperature, optimizing the winding device and the doffing device, using standard test methods for quality control, and real-time monitoring and adjustment of production parameters. I hope this article will help you understand how to ensure that the strength and elongation of the yarn meet the standards in the winding of polyester hot-melt yarn.