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Analysis of common problems in textile sizing1
1 Causes of formation of yarn hairiness and improvement measures Yarn hairiness can be divided into three categories: original yarn hairiness (primary hairiness), sizing hairiness (secondary hairiness), and regenerated hairiness (hairiness produced by weaving). 1.1 Original yarn hairiness The reasons for the formation of original yarn hairiness have been studied in depth by scholars. During the spinning process, the fibers in the twisting triangle are subjected to the dual action of tension and twisting force, resulting in centripetal force. The fibers transfer inside and outside repeatedly, so that one or both ends of the fibers are exposed outside the yarn body, and finally hairiness is formed. 1.1.1 Change law The hairiness of original yarn starts from spinning and increases in winding. After the warp and winding, both long hairiness and short hairiness will increase exponentially, as shown in Table 1. 1.1.2 Distribution law For cop yarns, the hairiness is the most in small yarns, the least in medium yarns, and a little more in large yarns; 1 mm The short hairiness of ~2 mm is the main component of yarn hairiness, and it is less harmful. Although the proportion of hairiness above 3 mm is not high, it is very harmful to weaving production. The hairiness of 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm and 8 mm of the JC 14.8 tex ring spinning cop was measured respectively The results were 482.06/10 m, 81.53/10 m, 22.19/10 m, 9.53/10 m, 4.86/10 m, 2.39/10 m, 1.49/10 m, 0.49/10 m. It can be seen that as the hairiness length increases, the cop hairiness decreases sharply. 1.2 Sizing hairiness Sizing hairiness (secondary hairiness) refers to the harmful long hairiness that is sized and produced during the sizing process. There are two characteristics of these sized unwanted hairiness. First, with the increase of PVA dosage and sizing rate, the degree of its harm to weaving also increases. Second, the sizing rate of sizing hairiness is greater than the sizing rate of yarn. From microscopic observation, the sizing rate of hairiness is estimated to be 1 to 2 times the weight of hairiness. Starched hairiness is even more harmful. 1.2.1 Reasons for the formation of improper selection of slurry and failure to follow“Similar compatibility”principle. The sizing has poor adhesion to the yarn, and the sizing film is not abrasion-resistant and has poor integrity. In the slurry formulation, the compatibility is unreasonable, and the tear strength and toughness of the serosa film are too high (especially when a large amount of fully alcoholylated PVA is used). In this way, it is easy to cause the sizing resistance to be large, the interface between the sizing film and the yarn is damaged, the sizing film is broken, and the sizing hairiness and falling objects are generated. The sizing rate is too high or too low. If the sizing rate is too high, the dry splitting resistance is increased; if the sizing rate is too low, the sizing liquid cannot fit the hairiness. At the same time, it should also be noted that the proportion of sizing to yarn penetration and coverage should be suitable for the needs of variety sizing. Over-penetration and insufficient penetration will have negative effects. The dryness of the sizing is also the cause of the sizing hairiness. The moisture regain of the sizing yarn is dry, the sizing film becomes brittle, the cohesion and softness will decrease, and the sizing is serious when the sizing is dry, which increases the hairiness of the sizing. 1.2.2 The selection of improvement measures slurry should first be based on“Similar compatibility”The principle is the principle, which is the basis of sizing and the foundation of sizing. Wrong selection of sizing, not to mention reducing hairiness, even the quality of sizing is difficult to guarantee. Secondly, the adhesiveness of the size is very important. Without good adhesiveness, there will be no good abrasion resistance. Without good abrasion resistance, sizing hairiness and regenerated hairiness (produced by weaving friction) are inevitable. Also pay attention to the film-forming properties of the slurry. It is not recommended to use the slurry that does not form a film as the main slurry, and it is possible to use a small amount. When sizing is compatible, it is necessary to consider that the tear strength of the serosal film should not be too high, otherwise the splitting resistance will be large. Therefore, PVA with different degrees of polymerization and alcoholysis should be carefully selected. Careful selection of the amount of PVA is an important principle for making good use of PVA and reducing sizing hairiness. Under certain conditions, using less or not PVA has a good effect on reducing hairiness. The size of the sizing rate should be determined according to the specific situation of the enterprise, and the appropriate sizing rate should be determined through experiments, and at the same time, the appropriate proportion of slurry penetration and coating should be considered. The proportion is not specified, only the range. Because the size of the sizing rate can only be compared with the same varieties of the enterprise, this is the most practical. When the sizing regains moisture, the hairiness increases, and when the moisture regains, the hairiness decreases. Everyone has this experience. According to the environmental conditions of the company's weaving workshop and the seasonal climate, a slightly larger resurgence is conducive to reducing hairiness and falling objects. 1.2.3 Other experience moisture-splitting sizing film. This is a widely recognized and effective experience in the sizing industry. Even if it is not pre-baked in layers, wearing a wet split rod is effective in reducing the dry split resistance. Layered pre-bake, the effect is remarkable. Layered pre-baking can reduce the coverage factor of the sizing during drying, which can effectively ensure the integrity of the sizing film and reduce the hairiness of the sizing. The surface of the drying cylinder is coated with a polytetrafluoroethylene anti-sticking layer. Reduce the peeling force between the drying cylinder and the sizing, make the sizing film complete, and reduce the hairiness of the sizing. Using high pressure sizing. Optimum control of sizing penetration, high-pressure sizing can make the sizing more close to the fiber on the main trunk of the yarn, so that the surface hairiness is more firmly attached.
1. ISO 5402-1: Specifies the flexometer method for testing leather flex resistance under repeated bending.
2. ISO 17694: Defines test methods for footwear upper and lining flex resistance, simulating real-world bending stress to assess long-term durability.
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