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Polyester blended yarns are widely used in the textile industry due to their excellent overall performance. Compared to pure fiber yarns, the spinning process for polyester blended yarns differs significantly. These differences are reflected in various stages, including raw material pretreatment, spinning process control, fiber ratio selection, and subsequent finishing.
Differences in Raw Material Preparation
Pure fiber yarns are typically made from a single fiber type, such as pure cotton, pure polyester, or pure wool, with relatively uniform raw material characteristics. Polyester blended yarns, on the other hand, require the simultaneous processing of multiple fibers, which vary significantly in length, diameter, softness, and physical and chemical properties.
Polyester fiber is a chemically synthesized fiber with high strength, elasticity, and abrasion resistance; natural fibers, such as cotton, have good moisture absorption and softness. Different fibers require different pretreatment methods. Polyester fibers generally require opening and cleaning to remove impurities, while natural fibers require the removal of impurities such as weeds and seed cotton.
The opening process before blending ensures that the two fibers are fully loosened and evenly mixed. The raw material mixing process for polyester blended yarns is more complex, requiring equipment with high levels of adjustment and control capabilities to ensure even fiber distribution and avoid clumping or fiber segregation.
Special Requirements for Carding and Blending Processes
During the spinning process, the carding step is responsible for straightening the fibers and removing impurities. The carding process for pure fiber yarns is relatively simple, with process parameters tailored to the characteristics of a single fiber.
During the carding stage, polyester blended yarns must balance the physical properties of different fibers. Polyester fibers are strong, elastic, and resistant to breakage, while natural fibers, such as cotton, are softer and more prone to breakage. Carding equipment must adjust the needle length, speed, and tension to ensure simultaneous and even straightening of both fibers, minimizing fiber breakage and yarn defects.
Blending equipment and control of the blending ratio are crucial to ensure that the polyester and natural fibers are thoroughly blended before entering the carding and drawing stages. Uneven blending can lead to unstable yarn properties, affecting both hand feel and finished product quality.
Adjustment and Optimization of the Spinning Process
The spinning process for polyester blended yarns requires adjustments tailored to the specific fiber characteristics. Polyester fibers have high elasticity, which can easily cause elastic recovery and crimping, making spinning tension control particularly important. The spinning tension of pure fiber yarns is relatively stable, with limited adjustment margins.
A variety of spinning technologies, including ring spinning, open-end spinning, and compact spinning, can be applied to polyester blended yarns. Ring spinning offers strong fiber adaptability but relatively low production efficiency. Open-end spinning offers high efficiency and is suitable for blended yarn production, but requires higher fiber length.
Spinning speed and tension must be flexibly adjusted based on the polyester content and fiber length. With high polyester content, yarn tension can be appropriately increased to enhance yarn strength and uniformity. With low polyester content, excessive tension should be avoided, as it may cause natural fiber breakage.
Yarn Quality Control and Defect Management
Polyester blended yarns are prone to quality issues such as fiber separation, yarn defects, end breaks, and uneven thickness. Pure fiber yarns present relatively limited problems, primarily related to fiber breakage and impurities.
Quality control for blended yarns focuses on ensuring an even distribution of different fibers and avoiding excessive amounts of either polyester or natural fibers in certain areas. During the spinning process, online testing equipment monitors yarn breakage rates and thickness variations in real time, allowing for timely adjustment of process parameters. Furthermore, static electricity is a prominent issue with polyester blended yarns, especially in dry environments. Using antistatic agents or humidity control equipment can effectively reduce static electricity accumulation, improving the production environment and yarn quality.
Differentiated Finishing Processes
After polyester blended yarn is spun, the finishing process must balance the properties of both synthetic and natural fibers. The finishing of pure fiber yarns primarily focuses on improving softness, shrinkage resistance, and color.
The finishing of blended yarns is more complex. The polyester component enhances the fabric's heat resistance and abrasion resistance, but the natural fiber component requires attention to prevent shrinkage and deformation. Chemical additives such as softeners and wrinkle inhibitors must be properly formulated to balance the properties of both fibers.
Dyeing processes also differ. Polyester blended yarns generally use step-dyeing or co-dyeing techniques to ensure that the different fibers achieve the desired color without affecting the hand feel. Dyeing pure polyester yarn is relatively simple, while dyeing pure natural fibers prioritizes color fastness and uniformity.
