What are the difficulties in producing polyester wool blended yarn

Polyester wool blended yarn (Polyester/Wool, T/W) is a high-end product in the textile field. It combines the natural warmth and drape of wool with the durability and wrinkle resistance of polyester, and is widely used in high-end fabrics such as suits, coats, and uniforms. However, this perfect combination is not easy, and its production process faces many technical difficulties.

1. The challenge of blending uniformity brought about by fiber heterogeneity

There are huge differences in physical and chemical properties between polyester fiber and wool fiber, which is the primary difficulty in producing T/W blended yarn. 

Differences in fiber length and fineness: Natural wool has a wide distribution range of fiber length and fineness, while polyester staple fiber is relatively uniform. In the process of carding, stripping, etc., it is difficult to achieve a completely uniform mixing of fibers with large lengths. This can lead to "bamboo joints" or "cloud spots" of the final yarn, affecting the uniformity of the strips and appearance of the fabric. 

Difference in physical properties: Polyester has high strength and good elasticity, while wool has high curl and soft feel. During the loosening and blending process, polyester fibers tend to hold together, while wool fibers are easily dispersed. To ensure that the two fibers achieve the ideal mixing ratio at the microscopic level, precise control of feeding, loosening and combing speed is required. 

Difference in dyeing performance: Polyester and wool have very different affinity for dyes. Polyester usually uses dispersed dyes, while wool uses acidic or reactive dyes. The dyeing of blended yarns requires the use of complex processes of "same bath, two colors" or step-by-step dyeing to accurately control the dyeing temperature, time, and pH value to avoid the occurrence of heterochromatic phenomena (i.e., the color depth or color light of the two fibers is inconsistent), which is a key technical difficulty in producing high-quality T/W yarns.

2. Precise control of process parameters and equipment matching

The production of T/W blended yarn requires fine adjustment of the process parameters of each link to adapt to the characteristics of the two different fibers. 

Combing link: Wool fibers are easy to damage and pill, while polyester fibers are smooth and difficult to hold. In the carding machine, it is necessary to choose a suitable Xilin needle cloth, Dorph speed and jaw roll configuration, which not only ensures that the loosening and carding are fully loosened, but also avoids damage to the wool fibers, and prevents the polyester fiber from being statically wound. 

Drawing link: The elastic modulus of polyester and wool are different. During the drafting process, the elongation and stress state of the two fibers are inconsistent. If the drafting multiple is too large or the speed does not match, it will cause damage to the fibers or even breakage, seriously affecting the strength and uniformity of the yarn. Therefore, it is necessary to conduct repeated trials and optimizations of draft multiples, roller spacing, etc. based on the blending ratio and fiber characteristics. 

Twist control: Twist is an important parameter that determines the strength, feel and luster of the yarn. After the polyester and wool are blended, the optimal twist is between pure polyester yarn and pure wool yarn. Too high twist will make the yarn feel thick and hard, affecting the drape feeling; too low twist will lead to insufficient strength and easy wool. How to find the best balance point is an important challenge in producing high-quality T/W blended yarn.

3. Strict requirements for back-stage finishing and quality control

The difficulties in the production of T/W blended yarn are also reflected in the subsequent process and strict quality control. 

Sizing and warping: T/W blended yarns usually have more yarn surface than pure polyester yarns. In the sizing and warping process, it is necessary to select appropriate slurry and sizing processes to reduce hair and improve the smoothness of the yarn to meet the needs of high-speed weaving. 

Weaving and post-organization: The weaving process requires precise control of the tension of the warp and weft yarns to prevent yarn breaks or defects in the fabric. In the post-organization (such as: setting and shrinking wool) process, the shrinking characteristics of wool and the thermal setting characteristics of polyester must be fully considered. Excessive heat treatment can damage the wool fiber and affect the feel; insufficient treatment will not achieve ideal dimensional stability. 

Quality inspection: High-quality T/W blended yarn requires strict inspection of multiple indicators, including fiber blending uniformity, strip dry uniformity, yarn strength, hairy index, color fastness, and pill resistance of finished fabric products. Deviations in any link may lead to unqualification of the final product. Especially in terms of blend uniformity and color difference control, it is necessary to use professional instruments and equipment to conduct precision inspection to ensure the stable quality of each batch of products.