Abstract:

Objective The wrapped effect has always been the core indicator in the market to judge the quality of the core spun yarns. In the market, the number of the wrapped fiber is always more than 80% to achieve the core filament being wrapped. The difficulty in achieving good wrapping effect lies in controlling the center position of the core wire. It is of great theoretical significance and application value to achieve high wrapping effect of yarn based on low outer fiber ratio and stable control of yarn structure, thereby improving the multi-component advantage of core yarn.

Method To achieve high yarn wrapping effect and structural stability, this research proposed a solution by installing a filament control device to adjust the spinning process and parameters. Low-elastic polyester filament with a linear density of 7.78 tex as the core yarn, cotton roving with different quantities of as wrapping fibers were used to spin cotton/polyester core-spun yarn by ring spinning. The critical wrapping ratio of core-spun yarn was explored. The relationship between the structure of core-spun yarn and the wrapping rate was analyzed. The concept of yarn section eccentricity was introduced, and the structure stability of yarn was characterized by combining yarn coverage rate and longitudinal appearance morphology.

Results The relative position of the polyester filament and cotton roving was controlled by the installed a filament positioning device. The component ratios of polyester filament and cotton roving in 8 sets of core-spun yarns are 75/25, 70/30, 65/35, 60/40, 55/45, 53/47, 52/48, 50/50; The density of core-spun yarn is 31.8, 25.5, 21.6, 19, 17.4, 16.5, 16, and 15.7 tex, respectively. 50 images were collected for each group of yarn with 100 times magnification, and the obtained image was binary-processed by Ostu algorithm to calculate the yarn coating rate. Compared with other binary processing methods, the Ostu algorithm had the smallest error probability and higher accuracy. When the component ratio of cotton roving was 53%, the coverage rate of core-spun yarns remained at 87.5%. When the component ratio of cotton roving was less than 53%, the coverage rate of core-spun yarns was lower than 85% and a large area of core polyester was exposed. It is concluded that critical coverage ratio of core-spun yarn was when the component ratios of polyester filament and cotton roving was 53/47. The average variation range of eccentricity of core yarn section under different polyester-cotton ratios was 8.8%~11.2%. The characterization of section eccentricity, yarn coverage, and longitudinal appearance morphology verified the effectiveness of the spinning process adopted in this laboratory.

Conclusion The experiment provides data support and characterization for the discussion of the critical coverage rate during spinning cotton/polyester core-spun yarn by ring spinning. The computer image processing method for calculating the core-spun yarn coverage rate was obtained, which is convenient to operate and accurate. In addition, the factors affecting the stability of core yarn structure are analyzed from the perspective of theory and spinning practice, and the stable control of core-sheath structure is achieved by adjusting the spinning process.

Key words: polyester/cotton core-spun yarn, coverage rate, yarn structural, spinning technology, eccentricity, blending ratio