Core yams are known to improve cotton yam properties. In this research, core yarns are spun by introducing filaments under tension into the yarn-forming zone of an ex perimental friction spinning apparatus. A 30-denier (3.3 tex) nylon monofilament and a black 75-denier (35f) nylon multifilament make up the core, and cotton fibers are used as the sheath. The effect of filament pre-tension on the structural parameters and mechanical properties of the core yarn is examined, and core yarn properties are com pared with those of equivalent 100% cotton yarns. The photographic and fiber tracing methods are used to consider the appearance of the yarns and the geometric position of the core in the core yarns. The results show that the appearance of the core yarn is similar to that of regular cotton yarns, with the exception of core yarns produced with 00 gf/fil pre-tension. Core yarn irregularity does not change with filament pre-tension, and it is less than that of cotton yam. Core yam strength significantly increases as filament pre-tension and filament percentage increase, and it is greater than that of cotton yarn. Core yarn elongation is less than that of cotton yarn at a low filament percentage and greater than that of cotton yarn at a high filament percentage.

We have studied the effects of suction air pressure on the structural parameters and mechanical properties of yarn. Changing the amount of suction air pressure improves the fiber extent in yam and yarn appearance. Therefore, photographic and fiber tracing methods are used to evaluate, respectively, yam appearance and fiber extent in the yam. To consider the effect of suction air pressure on yarn diameter, yam tension at the yarn-forming zone and yam diameter are measured simultaneously on a friction spinning machine using various levels of suction air pressure, and then the relationship between them is considered using the cross correlation method. The results show that at high suction air pressure, yarn di ameter, yarn unevenness, and yam irregularity decrease, while fiber extent in the yarn and twist efficiency increase. On the other hand, the value of the correlation coefficient demonstrates that there is a high correlation between variations in yam tension and yarn diameter. The results of yam mechanical property measurements show that at high suction air pressure, yam tenacity increases and yarn elongation decreases. Results are reported from experiments on 100% cotton yams.

Image processing has been applied to actual blended yarns made from wool/wool and wool/mohair, and the blend state (fiber arrangement) of the yarns analyzed. Yarn about 4 mm long (310 pixels) was processed in each image. The projected area of white and black fibers on the yarn surfaces, the blend ratios, and the sizes of clusters were determined. Further, when several scores of yarn images laid in a row were put into the system, blend irregularity curves could be obtained. From these curves, variance-length curves of blend irregularity were calculated, and a total variance, average values, etc., were determined. The analysis showed that the wool/wool yarn was well blended compared with the wool/mohair, because the former was smaller in blend ratio variance than the latter, was also smaller in cluster size and its variance, and further was smaller in the total variance of the variance-length curve for blend irregularity. With this system, such differences in the blend state of an actual blended yarn, which can hardly be distinguished with the naked eye, can be estimated.

We have analyzed the tension distribution along the yarn tail in the yarn-forming zone of a friction spinning machine by considering the effective parameters of the torque applied to the yarn tail. Tension is applied to the yarn tail by suction air pressure and rotation of friction rollers. The yarn tension in the yarn-forming zone is measured for various yarn counts and suction air pressures. The effects of the parameters on yarn tension are considered in a theoretical analysis based on tension distribution along the conical yarn tail. Theoretical results are compared with me experimental data. The results of this research show that yarn tension increases with increasing suction air pressure and yarn size in tex, and yam diameter decreases with increasing suction air pressure for the same yarn size. Therefore, because of the low tension experienced with fine yarns, it is difficult to properly produce such yarns through friction spinning.

In this research, a computer image processing system is used to evaluate the blend state (fiber arrangement) or uneven distribution in blended yarns. Pan I presents an investigation of the precision and effectiveness of the system using three kinds of model yarns, whose numbers of component filaments, blend ratios, and blend states have been predetermined. The method of image input, various image processing techniques, and a statistical analysis are examined based on the model yarns. The results show clearly that with this system, the diameter and area ofone fiber can be measured, the blend ratio of black and white fibcrs in a short sample length can be accurately determined, and the size of a cluster can be quantitatively evaluated.