Measuring the hairiness of a rotor-spun yarn on the Uster Tester 3 at different speeds

A low-twist rotor-spun yarn of 18.5 tex was tested for yarn hairiness and evenness on an Uster Tester 3 at speeds of 25, 100, and 400 m/min. Both spinning and rewound packages were tested. The results show that yarn hairiness measured at 25 and 100 m/min is lower than that obtained at 400 m/min, and the difference is statistically significant at the 5% level. This is true for both the original and rewound yarns. However, in contrast to the original yarn, the standard deviation of hairiness for the rewound yarn is significantly lower at 400 m/min than at 25 and 100 m/min. Test speed has little effect on the yarn-irregularity CV% for both the original and the rewound yarn, but the irregularity of the rewound yarn is consistently higher. The difference in yarn hairiness can be largely attributed to the frictional rubbing of the yarn surface by the yarn guides on the tester. The air flow generated during hairiness testing is also believed to play a part in the hairiness difference. Furthermore, it is shown that the hairiness readings gradually reduced as successive layers of yarn on the same package were tested, whereas a similar trend was not observed for yarn irregularity. This within-package variation in yarn hairiness may be caused by the increased compacting from neighbouring yarns on the inner layers of yarn as the package builds up. Rewinding tends to reduce the within-package variation in yarn hairiness.