A new approach to improve the bulkiness of worsted grade wool yarn

In this research, attempts are made to apply an unconventional draft system to improve the bulkiness of worsted yarn made wholly from wool. The general concept of this research is focused on an uneven length distribution of wool fibers and on the principle of the roller drafting system. Modification of the drafting system as well as various roller gauge adjustments provides an appropriate condition to produce a yarn with different physical specifications. A traditional ungrooved and smooth roller is used instead of the traditional grooved roller in the middle top roller of the drafting system and the distance between the front and middle roller pairs of different gauges are adjusted to produce the samples. The results of this research show that the yarn diameter and bulkiness strongly depend on the roller gauge of the drafting system. The yarn produced with the ungrooved roller as the middle top roller of the drafting system shrinks more after immersing in hot water by comparison with the same yarn produced conventionally. The higher shrinkage of the yarns results in higher lateral expansion and higher increases of yarn diameter and bulkiness. Other results show that, the ungrooved roller does not alter the yarn strength and irregularity. According to the results, the highest volume of the yarn produced with the ungrooved roller can be achieved at a gauge adjustment of 12.2 cm in which the frequency of the fibers longer than the roller gauge in the staple diagram is about 8.4%. Consequently, the proper roller gauge of the drafting system should be determined from the staple diagram of the fibers and adjusted to obtain about 8.4% of fibers with a length of longer than the gauge.