Thesis Details

Thesis Title: The effects of sliver trash content and key fiber properties on the quality of 100% cotton and 50/50 polyester/cotton air-jet spun yarns
Thesis Author: Steven Hopkins
Abstract: Air-jet spinning has proven to be an economical and high-quality method of spinning, leading yarn manufacturers to embrace the system for certain product lines. Air-jet yarns are more even, have lower defect levels, and offer better pill resistance than comparable ring or open-end yarn. Another advantage of air-jet spinning is that the system spins yarn directly from sliver and delivers a wound package suitable for either weaving or knitting, eliminating costly processes. Currently, however, the vast majority of yarns spun on this spinning system are composed of man-made fibers or blends. Research has also indicated that fiber length, short fiber content, and fiber tenacity play vital roles in determining the quality of air-jet spun yarn. However, little research existed on the effects of trash content on the air-jet system. This research was conducted to determine the fiber properties that must be controlled in the mill, as well as the preparatory processing necessary for the spinning of high-quality air-jet yarns from widely available Delta cotton. For this research, cotton stock from the Delta growing region was used to spin 100% cotton yarns on the air-jet system. In addition, the cotton stock was blended with polyester at the drawframe in order to determine the effects of fiber properties and processing parameters on the quality of blended yarns. Eighteen conditions representing various processing sequences including two cleaning lines, three levels of waste extraction under the lickerin at carding, and three levels of noil removal at combing were spun into 30/1 yarn on the Murata air-jet spinning system from a single laydown of Delta cotton. This approach was used to obtain different fiber properties in finisher sliver, as well as to define the effects of processing parameters on air-jet yarn qUality. Finally, the cost of waste extracted from opening through spinning was correlated with yarn quality in order to determine the economic effects of increased waste extraction on specific yarn quality parameters. The resultant yarns were tested at the Institute of Textile Technology and knit into single-jersey fabric for the evaluation of fabric properties, including appearance and pill resistance. The results of this research indicate that it will be difficult to efficiently spin 100% cotton yarns from currently available Delta cotton varieties on the current air-jet spinning system. Short fiber content, trash level, and fiber alignment in sliver are the most critical parameters that must be controlled in the mill in order to maximize the quality of 100% cotton and 50/50 polyester/cotton air-jet spun yarns. Increased short fiber content was associated with decreased strength and poor evenness. Trash content has a detrimental influence on the strength, evenness, and defect levels of air-jet yarns. Yarn quality was greatly improved through the use of combed stock because of the removal of short fiber, trash, and neps from the sliver, resulting in a stronger, more even yarn with fewer defects than carded yarns. However, it should be noted that increased combing intensity above 12 % noil removal did not significantly improve the quality of 100% cotton yarns. Therefore, the additional raw material cost involved in extracting more waste did not result in significant improvements in yarn qUality. For the drawframe blended yarns, however, there was an improvement in strength, evenness, and defects as the cotton combing intensity was increased to 18% noil removal due to the increased removal of short fiber, trash, and neps, as well as improved length uniformity of the fibers in the sliver, resulting in improved drafting at spinning with a corresponding increase in yarn quality.