Thesis Details

Thesis Title: Effects of fiber denier, fiber length, and finish type and level on open-end viscose rayon yarn properties
Thesis Author: Elizabeth Elam
Abstract: Fiber producers have recently enjoyed an increasing trend in the popularity of their viscose rayon products. In the apparel market, for example, rayon fabrics have made the move to expensive, high fashion garments. The increase in rayon popularity has been largely due to development of the open-end spinning system. Rayon staple is more expensive than other fibers such as polyester and cotton, so it is not economically practical to spin 100 percent rayon yarn on the ring system for most applications. However, increased package size, increased speeds, and labor savings make the open-end system an economical way to process rayon yarn. The problem today is lack of information. Much work has been done by the Institute of Textile Technology and others on polyester and cotton, but limited research has been published relating viscose rayon fiber properties to open-end yarn properties. Lack of data is remedied by this thesis which will help fiber producers and staple yarn manufacturers to understand the important relationships. To study the effects of rayon fiber length, denier, finish type, and finish level on open-end yarn properties, a classical factorial design was used with two levels of each fiber property. The levels for each variable were chosen so that they were wide enough to show significant effects and interactions yet still within practical processing limits: Fiber Length: Denier: Finish Level: Finish Type: 1 1/4 in., 1 1/2 in. 1.1, 1.5 0.2%, 0.4% regular finish high cohesion finish High tenacity, regular viscose staple with the properties listed above was produced by Courtaulds Fibers Inc. Sixteen bales of rayon fiber, each representing an experimental condition, were processed into 30/1 cotton count yarn. The yarn was produced on an Autocoro open-end spinning system at two different combinations of rotor speed and diameter: 65,000 rpm, 40 mm rotor; and 80,000 rpm, 33 mm rotor. Each of the 32 yarn lots was evaluated in terms of processing performance and final yarn quality. RotorRing evaluations indicated that the longer fiber and the finer denier fiber led to higher fiber cohesion, and the longer fiber exhibited easier opennability. In addition, the longer fibers and the finer denier fibers produced yarns of much higher quality than the shorter and coarser fibers; however, these fibers also resulted in lower apparent dye uptake as measured by K/S level. An increase in finish level had a lubricating effect on the fiber, as it resulted in lower fiber-to-fiber cohesion. The higher finish level significantly reduced the number of ends down at spinning. It also resulted in higher yarn elongation, better evenness, and fewer thin places in the yarn. Although the type of finish did not affect as many yarn properties as the other fiber parameters, the higher cohesion finish did result in higher single-end strength and elongation. Finally, at the higher speed and correspondingly smaller rotor diameter, ends down rates were significantly increased and yarn quality deteriorated. This research has shown that practical changes in rayon fiber properties can drastically change yarn processing performance and final yarn qualities. The results will allow rayon fiber producers in cooperation with staple yarn manufacturers to engineer rayon fiber for maximum productivity and the best yarn quality possible.