Studies on fiber-process-structure-property relationships in air-jet spinning - Part II: Model development

The effect of first-nozzle pressure, second-nozzle pressure, yarn count, and blend ratio on the tenacity, elongation, and evenness of microdenier polyester-fiber/cotton blended air-jet-spun yarns is studied. A mixed-effects model using a nested factorial design is chosen as the experimental design. For a given second-nozzle pressure, the first-nozzle pressure at which maximum yarn strength is achieved depends on the yarn count and not on the blend ratio. As the yam becomes finer, the optimum first-nozzle pressure decreases. Depending on the effects of changes in yarn evenness and structure with increasing first-nozzle pressure, yarn strength either decreases after reaching an optimum or levels off. The tenacity of the yarn increases as the yarn count becomes finer. Second-nozzle pressure interacts with the yarn count in determining the yarn tenacity. The optimum second-nozzle pressure increases as the yarn becomes finer. First-nozzle pressure affects the yarn breaking elongation, and the trend is same as that of the tenacity for coarser counts. However, as the count becomes finer, the maximum breaking elongation is achieved at higher first-nozzle pressures. An increase in the second-nozzle pressure reduces the yarn breaking elongation, but the trend depends on the yam count. An increase in first-nozzle pressure increases the yarn U% and imperfections for all counts and blend ratios. Second-nozzle pressure does not affect yarn evenness and imperfections. Fiber-process-structure-property models for microdenier polyester-fiber/cotton blended yarns are developed. Stepwise regression techniques were used to model the material-process-structure relationships, the material-structure-property relationships, and the material-process-property relationships in air-jet spinning. Based on these models, a generalized model that identifies the strong and weak relationships and the direct and indirect relationships between various classes of parameters in air-jet spinning is proposed.