Thesis Details

Thesis Title: The Influences of Yam Pre-Orientation and Critical Draw-Warping Parameters on Streaks in Polyester Warp Knit Pile Fabrics
Thesis Author: Pamela Roberts
Abstract: Streaks are a major contributor to off-quality in warp knit applications. A majority of the yarns going into warp knitting fabrics are draw-warped. The offquality produced could be attributed to the draw-warping process, which is fairly new to the industry. Also, few or no modifications have been made to the feeder yarns, POY, that are being introduced into the process. Although extensive technological improvements to the draw-warping process have been made, quality problems still exist. These problems are related to both the warper design and the feeder yarns, POY. There has been little research to determine how POY properties and drawwarping parameters such as draw ratio, draw temperature and draw speed affect physical and morphological properties, and dye uptake characteristics of textile fibers. This thesis investigated these relationships to define feeder yarn characteristics suitable for draw-warping and to establish process parameters that prevent off-quality, such as streaks. To determine the impact of POY properties and draw-warping parameters, twenty-four conditions were produced. The resulting yarn samples were warp knit as pile in automotive fabric, and the fabric was dyed and finished competitively. Yarn samples from each condition were subjected to a variety of tests to characterize the fiber and yarn morphological properties, physical properties, and dyeing behavior. The study involved draw ratios from 1.650 to 1.743, draw temperatures ranging from 170°C to 215 DC, and different feeder yarn pre-orientation levels. Results revealed that large ranges in temperature affected tenacity, shrinkage, percent crystallinity, sonic modulus, and dye uptake. Draw ratio significantly affected fiber properties such as elongation, shrinkage, sonic modulus, and fiber dye uptake. Since these factors altered the internal structure of the fibers, dye uptake and light reflectance changed. In addition, changes in the fiber morphology and physical characteristics altered the pile angle. These factors contributed to streak formation in the finished fabric. From the results, the following general conclusions can be made: 1. Variation in POY affects dye uptake, which contributes to streaks. 2. Inconsistent drawing across the warp sheet can promote streaks. 3. Draw-warping temperature, if not optimized, will intensify POY variation. 4. Proper selection of draw-warping parameters may reduce streak propensity.