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Abstract:
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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.
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