| Aramid and ultra-high molecular-weight polyethylene (UHMWPE) fibers are known as high tenacity high modulus fibers. These fibers are well-known as their trade names, KevlarRTM (DuPont(TM)) for aramid fiber and SpectraRTM (Honeywell) for UHMWPE. Even though the fibers' excellent tensile properties, the production cost has been a high barrier for those fibers to be broadly used in technical textiles applications.;Polyesters, including poly(ethylene terephthalate) (PET) and nylons are typically used in some technical textiles applications, such as automotive safety, geotextile, narrow fabric, offshore mooring, rope and cordage. Those polymeric fibers are produced by melt spinning process. The production cost for melt spinning process is significantly cheaper than the cost for aramid or high molecular weight polyethylene fibers, yet the polyester and nylon fibers have acceptable tensile strength to be used in technical textile applications. However, the tenacity of a commercial polyester or nylon yarn for technical textile applications is limited to 9-10 g/d. Over 10 g/d is very difficult to reach.;All in all, to acquire high performance fibers via significantly lower production cost than now; engineers and scientists in industry and in academia are still doing a research to find new materials and/or processes. In this study, poly(ethylene terephthalate) (PET) was used to produce high performance fibers. Utilizing horizontal isothermal bath (HIB) during the melt spinning process allowed the production of high performance PET fibers via changing the threadline dynamics.;In 2010, a result that is related to a PET monofilament having the high tenacity of 9.55 g/d was published by Peng Chen et. al. at NC State prior to this study. However, it has never been done to calculate the drag force, which is known as the key force that causes to increase the tensile properties of HIB fibers extraordinarily. Hence, in the first section of this study, the drag force was calculated when air (20 °C), water (80 °C), and triethylene glycol (TEG) (115 °C) were used as the medium, respectively. Both of drag force results and tensile property results increased in the same order of air (control), water, and TEG. Hence, it is probable that the drag force equation can be utilized as a good tool to predict the final sample's tensile properties before performing experiments.;The studies on HIB in the past were based on monofilament process. Multifilament yarn production with the HIB has not been possible or not been challenged because high volume of liquid splash from the HIB during the process. In the second section, liquid splashing issue was challenged, and by modifying the design of HIB lid, the amount of splash significantly decreased. As a result, 20-multifilament yarn production was achieved with utilizing the HIB! This is a great step forward for the HIB process to be applied to the industrial process.;In the third section, achieving the tenacity higher than 9.55 g/d was challenged, and investigation of the structure-property relationships via various characterization methods was done. By passing 20-multifilament yarn through the TEG at 115 °C, winding up the yarn at 2,500 m/min, and post-drawing it at the draw ratio of 1.24; tenacity of 10.24 +/- 0.43 g/d, modulus of 114.17 +/- 10.49 g/d, and elongation at break of 13.49 +/- 1.09 % were acquired. In the third study, four different types of fibers were produced; and they are control as-spun, control drawn, HIB as-spun, and HIB drawn fibers. The percent crystallinity, degree of orientation, and the tensile properties were all increased in the same order of control as-spun, control drawn, HIB as-spun, and HIB drawn fibers. |
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