Effects of modified air quenches on the high‐speed melt spinning process

Abstract

SYNOPSISA high molecular weight polyethylene terephthalate was spun into fibers in the speed range from 3,000-7,000 mpm. The effect of modifying threadline dynamics through a combination of enhanced and/or retarding air quenches on the resulting spinning performance, fiber structure, and mechanical properties was examined. Particular combinations of these threadline temperature profile modifications were shown to result in significant improvements in spinning performance and as-spun fiber structure. Extensive characterization of select fiber samples revealed higher orientation and crystallinity, larger crystal dimensions, and greater mechanical properties. These results also demonstrated the ability to provide continued improvement in fiber properties at very high take-up speeds where typically a decline is observed. It is concluded that the threadline temperature profile can be altered in such a way as to significantly enhance the resulting spinning performance and fiber structure over a wide range of take-up speeds.

Properties of high-speed spun high molecular weight poly(ethylene terephthalate) filaments

“…The birefringence of this study increases rapidly from a relatively low take‐up velocity of 2.5 km/min and then levels off at around 5 km/min. The relatively high value of birefringence obtained in this study is basically related to the high melt draw ratio and is consistent with the result of Hotter et al14 who modified the air quench with the heating chamber to give a retarded air quench and, hence, improved the orientation.…”

“…In general, maximum take‐up velocity without spin line breakage for high molecular weight PET is lower than that for low molecular weight PET. Reported maximum take‐up velocities for high molecular weight PET are 6–6.5 km/min without any quench modifications9, 13 and 7 km/min with the zone heating chamber 14. A relatively low take‐up velocity limit in this study, regardless of the use of the shroud heater, is believed to be due to the notably higher melt draw ratio.…”

“…Focusing on the quenching conditions, the shroud heater located just below the spinneret is similar to the on‐line zone heating chamber used in the study of Hotter et al14 They set a zone heating chamber at a high temperature close to the spinneret and found that the retarded air quench due to a heating chamber grants improved stability to the spinning at very high take‐up velocities and yields a continued development in orientation beyond the take‐up velocity range where a decline is usually observed. With the shroud heater, it is confirmed that the air quenching does not take place before filaments reach the quenching chamber.…”

“…High molecular weight PET, whose IV is higher than 0.9 dL/g, matches with the filament for a high‐performance end use such as tire cord for which a high modulus and dimensional stability are indispensable. Relatively little attention has been paid to the high‐speed spinning of high molecular weight PET except for studying the effect of molecular weight on high‐speed spinning9, 13 and for achieving improved mechanical properties by modifying threadline dynamics through controlled air quenching14 or a liquid isothermal bath spinning process 15, 16. This work aimed to characterize the physical structure and properties of PET filaments spun at high speed from high molecular weight PET and to present the effects of molecular weight and processing parameters on the properties of high‐speed spun PET filaments in detail by comparing them with the data reported by other researchers.…”

Thermal shrinkage stress in high‐speed‐spun, high molecular weight poly(ethylene terephthalate) filaments

“…Thermomechanical properties of high‐speed‐spun PET filaments have also been reported for low molecular weight PET 13–15. There have been some studies on the high‐speed spinning of high molecular weight PET, including studies on the effect of molecular weight on high‐speed spinning16, 17 and the modification of threadline dynamics to achieve improved mechanical properties 18, 19. However, relatively little attention has been paid to the shrinkage and shrinkage‐stress behavior of high‐speed‐spun, high molecular weight PET filaments.…”