On-line wide-angle x-ray scattering measurements during high-speed melt-spinning of poly(Ethylene Terephthalate) fiber

We report results of on-line wide-angle X-ray scattering (WAXS) measurements for melt spinning process of poly(ethylene terephthalate) (PET). In order to obtain good results, we have conducted experiments by paying attention as much as possible. First of all, a special experimental set-up has been developed by employing a purge box which contains the spin line and the X-ray detector (imaging plate), as well, with helium gas purge, in order to minimize noise level due to air scattering. Furthermore, a high-molecular weight PET sample prepared by solid-state polymerization was used in order to increase the spin line stress, which accommodates us with starting of orientation-induced crystallization at low take-up velocities. A special care to minimize the swaying of the spin line has been taken as well by employing a perforated metal guard inside the spinning tube which covers the spin line from the spinneret to the winder with insertion of the helium gas purge box in the middle. This worked well for suppression of the air turbulence. By such special experimental treatments, we have succeeded in conducting on-line two-dimensional WAXS measurements during the high speed melt spinning of PET fibers with the take-up velocity of 1600m/min. As a high brilliant X-ray source, we utilized SPring-8 (Japan Synchrotron Radiation Research Institute, Harima, Japan). The combination of above mentioned techniques enabled us to obtain crystalline reflections from oriented crystals with only 2min exposure. Nevertheless, we observed no appreciable change in crystallinity and orientation of crystallites along the spin line. It is because the control of positioning the neck point where the crystallization sets in was sensitively influenced by the ambient gas condition. Further special care to overcome this difficulty should be taken in our future study. © 2013 The Society of Materials Science, Japan.