Structure and properties of syndiotactic polystyrene fibers prepared in high-speed melt spinning process |
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| Authors: | Yoshiaki Hada Haruo Shikuma Hiroshi Ito Takeshi Kikutani |
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| Institution: | (1) Department of Organic and Polymeric Materials, Graduate School of Science and Engineering, Tokyo Institute of Technology, 152-8552 Tokyo, Japan;(2) Idemitsu Kosan Co. Ltd., 299-0193 Chiba, Japan;(3) Present address: Shiga Industrial Support Plaza, 522-0057 Shiga, Japan |
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| Abstract: | High-speed melt spinning of syndiotactic polystyrene was carried out using high and low molecular weight polymers, HMs-PS and LMs-PS, at the throughput rates of 3 and 6 g/min. The effect of take-up velocity on the structure and properties of as-spun fibers
was investigated. Wide angle X-ray diffraction (WAXD) patterns of the as-spun fibers revealed that the orientation-induced
crystallization started to occur at the take-up velocities of 2–3 km/min. The crystal modification wasα-form. Birefringence of as-spun fibers showed negative value, and the absolute value of birefringence increased with an increase
in the take-up velocity. The cold crystallization temperature analyzed through the differential scanning calorimetry (DSC)
decreased with an increase in the take-up velocity in the low speed region, whereas as the melting temperature increased after
the on-set of orientation-induced crystallization. It was found that the fiber structure development proceeded from lower
take-up velocities when the spinning conditions of higher molecular weight and lower throughput rate were adopted. The highest
tensile modulus of 6.5 GPa was obtained for the fibers prepared at the spinning conditions of LMs-PS, 6 g/min and 5 km/min, whereas the highest tensile strength of 160 MPa was obtained for the HMs-PS fibers at the take-up velocity of 2 km/min. Elongation at break of as-spun fibers showed an abrupt increase, which was
regarded as the brittle-ductile transition, in the low speed region, and subsequently decreased with an increase in the take-up
velocity. There was a universal relation between the thermal and mechanical properties of as-spun fibers and the birefringence
of as-spun fibers when the fibers were still amorphous. The orientation-induced crystallization was found to start when the
birefringence reached — 0.02. After the starting of the orientation-induced crystallization, thermal and mechanical properties
of as-spun fibers with similar level of birefringence varied significantly depending on the processing conditions. |
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| Keywords: | Syndiotactic polystyrene High-speed melt spinning Orientation-induced crystallization Negative birefringence |
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