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정호규,Takeshi Kikutani 한국섬유공학회 1999 한국섬유공학회지 Vol.36 No.11
High-speed melt spinning of single and bicomponent fibers of poly ethylene terephthalate (PET) and nylon 6 was carried out. The structure changes in the individual components of the single and bicomponent fibers with take-up velocity were investigated by birefringence, wide-angle x-ray diffraction, and DSC. The orientation crystallization of PET in the bicomponent fiber was enhanced in comparison with the pure PET fiber, while the orientation of the PET component increased with decreasing the PET content. On the other hand, the orientation of the nylon 6 component was lower than that of the corresponding single component fiber. The cold crystallization temperature of PET in the bicomponent fiber was lower than that of the pure PET fiber. It was also lowered with decreasing PET content. The crystal formation of PET in the bicomponent fiber occurred at a lower take-up velocity than that of the pure PET fiber. In high speed spinning, neck-like deformation was also observed in the bicomponent spinning. The neck-like deformation of PET occurred at a position closer to the spinneret than that of nylon 6, mean-while the position of the neck-like deformation of the 1:3 bicomponent fiber was observed at a position closer to the spinneret than that of the pure PET fiber.
Poly(ethylene 2,6-naphthalene dicarboxylate) 섬유의 고속방사에 따른 미세구조 형성과 물성
조현혹,이화경,김주애,Takeshi Kikutani 한국섬유공학회 2001 한국섬유공학회지 Vol.38 No.11
PEN fibers of two different molecular weights. low and high, were prepared by high-speed melt spinning. The fine structure and physical properties of PEN fibers were investigated with various techniques such as wide-angle X-ray diffraction, birefringence, density. DSC, dynamic viscoelasticity, and tensile testing. From the WAXD test, PEN fibers of high molecular weight was found to have a reflection peak associated with orientation-induced crystallization that started to appear at take up velocities above 3km/min. In this region, the crystalline structure was dominated by $\beta$ form crystal. This tendency was also confirmed by DSC thermogram, density, and birefringence data. In the DSC thermograms, the melting peak shifted to higher temperature with increasing take-up velocity, while the area of cold crystallization peak decreased. Especially, the temperature of melting peak increased remarkably with increasing take-up velocity in the range of 2$65^{\circ}C$ to 298$^{\circ}C$ for PEN fibers of high molecular weight. Mechnaical properties of the two PEN fibers were relatively improved by the high-speed melt spinning at higher spinning speeds. However, the initial modulus and tenacity of PEN fibers of high molecular weight decreased slightly at the take-up velocity of 7km/min.
Hada Yoshiaki,Shikuma Haruo,Ito Hiroshi,Kikutani Takeshi The Korean Fiber Society 2005 Fibers and polymers Vol.6 No.1
High-speed melt spinning of syndiotactic polystyrene was carried out using high and low molecular weight polymers, HM s-PS and LM s-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 was a-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 (OSC) 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 LM s-PS, 6 g/min and 5 km/min, whereas the highest tensile strength of 160 MPa was obtained for the HM s-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.
Polymer structure and properties in micro- and nanomolding process
Hiroshi Ito,Hajime Suzuki,Kunihiko Kazama,Takeshi Kikutani 한국물리학회 2009 Current Applied Physics Vol.9 No.2
Injection molding of thin-wall parts with micro/nano-scale patterns using various polymers was performed to clarify the processability and surface replication of molded parts. Effects of process conditions on processability, higher-order structure and surface properties of molded parts were evaluated. The optical anisotropy in the vicinity of the gate became higher than at any other positions. The height replication ratio of surface patterns increased with increasing injection speed, holding pressure, injection temperature and mold temperature. In the case of nanomolding, negative birefringence toward the flow direction appeared higher than at the skin–shear region from the observation of skin–shear and core structure inside molded parts. Thus, the molecular orientation axis was oriented along the thickness direction because of deformation during the demolding process. Thermal stability of nano-surface patterns was influenced by the size of surface features and internal higher-order structure.