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Rheological Properties and EMI Shielding Efficiency of PC/CNT Composite
승유택,변노석,김우년,이헌상,금종구 한국화학공학회 2007 화학공학의이론과응용 Vol.10 No.1
Polycarbonate (PC)/carbon nanotube (CNT) composites were prepared by twin screw extruder. Rheological properties and electromagnetic interference shielding efficiency (EMI SE) of PC/CNT composites were measured by advanced rheometric expansion system (ARES) and network vector analyzer. The results of rheological properties, EMI SE, and electric conductivity are presented.
Crystallization Kinetics of Polypropylene with Repeated Extrusion
김종성,승유택,김우년,곽동환,홍존희 한국화학공학회 2007 화학공학의이론과응용 Vol.10 No.1
Crystallization kinetics of the polypropylene (PP) block copolymer and recycled PP block copolymer was studied by DSC and optical microscopy. The recycled PP samples were prepared using a twin screw extruder. In the study of the crystallization rate, the half crystallization time of the PP samples was increased as increasing the number of the extrusion time. From the isothermal kinetics at 130oC, the crystallization rate was decreased as increasing the number of the extrusion time. Also in the results of Avrami plot, the overall crystallization rate constant (K) was decreased as increasing the number of the extrusion time. From the optical microscopy, the number of the spherulite growth site was decreased as increasing the number of the extrusion. The result of the optical microscopy was consistent with the isothermal crystallization and Avrami plots at 130oC. From the results of the crystallization rate, isothermal crystallization kinetics, Avrami plots, and optical microscopy, it was suggested that the crystallization of the PP copolymer was decreased as increasing the number of the extrusion time.
Rheological Properties and Wall Slip Velocity of Polycarbonate / Carbon Fiber Composite
변노석,승유택,김우년,이헌상,금종구 한국화학공학회 2007 화학공학의이론과응용 Vol.10 No.1
Polycarbonate (PC) / carbon fiber (CF) composites were prepared by twin screw extruder at 250℃. Rheological behavior of PC / CF composites with carbon fiber was investigated. The PC / CF composites were characterized by advanced rheometric expansion system (ARES) and capillary rheometer. As increasing the fiber length and the fiber content, storage and loss modulus of the PC / CF composites were increased. From the rheological measurements of the PC / CF composites, the wall slip behavior is demonstrated from the capillary rheometer data. To measure the wall slip velocity, rotational rheometer was investigated at various gap distances of the parallel plates. From the above measurements, it is suggested that the wall slip velocity is increased as the shear stress is increased. Also, the wall slip velocity is invested within the CF content from the ARES.
Synthesis and Characterization of Polyurethane/Clay Nanocomposite
김상균,서원진,승유택,신민철,김우년 한국화학공학회 2007 화학공학의이론과응용 Vol.10 No.1
Clay / polyurethane nanacomposites were synthesized from covalent bond between clay and polymeric 4,4’ diphenylmethane diisocyanate (PMDI) by in-situ intercalation process. Silanol group of clay and NCO group of PMDI were reacted for 24 hours, 3000 rpm maintaining 50℃. The FT-IR analysis of the modified clay demonstrated that NCO characteristic peak was observed in FT-IR analysis of the modified clay after modification reaction. The 2θ of the nanocomposite synthesized with the modified clay was disappeared. The flexural and tensile strength of the clay/polyurethane nanocomposite using the modified clay showed that the maximum strengths were with 3 wt % of the modified clay. The Tg of the nanocomposite decreases with an increase in the modified clay. We suggest that the decrease in the Tg of the clay/polyurethane nanocomposite with the modified clay content might be due to an increase in the chain flexibility of polyurethane backbones. Acknowledgement: This research was supported by a grant (code BC1-102) from Carbon Dioxide Reduction & Sequestration Research Center, one of the 21st Century Frontier Programs funded by the Ministry of Science and Technology of Korean government.