The Experts below are selected from a list of 144 Experts worldwide ranked by ideXlab platform
Jae Heung Lee - One of the best experts on this subject based on the ideXlab platform.
-
Polycarbonate/Montmorillonite Nanocomposites Prepared by Microwave-Aided Solid State Polymerization
Macromolecular Chemistry and Physics, 2004Co-Authors: Youngjae Yoo, Kil-yeong Choi, Jae Heung LeeAbstract:Polycarbonate/montmorillonite (MMT) nanocomposites were prepared by microware solid-state polymerization. The MMTs were modified with alkyl ammonium salt. Pre-intercalated polycarbonate nanocomposite was prepared using two conventional methods; a Melt Process and a solution Process. Melt Processing was accomplished in a Haake internal mixer for 30 mins at 180°C. Solution Processing was accomplished in a homogenize using chloroform. The wide-angle X-ray diffraction (WAXD) peak indicating the gallery size of MMTs was shifted to lower levels after the pre-intercalation Process. Subsequently, microwave solid-state polymerization converted the pre-intercalated nanocomposite into the exfoliated nanocomposite. WAXD revealed that exfoliation and/or further intercalated structures were obtained when comparing the results from the micro-wawe solid-state polymerization using oil heating. This means that microwave solid-state polymerization using oil heating. It was shown that conventional Melt and solution Processing of MMT and polycarbonate prepolymer yielded intercalated nanocomposites with interlayer spacing of 2.5 and 2.7 nm respectively. Microwave solid-state polymerized nanocomposite showed the exfoliated and/or intercalated structure, whereas conventional solid-state polymerization using oil heating only increased the gallery size of MMT. The thermal decomposition behavior and morphologies were investigated by thermogravimetric analysis (TGA) and transmission electron microscopy (TEM).
Youngjae Yoo - One of the best experts on this subject based on the ideXlab platform.
-
Polycarbonate/Montmorillonite Nanocomposites Prepared by Microwave-Aided Solid State Polymerization
Macromolecular Chemistry and Physics, 2004Co-Authors: Youngjae Yoo, Kil-yeong Choi, Jae Heung LeeAbstract:Polycarbonate/montmorillonite (MMT) nanocomposites were prepared by microware solid-state polymerization. The MMTs were modified with alkyl ammonium salt. Pre-intercalated polycarbonate nanocomposite was prepared using two conventional methods; a Melt Process and a solution Process. Melt Processing was accomplished in a Haake internal mixer for 30 mins at 180°C. Solution Processing was accomplished in a homogenize using chloroform. The wide-angle X-ray diffraction (WAXD) peak indicating the gallery size of MMTs was shifted to lower levels after the pre-intercalation Process. Subsequently, microwave solid-state polymerization converted the pre-intercalated nanocomposite into the exfoliated nanocomposite. WAXD revealed that exfoliation and/or further intercalated structures were obtained when comparing the results from the micro-wawe solid-state polymerization using oil heating. This means that microwave solid-state polymerization using oil heating. It was shown that conventional Melt and solution Processing of MMT and polycarbonate prepolymer yielded intercalated nanocomposites with interlayer spacing of 2.5 and 2.7 nm respectively. Microwave solid-state polymerized nanocomposite showed the exfoliated and/or intercalated structure, whereas conventional solid-state polymerization using oil heating only increased the gallery size of MMT. The thermal decomposition behavior and morphologies were investigated by thermogravimetric analysis (TGA) and transmission electron microscopy (TEM).
W.-k. Yuan - One of the best experts on this subject based on the ideXlab platform.
-
Supercritical carbon dioxide-assisted solid-state free radical grafting of methyl methacrylate onto polypropylene
Journal of Supercritical Fluids, 2007Co-Authors: G.-s. Tong, T. Liu, L. Zhao, W.-k. YuanAbstract:The work reported in this paper was aimed at exploring the advantages of using supercritical carbon dioxide (scCO2) as an environmentally benign solvent and swelling agent for carrying out the free radical grafting Process of vinyl monomers onto isotactic polypropylene (PP) in the solid state. Methyl methacrylate (MMA) was chosen as a grafting monomer. Results showed several scientifically interesting and industrially relevant advantages of the scCO2-assisted solid-state grafting Process over a classical solid-state or Melt Process. First, compared to a classical solid-state grafting Process the overall reaction rate of the scCO2 assisted one became less diffusion-controlled and more reaction-controlled because of enhanced diffusion of MMA and the initiator in the PP. Second, the CO2 pressure itself constituted an additional and sensitive Process parameter capable of significantly modifying the monomer grafting yield and the product quality. Third, the scCO2-assisted solid-state Process produced much higher MMA grafting contents and longer MMA grafts than the classical solid-state and Melt Processes did.
Y. Wei-kang - One of the best experts on this subject based on the ideXlab platform.
-
Supercritical carbon dioxide assisted solid-state grafting Process of maleic anhydride onto polypropylene
Industrial and engineering chemistry research, 2005Co-Authors: L. Tao, H. Guo-hua, T. Gang-sheng, Z. Ling, C. Gui-ping, Y. Wei-kangAbstract:The work reported in this paper aimed at exploring the advantages of using supercritical carbon dioxide (scCO2) as an environmentally benign solvent and swelling agent for carrying out the grafting Process of maleic anhydride onto polypropylene in the solid state. The effects of scCO2 on the Melting temperature and Melting enthalpy of an isotactic polypropylene (iPP) were investigated first in order to define the upper reaction temperature and CO2 pressure limits. The effects of various factors on the grafted anhydride content and on changes in the molecular-scale and microscale structures of the resulting iPP were then investigated. Those factors included the reaction time, monomer and initiator concentrations, reaction temperature, CO2 pressure, and size of the iPP particles. Results showed that the scCO2-assisted solid-state grafting Process of maleic anhydride onto iPP did have some scientifically interesting and industrially relevant advantages over the classical solid-state or Melt Process. Among them, it is worth pointing out that the CO2 pressure itself constituted an additional and sensitive Process parameter capable of significantly modifying the overall reaction pathway and the product quality. For example, without CO2, the solid-state grafting Process was diffusion-controlled. Under scCO2, it became reaction-controlled. The CO2 pressure could also regulate the anhydride content with ease. On the other hand, the degree of iPP chain scission was not reduced under scCO2 compared to that of the classical Melt Process.
Kil-yeong Choi - One of the best experts on this subject based on the ideXlab platform.
-
Polycarbonate/Montmorillonite Nanocomposites Prepared by Microwave-Aided Solid State Polymerization
Macromolecular Chemistry and Physics, 2004Co-Authors: Youngjae Yoo, Kil-yeong Choi, Jae Heung LeeAbstract:Polycarbonate/montmorillonite (MMT) nanocomposites were prepared by microware solid-state polymerization. The MMTs were modified with alkyl ammonium salt. Pre-intercalated polycarbonate nanocomposite was prepared using two conventional methods; a Melt Process and a solution Process. Melt Processing was accomplished in a Haake internal mixer for 30 mins at 180°C. Solution Processing was accomplished in a homogenize using chloroform. The wide-angle X-ray diffraction (WAXD) peak indicating the gallery size of MMTs was shifted to lower levels after the pre-intercalation Process. Subsequently, microwave solid-state polymerization converted the pre-intercalated nanocomposite into the exfoliated nanocomposite. WAXD revealed that exfoliation and/or further intercalated structures were obtained when comparing the results from the micro-wawe solid-state polymerization using oil heating. This means that microwave solid-state polymerization using oil heating. It was shown that conventional Melt and solution Processing of MMT and polycarbonate prepolymer yielded intercalated nanocomposites with interlayer spacing of 2.5 and 2.7 nm respectively. Microwave solid-state polymerized nanocomposite showed the exfoliated and/or intercalated structure, whereas conventional solid-state polymerization using oil heating only increased the gallery size of MMT. The thermal decomposition behavior and morphologies were investigated by thermogravimetric analysis (TGA) and transmission electron microscopy (TEM).