• Polymer(Korea)
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• v.24 no.4
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• pp.437-444
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• 2000

Propylene polymerizations were carried out by using rac-Et(Ind)$_2$ZrCl$_2$ (Zirconocene catalyst) and a commercial third generation Ziegler-Natta catalyst in a semibatch reactor. From the polymerization reactions, the optimum reaction conditions and the physical properties of polymers produced from each catalyst system were investigated. The optimum reaction temperatures of rac-Et(Ind)$_2$ZrCl$_2$ and Ziegler-Natta catalyst were 5$0^{\circ}C$, 4$0^{\circ}C$, respectively. On the basis of the results for the produced polymer particle size distributions and the catalytic activities of polymerization reaction, the reaction temperature should be considered as an important factor for the successful polymerization reactions. Especially, the polymer was conglomerated in the higher reaction temperature. It was found that there was an upper limitation to co-catalyst concentration. Reaction rates and polymer yields rather decreased with increasing the concentration of to-catalyst, i.e., MAO and TEAl affected only polymerization activities, but the PEEB in Ziegler-Natta catalyst system affected isotactic indexes of produced polymer as well as activities. Based on these observations, the production yield seems to exhibit a first order lineal relationship to the partial pressure of monomer.

• Bulletin of the Korean Chemical Society
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• v.16 no.7
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• pp.661-666
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• 1995

The surface structure of the adsorption site for the identification of active sites involved in the Ziegler-Natta catalyst was studied by surface science techniques. As an example of a real catalyst, TiCl3 single crystals were prepared in a gradient furnace designed for this study and characterized by Auger Electron Spectroscopy (AES) and Low Energy Electron Diffraction (LEED) under ultrahigh vacuum condition. The chlorine covered Ti (0001) surface was employed as a model catalyst for the study of Ziegler-Natta catalyst. The diffuse LEED (DLEED) technique for the surface structural determination was applied to this disordered chlorine adsorbed on Ti (0001) surface. The diffuse scattering intensities were measured by a TV-computer method using a low light level video camera. From an analysis of two catalyst systems, the informations for the surface structure of the model catalyst surfaces were derived.

• Elastomers and Composites
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• v.53 no.3
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• pp.158-167
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• 2018

In this study, in-situ trans-selective polymerization of isoprene was carried out using titanium-based Ziegler-Natta catalysts. The catalysts were prepared by high-energy ball milling. Individually Large-inner-diameter carbon nanotubes (CNTL), and hydroxylated carbon nanotubes (CNTOH), along with magnesium chloride ($MgCl_2$) were used as the carriers for the catalysts. The optimum ball-milling time for preparing the $CNT/MgCl_2/TiCl_4$ Ziegler-Natta catalysts was 4 h. The $CNTOH/MgCl_2/TiCl_4$ catalyst showed a higher efficiency than that of the $CNTL/MgCl_2/TiCl_4$ catalyst, based on the rate of polymerization. The effects of the CNT-filler type on the isoprene polymerization behaviors and polymer properties were investigated. The morphologies of the trans-1,4-polyisoprene (TPI)/CNT and TPI/CNTOH nanocomposites exhibited a tube-like shape, and the CNTL and CNTOH fillers were well dispersed in the TPI matrix. In addition, the thermal stability of TPI significantly increased upon the introduction of a small amount of both CNTL/CNTOH fillers (0.15 wt%), owing to the satisfactory dispersion of the CNTL/CNTOH in the TPI matrix.

• Polymer(Korea)
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• v.29 no.4
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• pp.321-330
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• 2005

In 1990's the Korean polyolefin industry boomed up through the development of magnificient polymerization catalysts. To understand the general situation of polymerization catalyst R & D, the various experimental results had been summarized for the investigation of not only the supported Ziegler-Natta catalyst used presently in polyolefin industry but also the metallocene catalysts applied for the preparation of special grade of polyolefin. In addition, it had been shown that the new polymeric materials were prepared by new developed catalyst, and the polymer in-situ nanocomposites could be obtained with the application of catalyst heterogenization procedures.

• Journal of the Korean Applied Science and Technology
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• v.33 no.4
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• pp.698-705
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• 2016

In this study, we have studied the polymerization of polyethylene wax using metallocene catalysts and its physical properties. Various polymerization conditions were tried for polymerization of polyethylene wax. We have evaluated hydrogen reactivity and studied on characteristics of polymerization effected by ligand structure of metallocene catalysts against Ziegler-Natta catalysts which are widely used for polymerization of polyethylene. We have also checked hydrogen used for chain transfer agent, molecular weight change and distribution by different ratios of ethylene gas. Finally, we suggest proper structure of metallocene catalysts for polymerization of polyethylene wax.

• Journal of the Korean Applied Science and Technology
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• v.34 no.4
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• pp.857-865
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• 2017

This study was conducted to analyze and characterize the properties of polyethylene wax polymerized and polymerized using various metallocene catalysts based on Indene and Cyclopentadien, which are different from Ziegler-Natta catalysts used in polyethylene polymerizatio n. The polymerization of polyethylene wax was carried out under various conditions by adjusting the polymerization temperature and the ratio of hydrogen gas used as a chain transfer agent and ethylene gas to metallocene catalysts containing ligands of different structures. The molecular weight and molecular weight distribution, The catalyst yields were compared and analyzed. As a result, the structure of a metallocene catalyst suitable for having a low molecular weight and a narrow molecular weight distribution was proposed and the ideal polyethylene wax could be polymerized.

• Macromolecular Research
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• v.15 no.3
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• pp.221-224
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• 2007

A silica-magnesium bisupport (SMB) was prepared by a sol-gel method for use as a support for a metal-locene/Ziegler-Natta hybrid catalyst. The prepared $rac-Et(Ind)_2ZrCl_2/TiCl_4$/MAO(methylaluminoxane)/SMB catalyst was applied to the copolymerization of ethylene with l-hexene using a variable triethylaluminum (TEA)/transition-metal (Ti) ratio and fixed MAO/transition-metal (Zr) ratio. The effect of the Al(TEA)/Ti ratio on the physical properties and chemical composition distributions (CCDs) of the ethylene-hexene copolymers produced by the hybrid catalyst was investigated. In the ethylene-hexene copolymers, two melting temperatures attributed to the metal-locene and Ziegler-Natta catalysts were clearly observed. The number of CCD peaks was increased from six to seven and the temperature region in which the peaks for the short chain branches of the ethylene-hexene copolymer were distributed became lower as the Al(TEA)/Ti ratio was increased from 300 to 400. Furthermore, the temperature regions corresponding to the lamellas in the copolymer became lower and those corresponding to the small lamellas in the copolymer became higher as the Al(TEA)/Ti ratio was increased from 300 to 400. In the copolymer produced with Al(TEA)/Ti = 500, however, only four CCD peaks were observed and the short chain branches were poorly distributed.

• Macromolecular Research
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• v.8 no.1
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• pp.34-43
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• 2000

The melt rheology of four binary blends of ethylene 1-octene copolymers (EOCs) which consist of one component by Ziegler-Natta and another by metallocene catalysts, was studied to elucidate miscibility in the melt by using torsion rheometer at 200$\^{C}$ and different shear rates. The four blend systems, designated into the FA+FM, SF+FM, RF+EN, and RF+PL blend, are divided and interpreted based on the melt index (MI), the density and the comonomer contents. The melt viscosity such asη', η", and η$\^$*/ is weight average value if the comonomer contents are similar, otherwise they show different manner. The experimental resole are analyzed based on the Cole-Cole plot of logη' uersus log η", the logarithmic plots of the dynamic storage modulus (G') versus the dynamic loss modulus (G") for various blend compositions, and the melt viscosity of 11', n", and f" as a function of blend compositions. As a cerise-quence, the FA+FM blend is miscible, but the SF+FM, RF+EN, and RF+PL blends are not in the melt. Thus miscibility of the blends studied in this communication is suggested to strongly influence by the comonomer contents rather than the density or the MI.

• Polymer(Korea)
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• v.25 no.6
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• pp.833-839
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• 2001

The crystallization characteristics of metallocene linear low density polyethylene was investigated by small angle light scattering and comparison was made with Ziegler-Natta linear low density polyethylene. The special efforts were made to find out the effects of branching number, length of branching and co-monomer content of m-LLDPE on the crystallization behavior of m-LLDPE. It was found that m-LLDPE has longer induction time to start crystallization from the amorphous state than that of conventional LLDPE with similar branching number, but the rate of crystallization seems not change much in both LLDPEs. Lowering of branching number in m-LLDPE resulted in both increasing of rate of crystallization and reducing induction time to crystallize. In general, the maximum size of spherulites of m-LLDPE is bigger than that of conventional LLDPE.

• Journal of the Korean Chemical Society
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• v.62 no.3
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• pp.191-202
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• 2018

The aim of this work is to study Monte Carlo simulation of ethylene (co)polymerization over Ziegler-Natta catalyst as investigated by Chen et al. The results revealed that the Monte Carlo simulation was similar to sum square error (SSE) model to prediction of stage II and III of polymerization. In the case of activation stage (stage I) both model had slightly deviation from experimental results. The modeling results demonstrated that in homopolymerization, SSE was superior to predict polymerization rate in current stage while for copolymerization, Monte Carlo had preferable prediction. The Monte Carlo simulation approved the SSE results to determine role of each site in total polymerization rate and revealed that homopolymerization rate changed from site to site and order of center was different compared to copolymerization. The polymer yield was reduced by addition of hydrogen amount however there was no specific effect on uptake curve which was predicted by Monte Carlo simulation with good accuracy. In the case of copolymerization it was evolved that monomer chain length and monomer concentration influenced the rate of polymerization as rate of polymerization reduced from 1-hexene to 1-octene and increased when monomer concentration proliferate.