• The Journal of Korean Academy of Prosthodontics
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• v.52 no.3
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• pp.195-201
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• 2014

Purpose: This study was designed to compare the amount of polymerization shrinkage of dual-cure resin cements according to different polymerization modes and to determine the effect of light activation on the degree of polymerization. Materials and methods: Four kinds of dual-cure resin cements were investigated: Smartcem 2, Panavia F 2.0, Clearfil SA Luting and Zirconite. Each material was tested in three different polymerization modes: self-polymerization only, immediate light polymerization and 5 minutes-delayed light polymerization. The time-dependent polymerization shrinkage-strain was evaluated for 30 minutes by Bonded-disk method at $37^{\circ}C$. Five recordings of each material with three different modes were taken. Data were analyzed using one-way ANOVA and multiple comparison Scheffe′test (${\alpha}$=.05). Results: All materials, except Panavia F 2.0, exhibited the highest polymerization shrinkage-strain through delayed light-activated polymerization. No significant difference between light activation modes was found with Panavia F 2.0. All materials exhibited more than 90% of polymerization rate in the immediate or delayed light activated group within 10 minutes. Conclusion: As a clinical implication of this study, the application of delayed light activation mode to dual-cure resin cements is advantageous in terms of degree of polymerization.

• Polymer(Korea)
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• v.29 no.1
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• pp.87-90
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• 2005

In this study, we have examined the exfoliation behavior of layered clay during in-situ polymeriztion with styrene by using real-time XRD analysis. The 4C1 beam line at the Pohang Accelerator Laboratory (PAL) was used for this study. Different exfoliation behaviors have been shown to depend on the cation exchange capacity (CEC) of clay and the chemical structure of organic modifiers. For 10A-MMT and 15A-MMT having high CEC, no peak shifts were observed on real-time XRD analysis during polymerization. However, 2$\theta$ for 25A-MMT and VDAC-MMT, each having low CEC’s as well as aromatic benzene moieties and vinyl groups, respectively, decreased as polymerization time increased.

• Journal of Power System Engineering
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• v.19 no.5
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• pp.86-92
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• 2015

p-DCPD were prepared by in-suit ROMP polymerization using $MoCl_5$ and $Et_2AlCl$. The results showed that $MoCl_5:Et_2AlCl:DCPD$ mole ratio of 1:2.0:350 had the curing-time of 60sec and crosslinking degree of 90.44%. The curing time of DCPD polymerization by $MoCl_5/Et_2AlCl$ was shortened, and monomer conversion and crosslinking degree were decreased with temperature and the number of moles of $MoCl_5$ and $Et_2AlCl$. $MoCl_5$ and $Et_2AlCl$ is damaged its function by the reaction with the air in the atmosphere and did't proceed the polymerization properly.

• Journal of Adhesion and Interface
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• v.10 no.1
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• pp.17-22
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• 2009

Polymer thin films were prepared by radio frequency (RF) plasma polymerization of phthalic anhydride (PA). First, monomer vaporization temperature ($100{\sim}160^{\circ}C$) was optimized by evaluating the thermal properties of thin films using differential scanning calorimeter (DSC) and measuring the root-mean-square (RMS) roughness with atomic force microscope (AFM) at the fixed plasma power of 10 W and time of 5 min in a continuous-wave (CW) mode. Plasma power (5~20 W) was then optimized by measuring the film solubility in solvents such as toluene, acetone, dimethylsulfoxide (DMSO) and 1 methylpyrrolidine (NMP). Next, pulsed mode plasma polymerization was also studied by varying the duty cycle of on-time (5, 20%) under optimized conditions of continuous-wave (CW) mode ($120^{\circ}C$, 10 W) in order to increase the anhydride functional groups. Finally, polymer thin films were characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analyzer (TGA) and ${\alpha}$-step.

• Applied Chemistry for Engineering
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• v.3 no.1
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• pp.172-178
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• 1992

The graft copolymerization of acrylonitrile(AN) onto chitosan film by using $F^{3+}(FeCl_3{\cdot}6H_2O)$ as a photosensitizer in an aqueous medium was carried out under ultraviolet(UV) irradiation. The grafted copolymer was identified by using IR spectroscopy and scanning electron microscope. The effects of various polymerization parameters involving monomer concentration, photosensitizer concentration, polymerization time and polymerization temperature were investigated. As monomer concentration and photosensitizer concentration were increased, the percent grafting was increased up to limiting value. And also the percent grafting was found to increase by increasing the polymerization time and temperature.

• Textile Coloration and Finishing
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• v.21 no.3
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• pp.19-25
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• 2009

Polymerization of tetraethoxysilane on a glass substrate was investigated by remote microwave plasma using argon with portions of nitrous oxide as carrier gas. Transparent layer like a thickness of 0.5 ${\mu}m$ 3 ${\mu}m$ were obtained, differing in chemical composition, depending on plasma power and treatment time as well as on ageing time. In general the milder the treatment and the shorter the ageing was, the higher was the content of organic structural elements in the layer. We have identified that the chemical structure of our samples composed of mainly Si O and Si C groups containing aliphatics, carbonyl groups. These results were obtained by X ray photon spectroscopy, Fourier transformed infrared spectroscopy, and scanning electron microscope combined with Energy dispersive X ray spectroscopy.

• Macromolecular Research
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• v.11 no.6
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• pp.495-500
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• 2003

UV-induced graft polymerization of glycidyl methacrylate (GMA) to a polypropylene (PP) membrane was carried out in the vapor phase with benzophenone (BP) as a photoinitiator. Attenuated total reflection Fourier transform infrared spectroscopy, atomic force microscopy (AFM), and scanning electron microscopy (SEM) were utilized to characterize the copolymer. The degree of grafting increased with increasing reaction time, increased UV irradiation source intensity, and increased immersion concentration of the BP solution. The optimum synthetic condition for the PP-g-GMA membrane was obtained with a reaction time of 2 hrs, a UV irradiation source intensity of 450 W, and an immersion concentration of the BP solution of 0.5 mol/L. The pure water flux decreased upon increasing the degree of grafting and increasing the amount of diethylamino functional group introduced. The analysis of AFM and SEM images shows that the graft chains and diethylamino groups of PP-g-GMA grew on the PP membrane surface, resulting in a change in surface morphology.

• Journal of the Korean Chemical Society
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• v.16 no.1
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• pp.46-49
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• 1972

Using an assumption of isoviscosity at the gel-point in the polymerization of divinylbenzene, the relations between viscosity equation, viscosity-molecular weight, and the chain transfer equation have been studied. A new equation for the calculation of chain transfer constant, $C_{tr}$, by measuring the gel time in place of the degree of polymerization has been suggested.

• Journal of the Korean Chemical Society
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• v.6 no.1
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• pp.64-68
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• 1962

The graft polymerization of styrene to polyvinyl alcohol using a photosensitizer(benzophenone) and ultraviolet light was studied. Styrene was grafted onto polyvinyl alcohol up to when polyvinyl alcohol was pre-immersed in water and irradiated by ultraviolet light for 24 hours styrene solution of benzophenone(0.01 molarity). The highest percentage of graft obtained in the grafting which was proceeded in the presence of water added immediately before irradiation was 29%. The grafting was proportional to irradiation time within a certain limit of time, i.e., 24 hours, and presumably was initiated at the surface. After a certain degree of grafting a definite maximum was reached. Graft polymer prepared in this experiment showed high resistance to various solvents.

• The korean journal of orthodontics
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• v.36 no.3 s.116
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• pp.198-206
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• 2006

With the introduction of the xenon plasma arc curing light and the LED curing light as orthodontic curing lights, the polymerizing time of orthodontic composites has clearly decreased. In contrast to various research cases regarding the polymerization time and bond strength of the xenon plasma arc curing light, not enough research exists on the LED curing light, including the appropriate polymerization time. The objective of this research was to compare the bond strength of the plasma curing light and the LED curing light in regards to the polymerization time. The polymerization time needed to achieve an appropriate adhesion strength of the bracket has also been studied. After applying orthodontic brackets using composite resin onto 120 human premolars, the plasma arc curing light and the LED curing light were used for polymerization for 4, 6, and 8 seconds accordingly. This research proved that the LED curing light provided appropriate bond strength for mounting orthodontic brackets even with short seconds of polymerization. The expensive cost and large size of the device limits the use of the plasma arc curing light, whereas the low cost and easy handling of the LED curing light may lead to greater use in orthodontics.