• Bulletin of the Korean Chemical Society
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• v.16 no.1
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• pp.58-62
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• 1995

Substituted 3-phenyl-1-silabutanes such as 3-phenyl-1-silabutane (1), 3-(2,5-dimethylphenyl)-1-silabutane (2), 3-(p-chlorotolyl)-1-silabutane (3), and 3-naphthyl-1-silabutane (4) were prepared in 62-96% yield by reduction of the corresponding substituted 3-phenyl-1,1-dichloro-1-silabutanes with LiAlH4. The dehydrogenative polymerization of the monomer silanes was carried out with Cp2MCl2/Red-Al (M=Ti, Hf) catalyst system. The molecular weight of the polymers produced ranged from 700 to 1300 (vs polystyrene) with degree of polymerization (DP) of 5 through 16 and with polydispersity index (PDI)=1.1-2.1. The dehydrogenative polymerization of the monomer silanes with Cp2TiCl2/Red-Al catalyst system occurred at a faster rate and produced somewhat higher molecular weights of polysilane than that with Cp2HfCl2/Red-Al catalyst system.

• Journal of Radiation Industry
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• v.4 no.4
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• pp.341-345
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• 2010

The surface functionalization of a fluoropolymer by ion beam-induced graft polymerization was described in this research. The surface of poly(tetrafluoroethylene) (PTFE) films were irradiated by a 150 keV $H^+$ ions, and 4-vinyl pyridine (4VP) as a functional monomer was then thermally graft polymerized on the irradiated surface. The surface properties of poly(4-vinyl pyridine) (P4VP)-grafted PTFE films were investigated in terms of grafting degree, wettability, chemical structure, and morphology. The results revealed that the surface of PTFE films was successfully functionalized by ion beam-induced graft polymerization of 4VP.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.305-308
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• 1997

The on-line calculation method is developed to obtain the temperature trajectory that brings the reactants to the desired state in batch styrene polymerization reactor. The temperature trajectory is obtained by applying the moments of the polymer concentration to the 2-step calculation method. The computer simulation is also carried out to verify the superiority of the on-line method to the off-line one. When a temperature disturbance of constant size is introduced, the off-line results shows considerable deviation from the target degree of polymerization. The on-line strategy set up a new trajectory to reach the desired state by using the current state of the reactor. Therefore, the on-line strategy deals with the changes of the system more adequately than the off-line strategy.

• Elastomers and Composites
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• v.33 no.2
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• pp.110-116
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• 1998

A new technology was introduced to the emulsion polymerization. It is the ultrasonic activation method which replaced a chemical initiator and the environmentally benign process. In this study, free radicals were produced by a pulse type ultrasound energy irradiation, then polystyrene latex was polymerized without chemical initiator. With ultrasonic energy density, the degree of polymerization, average molecular weight, and particle size were increased, but the polydispersity index for the molecular weight and the particle size were decreased. The optimum condition of emulsifier concentration and temperature was found to be 1.0 wt.% SDS and $40^{\circ}C$, respectively. As a result, the emulsion polymerization process without chemical initiator was proved to be comparable to common latex properties such as average molecular weight, molecular weight distribution, particle size, etc.

• Journal of the korean academy of Pediatric Dentistry
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• v.46 no.1
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• pp.1-9
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• 2019

The aim of this study was to compare the degree of conversion and polymerization shrinkage of low and high viscosity bulk-fill giomer-based and resin-based composites. Two bulk-fill giomer (Beautifil Bulk Restorative (BBR), Beautifil Bulk Flowable (BBF)), two bulk-fill (Tetric N-Ceram Bulk-fill (TBF), SureFil SDR flow (SDR)) and two conventional resin composites (Tetric N-Ceram (TN), Tetric N-flow (TF)) were selected for this study. The degree of conversion was measured by using Fourier transform infrared spectroscopy. Polymerization shrinkage was measured with the linometer. For all depth, BBR had the lowest degree of conversion and SDR had the highest. At 4 mm, the degree of conversion of low and high viscosity bulk-fill giomer resin composites was lower than that of bulk-fill resin composites (p < 0.05). At the depth between 2 mm and 4 mm, there were significant difference with TBF, TN and TF (p < 0.05), while no significant difference in the degree of conversion was measured for BBR, BBF and SDR. Polymerization shrinkage of six resin composites decreased in the following order: TF > SDR > BBF > TBF > TN and BBR (p < 0.05). Polymerization shrinkage of bulk-fill giomer resin composites was lower than that of bulk-fill resin composites (p < 0.05). From this study, it is found that the bulk-fill giomer resin composites and TBF were not sufficiently cured in 4 mm depth. The degree of conversion of low and high viscosity bulk-fill giomer resin composites was significantly lower than bulk-fill resin composites in both 2 mm and 4 mm depths. Therefore, such features of bulk-fill giomer resin composites should be carefully considered in clinical application.

• Journal of the Korean Applied Science and Technology
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• v.26 no.4
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• pp.428-433
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• 2009

Cellulose triacetate (CTA) was prepared from cotton linter and pulps which contain various contents of $\alpha$-cellulose. CTA which contains 2.8 of degree of substitution (DS) and 222 of degree of polymerization (DP) was obtained from V-81 pulp under the heterogeneous system. The DS was measured by the titration method, and the DP was obtained by measurement of viscosity. FT-IR spectometer (FT-IR 6300, JASCO) was used to analyze the chemical structure of raw materials and cellulose triacetate, and X-ray diffractometer (X-pert MPD PW3040, Philips) was used to confirm the crystal structure and to calculate the relative crystallinity index (RCI). As $\alpha$-cellulose content in pulp increased, the acetylation yield increased. Besides with a kind of pulp, it contains insoluble residue which was mainly formed due to the formation of glucomannan triacetate and xylan diacetate during the esterification.

• Journal of Adhesion and Interface
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• v.3 no.1
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• pp.13-19
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• 2002

We have studied on the surface and adhesion properties for acrylic terpolymers, having both hydrophobic and hydrophilic side chains, synthesized via solution polymerization. In order to develop a waterborne material. we tried to synthesize these terpolymers via emulsion polymerization. The polymeric emulsion synthesized was mainly composed of methyl methacrylate (MMA), methoxy-polyethyleneglycol methacrylate (MPEGMA) having hydrophilic side chains and methoxypolypropyleneglycol methacrylate (MPEGMA) having hydrophobic side chains. The viscosities of this series increased with an increase in the content of the co-monomer such as MPEGMA and (MPEGMA). This behavior resulted in the increase in the diameter and heterogeneity of the emulsion particle via AFM observation. Furthermore. the tensile adhesion strength and 90-degree peel strength of the adhesive of these polymeric emulsions were measured. In the case of polymeric emulsion composed of the same content of both hydrophilic and hydrophobic component, the adhesion property showed the highest value. However, since the adhesion properties as a practical applicable adhesive were poor, some improvements were required. When the composition above was modified with butyl acrylate (BA), the improvement effect on adhesion strength was accepted. In particular, 90-degree peel strength increased up to a maximum of 400% of the original value.

• Journal of Powder Materials
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• v.24 no.2
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• pp.147-152
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• 2017

Spherical-type zirconia granules are successfully fabricated by a spray-drying process using a water solvent slurry, and the change in the green density of the granule powder compacts is examined according to the organic polymers used. Two organic binders, polyvinyl alcohol (PVA) and 2-hydroxyethyl methacrylate (HEMA), which are dissolved in a water solvent and have different degrees of polymerization, are applied to the slurry with a plasticizer (polyethylene glycol). The granules employing a binder with a higher degree of polymerization (PVA) are not broken under a uniaxial press; consequently, they exhibit a poor green density of $2.4g/cm^3$. In contrast, the granule powder compacts employing a binder with a lower degree of polymerization (HEMA) show a higher density of $2.6g/cm^3$ with an increase in plasticizer content. The packing behavior of the granule powders for each organic polymer system is studied by examining the microstructure of the fracture surface at different applied pressures.

• Journal of Radiation Industry
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• v.6 no.4
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• pp.317-322
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• 2012

In this study, the preparation of a temperature-responsive poly(N-isopropylacrylamide) (PNIPAAm)-grafted surface was performed using an eco-friendly and biocompatible ion beam-induced surface graft polymerization. The surface of a perfluoroalkoxy (PFA) film was activated by ion implantation and N-isopropylacrylamide (NIPAAm) was then graft polymerized selectively onto the activated regions of the PFA surfaces. Based on the results of the peroxide concentration and grafting degree measurements, the amount of the peroxide groups formed on the implanted surface was dependant on the fluence, which affected the grafting degree. The results of the FT-IR-ATR, XPS, and SEM confirmed that the NIPAAm was successfully grafted onto the implanted PFA. Moreover, the contact angle measurement at different temperatures revealed that the surface of the PNIPAAm-grafted PFA film was temperature-responsive.

• Journal of Korean Ophthalmic Optics Society
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• v.17 no.2
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• pp.135-141
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• 2012

Purpose: Polymerization of HEMA(2-hydroxyethyl methacrylate) which can be used in the soft contact lens has been performed by using electron beam(EB) irradiation, and examined the best condition for the polymerization. Comparing the physical properties of the contact lenses to the one fabricated by thermal polymerization method, we check the use possibility of the EB irradiation to the fabrication of the soft contact lens. Methods: We investigated the degree of polymerization of the HEMA according to the composition of the monomer, the additive ratio and the dose of electron beam (0~120 kGy). The degree of polymerization was measured depending on the EB dose to research the best synthetic condition under the EB irradiation. The physical properties of the contact lens such as water content(%), oxygen transmissibility(Dk/t) and optical transmittance were analysed by using the FT-IR results with comparing the two different polymerization method (thermal and electron beam polymerization) with same additive ratio. Results: When the dose of electron beam was above 100 kGy, the degree of polymerization of HEMA was above 99% with regardless using cross-linker and initiator. The water content of the lens fabricated by EB method showed 10% higher than the one by the thermal method which was 40%. The lens fabricated by EB method also showed higher oxygen transmissibility(Dk/t) as same with the water content, and showed twice higher value in the lens fabricated by pure HEMA. According to the FT-IR results, hydrophilic property of the lens fabricated by EB method was increased due to increasing the intermolecular hydrogen bonding. It showed above 90% optical transmittance in the visible range of wavelength on the contact lenses fabricated by the both of two different polymerization method. Conclusions: The polymerization of HEMA without cross-linker and initiator was successful above 100 kGy of EB irradiation. Moreover the lens fabricated from the polymer synthesized by pure HEMA with 100 kGy of EB showed the highest water content and oxygen transmissibility. Therefore EB irradiation is another possible method to synthesize the polymer which can be used for the soft contact lens.