• Elastomers and Composites
• /
• v.45 no.4
• /
• pp.256-262
• /
• 2010

Dispersion polymerization of methyl acrylate, ethyl acrylate, butyl acrylate, and glycidyl methacrylate were performed in supercritical $CO_2$ at $80\;^{\circ}C$ and 346 bar. Glycidyl methacrylate linked poly(dimethylsiloxane) (GMS-PDMS) surfactant, which was prepared by linking glycidyl methacrylate to monoglycidyl ether terminated PDMS with amino-propyltriethoxysilane, was used as surfactant for the dispersion polymerization in $CO_2$. The yield of the poly(alkyl acrylate) polymers, synthesized in $CO_2$ medium, decreased as the alkyl tail of the acrylate monomers increased. Poly(glycidyl methacrylate) and poly(methyl acrylate) were produced in bead form whereas poly(ethyl acrylate) and poly(butyl acrylate) were viscous liquid. The poly(glycidyl methacrylate) particles had a number average diameter of 2.45 ${\mu}m$ and monodisperse distribution. The poly(methyl acrylate) had a number average diameter of 0.52 ${\mu}m$ and the particle size distribution was bimodal. The glass transition temperatures ($T_g$) of the poly(glycidyl methacrylate) and the poly(alkyl acrylate) products were 4~9 K higher than the $T_g$ of the corresponding acrylate polymers synthesized in conventional processes.

• Elastomers and Composites
• /
• v.43 no.1
• /
• pp.39-48
• /
• 2008

Peel strength of epoxy adhesives can be increased by adding some amounts of XNBR. In this case, thermal resistance of the adhesive will be decreased by decrease of glass transition temperature of the adhesive. Epoxy resin modified with siloxane-imide was synthesized to improve thermal resistance and peel strength of the adhesive, after that the properties of modified epoxy resin were compared with the commercial epoxy resin. When 5% XNBR was added to 30% modified epoxy resin, this adhesive showed 0.42 N/mm of peel strength and $155^{\circ}C$ of glass transition temperature. These properties are enough compared to the required properties by the industry, i.e., 0.3 N/mm and $150^{\circ}C$, respectively. Weight loss of the modified epoxy resin by the treatment of nitric acid and 0.1N NaOH was reduced, but weight gain by the humid condition was increased by the presence of benzene ring and imide ring. 30% modified epoxy resin blended with 5% XNBR showed 220% improvement in tensile strength and elongation compared to the case of common epoxy resin. This is due to the flexibility of the siloxane in the modified epoxy resin.

• Elastomers and Composites
• /
• v.49 no.2
• /
• pp.110-116
• /
• 2014

We investigated the effect of the concentration of stannous 2-ethylhexanoate catalyst on the esterification rate between adipic acid (AA) and each of two PEG oligomers, diethylene glycol (DEG) and polyethylene glycol (PEG600). The concentration of the catalyst was varied from 0.15 to 2.0 wt.%. To attach hydroxy group to each end of the poly(oxyethylene-co-adipate) synthesized from AA and the PEGs, the esterification was performed with excessive PEG oligomers ([PEG]/[AA]=2) at $170^{\circ}C$. The degree of polymerization of the poly(oxyethylene-co-adipate)diol products were three. The apparent rate constant ($k_{app}$) of the esterification between AA and DEG shows the first order dependency on the catalyst concentration ($k_{app}=0.88[C_{cat}]$), whereas the $k_{app}$ of the esterification between AA and PEG600 has a relation of $k_{app}=0.123[C_{cat}]^{0.55}$ with the catalyst concentration. It is expected that the rate of esterification between AA and DEG has a non-linear dependency on the catalyst concentration as the catalyst concentration approaches to 0.22M.

• Elastomers and Composites
• /
• v.49 no.2
• /
• pp.103-109
• /
• 2014

Blends of emulsion SBR (E-SBR) and solution SBR (S-SBR) were prepared, and their microstructures (styrene, 1,2-unit, cis-1,4-unit, and trans-1,4-unit contents) were analyzed by Fourier transform infrared spectroscopy (FTIR) with transmittance mode. Method to measure absorbance by valley-to-valley baseline (TV) is objectively reasonable, but has a demerit which peak intensity of the cis-1,4-unit cannot be correctly measured. In order to obtain information for the four microstructures including cis-1,4-unit, measurement methods without correction (TM) and correction to 99% transmittance (TB) were compared to the TV method. Results obtained by the TB method were closer to those obtained by the TV one than those obtained by the TM. The microstructures were determined from the absorbances obtained by the TM and TB methods according to the ISO/FDIS 21561:2005(E). Variations of the styrene, 1,2-unit, and trans-1,4-unit contents with the blend ratio of E-SBR/S-SBR showed relatively good linearities, and there was no big difference between results obtained by the TM and TB methods. Variations of the cis-1,4-unit content with the blend ratio absolutely did not show linearities irrespective of the TM and TB methods.

• Journal of the Korean Magnetics Society
• /
• v.18 no.4
• /
• pp.136-141
• /
• 2008

In this study, the magnetic(static and high-frequency) and microwave absorbing properties have been investigated in Ru-Co substituted M-hexaferrites($BaFe_{12-2x}Ru_xCo_xO_{19}$). The powders and sintered specimens were prepared by conventional ceramic processing technique. With the calcined powders, the composite specimens were prepared using the silicone rubber as a matrix material. The substitution ratio of Ru-Co to obtain in-plane magnetic anisotropy, thus having the minimum coercivity, is much smaller (about x=0.3) than the previously reported Ti-Co substituted specimen. Owing to this low substitution, the specimen has a large value of saturation magnetization($M_s$=65 emu/g). Ferromagnetic resonance behavior and microwave absorbing frequency band is strongly influnced by the coercvity which can be controlled by Ru-Co substitution ratio. It is found that the M-hexaferrites with planar magnetic anisotropy by doping Ru-Co in both sintered and composite form have superior microwave absorbing properties in GHz frequency range.

• Korean Journal of Optics and Photonics
• /
• v.28 no.5
• /
• pp.213-220
• /
• 2017

This paper proposes how to fabricate an educational Mach-Zehnder interferometer that is easy to align and inexpensive, using 3D printers and semiconductor lasers. The interferometer consists of a body $165mm{\times}120mm{\times}57mm$ in size, mirror mounts, a laser holder, beam splitters, and so on. The laser path is adjusted by 4 mirror mounts, each comprised of rubber bands, small metal wires, and a screw. The interference fringe is enlarged by the lens at the final stage. The refractive index of a slide glass was measured by counting the number of moving interference fringes while the slide glass, inserted into one of the two interferometer arms, is rotating. The formula for the refractive index as a function of the optical-path difference and rotation angle was obtained, and used to calculate the refractive index of glass from the interferometer experiment. The use of a rotating glass in one arm of the interferometer nullifies the need for a precision stage, which despite its high cost is often required to observe the moving interference fringe in the classroom. Therefore, the 3D-printed Mach-Zehnder interferometer proposed in this paper can be very useful for education, because of its affordability and performance. It enables students to perform both qualitative and quantitative studies using a 3D-printed interferometer, such as measuring the refractive index of a glass sample, and the wavelength of light.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.25 no.4
• /
• pp.433-440
• /
• 2019

Offshore working environments such as ships, offshore oil and gas plants, and offshore wind turbines are isolated and directly exposed to rough seas, which pose high risks of safety accidents. Therefore, all workers in offshore plants should be able to cope with emergency situations and must be qualified according to relevant laws and regulations such as the International Convention on Standards of Training, Certification and Watchkeeping for Seafarers (STCW Convention) and Offshore Petroleum Industry Training Organization (OPITO) standards. In particular, marine workers should be able to perform cardiopulmonary resuscitation (CPR) in isolated locations or enclosed and confined spaces such as those in life-boats, life-rafts, rescue-boats, etc. Because the floor material is made of rubber, it may be difficult to perform chest compressions in life-rafts used to escape from emergency situations in ships or offshore plants. Chest compressions performed on life-rafts may reduce the accuracy of CPR and increase fatigue for those providing aid. To measure the accuracy and fatigue of those performing CPR in life-rafts, 15 experimenters with more than five years of experience as first aid instructors were exposed to different CPR environments in a marine safety training center equipped with an artificial wave generator. The results showed that the accuracy of CPR in the classroom was 99.6 %, but that in various life-raft environments was only 84 %. T-verification of the two sites confirmed the reduced accuracy of CPR performed on life-rafts. CPR on life-rafts should be performed in groups of two and with the use of automated chest compression devices.

• Fire Science and Engineering
• /
• v.32 no.6
• /
• pp.1-6
• /
• 2018

This study is to analyze the characteristics of the yellow insulation ring type of the CSST used for tubing when it is artificially deteriorated and damaged by burning. The CSST for tubing consists of a tube, protective coating, nut, yellow insulation ring, packing, and socket. In addition, it is thought that a yellow insulation ring and rubber packing were used to connect the tube and socket in order to improve the airtightness and insulation performance. The result of the verification of the data acquired from the tests in the 95% confidence interval shows that the Anderson-Darling (AD) and P value were analyzed to be 0.945 and 0.015, respectively. This confirms that the test data of the CSST for tubing is reliable. The analysis of the arithmetic mean of the insulation resistance of a CSST showed that the CSST damaged by burning by a torch, and the one damaged by electrical burning, was $16.7k{\Omega}$ (the greatest relatively) and $208{\Omega}$ (the lowest), respectively, while it was $1.72k{\Omega}$ in the case of a normal product. Therefore, the analysis result of the insulation resistance of the CSST collected from the scene of a fire can be utilized to examine the cause of damage by burning. In addition, it was found that when the maximum current of 97 A was applied to the CSST for about 5 s using a Primary Current Injection Test System (PCITS) the protective film and insulation ring of the CSST has no difference from that of a normal product. However, a part of the metal tube was melted.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.9
• /
• pp.20-28
• /
• 2019

This study comparatively analyzes general walking shoes on the conical top foundation of the ground condition and the pressure distribution during walking with shoes that are currently under development. Two categories of footwear were used: general footwear and a footwear conical top foundation that is currently under development. Experiments were carried out on hard ground and sandy soil in 15 male twenties that satisfy the conditions of normal foot wearing 260 mm. The pressure during walking was measured using Techstorm's Wireless Insole System, and foot pressure was measured in 7 zones of the foot. Studies have shown different maximum forces, average pressures, and pressure distributions depending on the shoe and ground conditions. This study shows that shoes with general low pressure dispersion effects depending on the feet in hard ground and sand ground are different from shoes with the conical top foundation that is currently under development. It is expected that it will be useful for the development of shoes that can be worn in all hard ground and sandy ground by selecting various rubber materials through further research.

• Journal of agricultural medicine and community health
• /
• v.44 no.3
• /
• pp.115-123
• /
• 2019

Objective: This study was conducted to examine the effects of a health promotion program on the health condition of rural elderly women implemented at primary health care posts using Korean Frailty Index. Methods: The research was designed a nonequivalent control group pretest-posttest setting. The participants in this study were 50 residents (intervention group: 25, control group: 25) selected from 4 villages 2 primary health care posts in J city Gyeongsangnam-do. The health promotion program was conducted at the primary health care posts twice a week for 12 weeks. This program consisted of basic exercises(Gukseondo + Theraband muscle strength training) and additional activities(including modified Theraband activity, rubber ball exercise, ball massage, nutrition class, singing class). Collected data were analyzed by descriptive statistics, paired t-test, and repeated measures ANOVA with SPSS 21.0. Results: Results of the health promotion program showed that the health conditions(measured by perceived health status, frailty score, upper/lower flexibility, maximum grip strength, dynamic balance test Timed Up and Go) of the experimental group(25) all statistical significantly improved. Conclusion: Study findings indicate that the health promotion program implemented at primary health care posts on rural elderly women is effective and can contribute to a developed health promotion program for local residents in the future.