• Journal of Adhesion and Interface
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• v.24 no.3
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• pp.77-85
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• 2023

In this research, polymeric anionic surfactants having various molecular weights and acid values were synthesized using a continuous stirred tank reactor (CSTR). The CSTR has an advantage of higher production rate and more constant product properties compared to batch and semi-batch reactors. The polymeric surfactants were made using butyl acrylate as a hydrophobic group and acrylic acid as a hydrophilic group. The synthesized polymeric surfactants were ionized with alkali solution and were used as an anionic surfactant. To investigate the properties as a surfactant, the properties of the synthesized surfactant, such as acid value, critical micelle concentration (CMC) and molecular weight, were measured. The results showed that the acid values of the polymeric surfactants were 60 to 380 and a number average molecular weight were 8,000 to 13,000 g/mol. Also, it was found that the CMC was around 0.01 g/ml, which showed similar level values with ordinary surfactant. To prove the performance of the polymeric surfactant, acrylic emulsion PSAs were synthesized using the acquired polymeric surfactant. The results showed that the maximum peel strength of 21.24 N/25mm when acid value was 150 and molecular weight was 8,500 g/mol. The values of peel strength and initial tack of acrylic emulsion PSAs using polymeric surfactant synthesized in this study showed much higher than those of reference PSAs synthesized using ordinary anionic surfactant, SDS (Sodium Dodecyl Sulfate) and SDS/TRX (Triton X-100).

• Composites Research
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• v.16 no.4
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• pp.74-79
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• 2003

Comparison of interfacial properties and microfailure mechanisms of oxygen-plasma treated poly(p-phenylene-2,6-benzobisoxazole(PBO. Zylon) and poly(p-phenylene terephthalamide)(PPTA, Kevlar) fibers/ epoxy composites were investigated using micromechanical technique and nondestructive acoustic emission(AE). Interfacial shear strength(IFSS) and work of adhesion, Wa of PBO or Kevlar fibers/epoxy composites increased by oxygen-plasma treatment. Plasma-treated Kevlar fiber shooed the maximum critical surface tension and polar term, whereas the untreated PBO fiber showed the minimum value. Microfibril fracture pattern of plasma-treated Kevlar fiber appeared obviously. Based on the propagation of microfibril failure toward core region. the number of AE events for plasma-treated PBO and Kevlar fibers increased significantly. The results oi nondestructive AE were consistent well with microfailure modes by optical observation in microdroplet and two-fiber composites tests.

• Composites Research
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• v.24 no.4
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• pp.11-16
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• 2011

Retention of interfacial shear strength (IFSS) of polymer composites at cryogenic temperature application is very important. In this work, single carbon tiber reinforced epoxy compositc was used to evaluate IFSS and apparent modulus under room and cryogenic temperatures. The property change of carbon and selected epoxy for particularly cryogenic temperature application were tested in tension and compression. Tensile strength and elongation of carbon fiber decreased at cryogenic temperature, whereas tensile modulus was almost same. On the other hand, epoxy matrix showed the increased tensile strength but decreased elongation. It can be due to maximum thermal contraction existing free volume in cryogenic temperature. IFSS increased up to $-10^{\circ}C$ and then decreased steadily. However, IFSS at cryogenic temperature was still similar to that at room temperature. This result is very useful to cryogenic application since selected epoxy toughness and interfacial adhesion can keep at such low temperature.

• Tribology and Lubricants
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• v.23 no.3
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• pp.130-133
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• 2007

Fuel cladding tubes in nuclear fuel assembly are held up by supporting grids because the tubes are long and slender. Fluid flows of high-pressure and high-temperature in the tubes cause oscillating motions between tubes and supports. This is called as FIV (flow induced vibration), which causes fretting wear in contact parts of tube and support. The fretting wear of tube and support can threaten the safety of nuclear power plant. Therefore, a research about the fretting wear characteristics of tube-support is required. The fretting wear tests were performed with supporting grids and cladding tubes, especially after corrosion treatment on tubes, in water. The tests were done using various applied loads with fixed amplitude. From the results of fretting tests, the wear amounts of tube materials can be predictable by obtaining the wear coefficient using the work rate model. Due to stick phenomena the wear depth was changed as increasing load and temperature. The maximum wear depth was decreased as increasing the water temperatures. At high temperatures there are the regions of some severe adhesion due to stick phenomena.

• Tribology and Lubricants
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• v.24 no.3
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• pp.129-132
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• 2008

Fuel cladding tubes in nuclear fuel assembly are held up by supporting grids because the tubes are long and slender. Fluid flows of high-pressure and high-temperature in the tubes cause oscillating motions between tubes and supports. This is called as FIV (flow induced vibration), which causes fretting wear in contact parts of tube and support. The fretting wear of tube and support can threaten the safety of nuclear power plant. Therefore, a research about the fretting wear characteristics of tube-support is required. The fretting wear tests were performed with supporting grids and cladding tubes, especially after corrosion treatment on tubes, in water. The tests were done using various applied loads with fixed amplitude. From the results of fretting tests, the wear amounts of tube materials can be predictable by obtaining the wear coefficient using the work rate model. Due to stick phenomena the wear depth was changed as increasing load and temperature. The maximum wear depth was decreased as increasing the water temperatures. At high temperatures there are the regions of some severe adhesion due to stick phenomena.

• Polymer(Korea)
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• v.31 no.4
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• pp.315-321
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• 2007

Aminated PONF-9-GMA ion exchange fabrics were synthesized by radiation induced graft copolymerization. Hybrid ion exchange fabrics combined with aminated PONF-g-GMA fabrics and anionic ion exchange resin were also fabricated by hot melt adhesion method and then their adsorption properties were investigated. Ion exchange capacity of the hybrid ion exchange fabrics was higher than ion exchange fabric and was lower than bead resin. The maximum value was 4.18 meq/g. Adsorption breakthrough time for vanadium of the hybrid ion exchange fabric was 550 min, which was faster than bead resin but slower than fibrous ion exchanger. The Breakthrough time of the hybrid ion exchange fabrics gets longer with increasing pH. The initial breakthrough time occurred around 400 min with increasing vanadium concentration.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.8
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• pp.511-517
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• 2016

Three-dimensional models of stenosis blood vessels were prepared using a 3D printer. The models included a straight pipe with axisymmetric stenosis and a pipe that was bent $10^{\circ}$ from the center of stenosis. A refractive index matching method was utilized to measure accurate velocity fields inside the 3D tubes. Three different pulsatile flows were generated and controlled by changing the rotational speed frequency of the peristaltic pump. Unsteady velocity fields were measured by a time-resolved particle image velocimetry method. Periodic shedding of vortices occurred and moves depended on the maximum velocity region. The sizes and the positions of the vortices and symmetry are influenced by mean Reynolds number and tube geometry. In the case of the bent pipe, a recirculation zone observed at the post-stenosis could explain the possibility of blood clot formation and blood clot adhesion in view of hemodynamics.

• Journal of the Microelectronics and Packaging Society
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• v.12 no.3 s.36
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• pp.213-217
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• 2005

The polymer light emitting diodes (PLED) with ITO/PEDOT:PSS/MEH-PPV/Al structure were prepared on ITO(indium tin oxide)/Glass substrates using PEDOT:PSS[poly(3,4-ethylenedioxythiophene):poly(styrene sulfolnate)] as the hole transport material and MEH-PPV[poly(2-methoxy-5-(2-ethyhexoxy)-1,4phenylenvinylene)] as emission material layer. The dependences on the surface roughnees and friction coefficient between film layers were investigated as a function of the MEH-PPV concentrations$(0.1\;wt\%\~0.9\;wt\%)$. The RMS values decreased from 1.72 nm to 1.00 nm as the concentration of MEH-PPV increased from $0.1\;wt\%\;to\;0.9\;wt\%$, indicating improvement of surface roughness. In addition, friction coefficients decreased from 0.048 to 0.035, which means the deteriorating of the adhesion condition. The PLED sample with $0.5\;wt\%$ of MEH-PPV showed the maximum luminance of $409\;cd/m^2$.

• The Journal of Korean Physical Therapy
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• v.25 no.2
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• pp.56-63
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• 2013

Purpose: This study was conducted in order to examine how an effective rehabilitation exercise program influences the activity of shoulder muscles, and to help the clinical application of a rehabilitation program, for prevention and relief of pain, adhesion, and joint stiffness of patients who undergo rotator cuff repair. Methods: Nine test subjects were placed randomly into each group for a total of 27 subjects and exercise program interventions according to the group were conducted for six weeks, after which maximum voluntary isometric contraction (%MVIC) value was re-measured for supraspinatus muscle, infraspinatus muscle, serratus anterior muscle, and middle deltoid muscle in all groups in order to compare changes in muscle activity before and after the experiment in order to perform comparative analysis of changes in muscle activity between groups, based on which four experimental hypotheses were confirmed. Results: Changes in muscle activity according to %MVIC showed a statistically significant difference (p<0.01) (p<0.001) in all muscles, except the middle deltoid muscle, and post-verification results showed that changes in muscle activity according to %MVIC were greater in test groups I and II, compared with the control group, for the supraspinatus muscle, infraspinatus muscle, and serratus anterior muscle. Conclusion: Therefore, rehabilitation through use of the methods described above should be applied efficiently in clinical settings and more research in development of much more efficient rehabilitation program interventions must be conducted.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.6
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• pp.1404-1411
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• 1993

This study was undertaken to investigate the corrosive wear charateristics upon various transformation condition of austempered low-alloy ductile cast iron in corrosive environments against mating specimen made of the hardened SM45C. The corrosive wear test was carried out by rubbing the annular surface of two test pieces in distilled water and aqueous solution at constant sliding speed of 0.5m/s. In severe wear region, the corrosive wear rate Wc increased hastily with NaCl concentration owing to intermetallic adhesion but Wc went down slowly in mild wear region due to lubricating effect of the corrosion product. The critical sliding distance decreased with increasing NaCl concentration due to increased generation rate of the corrosion product and the specific corrosive wear rate has maximum in 1% NaCl aqueous solution at mild wear region. With the variation of matrix, the corrosive wear resistance of the fine acicular bainite was higher than that of coarse upper bainite because of reducing the local cell reaction by carbides. A growth in volume fraction of retained austenite in matrix increased the Wc due to soften surface, but has a declining tendency of Wc in mild wear region.