• Polymer(Korea)
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• v.37 no.5
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• pp.571-578
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• 2013

Polyamide12 (PA12) is blended with ethylene propylene diene rubber (EPDM) at various compositions in the presence of maleated EPDM (mEPDM) to afford blend materials having the characteristics of thermoplastic elastomer (TPE). The EPDM/PA12 melt-blends are further irradiated with electron-beam (e-beam) at 0~100 kGy dosage, yielding selective crosslinking between EPDM chains while retaining melt-processibility originated from PA12 phase. mEPDM acts as a compatibilizer and affords additional improvements in mechanical properties of the EPDM/PA12 blend. With 25 kGy of e-beam irradiation and mEPDM, the EPDM/PA12 blends successfully exhibit TPE behaviors with reasonable elastomeric and mechanical properties.

• Elastomers and Composites
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• v.45 no.3
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• pp.217-222
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• 2010

Paved roads are suffered from the permanent plastic deformation in hot summer and cracks in cold winter, which are detrimental to safe driving. This leads to necessity of modification of asphalt to resist those deformation. In this study, two kinds of modifiers were examined; organic polymers and a photoinitiator which is activated by ultraviolet lay. The mechanical and rheololgical properties of modified asphalts were examined using UTM and rheometer. Results showed that the properties were varied depending on the types of polymer and irradiation time. UV irradiation increased the tensile strength and storage modulus of thermoplastic polymer-modified asphalt, however UV was not effective on thermoset polymer. According to long term ultraviolet curing test, properties of the polymer/photoinitiator-modified asphalt did not decrease, but rather increase for 20 years. This indicates that the useful life of the asphalt could be extended by addition of photoinitiator.

• Polymer(Korea)
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• v.32 no.6
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• pp.598-602
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• 2008

In this study we prepared crosslinked separators with the improved thermal stability by irradiating a commercial polyethylene (PE) separator for lithium secondary battery with an electron beam, and the thermal and mechanical properties of the prepared separators were evaluated as a function of the absorption dose. The thermal shrinkage of electron beam irradiated separator was decreased with increasing absorption dose. As a result of the shutdown behavior using an AC impedance, it was observed that the irradiated separator had the better shutdown function than the unirradiated separator. The modulus of the irradiated separator was enhanced as the absorption dose was increased, while the tensile strength and the break elongation of the irradiated separator were decreased.

• Elastomers and Composites
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• v.40 no.2
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• pp.112-118
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• 2005

Influence of a silane coupling agent on the reatraction behaviors of NR vulcanizates reinforced with carbon black and c lay was studied. Bis-(3-(triethoxysilyl)-propyl )-tetrasulfide (TESPT) was used as a silane coupling agent. The vulcanizates containing the silane coupling agent were, on the whole, recovered faster than those without the silane coupling agent. However, for the vulcanizate with the higher clay content at low temperature region (below $-12^{\circ}C$), the vulcanizate containing the silane coupling agent was recovered slower than that without the silane coupling agent. The recovery difference of the vulcanizates with and without silane coupling agent decreased with increase of clay content. The experimental results were explained with crosslink density, modulus, and bound rubber content.

• Elastomers and Composites
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• v.33 no.4
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• pp.267-273
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• 1998

Isocyante terminated urethane prepolymers were synthesized by the reaction of 4,4'-dimethyl phenyldiisocyanate(MDI) and ester type polyols such as ethylene glycol/ butanediol adipate(EBA), neopentylglycol/butanediol adipate (NBA) and hexanediol adipate (HA) . All of the NCO-terminated urethane prepolymers are solid at room temperature, but they become mobile enough to be disposed onto a substrate upon heating about $80^{\circ}C$. Subsequently, they are solidified and cured through the reaction with moisture. Tensile behavior of the ore-thane hotmelt exhibits characteristic features depending on the type of polyol. The adhesive strength determined by single lap shear joint is higher in order of HA, NBA and EBA based ore thane hotmelt, which can be correlated with the magnitude of breaking energy of the cured films. The failure mode are cohesive for all cases and the adhesive strength increases as the test is performed faster. This indicates that the strength of the adhesive joint is primarily dependent upon the bulk properties of the adhesives.

• Journal of Adhesion and Interface
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• v.22 no.4
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• pp.144-152
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• 2021

Understanding charge transfer across the interface between organic semiconductor and gate insulator gives insight into the development of high-performance organic memory as well as highly stable organic field-effect transistors (OFETs). In this work, we firstly unveil a novel interfacial charge transfer mechanism, in which hole transfer from organic semiconductor to polymer insulator was nonlinearly boosted by localized states coupling. For this, OFETs based on rubrene single crystal semiconductor and Mylar gate insulator were fabricated via vacuum lamination, which allows stable repetition of lamination and delamination between semiconductor and gate insulator. The surfaces of rubrene single crystal and Mylar film were selectively degraded by photo-induced oxygen diffusion and UV-ozone treatment, respectively. Consequently, we found that the interfacial charge transfer and resultant bias-stress effect were nonlinearly boosted by coupling between localized states in rubrene and Mylar. In particular, the small number of localized states in rubrene single crystal provided fluent pathway for interfacial charge transport.

• Korean Chemical Engineering Research
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• v.55 no.5
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• pp.690-697
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• 2017

In this study, styrene-isoprene-styrene (SIS)-styrene-butadiene-styrene (SBS) modified asphalt was prepared for waterproof-sheet to measure its properties including softening point, penetration, low temperature flexibility, viscosity and adhesion. Then the properties of SIS-SBS modified asphalt imparted with self-healing were optimized to seek for optimal compositions of SIS and SBS versus asphalt according to response surface methodology (RSM). As the content of SBS or SIS was increased, both properties of softening point and viscosity, measured at high temperature, were increased with a statistical significance. However, the increments of softening point and viscosity per unit content of SBS added, were observed to be greater than those per unit content of SIS added, respectively. It was due to the difference of thermal properties of SBS and SIS at high temperature that the cross-linking degree of SBS was increased by gelation accompanied with the increase of viscosity, while chain-entanglement of SIS was relatively reduced owing to a chain scission of poly(isoprene) blocks causing the decrease of viscosity. To the contrary, SIS-SBS modified asphalt showed a behavior of the least elasticity resulting in both the maximum of penetration and adhesion, measured at room temperature, as well as the lowest low temperature flexibility at the composition of SIS, 4 g and SBS, 8.5 g based on asphalt, 63 g.

• Journal of the Korea Concrete Institute
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• v.24 no.1
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• pp.3-14
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• 2012

This paper describes experimental results on the seismic performance of SHCC (strain-hardening cement composite) infill wall for improving damage tolerance capacity of non-ductile frame. To investigate the effect of tensile strain capacity and cracking behavior of SHCC materials on the shear behavior of SHCC infill wall, three infill walls were fabricated and tested under cyclic loading. The test parameter in this study is a type of cement composites; concrete and SHCCs. The two types of SHCC materials were prepared for infill walls. In order to induce crack damages into the mid-span of the infill wall, each infill wall had two 100-mm-deep-notches on both sides. Test results indicated that SHCC infill walls showed superior crack control capacities and much larger drift ratios at the peak loads than RC (reinforced concrete) infill wall, as expected. In particular, due to the bridging actions of the reinforcing fibers, SHCC matrix used in this study would delay the stiffness degradation of infill wall after the first inclined cracking. Moreover, from the damage classes based on the cracks' maximum width in the infill walls, it was observed that PIW-SHD specimen possessed nearly threefold seismic capacities compared to PIW-SLD specimen. Also, from the results on the strain of diagonal reinforcements, it can be concluded that the SHCC matrix would resist a part of tensile stresses transferred along steel rebar in the infill wall.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.5
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• pp.93-98
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• 2017

The fixing behaviors of raw silk yarns treated with melamine and formaldehyde at a molar ratio of 1:3 for trimethylolmelamine were investigated. Sericin was fixed during the fixing process, but a part of sericin I was removed simultaneously by hot water. The weight losses by fixing and the degumming losses by degumming greatly decreased with increasing concentrations of melamine and formaldehyde. The silk yarns fixed with 0.011 M melamine and 0.033M formaldehyde were significantly degummed due to the insufficient fixation of sericin and the alkaline hydrolysis of sericin by sodium carbonate during the degumming process. On the other hand, the silk yarns fixed with 0.055M melamine and 0.165M formaldehyde were degummed slightly (the degumming losses of 3-8%) due to the strong fixation of sericin, which might result from the many cross-linkages between the sericin I molecules, which were formed by trimethylolmelamine. Those fixed with the fixing solution containing 15% owf softener showed the lowest weight and degumming losses because under the condition of 15% owf softener, the cation of the softener can effectively form ionic bonds with the negatively charged side chain of aspartic acid in sericin. In addition, van der Waals' forces may be also formed between the hydrophobic tail of the softener and the hydrophobic region of sericin, which may help inhibit the removal of sericin I.

• Journal of the Korea Concrete Institute
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• v.22 no.5
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• pp.617-624
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• 2010

This paper reports on a comprehensive study on the mechanical properties of expansive fiber-reinforced strainhardening cement composite (SHCC) materials containing various replacement levels (0, 8, 10, 12 and 14%) of an expansive admixture and 1.5% polyethylene (PE) fibers volume fraction. A number of experimental tests were conducted to investigate shrinkage, compressive strength, flexural strength, and direct tension behavior. Test results show that as expected, the different replacement levels of an expansive admixture have an important effect on the evolution of the free shrinkage of SHCC with a rich mixture. At the volume fraction of 1.5%, PE fibers in normal SHCC reduce free shrinkage deformation by about 30% in comparison to plain mortar. The replacement of an expansive admixture in SHCC material has led the SHCC to a better initial cracking behavior. Enhanced cracking tendency improved mechanical properties of SHCC materials with rich mixtures. Note that an increase in the replacement of expansive admixture from 10% to 14% does not lead to a significant improvement for mechanical properties; this implies that the replacement of 10% expansive admixture is sufficient.