• Elastomers and Composites
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• v.36 no.2
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• pp.111-120
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• 2001

Mechanical properties and their adhesion behavior with zinc- and brass-plated steel cords of natural rubber/acrylonitrile-butadiene blend compounds were investigated as a function of blend ratio. The Mooney viscosity and stress relaxation time were found to be lowered with increasing NBR content. Tensile modulus generally increased with increasing NBR content. Tensile stress at break stayed constant up to about 40 phr and showed minimum at $50{\sim}60 phr$, and thereafter increased with increasing NBR content. Strain at break decreased linearly below 50 phr, and above the level it showed nearly constant value. Based on the abrupt drops in elastic modulus and tan ${\delta}$ peak, the glass transition temperature of NR and NBR were found to be -55 and $-10^{\circ}C$, respectively. In the case of NR/NBR blend compounds, two distinct transition points were observed and each transition position was not affected by NBR level indicating an incompatible nature of NR/NBR blend system. The pullout force and rubber coverage decreased to the level of about 40% to that of pure m compound, when the 50 phr of NR was replaced by NBR. However, the pure NBR compound showed the comparable adhesion performance with NR(${\sim}90%$). The sulfur concentration was found to become lower with the increased NBR content at the adhesion interface based on the Auger spectrometer results, representing a lack of adhesion layer formation, and this was explained for a possible cause of low adhesion performance with adding NBR.

• Journal of Adhesion and Interface
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• v.11 no.2
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• pp.57-62
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• 2010

Photo-curable material can be crosslinked among molecules by light source such as UV and visible light materials. Material properties are controlled by crosslink reaction. Shrinkage is occured during the curing reaction of material structure. Phenomenon of shrinkage stress occurs inside the product and reduce the stability of the product causes problems. Heat shrink the evaluation of the phenomenon has been formalized. But the evaluation of photo shrink is not enough. In this experiment, real-time contract with shrinkage tester phenomena and analysis degree of shrinkage of the material differences. According to the research, experimental results and theoretical analysis of the results were big differences. Shrinkage, especially for a number of different functional groups that were very different theory. These differences are occurred by the molecular structure different and not enough reaction.

• Proceedings of the Materials Research Society of Korea Conference
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• 1996.05a
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• pp.24-24
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• 1996

• Polymer(Korea)
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• v.34 no.3
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• pp.226-236
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• 2010

UV irradiated acrylic pressure sensitive adhesives(PSAs) are prepared to be used for thermal pad in plasma display panel(PDP). The effect of the chemical structure of side-chain in comonomer and of crosslinking agent on wet-out property of acrylic PSAs in wide temperature range were investigated. The correlationship between viscoelastic behavior and adhesion properties, such as tack and peel strength, was also studied. The experimental results supported that wet-out and adhesion properties of acrylic PSAs were enhanced inversely proportional to side-chain length of comonomer in wide temperature range. The peel energy clearly increased in acrylic PSAs prepared by using di(ethylene glycol) dimethylacrylate (DEGDMA) for crosslinking agent. The results might be due to the difference in the glass transition temperature and viscoelastic behavior of acrylic PSAs.

• Polymer(Korea)
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• v.24 no.6
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• pp.877-885
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• 2000

PLA, PGA and PLGA films were treated with chloric acid mixture solution [70% perchloric acid (HClO$_4$)/potassium chlorate (KClO$_3$) aq. saturated solution, 3 : 2] to increase surface wettability and thus cell compatibility. The surface-treated PLA, PGA, and PLGA films were characterized by the measurement of water contact angle, electron spectroscopy for chemical analysis, and scanning electron microscopy. Surface wettability of chloric acid-treated PLA, PGA, and PLGA film surfaces was gradually increased with increase of treatment time. Unlike EtOH pre-treatment, chloric acid-treated polymer films maintain hydrophilic surface after drying. In cell adhesion test, fibroblasts were cultured on the chloric acid-treated film surfaces for 1 and 2 days. As the surface wettability increased, the cell adhesion on the surface were increased. In conclusion, this study demonstrated that the surface wettability of polymer plays an important role for cell adhesion and proliferation behavior.

• Journal of the Korean Ceramic Society
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• v.32 no.4
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• pp.405-412
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• 1995

In order to estimate the wettability of the borosilicate glasses with different composition on the noble metals of gold and silver, the measurements of the contact angle between the solid and the liquid were made at various temperatures and holding times using the sessil-drop method. The wetting behavior and the adhesion of the phases were strongly influenced by the thermal or the physical characteristics of the materials. The dependence of wetting angle ($\theta$) on the holding time (t) could be represented by the relation of $\theta$=a.tb, whereby the wettability of the systems was quantitatively compared. Also with increasing content of borosilicate glass in the glass-gold matrix composite, the tensile strength was decreased whereas the elastic modulus was increased.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.11
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• pp.2436-2441
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• 2002

Finite element technique considering adhesive forces is proposed and applied to analyze the behavior of elastic hemispherical asperity adhesively contacting the plane surface of semi -infinite rigid body. It is demonstrated that the finite element model simulates interfacial phenomena such as jump -to-contact and adhesion hysteresis that cannot be simulated with the currently available adhesive contact continuum models. This simulation aiso provides valuable information on contact pressure, contact region and stress distributions. This technique is anticipated to be utilized in designing a low-adhesion surface profile for MEMS/NEMS applications since various contact geometries can be analyzed with this technique.

• Journal of the Korean Wood Science and Technology
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• v.37 no.2
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• pp.155-163
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• 2009

This study examined the thermal stability of PLA-WF bio-composites. Wood flour (WF)-filled PLA bio-composites were reinforced with the flame retardants, Melamine pyrophosphate (MPP), resorcinol bis (diphenyl phosphate) (RDP) and zinc borate (ZB). The flame retardant was compounded with PLA and natural biodegradable filler. The thermal properties of the biodegradable polymer and bio-composites reinforced with the flame retardant were measured and analyzed by DSC, DMA and TGA. The results showed that the flame retardant-reinforced biodegradable bio-composite exhibited improved thermal properties.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.13 no.1
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• pp.97-103
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• 2000

This paper deals with residual stresses induced at the viscoelastic adhesive layer between the semiconductor chip and the leadframe during adhesion process. The adhesive layer has been assumed to be“thermorheologically simple”. The time-domain boundary element method(BEM) has been employed to investigate the behavior of interface stresses. Numerical results show that very large stress gradients are present at the interface corner and such singularity might lead to local yielding or edge delamination.

• Journal of the Microelectronics and Packaging Society
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• v.9 no.4
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• pp.31-34
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• 2002

For the mold die sticking mechanism, the major explanation is that the silica as a filler in EMC (epoxy molding compound) wears die surface to be roughened, which results in increase of adhesion strength. As the sticking behavior, however, showed strong dependency on the EMC models based on the experimental results from different semiconductor manufacturers, chemisorption or acid-base interaction is apt to be also functioning as major mechanisms. In this investigation, the plasma source ion implantation (PSII) using $O_2, N_2$, and $CF_4$ modifies sample surface to form a new dense layer and improve surface hardness, and change metal surface condition from hydrophilic to hydrophobic or vice versa. Through surface energy quantification by measuring contact angle and surface ion coupling state analysis by Auger, major governing mechanism for sticking issue was figured out to be a complex of mechanical and chemical factors.