• Fibers and Polymers
• /
• v.7 no.1
• /
• pp.51-56
• /
• 2006

Power net fabric is one of the highly extensible two-way fabrics. Power net structure shows special characteristics in the wearing of final functional clothes. This research evaluated effects of treatment temperature on proportional extensibility and shrinkage ratio of spandex at a given wale length. As treatment temperature increased, extensibility increased proportionally to the standard length of the sample and the shrinkage ratio in the direction of course and wale increased. The pulling-out length increased proportionally to the standard length of the sample. However it was affected by the effect of treatment time and temperature due to the thermal properties of spandex filament yarn.

• Journal of Powder Materials
• /
• v.23 no.3
• /
• pp.195-201
• /
• 2016

Composite materials consisting of pure aluminum matrix reinforced with different amounts of graphite particles are successfully fabricated by mechanical ball milling and spark plasma sintering (SPS) processes. The shrinkage rates of the composite powders vary with the amount of graphite particles and the lowest shrinkage value is observed for the composite with the highest amount of graphite particles. The current slopes of time increase with increase in the amount of graphite particles whereas the current slopes of temperature show the opposite trend. The highest thermal conductivity is achieved for the composite with the least amount of graphite particles. Therefore, the thermal properties of the composite materials can be controlled by controlling the amount of the graphite particles during the SPS process.

• Journal of the Korean Ceramic Society
• /
• v.43 no.5 s.288
• /
• pp.293-298
• /
• 2006

For substrate glass applied to PDP (Plasma Display Panel), it has been developed many glass compositions that have to not only meet the specifications of PDP but also satisfy the float process as production technology. In the present work several compositions with no deformation at PDP processing temperature and thermal expansion coefficient of $83{\sim}9{\times}10^{-7}/K$ were designed. Based on viscosity at high temperature and liquidus temperature for those compositions, three candidate compositions named T-2, T-4, T-6 were selected finally. It was examined additionally that thermal shrinkage at PDP processing temperature and visible transmittance. The properties of T-series were compared with those of commercial glasses and discussed from the view point of PDP device and glass production.

• Journal of Welding and Joining
• /
• v.18 no.5
• /
• pp.84-89
• /
• 2000

Friction welding of titanium and aluminium is numerically modeled by the axisymmetric thermal elastic-plastic analysis. In titanium/aluminium friction welding, heat transfers into the titanium substrate to a distance of z=10(mm) on the side of the bondline and into the whole region of the aluminium substrate having the large thermal conductivity. Adjacent to the bondline, $^{\sigma}r\;and\;^{\sigma\theta}$ are tensile in the substrate whose thermal shrinkage is large, and are compressive in the substrate whose thermal shrinkage is small. $\sigma_z$ along the radial direction is large tensile at the periphery of the component. Plastic strain occurs only close to the bondline in the aluminium substrate. In the components of plastic strain, $\varepsilon^p_r\;and\;\varepsilon^p_{\theta}$ have positive values and $\varepsilon^p_r$ has large negative value. However, $\varepsilon^p_r$ is produced not because of the severity of the mechanical restraint condition, but on purpose to satisfy the condition of the volume constant. A plastic work is proposed as a measure to evaluate the mechanical severity. The plastic work is larger in the aluminium substrate than that in the titanium substrate. The mechanical condition is severer in the aluminium substrate.

• Journal of the Korea Concrete Institute
• /
• v.13 no.4
• /
• pp.362-370
• /
• 2001

The internal or external restraint of thermal and dry shrinkage movements could thus generate tensile stresses in concrete pavement for early traffic opening. Restrained shrinkage and thermal stresses could produce microcracks in concrete which increase its permeability and accelerate its long-term deterioration under weathering and load effects. Fiber reinforced concrete is an effective approach to the control of microcrack and crack development under tensile stresses. This study aims at evaluation of the durability of high early strength concrete for early traffic opening and increase of service life. Three different types of regulated-set cement which recently has been used much in Korea were adopted. Fibers were added and their mixtures were compared with plain high early strength concrete mixture. The use of fibers increased durability performance of high early strength concrete using regulated-set cement than the corresponding plain mixtures.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2007.06a
• /
• pp.413-413
• /
• 2007

In recent years, flexible display devices such as liquid crystal display (LCD), organic light emitting diode (OLED), etc. have attracted considerable interest in a wide variety of applications. Polymer substrate is absolutely necessary to realize this kind of flexible display devices. Using the polymer as a substrate, there are lots of advantages including not only mechanical flexibility such as rolling and bending characteristics but also light weights, low cost and so on. In detail, thickness and weights is only one forth and one second of glass substrate, respectively. However, it needs low temperature below $150^{\circ}C$ in the fabrication process comparing to conventional deposition process. The polymer substrate is not thermally stable as much as the glass substrate so that some deformation can be occurred according to variation of temperature. In particular, performance of devices can be easily deteriorated by shrinkage of substrate when heating it. In this paper, pre-annealing and deposition of buffer layer was introduced and studied to solve previously mentioned problems of the shrinkage and followed shear stress.

• Polymer(Korea)
• /
• v.37 no.6
• /
• pp.711-716
• /
• 2013

The effect of chain orientation and relaxation on the characteristics of poly(ethylene naphthalate) (PEN) flexible substrate has been studied. It was found that the coefficient of thermal expansion (CTE) of PEN under $100^{\circ}C$ decreased as low as $20ppm/^{\circ}C$ due to the lowering of chain mobility by chain orientation. The thermal shrinkage was found to appear near glass transition temperature because of chain relaxation. It could be minimized by thermal annealing but CTE increased again up to $70ppm/^{\circ}C$ which was 65% of intrinsic CTE of PEN. Unstrained thermal annealing made possible to avoid the thermal shrinkage with maintaining low CTE obtained by chain orientation. Chain orientation did not affect the optical transmittance; however, thermal annealing caused the decrease of optical transmittance up to 5%. This was understood by the minor crystallization due to the thermal annealing near glass transition temperature.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2004.08a
• /
• pp.1212-1215
• /
• 2004

Diffraction modes of holographic grating were fabricated with polyurethane acrylates(PUA). Two types of silica (AEROSIL 200 and AEROSIL R812) were added to reduce the shrinkage of polymer matrix. It was founded that shrinkage of PUA composite film was reduced with the addition of silica. HPDLC based PUA/silica composite also showed high diffraction efficiency. The morphology of the resultant gratings was analyzed by using scanning electron microscopy(SEM) and Tg of the polymer matrix by dynamic mechanical thermal analysis(DMTA).

• Journal of Ceramic Processing Research
• /
• v.19 no.6
• /
• pp.504-508
• /
• 2018

Diopside is a ceramic material with excellent physical and chemical properties. However, when it is applied as an LED packaging material, heat dissipation of the LED element is not sufficient due to its relatively lower thermal conductivity, which may cause degradation of the LED function. In this study, glass-ceramics based on a $ZrO_2-CaO-MgO-SiO_2$ system, in which diopside is the main crystal phase, were prepared by heat-treating the glass, which was composed of zircon ($ZrO_2-SiO_2$) powders and diopside ($CaO-MgO-2SiO_2$) powders. The possibility of using the glass-ceramics as a packaging material for LEDs was then investigated by analyzing the density, shrinkage, thermal conductivity, and phases generated according to the amount of zircon powder added. The density and shrinkage of specimens decreased slightly and then increased again with the amount of $ZrO_2-SiO_2$ added within a range of 0~0.38 mol. Even though the crystal phase of zircon does not appear in the $ZrO_2-CaO-MgO-SiO_2$ system, the glass containing 0.38 mol zircon powder showed the highest thermal conductivity, 1.85 W/mK, among the specimens fabricated in this study: this value was about 23% higher than that of pure diopside. It was found that the thermal conductivity of the glass-ceramics based on a $ZrO_2-CaO-MgO-SiO_2$ system was closely related to the density, but not to the phase type. Zirconia ($ZrO_2$), a component oxide of zircon, plays an important role in increasing the density of the specimen. Furthermore the thermal conductivity of glass-ceramics based on a $ZrO_2-CaO-MgO-SiO_2$ system showed a nearly linear relationship with thermal diffusivity.

• Food Science of Animal Resources
• /
• v.38 no.1
• /
• pp.143-151
• /
• 2018

The effects of proteolytic enzymes (bromelain and bromelain+papain) and a ginger extract were assessed on collagen content and solubility, thermal shrinkage temperature of connective tissue, pH, cooking loss, drip loss, and Warner-Bratzler shear force (WBSF) of M. pectoralis profundus isolated from the beef brisket cut. Both proteolytic enzymes and ginger extract led to a significant increase in cooking loss and collagen solubility compared with untreated controls. On the other hand, the peak ($T_p$) thermal shrinkage temperature markedly decreased in all treatments compared with those in controls. Samples treated with bromelain, bromelain + papain, and ginger extract showed a significant decrease in WBSF by 36%, 40%, and 37%, respectively, compared with untreated controls. Our findings suggest that ginger extract are useful for post-mortem tenderization of meat containing high levels of collagen, compared to control even though, bromelain and bromelain + papain treatments have higher collagen solubility than ginger extract.