• Journal of the Korean Wood Science and Technology
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• v.23 no.2
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• pp.55-69
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• 1995

The primary objective of this research was to investigate optimum manufacturing condition of thin composite panels composed of sawdust, polyethylene film and polypropylene net. At the study the experiment was designed to make thin board in which sawdust offers effectiveness as core composing material, polyethylene as adhesive with added urea resin, and polypropylene as stiffness and flexibility in the composition panel. 100 types of thin composite panels were manufactured according to press-lam and mat-forming process of various hot pressing conditions(pressure, temperature and time). They were tested and compared with control boards on bending properties(MOR, MOE, SPL, WML), internal bond strength, thickness swelling, linear expansion and water absorption. At the same time the visual inspections of each types of panels were accomplished. The physical and mechanical properties of composite types passed by visual inspection were analyzed by Tukey's studentized range test. From the statistical analysis, the optimum manufacturing condition of thin composite panels were selected. Compared with two manufacturing processes, mat-forming process performed better than press-lam process in all tested properties. The optimum manufacturing conditions resulted from the experiment and statistical analysis were able to determine as following: the press temperature was shown the most good result at 130$^{\circ}C$ in mat forming process and 140$^{\circ}C$ press lam process, the press time 4 min in both processes, but the press pressure was 25-10kg/$cm^2$ in mat forming and 15k/$cm^2$ press lam process.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.14 no.4
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• pp.77-82
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• 2000

This paper describes the self healing characteristics of a metalized polypropylene film(MPPF) by voids under a.c condition. PDIVs were increased with the number of pre-self healing due to void defects, and several pre-self healing events took place at lower voltage than the critical breakdown voltage of a PPF. Self healing mainly occurred at pin tips, wrinkle sides, and cross points of wrinkles, and the main self healing voltage was increased with PPF thickness. The burn out area at self healing was increased with the applied voltage, and the peak currents in a grounding conductor at self healing was also increased with the applied voltage.

• Food Science and Preservation
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• v.13 no.1
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• pp.1-7
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• 2006

The effects of packaging material and method on quality of fresh-cut mushrooms (Agaricus bisporus Sing.) were investigated in terms of weight loss, surface color, phenolics, vitamin C and sensory characteristics during storage at $5^{\circ}C$. The fresh-cut mushrooms were subjected to passive, gas exchange and vacuum packaging conditions at st. Polyethylene film (PE), polypropylene film (PP), anti-fogging film (AP) and pen orated film (PF) were used for the passive packaging. The mixed gas of $5\% CO_2/\;2\%O_2$ (MA1) and $10\%CO_2/\;2\%O_2$(MA2) were applied for the gas exchange packaging. The respiration rate of sliced mushroom was 1.27 times higher than intact mushroom at $5^{\circ}C$. Gas concentrations in the passive packaging were $1-2\%\;O^2\;and\;5-16\%m$ during storage of sliced mushrooms for 14 days at $5^{\circ}C$, and levels of the gases were different by the films used The mushroom in perforated film (PF) showed the highest weight loss of $4.56\%$. Anti-fogging film (AF) was somewhat effective for prevention of the weight loss compared with other films after 14 days storage. The mushrooms in MA1 and MA2 packages showed lower delta L value than in other films. PE packaging mitigated decrease of free and bound phenolics during storage. The mushrooms in MA2 kept better quality in sensory aspect, and then in MA1, PE and PP in order during storage at $5^{\circ}C$.

• Journal of the Korean Wood Science and Technology
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• v.34 no.5
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• pp.88-97
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• 2006

Wood flour (WF)-recycled polypropylene (RPP) composites composed of 50% WF of Eucalyptus deglupta Blume species, 50% RPP, various contents of maleic anhydride (MAH) modifier (0; 1; 2; 5; 5; 7.5; and lo%), and 15% dicumyl peroxide (DCP) initiator (based on MAH weight) were subjected to weather for 1 year and subterranean termite (Coptotermes cuwignathus HOLMGREN) and dry wood termite (Cryptotermes cynocephalus LIGHT) for 3 and 4 weeks, respectively. WF-RPP composites with 2.5% MA modifier had tensile strength, breaking elongation and Young's modulus about 2.2, 2.3, and 1.2 times, respectively higher compared to MAH-free composites. The WF-RPP composites with or without MAH modifier had 5.5 times higher resistance to weather compared to RPP film alone. The color of the WF-RPP composites with or without MAH modifier became lighter after exposures to the weather. The WF-RPP composites with or without MAH modifier are resistant to subterranean termite Coptotermes curvignathus HOLMGREN and dry wood termite Cryptotermecs cynocephalus LIGHT under the experimental condition adopted.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.3
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• pp.231-234
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• 2016

Pouch film is manufactured by laminating aluminum foil, polyamide film and polypropylene film with an adhesive or extrusion resin. However, a surface treatment is required for the aluminum because bonding does not occur easily between the aluminum foil and the polymer film. Thus, for this study, surface treatment experiments were performed in order to confirm the effect on adhesion strength. First, a variety of surface treatment solutions were coated on aluminum foil, and contact angle and surface morphology analysis was carried out for the surface-treated aluminum. For lamination of the surface-treated aluminum foil with polyamide film, a polyurethane base adhesive was prepared for the adhesive strength test specimens. The adhesive strength between the aluminum foil and the polyamide film of the resulting specimens was measured (UTM). With such an experiment, it was possible to evaluate the effect on adhesive strength of the various surface treatments.

• Korean Journal of Food Science and Technology
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• v.37 no.6
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• pp.933-938
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• 2005

To investigate pertinent packaging treatment of fresh-cut potatoes (Solanum tuberosum L.), potato cubes were subjected to passive, gas exchange, and vacuum packaging conditions. Low density polyethylene film (LDPE), polypropylene film (PP), anti-fogging film (AP), and perforated film (PF) were used as passive packaging treatments. Mixed gases of 5% $CO_2/5%\;O_2$ (MA1) and 10% $CO_2/5%\;O_2$ (MA2) were applied as gas exchange packaging. Packs filled with cubes were kept at $5^{\circ}C$, and changes in weight loss, surface color, vitamin C content and sensory quality of cubes were analyzed during storage. Respiration rate of cubes was 2.11 times higher than that of intact raw potatoes at $5^{\circ}C$. Gas concentrations in passive packaging was maintained at 1-2% $O_2$ and 4-14% $CO_2$ after 7 days. Gas levels changed depending on films used. Cubes packed in PP and MA2 showed lowest weight loss and browning during storage. Firmness of cubes was not affected by packaging treatment. Vitamin C content was highest in cubes packed with AF. Cubes packed in MA2 showed highest quality upto 10days storage, followed by those packed in PP and AF.

• International Journal of Concrete Structures and Materials
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• v.6 no.4
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• pp.251-256
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• 2012

This paper presents an experimental study on the pore and penetration of chloride in seashore concrete depending on types of curing forms. Three types of concretes (Plain concrete, MSF concrete and FA concrete) with four different form types (wood, coating wood, steel and polypropylene film) were examined. The test results show that the air volume in concrete was relatively higher with steel and polypropylene forms than others, and wood form shows the least air volume. The penetration of chloride depending on type of form is showed a wide variability, that is, the values on plain concrete, MSF concrete and FA concrete are 115.2, 125.5 and 121.6 %, respectively. Based on the present study, concrete should be considered the conditions of curing form-type for durable concrete.

• Elastomers and Composites
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• v.21 no.2
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• pp.121-128
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• 1986

Studies has been carried out on the characteristics of thermally stimulated current for polypropylene in the temperature range of $293[^{\circ}K]{\sim}403[^{\circ}K]$. The main peak observed at $366[^{\circ}K]$, as may be $\beta$ peak in conventional nomination, is believed to be depolarization current originated from the relaxation of "CO" group in monomer structure. The activation energy for the observed peak has been concluded to be in the range of $0.6{\sim}0.7[(eV]$ at $360[^{\circ}K]$ by the initial rise method. Furthermore, the initial density of carriers were calculated about $10^{22}/m^3$

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.10a
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• pp.68-72
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• 2000

In order to estimate spatial charging process in the corona charging which has been used to make polymer electret, the electrical properties of polypropylene film were obtained from Thermally Stimulated Current (TSC) measurements after corona charging between knife electrode and cylinder electrode with the voltages of -5, -6, -7 and -8[kV], respectively. And then the electrostatic contour and the electric field vector were also simulated by using Finite Element Method (FEM). The edge effect around edge of knife electrode affected the electrostatic contour on surface of specimen and the electric field concentration inside specimen. The uneven charging state in the electret due to the mistake on design could be calculated and so the optimal design of corona charging device which is appropriate to various materials is come to be practicable.

• Proceedings of the KIEE Conference
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• 1999.07e
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• pp.2389-2391
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• 1999

This paper describes the self-healing characteristics which plays an important role in high voltage capacitors. In this experiment, artificial voids were simulated in MPPFs, and the self-healing voltages were measured by varying the diameter of the voids and the thickness of the MPPFs. As a result, the self-healing voltage and the burn-out area were increased with the increment in the void diameter and the thickness of MPPF.