• Journal of the Korean institute of surface engineering
• /
• v.54 no.2
• /
• pp.90-95
• /
• 2021

Surface modification technique enabling the control of condensation provides various benefit in various engineering systems, such as heat transfer, desalination, power plants, and so on. In this study, lubricant oil-impregnation into Teflon-coated nanoporous anodic oxide layer of aluminum to enhance a de-wetting and mobility of water droplet on surface. Due to the surface treatment improving water-repellency, the condensation mode is changed to dropwise, thus the frequency of sliding condensed water droplet on surface is increased. For these reasons, the surface of oil-impregnated Teflon-coated nanoporous anodic aluminum oxide shows significantly enhanced condensation heat transfer compared to bare aluminum surface. In addition, the porosity of anodic aluminum oxide affected the mobility of water droplet even with oil-impregnation and Teflon-coating, indicating that the optimization of porous structure of anodic oxide is required for maximizing the condensation heat transfer.

• Korean Journal of Plant Resources
• /
• v.27 no.4
• /
• pp.380-391
• /
• 2014

Plants as well as crops are damaged by a combination of the hot and dry winds that has been a major factor in the reduction of crop production. A means to protect them from damaging conditions is to consider a coating material. In this study, we established laboratory screening methods to find a coating material to protect a crop from rapid transpiration caused by various factors. In a test measuring the weight loss of kidney bean seedlings for 6 days, Avion treatments decreased its weight loss (P=0.05). Owing to long-time spend in completing this assay, we performed a more simple method using a cobalt chloride paper strip, which changes from blue to red colors under water condition. Beewax, guagum, paraffin liquid, soybean oil, and PE-635 gave a waterproofing effect above 37 and 43% at 0.5 and 1 h after treatment, respectively. However, these tested materials did not show significant waterproofing results at 2 h. Although the methods produced reasonable results, a screening method to obtain more objective data is needed. An alternative is to use an instrument that can detect the transpiration of crop leaves. In a preliminary test using barley leaves, a portable photosynthesis system showed transpiration inhibition of 2% soybean oil and 10 times-diluted Avion under field conditions. In another test using the leaves of maize seedlings and apricot tree, 2% liquid paraffin and plant oils such as apricot oil, linseed oil, olive oil, and soybean oil showed significant transpiration inhibition (P=0.05). Especially, paraffin liquid and soybean oil selected from above tests gave good transpiration inhibitory effects against rice at 2%. In addition, the mixture of 2% soybean oil and a spreader showed more elevated inhibition results comparing with soybean oil or the spreader alone indicating that the spreader may be attributed to more uniform diffusion of the hydrophobic material onto the leaf surface of maize seedlings. The hydrophobic material coated physically the stomata and cuticle layers on leaf surfaces of rice. These hydrophobic materials screened in this study are expected to be used as plant coating materials.

• Journal of Adhesion and Interface
• /
• v.21 no.2
• /
• pp.58-64
• /
• 2020

This paper describes a simple approach for preparing a superhydrophobic and superoleophobic coating via spraying the mixture of UV-curable polyurethane acrylate and silica nanoparticles dispersed in a solvent. The prepared surface structures can be controlled by changing the types of solvents, the concentration of the polymer, and the amount of spraying. Superhydrophobicity and superoleophobicity are quantified by measuring the contact angle of water and oil, respectively. We also demonstrate the mechanism of spray coating with maximized superhydrophobicity and superoleophobicity through the analysis of re-entrant surface structures. At the appropriate amount and the composition of mixed solutions, the contact angle hysteresis of water and oil on the prepared surface is less than 2° and 30°, respectively. In addition, it shows excellent water-repellent and oil-repellent properties such that the oil droplet bounces off the surface.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.36 no.4 s.107
• /
• pp.49-59
• /
• 2004

This study was carried out to obtain the basic data for producing higher functional coating agents for pulp mold by evaluating various kinds of starch derivatives. At that time, four kinds of starch derivatives were manufactured for making coating agents respectively. Physical properties of coated paperboards were tested. Conclusions obtained from this results were as follows. The water and oil resistance of hydroxypropylated, cyanoethylated and carboxymethy­lated starch were high when degree of molar substitution(DS) of propylene oxide, acrylonitrile and sodium monochloroacetate were 0.18, 0.07 and 0.009, respectively. Also, the those of crosslinked starch were high when degree of crosslinking of epichlorohydrin was 0.02. Consequently, $8\%$ solution of carboxymethylated starch made with DS 0.009 of monochloroacetate was the best among coating agents from starch derivatives men­tioned above.

• Journal of Microbiology and Biotechnology
• /
• v.20 no.9
• /
• pp.1348-1350
• /
• 2010

Conidia of Beauveria bassiana ARSEF-7060, produced in millet amended with plant oils such as sunflower, corn, or cotton seed oil, were exposed to $45^{\circ}C$ of wet heat for 90 min. Conidia from millet+corn oil medium had the highest thermotolerance [$LT_{50}$ (median survival time): 45.7 min]. The mycotized millet grains were coated with each of the same plant oils as a granular formulation and subjected to $50^{\circ}C$ of dry heat for 8 h. Corn oil coating ($LT_{50}$: 8.68 h) was superior to sunflower and cotton seed oil coatings, suggesting the feasibility of using corn oil to increase conidial thermotolerance.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 2002.10b
• /
• pp.51-52
• /
• 2002

We report results on microtribological studies of chemically grafted nanoscale polymer layers of different architecture with thickness below 30 nm. We have fabricated the molecular lubrication coatings from elastomeric tri-block copolymers and tested two different designs of corresponding nanocomposite coatings. We observed a significant reduction of friction forces and an increase of the wear stability when a minute amount of oil was trapped within the grafted polymer layer. These polymer gel layers exhibited a very steady friction response and a small value of the coefficient of friction as compared to the initial polymer coating. A polymer 'triplex' coating has been formed by a multiple grafting technique. The unique design of this layer Includes a hard-soft-hard architecture with a compliant rubber interlayer mediating localized stresses transferred through the topmost hard layer. This architecture provides a non-linear mechanical response under a normal compression stress and allows additional dissipation of mechanical energy via the elastic rubber interlayer.

• Journal of Mechanical Science and Technology
• /
• v.20 no.3
• /
• pp.358-365
• /
• 2006

The hydraulic pump of an Electro-hydrostatic Actuator should be able to quickly feed large volume of oil into hydraulic cylinder in order to reduce the response time. On the other hand, it should be also able to precisely dispense small amount of oil through low-speed operation so that the steady state position control error of the actuator can be accurately compensated. Within the scope of axial piston type hydraulic pumps, this paper is focused on the investigation how the surface treatment of their cylinder barrel with TiN plasma coating can contribute to the reduction of the friction and wear rate of valve plate in the low-speed range with mixed lubrication. The results showed that the friction torque of the valve plate mated with a TiN coated cylinder barrel could be reduced to 22% of that with an uncoated original one when load pressure was 300 bar and rotational speed 100 rpm. It means that the torque efficiency of the test pump was expected to increase more than 1.3% under the same working condition. At the same time, the wear rate of the valve plate could be reduced to $40\sim50%$.

• Journal of the Korean Wood Science and Technology
• /
• v.34 no.3
• /
• pp.30-37
• /
• 2006

The present study examined the formaldehyde (HCOH) emission characteristic of various wood-based panel used in interior design, and measured changes in formaldehyde emission when a number of VOC reduction methods were applied. Formaldehyde emission showed a clear tendency of increase with the rise of temperature, and the concentration of formaldehyde emitted changed according to the preprocessing condition before measuring. Formaldehyde emission from wood board after bake out treatment was lower than that of the control group. When specimens were coated with urethane, cashew, water, oil stain, they generally showed the decrease of formaldehyde emission, although varying according to finishing material, and when edge sealing was applied the decrease became significant. $TiO_2$ coating was more effective in decreasing formaldehyde under ultraviolet lamps than under ordinary lamps. When the irradiation of ultraviolet lamps gets longer, formaldehyde emission decreased.

• Proceedings of the Polymer Society of Korea Conference
• /
• 2006.10a
• /
• pp.354-354
• /
• 2006

Alginic acid-silica hydrogel films was prepared for testing as protective coating materials for PTFE OD membranes. Unprotected hydrophobic membranes are subject to wet-out when contacted by surface-active agents. Films were characterised using SEM, XRD, DSC, mechanical strength measurements, and water-swelling measurements. In OD trials using coated membranes, no wet-out occurred over the 15 h duration of three consecutive 5 h OD trials using orange oil-water mixtures. In the case of detergent solutions, the coating afforded protection to the membrane for 4-5 h. In a separate trial, no wet-out occurred when the coated side of the membrane was placed in contact with 1.2 wt % orange oil for 72 hours.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.21 no.1
• /
• pp.78-85
• /
• 1979

In order to obtain the basic data for designing optimum flat plate solar air heaters, which can be operated with relatively low temperature for drying farm products, 8 different treatment of solar air heaters were devised and tested for their heating performances and efficiencies. The results were analised and summarized as follows. 1. The primary factors, structure of air path (C), black coating materials (A) and bottom coating methods (B) showed very high significant effect of far above 1% level. With respect to the mutual multiplying effect of secondary factors, 1% level of significance was found with coating materials and methods (AB), and 5% level of significance was found with coating materials and air path structure (AC). 2. The heating performance of the air heaters with winding air path showed about twice those with straight air path. 3. The Korean black ink which is less expensive than dim oil paint showed 3-4% better heating efficiencies as the black coating material of flat plate solar air heaters. 4. The heating efficiencies of the solar air heaters whose bottoms were not black coated were 2-3% higher than those with black coated bottoms. 5. The highest heating efficiency of solar air heater among 8 different treatment was found in the plot of Korean black ink-bottom not coated-winding air path showing 29.0-34.5%