• Journal of the Society of Cosmetic Scientists of Korea
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• v.45 no.3
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• pp.237-254
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• 2019

This study is focused on the effect of sodium stearate, which is a hydrophilic gelling agent affecting on the hardness of O/W solid sunscreen cosmetic. The sunscreen of the O/W (oil in water) type is stable, good in use, and relatively easier to stabilize than the sunscreen of the W/O (water in oil) type. Methods for increasing the stability by using emulsifiers, electrolytes, and wax or oil have been studied for solid sunscreen. This study was intended to develop a solid sunscreen stabilized by increasing the hardness using sodium stearate as an O/W type containing more than 40% moisture. Response surface methodology (RSM) was used to analyze the factors affecting the hardness of cosmetics, and sodium stearate, polyol and oil were used for each factor. The hardness and the reaction value was measured using a rheometer. As a result, sodium stearate showed a meaningful value (p < 0.05) among the three factors affecting hardness. In addition, the use of sodium stearate as a hydrophilic gelling agent increased the usability and stability of the solid sunscreen.

• Korean Chemical Engineering Research
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• v.60 no.2
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• pp.282-288
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• 2022

Facial masks have become indispensable in daily life to prevent infection and spread through respiratory droplets in the era of the corona pandemic. To understand how effective two different types of masks (i.e., KF-94 mask and dental mask) are in blocking respiratory droplets, i) we preferentially analyze wettability characteristics (e.g., contact angle and contact angle hysteresis) of filters consisting of each mask, and ii) subsequently observe the dynamic behaviors of microdroplets impacting at high velocities on the filter surfaces. Different wetting properties (i.e., hydrophobicity and hydrophilicity) are found to exhibit depending on the constituent materials and pore sizes of each filter. In addition, the pneumatic conditions for stably and uniformly dispensing microdroplets with a certain volume and impacting behaviors associated with the impacting velocity and filter type change are systematically explored. Three distinctive dynamics (i.e., no penetration, capture, and penetration) after droplet impacting are observed depending on the type of filter constituting the masks and droplet impact velocity. The present experimental results not only provide very useful information in designing of face masks for prevention of transmission of infectious respiratory diseases, but also are helpful for academic researches on droplet impacts on various porous surfaces.

• Korean Chemical Engineering Research
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• v.43 no.1
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• pp.53-59
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• 2005

In this study, the supercritical electroplating was investigated by forming macroemulsion of electroplating solution using surfactant in supercritical $CO_2$. The fluorinated analogous AOT surfactant, sodium salt of bis (2,2,3,3,4,4,5,5-octafluoro-1-pentanol) sulfosuccinate which has both '$CO_2$ philic' chains and 'hydrophilic' head group was used as a surfactant, and Ni plate and Cu plate were used as the anode and the cathode, respectively. Electroplating was carried out in the conventional method and the supercritical macroemulsion and both results were compared. The supercritical electroplating was carried out in various concentration of surfactant such as 2, 4, 7 wt%, the volume ratio of Ni-plating solution to $CO_2$ was varied in the range of 10-70 vol%, and propane was used as a supercritical fluid instead of $CO_2$. According to the experimental results, the plated surface of Ni on Cu plate performed in supercritical macroemulsion was better than that, in conventional state. In the image of Ni surface plated on Cu plate in supercritical state, there were fewer pin-holes and pits comparing with that in the conventional process. The current and conductivity was increased as the volume ratio of Ni-plating solution to $CO_2$ was increased and the current and the amount of Ni plated on Cu plate were decreased as the concentration of surfactant become higher. In addition, in case of the continuous phase, using $CO_2$ was more effective than using $CO_2$.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.6
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• pp.9-16
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• 2000

In order to achieve stiction-free polysilicon surfaces, we have suggested a new class of chemical coating precursors and confirmed their excellent characteristics. The strategy is to adopt dialkyldichlorosilanes (DDS, $R2SiCl_2$) instead of monoalkyltrichlorosilanes (MTS, $RSiCl_3$) such as octadecyltrichlorosilane (OTS) or 1H,1H2H,2H-perfluorodecyltrichlorosilane (FDTS). Dichlorodimethylsilane (DDMS, $(CH_3)2SiCl_2$) in this study is commercially available DDS with two short chains. DDMS in aprotic media spontaneously deposits on the hydrophilic polysilicon surface, which is completely changed to hydrophobic one. When polysilicon surface is exposed to DDMS solution at room temperature, anti-stiction property and hydrophobicity are clearly comparable to FDTS. DDMS is even superior to MTS in reliability and easy handling, which provides high yield. Since interactions among precursor molecules are reduced, conglomeration both in homogeneous solution and on surface can be effectively avoided. Even the cantilevers of 3 mm in length can be protected successfully from the stiction and the final quality of the modified surfaces is much less dependent on temperature. And no difference was found between the processes in ambient environment and in dry box. In addition, DDMS has advantages of remarkably reduced process time and low cost.

• Applied Chemistry for Engineering
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• v.3 no.4
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• pp.730-738
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• 1992

Filtration characteristics according to membrane materials were studied In the ultrafiltration of anaerobic digestion broth as a post treatment method. A series of resistances for different membranes were quantitatively assessed on the basis of the resistance-in-series model. Flux behavior observed with the digestion broth was irrelevant to initial water permeabilities of each membrane. The fluoro polymer membrane showed the most significant improvement of flux with increase of cross-flow velocity, which suggests that the cake layer formed on this membrane is more weakly attached to the membrane surface than those on the other membranes. Flux reduction during longtime running was attrib-used to the polarization layer resistance ($R_p$) as well as the fouling layer resistance($R_f$). Continuous increase of $R_p$ may reflect the variation in the characteristics of cake layers, which could result from size, shape, and structure changes due to lysis and growth of biomass. Hydrophilic cellulosic membrane had a much lower fouling tendency than hydrophobic polysulfone membrane. The depressurization method induced a small increase in flux of $5-10L/m^2/h$. During washing and cleaning, filtrability of each membrane was rapidly recovered within 15 minutes until a stationary value was reached.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.2
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• pp.120-129
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• 2023

Marine structures are subject to damage not only from sea salt but also from the adhesion of marine microorganisms and suspended particles, which cause additional damages. In order to prevent this, periodic coating is employed in the case of vessels to maintain the necessary performance. However, it is true that periodic coating is difficult for concrete or steel support structures, and there is a risk of marine environmental pollution. In this study, authors developed an anti-fouling coating agent using eco-friendly materials that possess hydrophilic cellulose nanofibers and AKD(alkyl ketene dimer). To achieve a homogeneous mixture, the content of cellulose nanofibers was fixed at 1 %, and AKD, distilled water, and waste glass were mixed using a digital mixer and homogenizer. The contact angle of the prepared coated surface was observed to be over 130°, indicating sufficient performance even in a water droplet flow test with a 15° slope, suggesting self-cleaning capability. Furthermore, through the analysis of viscosity characteristics at different temperatures, it was confirmed that the application is feasible at room temperature. Microstructure analysis also verified that the coating agent is uniformly applied to the concrete surface.

• The Korean Journal of Pesticide Science
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• v.6 no.1
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• pp.16-24
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• 2002

Research trends in the measurement of foliar uptake of pesticides and the recently proposed action mechanism of the surfactant-induced uptake of pesticides were reviewed with the related reports and studies. Major techniques used in those fields are bioassay, radiotracer techniques with leaves or cuticular membrane. Recently, a new method using Congo Red as a tracer was proposed. The limiting factor in the pesticides uptake into leaves is the waxy layer which consists of the epicuticular and cuticular wax. Physico-chemical parameters such as molar volume, water solubility and partition coefficient of pesticides have limited influences on the pesticide uptake into leaves. Polydisperse ethoxylated fatty alcohol surfactants are well known as the good activator for many pesticides. It is now generally agreed that uptake activation is not related to the intrinsic surface active properties of surfactants such as surface activity, solvent property, humectancy and critical micelle concentration. Recent studies using ESR-spectroscopy revealed that the surfactants have an unspecific plasticising effect on the molecular structure of the wax and cuticular matrix, leading to increased mobilities of pesticides. Penetration of surfactants into waxy layer altered the pesticide mobility in wax and the partition coefficient of pesticide, and then the pesticides penetration into leaves was enhanced temporally. The enhancing effect of surfactant could be significantly different depending on the carbon number of aliphatic moiety and the number of ethoxy group in polyoxyethylene chain of surfactants. It is suggested that the rate of penetration of surfactants should have a significant relationship with the rate of penetration of pesticides.

• The Journal of Korean Academy of Prosthodontics
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• v.33 no.3
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• pp.569-583
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• 1995

Disinfection of dental impressions are necessary due to contamination with patient’s saliva and blood, which is a potential for cross-infection. The purpose of this study was to evaluate the effects of disinfection of four hydrophilic rubber impression materials with three disinfecting solutions, on the dimensional stability and surface hardness of improved stone casts. Three hydrophilic vinyl polysiloxane impression materials(Express, Reprosil, Exafine) and one polyether impression material(Impregum-F) were mixed according to the manufacturer’s directions and impressions were made on a ADA specification No. 19 stainless-steeldie. On removal of the impressions, each impression was immersed in one of the disinfectants(Banicide, Potadine, Clorox) for 10 minutes. After disinfection, type IV improved stone. casts were poured. On this cast, the linear dimension and surface hardness were measuredusing a Measurescope(Nikon, Japan) and a Barcol hardness tester(Barber, Colman Co U. S. A). The results were as follows : 1. The improved stone casts from disinfected Reprosil and Impregum-F impression material did not show dimensional changes(P>0.01). Those from disinfected Express and Exafine impression material showed dimensional changes(P<0.01). The amount of shrinkage was not clinically significant. 2. The improved stone casts from disinfected Express impression material did not exhibit changes in surface hardness(P>0.01), but those from disinfected Reprosil, Exafine, Imp regnum-F impression material showed changes in surface hardness(P<0.01). 3. The dimensinal stability and surface hardness of the improved stone casts were satisfactory using Banicide on Express, all disinfectants used in this study on Reprosil, Potadin and Clorox on Exafine, Banicide and Clorox on Impregum-F. According to these results, immersion disinfection of hydrophilic rubber impression mate rials did not adversely affect the resultant casts. Nevertheless compatibility tests of impression materials and disinfectants should be done when disinfecting impressions.

• Journal of the Korean Vacuum Society
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• v.8 no.3B
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• pp.262-268
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• 1999

Polycarbonate (PC) and Polymethylmethacrylate (PMMA) surface was modified by ion assisted reaction (IAR) technique to obtain the hydrophilic functional groups and improve the wettability. In conditions of ion assisted reaction, ion beam energy was changed from 500 to 1500eV, and ion dose and oxygen gas blown rate were fixed $1\times10^{16}$ ions/$\textrm{cm}^2$ and 4ml/min, respectively. Wetting angle of water on PC and PMMA surface modified by $Ar^+$ ion without blowing oxygen at 4ml/mon showed $5^{\circ}$ and $10^{\circ}$. Changes of wetting angle with oxygen gas and $Ar^+$ ion irradiation were explained by considering formation of hydrophilic group due to a reaction between irradiated polymer chain by energetic ion irradiation and blown oxygen gas. X-ray photoelectron spectroscopy analysis shows that hydrophilic groups such as -C-O, -(C=O)- and -(C=O)-O- are formed on the surface of polymer by chemical interaction. The polymer surface modification using ion assisted reaction only changed the surface physical properties and sept the bulk properties. In comparison with other modification methods, the surface modification by IAR treatment was chemically stable and enhanced the adhesion between metal and polymer surface. The applications of various kinds of polymer surface modification methods, metal and polymer surface. The applications of various kinds of polymer surface modification could be appled to the new materials about hydrophilic surface properties by IAR treatment. The adhesion between metal film and polymer measured by Scotch tape test whether the hydrophilic surfaces could improve the adhesion strength or not.

• Membrane Journal
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• v.23 no.3
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• pp.204-210
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• 2013

Recently, many applications with grapheneoxide (GO) have been reported. But GO membrane for water treatment has not been developed. In this study we prepared polyvinylidene difluoride (PVdF) nanofiber/GO hybrid membrane (FG) for the microfiltration application. The PVdF substrate membrane was prepared by using the electrospinning method with a solution of PVdF in N,N-dimethylacetamide (DMAc) and acetone. GO sheets used in this study were prepared by modified Hummer's method. The PVdF/GO hybrid membrane was finally prepared by spraying the GO solution dispersed in ethanol on the PVdF nanofiber. The successfully prepared FG was thoroughly examined by SEM, Raman, contact angle, porometer and UTM, and water-flux was measured with designed cell (Dead-End Cell). From the contact angle results, it was found that the surface of FG membrane was reformed by hydrophilic property and the water permeability was increased about 2.5 times than that of the nascent PVdF membrane, indicating the possible alternative of the commercial MF membrane.