• The Korean Journal of Rheology
• /
• v.10 no.4
• /
• pp.195-201
• /
• 1998

We have studied the rheological and electrical properties of two types of electrorheological (ER) fluids based on semi-conductive polymers (poly(p-phenylene) and polyaniline). These semi-conductive polymer-based suspensions showed a dramatic increase in viscosity on the application of the static electric field due to the large value of conductivity ratio between particle and medium. The dynamic yield stresses of these ER suspensions exhibited a quadratic dependence on electric field strength at low electric fields and a linear one for high fields. They showed a maximum and then decreased with increasing bulk conductivity of particles. These yield stress behaviors under the static electric field were found to be closely related to the dielectric properties, which is in accord with Maxwell-Wagner interfacial polarization induced by the conductivity effects. In order to achieve better understanding of interfacial polarization effect on ER response and to improve the stability of ER suspension, different kinds of surfactants were employed for controlling the ER activity as well as for enhancing the colloidal stability of suspensions.

• Applied Chemistry for Engineering
• /
• v.19 no.3
• /
• pp.351-356
• /
• 2008

Titania nanoparticles were prepared by controlled hydrolysis of titanium tetraisopropoxide (TTIP) in water-in-oil (W/O) and microemulsion stabilized with a nonionic surfactant, N P-10 (Polyoxyethylene Nonylphenol Ether: $C_9H_{19}C_6H_4(OCH_2CH_2)_{10}OH$)). The nanosized particles prepared in W/O microemulsion were characterized by FT-IR, TEM, XRD, TGA, and DTA. In addition, the photocatalytic degradation of p-nitrophenol has been studied by using a batch reactor in the presence of UV light in order to compare the photocatalytic activity of prepared nanosized titania. The nanaosized titania particles calcined at $300{\sim}600^{\circ}C$ showed an anatase structure, but it transformed to a rutile phase above $700^{\circ}C$ of calacination temperature. With an increase of $W_o$ ratio, the crystallite size increased but photocalytic activity decreased. The titania synthesized at $W_o=5$, R = 2, and calcined at $400{\sim}500^{\circ}C$ showed the highest activity on the photocatalytic degradation of p-nitrophenol.

• Journal of Conservation Science
• /
• v.35 no.2
• /
• pp.159-168
• /
• 2019

Plasticizers, which are added to plastics, can cause exudation, which means that the plasticizer comes out from surface of the plastics. This causes the surface of plastic artworks to become sticky, and this allows dust and pollutants to become attached to the surface. Therefore, in this study, the degradation characteristics and chemical cleaning methods of each type of plasticizer are evaluated using PVC specimens. To evaluate the degradation characteristics and chemical cleaning methods, microscopic observation, chromaticity and weight measurement, and FT-IR spectroscopy were performed. The results showed that PVCs containing different plasticizers have different degradation patterns. Especially, the PVC containing TOTM showed discoloration and exudation. In the evaluation of the chemical cleaning methods, ethyl alcohol and KOH solution showed good effects, but their stability was not good. Surfactant was found to have a good cleaning effect and stability as a cleaner for exudated plasticizers.

• Applied Chemistry for Engineering
• /
• v.16 no.5
• /
• pp.705-711
• /
• 2005

The reaction of lauric acid vinyl ester with n-butanol was established to give lauric acid butyl ester by subtilisin A-catalyzed transesterification in organic media containing nonionic surfactants. Pyridine has been used as an organic solvent since it provides higher yields than other organic solvents. However, because of stench of pyridine, compounds enzymatically synthesized in pyridine may be unsuitable as ingredients for foods and drugs. Hence, in order to select an organic solvent to replace pyridine, sugar esters were synthesized with the protease in various organic media. However, no solvent paralleled pyridine in yields. On the basis of this result, pyridine-based W/O microemulsions containing nonionic surfactants and water were used in enzymatic synthesis of the sugar ester, and when Tween 60, Brij 56, or 1-O-octyl-${\beta}$-D-glucopyranose was used for the W/O microemulsions, the yield was higher.

• Journal of the Korean Chemical Society
• /
• v.37 no.5
• /
• pp.496-502
• /
• 1993

Spectrophotometric determination of rare earth elements with MTB and the composition ratio were investigated in the presence of surfactants of cetylpyridinium chloride (CPC), Triton X-100, dodecyltrimethylammonium bromide (DTMAB) and cetyltrimethylammonium bromide (CTMAB) at pH 6.5. The colour development between MTB and rare earths in the presence of cationic surfactants was very stable and more sensitive than that in the absence of surfactants. The largest absorbance increase was provided by CPC, which was therefore chosen for determination of rare earth elements. REE-MTB-CPC complex has absorption maxima at 650 nm and obeys the Beer's law in the range of 0∼100 ng/ml. Molar absorptivity is $6.6{\sim}9.4{\times}10^4\;mol^{-1}l\;cm^{-1}$.

• Applied Chemistry for Engineering
• /
• v.10 no.7
• /
• pp.974-978
• /
• 1999

This study was concerned with the scouring effect of anionic surfactants, PAPE(sodium polyoxyethylene alkyl phosphoric ester) for cotton fibres. Sodium polyoxyethylene(7) nonylphenyl phosphoric ester(CPB-1) and the sodium polyoxyethylene(7) tridecyl phosphoric ester(CPB-2) were synthesized by the phosphoric esterification reaction from NP-7(polyoxyethylene(7) nonylphenyl ether) and TDA-7(polyoxyethylene(7) tridecyl ether) as scouring agents. Defoaming ability, fibre wetting time and absorbency rate of scouring agents were investigated. Being compared with the conventional scouring agent(Ultravon GP; Ciba-guyge Co.), CPB-1 and CPB-2 showed a higher defoaming ability in the cotton scouring process at room temperature. And CPB-1 has a higher wetting effect than the agents, CPB-2 or GP in distilled water bath but CPB-2 showed more scouring effect in 1.2 wt % NaOH solution bath.

• Journal of the Korean Chemical Society
• /
• v.50 no.5
• /
• pp.355-361
• /
• 2006

The critical micelle concentration (CMC) and the counterion binding constant (B) in a mixed micellar state of the sodium dodecylbenzenesulfonate (DBS) with the polyoxyethylene(23) lauryl ether (Brij 35) at 25oC in water and aqueous solutions of n-butanol (0.1M, 0.2M, and 0.3M) were determined as a function of a1 (the overall mole fraction of DBS) by the use of electric conductivity method and surface tensiometer method. Various thermodynamic parameters (Xi, i, Ci, aiM, , and Hmix) were calculated by means of the equations derived from the nonideal mixed micellar model. The effect of n-butanol on the micellization of the DBS/Brij 35 mixtures has been also studied by analyzing the measured and calculated thermodynamic parameters.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2009.11a
• /
• pp.23.1-23.1
• /
• 2009

ZnO is of great interest for various technological applications ranging from optoelectronics to chemical sensors because of its superior emission, electronic, and chemical properties. In addition, vertically well-aligned ZnO nanorods on large areas with good optical and structural properties are of special interest for the fabrication of electronic and optical nanodevices. To date, several approaches have been proposed for the growth of one-dimensional (1D) ZnO nanostructunres. Several groups have been reported the MOCVD growth of ZnO nanorods with no metal catalysts at $400^{\circ}C$, and fabricated a well-aligned ZnO nanorod array on a PLD prepared ZnO film by using a catalyst-free method. It has been suggested that the synthesis of ZnO nanowires using a template-less/surfactant-free aqueous method. However, despite being a well-established and cost-effective method of thin film deposition, the use of magnetrons puttering to grow ZnO nanorods has not been reported yet. Additionally,magnetron sputtering has the dvantage of producing highly oriented ZnO film sat a relatively low process temperature. Currently, more effort has been concentrated on the synthesis of 1D ZnO nanostructures doped with various metal elements (Al, In, Ga, etc.) to obtain nanostructures with high quality,improved emission properties, and high conductance in functional oxide semiconductors. Among these dopants, Ga-doped ZnO has demonstrated substantial advantages over Al-doped ZnO, including greater resistant to oxidation. Since the covalent bond length of Ga-O ($1.92\;{\AA}$) is nearly equal to that of Zn-O ($1.97\;{\AA}$), high electron mobility and low electrical resistivity are also expected in the Ga-doped ZnO. In this article, we report the successful growth of Ga-doped ZnO nanorods on c-Sapphire substrate without metal catalysts by magnetrons puttering and our investigations of their structural, optical, and field emission properties.

• Journal of the Korean Chemical Society
• /
• v.41 no.1
• /
• pp.12-17
• /
• 1997

The critical micelle concentrations(CMC*) and the counterion binding constants(B) in a micellar state of the mixed surfactant systems of sodium dodecylsulfate(SDS) with sodium dodecylbenzenesulfonate(DBS) at 25℃ in pure water and in aqueous solutions of n-butanol were determined as a function of α1 (the overall mole fraction of SDS) by the use of electric conductivity method. Various thermodynamic parameters(Xi, γi, Ci, aiM, β, ΔHmix and ΔGm0 for the micellization of SDS/DBS mixtures were calculated and analyzed by means of the equations derived from the nonideal mixed micelle model. The effect of n-butanol on the mixed micellization of SDS/DBS mixtures have been measured and analyzed by comparing the values of the thermodynamic parameters in pure water with those in aqueous solutions of n-butanol(0.1 M, 0.2 M, and 0.3 M).

• KSBB Journal
• /
• v.21 no.5
• /
• pp.394-400
• /
• 2006

When the papain, which is a sort of Cystein protease, is applied to the outer skin, it decomposes the protein which forms the peeled outer skin and speeds up metabolism. Therefore, it is one of the most important cosmetics compositic which keeps the function of skin normal. When the papain is used in cosmetics with surfactant, the activity of papain is reduced rapidly. In this study, the modified papain with extreme stability negative ionic environment was developed by directed evolution