• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.21 no.2
• /
• pp.634-643
• /
• 2020

In this study, the rheological and tribological properties of urea grease were studied according to the type and amount of polytetrafluoroethylene (PTFE) powders added to the urea grease, which is the most widely used among solid lubricants, to develop an optimal lubrication system. Urea grease was synthesized using 4,4'-methylenebis(phenyl isocyanate)(MDI), oleylamine, and cyclohexylamine, and PTFE powders prepared by dispersion or suspension polymerization process were then added. The basic rheological and tribological properties of the prepared greases were compared. The worked penetration numbers of urea grease decreased with increasing amount of PTFE powders, but both PTFE powders caused no significant changes in heat resistance and copper corrosion resistance. The shear viscosity increased with increasing PTFE powder content, and the dispersion-type PTFE powder was more effective in increasing the viscosity. In the value of the loss coefficient = 1, the shear stress was higher for the grease containing PTFE powders than the non-PTFE added grease, and the dispersion-type PTFE-added grease showed higher viscosity than the suspension-type PTFE-added grease. Finally, urea grease was found to have a low-performance improvement in terms of wear reduction effects by adding PTFE powders, but the load-bearing performance was up to 2.5 times higher for the dispersion-type PTFE and five times higher for the suspension-type PTFE.

• Membrane Journal
• /
• v.20 no.2
• /
• pp.142-150
• /
• 2010

A series of anion exchange composite membranes were prepared and characterized for electrodialysis processes used in the removal of nitrate nitrogen and ions in groundwater. The membranes were prepared as follows; first, fabric substrates were fully impregnated with monomer mixtures of vinylbenzylchloride (VBC), divinylbenzene (DVB), Styrene (ST) and $\alpha,\alpha$-Azobis(isobutyronitrile) (AIBN). Second, they were thermally polymerized to yield crosslinked poly (VBCST- DVB)/fabric composite membranes. Finally, the membranes were treated with trimethylamine (TMA) / acetone to give $-N^+(CH_3)_3^-$-containing poly(VBC-ST-DVB)/fabric membranes. The basic membrane properties such as ion exchange capacity (IEC), electric resistance and water content of the resulting membranes were measured as a function of VBC/DVB and TMA/Acetone content. As a result, the composite membranes showed lower electric resistance and higher IEC than commercial anion exchange membranes (AMX, Astom). Electrodialysis tests using the prepared membranes were carried out for the removal of various ions such as $NaNO_3$, $MgSO_4$ and NaF for 60 minutes. The results showed that the ions were removed below 1 mg/L within about 15 minutes which indicates that the anion exchange membranes prepared here could be applied to the electrodialysis process. as can be seen in the following that the ion conductivity values were almost no change after 15 minutes electrodialysis.

• Polymer(Korea)
• /
• v.39 no.2
• /
• pp.210-218
• /
• 2015

The reaction behavior of rigid polyurethane foams were studied on the effects of gelling catalysts of amine type, such as; dimethylcyclohexyl amine (DMCHA) and of potassium type, such as; potassium octoate (PO). Rigid polyurethane foams were provided with polymeric 4,4'-diphenylmethane diisocyanate, polyester polyol, silicone surfactant, blowing agent and a few gelling catalysts. As the contents of catalyst, DMCHA increased from 0 to 2.0 g, the reaction time decreased from ca. 330 to ca. 35 sec and due to the exothermic reaction, the maximum temperature increased from ca. 217 to ca. $234^{\circ}C$, respectively. As the contents of PO increased from 0 to 2.5 g, the reaction time decreased from ca. 79 to ca. 38 sec and the maximum temperature increased from ca. 182 to ca. $271^{\circ}C$, respectively. The kinetic parameters were calculated and the conversions were based on the temperature rising method of adiabatic process. As the content of DMCHA increased, the rate constant $k_0$ increased. But in the case of PO catalyst, $k_0$ did hardly depend upon its amount, and showed us similar reaction rate constants.

• Applied Chemistry for Engineering
• /
• v.23 no.2
• /
• pp.232-240
• /
• 2012

Bio-diesel (BD) is the mono alkyl esters of long chain fatty acids derived from renewable feed stocks like vegetable oils or animal fats. Bio-diesel shows poorer fuel properties than that of diesel fuel in a cold condition. For the diesel fuel, many cold flow improvers have been developed; however, since primary ingredients of bio-diesel are different from those of the diesel fuel, there is a limit to the cold flow improvement when the same cold flow improvers are added to bio diesel. In this study, to improve low temperature properties of bio-diesel, we developed a cold flow improver using an alkyl methacrylate monomer, prepared via ester reaction, and maleic anhydride and also conducted a ring opening reaction using amine. We characterized the products using $^1H-NMR$, FT-IR and GPC methods. In addition, the cold flow improvements of the products in Soybean BD and Palm BD in the concentration rage of 1000~10000 ppm were investigated. It was found that the addition of LMA2SMA6MA2-C8A in Soybean BD improved the pour point by $12.5\;^{\circ}C$.

• Journal of the Society of Cosmetic Scientists of Korea
• /
• v.41 no.4
• /
• pp.303-313
• /
• 2015

Titrated extract of Centella asiatica (TECA), which is poorly soluble in water is well known for wound healing and anti wrinkle agent. This study was conducted to find the optimum condition for the preparation of water in oil in water ($W_1/O/W_2$) emulsion containing TECA. Solubility of TECA were measured by UV spectrophotometer. 2.55 g of TECA was dissolved in solution composed of dipropylene glycol (40.0 g), ethanol (20.0 g), and water (10.0 g). Factors affecting stability of the emulsions ($W_1/O$, $W_1/O/W_2$) was investigated. The optimum conditions for the preparation of $W_1/O$ emulsion was composed of dipropylene glycol : ethanol : water : TECA in a weight ratio of 40.0 : 20.0 : 10.0 : 2.5 for water phase and squalane : cetyl PEG/PPG-10/1 dimethicone : cetearyl alcohol in a weight ratio of 22.5 : 4.0 : 2.5 for oil phase. The optimum conditions for the preparation of $W_1/O/W_2$ multiple emulsion was composed of water : $W_1/O$ emulsion : polysorbate 80 : carbomer : triethanolamine in a weight ratio of 55.8 : 40.0 : 4.0 : 0.1 : 0.1.

• Polymer(Korea)
• /
• v.33 no.2
• /
• pp.158-163
• /
• 2009

In this study, we synthesized a series of dendritic polystyrene-b-linear poly (t-butyl acrylate) copolymers with well-defined molecular architectures. The hydroxyl group located at the focal point of the second generation dendron bearing polystyrene ($M_n$ = 1000 g/mol) peripheries was converted into amine group via the following stepwise reactions: 1) tosylatoin, 2) azidation, and 3) reduction. On the other hand, the linear poly (t-butyl acrylate)s were prepared by an atom transfer radical polymerization (ATRP) of t-butyl acrylate where benzyl 2-bromopropanoate and Cu(I)Br/PMDETA were used as initiator and catalyst, respectively. To convert the end group of prepared poly (t-butyl acrylate) s into carboxylic acid, a debenzylation was performed using Pd/C catalyst under $H_2$ atmosphere. In the final step, dendritic-linear block copolymers were obtained through a simple amide coupling reaction mediated by 4-(dimethylamino) pyridine(DMAP) and N,N'-diisopropylcarbodiimide(DIPC). The resulting diblock copolymers were shown to have well-defined molecular weights and narrow molecular weight distributions as supported by $^1H$-NMR spectroscopy and gel permeation chromatography(GPC).

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.19 no.5
• /
• pp.459-468
• /
• 1986

This study was attempted to process low-sodium salt fermented small shrimp as substitutes for traditional high-sodium salt fermented one which has widely been favored and consumed in Korea. Low-salt fermented small shrimp was prepared with $4\%$ sodium chloride and $4\%$ potassium chloride, and various additives such as $0.5\%$ lactic acid, $6\%$ sorbitol and $4\%$ ethylalcohol extract of red pepper as preservatives and flavor enhancers. And the changes of taste compounds, volatile compounds and fatty acid composition in low-salt fermented small shrimp were analyzed and compared with those of conventional $20\%$ sodium salt fermented one during the fermentation of 120 days at $25{\pm}3^{\circ}C$. The most favorable taste for fermented small shrimp were reached at 60 days of fermentation. Judging from sensory evaluation, little difference of taste was detected between the low-salt fermented small shrimp and high-sodium salt fermented one. The principal taste compounds in fermented small shrimp were free amino acids, and betaine and nucleotides and their related compounds played an assistant role. The major amino acids in fermented small shrimp were glutamic acid, leucine, proline, glycine, lysine and aspartic acid. The major fatty acids in fermented small shrimp samples were 16:0, 20:5, 22:6, 16:1 and 18:1, and unsaturated fatty acids decreased slightly while saturated fatty acids increased during fermentation. At 60 days of fermentation 8 kinds of volatile fatty acids (acetic acid, propionic acid, isobutyric acid, butyric acid, isovaleric acid, valeric acid, isocarproic acid, carproic acid), 6 kinds of carbonyl compounds (ethanal, propanal, 2-methylpropanal, 3-methylbutanal, pentanal, 2-methylpentanal), and 3 kinds of volatile amines (methylamine, trimethylamine, isopropylamine) were identified.