• Clean Technology
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• v.14 no.3
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• pp.193-203
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• 2008

A surfactant is used to assist the effect of cleaning, dispersibility and adhesion during leather manufacturing process. Existing surfactant for that process includes many hydrophilic groups that may cause problem such as stain, bad water resistance and poor durability, etc. It is potential problem to make high-performance property for future leather market. In this study, we have synthesized the fluorinated surfactant of which property decreases surface tension, increases dispersion, cleaning effect and the better chrome absorption by the high bond energy of C-F to complement weakness that the present alkyl derivative surfactants have. Using fluorinated surfactant, we can confirm that dispersion is increased, chrome absorption ratio is augmented with high osmosis and coherence, chrome content in the tanning waste water is reduced, BOD and COD contents are diminished and physical characteristics are improved.

• Journal of the Korean Wood Science and Technology
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• v.38 no.4
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• pp.316-322
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• 2010

The research attempted to develop a wood adhesive based on waste cooking oil, using ozonification technology for the chemical structure modification. The waste cooking oil (WCO) was reacted with $O_3$ for different times; 1 h, 2 h, and 3 h. The chemical structure modifications of the ozonized WCOs were examined by Fourier transform Infrared (FT-IR) spectrum. The FT-IR spectrum of WCO had an absorbance peak at 3,010 $cm^{-1}$ that was the characteristic peak of the unsaturated double bonds. As ozone treatment time increased, the peak of the double bond was disappeared and carboxyl peak appeared at 1,700 $cm^{-1}$. Especially, the double bond of 3 hrs-ozonized WCO was vanished almost. In results of the dry bonding strengths of the 3 hrs-ozonized WCO mixed with polymeric methylene diphenyl diisocyanate (pMDI) were the strengths of weight ratio of 3hrs-ozonized WCO : pMDI, 1 : 0.5, 8.08 kgf/$cm^2$, 1 : 0.75, 9.53 kgf/$cm^2$ 1 : 1, 44.16 kgf/$cm^2$, 1 : 2, 58.08 kgf/$cm^2$, 1 : 3, 61.41 kgf/$cm^2$, and 1 : 4, 46.95 kgf/$cm^2$. Therefore, it was found that the optimum equivalent ratio was formed at the ratio of 1 : 2 or 1 : 3. Under wetting the bonding strength of 1 : 3 ratio was appeared higher than that of 1 : 2 ratio, while the results obtained from hot-water and cyclic boiling shear test were similar.

• Korean Chemical Engineering Research
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• v.54 no.4
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• pp.519-526
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• 2016

Biomass derived jet fuel is proven as a potential alternative for the currently used fossil oriented energy. The efficient production of jet fuel precursor with special molecular structure is prerequisite in producing biomass derived jet fuel. We synthesized a new jet fuel precursor containing branched $C_{15}$ framework by aldol condensation of furfural (FA) and ethyl levulinate (EL), where the latter of two could be easily produced from lignocellulose by acid catalyzed processes. The highest yield of 56% for target jet fuel precursor could be obtained at the optimal reaction condition (molar ratio of FA/EL of 2, 323 K, 50 min) by using KOH as catalyst. The chemical structure of $C_{15}$ precursor was specified as (3E, 5E)-6-(furan-2-yl)-3-(furan-2-ylmethylene)-4-oxohex-5-enoic acid ($F_2E$). For stabilization, this yellowish solid precursor was hydrogenated at low temperature to obtain C=C bonds saturated product, and the chemical structure was proposed as 4-oxo-6-(tetrahydrofuran-2-yl)-3-(tetrahydrofuran-2-yl)-methyl hexanoic acid ($H-F_2E$). The successful synthesis of the new jet fuel precursors showed the significance that branched jet fuel could be potentially produced from biomass derived FA and EL via fewer steps.

• Composites Research
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• v.30 no.6
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• pp.371-378
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• 2017

In this study, hygroelastic behavior of thermosetting epoxy is predicted by molecular dynamics simulations. Since consistent exposures to humid environments lead to macroscopic degradation of polymer composite, computational simulation study of the hygroscopically aged epoxy cell is essential for long-time durability. Therefore, we modeled amorphous epoxy molecular unit cell structures at a crosslinking ratio of 30, 90% and with the moisture weight fraction of 0, 4 wt% respectively. Diglycidyl ether of bisphenol F (EPON862) and triethylenetetramine (TETA) are chosen as resin and curing agent respectively. Incorporating equilibrium and non-equilibrium ensemble simulation with a classical interatomic potential, various hygroelastic properties including diffusion coefficient of water, coefficient of moisture expansion (CME), stress-strain curve and elastic modulus are predicted. To establish the structural property relationship of pure epoxy, free volume and internal non-bond potential energy of epoxy are examined.

• Journal of the Korean Wood Science and Technology
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• v.32 no.1
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• pp.67-72
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• 2004

Wood/polyethylene panels were manufactured from Populus alba × glandulosa particles and low density polyethylene particles at three mixing rates, 50:50, 60:40, and 70:30. A total of 15 wood/polyethylene panels was made at 145℃ and 5 minutes hot-press time. Wood/polyethylene panels were tested for internal bond, bending, and dimensional stabilities such as thickness swell and water absorption. Panel performance data were analyzed using the SAS programing package. The test results of the wood/polyethylene panels showed that as the polyethylene mixing rates were increased, the panel property values increased. Based on panels' dimensional stabilities, the optimum wood/polyethylene mixing ratio appeared to be 60:40.

• Journal of the Korea Concrete Institute
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• v.25 no.4
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• pp.439-446
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• 2013

The objective of this study is to evaluate the workability and various mechanical properties of heavyweight magnetite concrete and examine the reliability of the design equations specified in code provisions. The main parameters investigated were the water-to-cement ratio and substitution level of normal-weight coarse aggregate (granite) for magnetite. The oven-dried unit weight of concrete tested ranged between 2446 and $3426kg/m^3$. The measured mechanical properties included compressive strength development, stress-strain curve, splitting tensile strength, moduli of elasticity and rupture, and bond stress-slip relationship of concrete. Test results revealed that the initial slump of heavyweight magnetite concrete increased as the substitution level of normal-weight coarse aggregate increases. The substitution level of normal-weight coarse aggregate had little influence on the compressive strength and tensile resistance capacity of heavyweight concrete, while it significantly affected the modulus of elasticity and stress-strain curves of such concrete. The design equations of ACI 349-06 and CEB-FIP provisions mostly conservatively predicted the mechanical properties of heavyweight magnetite concrete, but the empirical equations for modulus of elasticity and splitting tensile strength need to be modified considering the unit weight of concrete.

• Applied Chemistry for Engineering
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• v.4 no.3
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• pp.627-636
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• 1993

Anionic acrylic resin utilizing macromer(TBMA-g-MMA) copolymer was synthesized by preparing (TBMA) macromer using anionic living polymerization, followed by graft copolymerization with MMA macromer. To control the anionic site content in graft copolymer, the relative composition((TBMA) macromer/MMA ratio) of the graft copolymer was controlled at 7/3, 10/90, 15/85, 20/80, 30/70, 40/60, 50/50 in weight content. In the course of anionic living polymerization of(TBMA) macromer, broad molecular weight distribution (1.4~1.5) was obtained by using n-butyllithium-diphenyethylene initiatior system at $-78^{\circ}C$. To introduce the double bond at the end of chain in termination step, methacryloyl chloride was reacted after insertion of benzaldehyde as capping material. Moreover, TBMA parts in graft copolymer were hydrolyzed in the presence of p-toluenesulfonic acid catalyst, and neutralization of graft copolymer with triethylamine was granted acrylic resin to anionic site. Molecular weight and molecular weight distribution of(TBMA) macromer were determined by GPC, and the hydrolysis of TBMA with neutralization of acrylic resin were determined by IR and NMR. From water dispersion and stability point of view, stable dispersion state appeared at low molecular weight(TBMA) macromer with a small TBMA content as a result of scrutiny about the relation to TBMA content and branch length for(TBMA) macromer molecular weight in graft copolymer.

• Restorative Dentistry and Endodontics
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• v.20 no.2
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• pp.463-486
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• 1995

The effect of moistening and air-drying of acid-conditioned dentin before priming on the formation of resin-dentin hybrid zone was investigated, Freshly extracted human molars were used and divided at random into 5 groups, Groups 1 - 3 consisted of specimens conditioned with 10 % phosphoric acid for 20 seconds; Group 1 served as a control in which the conditioned dentin was simply blot-dried with a damp facial tissue; Group 2 was air dried for 30 seconds ; Group 3 was air dried for 30 seconds and immediately remoistened for 10 seconds with air-water syringe. and then the specimen was blot-dried with a damp facial tissue. Groups 4-5 were not acid conditioned ; In group 4, the smear layer on the dentin was blot dried before primer placement; Group 5 was air dried only for 30 seconds, The acetone-based primer and bonding agent of All Bond 2 (Bisco. Inc., USA) and composite resin (Z-100, 3M Dental products, USA) were applied for acid conditioned dentin and non-conditioned dentin. The morphologic ultrastructure of resin-dentin hybrid zone was examined by the use of SEM and TEM. and the existence of inorganic material and analysis of Ca/P weight-percent ratio in the resin-dentin hybrid zone were revealed by the EDAX, The results were as follows : 1. In the moistened specimens from acid-conditioned groups, the resin penetrated about 3-$4{\mu}m$ into dentin and the denatured collagen smear layer was not present at the surface. The resin tag was formed to a thickeness of 3-$4{\mu}m$ at the upper part of dentinal tubule and compactively connected to each other by means of many lateral branching. 2. In the air-dried specimens from acid-conditioned groups, the resin penetrated about 2.0-$2.5\;{\mu}m$ into dentin and an upper thin black layer to a thickness of 30-35nm was identified between adhesive resin and demineralized collagen layer. The resin tag to have a diameter of $2.5{\mu}m$ was formed at the upper part of dentinal tubule. However the funnel shape of the tag was not notable compared to the moistened specimens. 3. In the remoistened specimens from acid conditioned groups, the resin penetrated about 2.0-$2.5{\mu}m$ into dentin and an upper black layer was not present. The resin tag at the upper part of dentinal tubule was formed less than $2{\mu}m$ and was weakly connected to each other by means of few lateral branching. 4. In the non-conditioned groups, the smear layer was formed to a thickness of $0.5{\mu}m$ at dentin surface. However, the resin-dentin hybrid zone was not identified by TEM. The evidence of resin penetration into intertubular and intratubular dentin did not show. 5. All the acid-conditioned groups showed that the detected calcium and phosphorus weight percent ratios at the $2{\mu}m$ upper portion from the resin-dentin interface into the resin were much higher than that at the $2{\mu}m$ lower portion from the resin-dentin interface to dentin. (P<0.01).