• Applied Chemistry for Engineering
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• v.24 no.4
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• pp.370-374
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• 2013

The effects of zinc chloride addition on pore development of porous carbon nanofibers prepared by polyacrylonitrile (PAN)/ N,N'-dimethylformamide (DMF) (10 wt%) electrospinning were investigated. The change of morphological and structural modification by zinc chloride activation was investigated by a scanning electron microscopy (SEM) analysis. $N_2$ adsorption isotherm characteristics at 77 K were confirmed by Brunauer-Emmett-Teller (BET) and Horvath-Kawazoe (H-K) equations, and the curves showed the Type I mode in the International Union of Pore and Applied Chemistry (IUPAC) classification, indicating that lots of micropores exist in the sample. In addition, specific surface areas and total pore volumes of porous carbons prepared by the zinc chloride activation were determined as 600~980 $m^2/g$ and 0.24~0.40 $cm^3/g$, respectively. As experimental results, many holes or demolished structures were found on the fiber surfaces after the zinc chloride activation as confirmed by a SEM analysis. It was also observed that various pore sizes were found to be depended on the adding content of zinc chloride in PAN/DMF solution in this system.

• Applied Chemistry for Engineering
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• v.29 no.5
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• pp.630-634
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• 2018

The recovery of paraffin components contained in the fraction as a part of improving the quality for the fraction of waste plastics pyrolysis oil (WPPO) was investigated by batch cocurrent 4 stages equilibrium extraction. The fraction at a distilling temperature of $120-350^{\circ}C$ recovered from WPPO by the simple distillation and a little water-added dimethylformamide (DMF) solution were used as a raw material and solvent, respectively. As the number of equilibrium extraction (n) and the carbon number of paraffin component increased, the concentration of paraffin component contained in the raffinate increased. The concentrations of $C_{12}$, $C_{14}$, $C16$ and $C_{18}$ paraffin components present in the raffinate recovered at n = 4 were about 1.2, 1.5, 1.6 and 1.8 times higher than those of using the raw materials, respectively. Recovery rates (residue rates present in raffinate) of paraffin components rapidly decreased with increasing n, and increased sharply with increasing the carbon number. Furthermore, it was possible to predict the recovery rates at n = 1 - 4 for all paraffin components ($C_7-C_{24}$) contained in the raw material. The raffinate recovered through this study is expected to be used as a renewable energy.

• Applied Chemistry for Engineering
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• v.3 no.1
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• pp.130-137
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• 1992

The Graft copolymerization of acrylonitrile(AN) and styrene(ST) onto chloroprene rubber(CR) were carried out with benzoyl peroxide(BPO) as an initiator. The synthesized graft copolymer(ACS) was separated from polymeric mixture by the extraction with ethyl acetate and n-hexane, acetone and methanol, dimethylformamide(DMF) and methanol mixed solvent systems. The graft copolymer obtained, acrylonitrile-chloroprene-styrene(ACS) was identified by IR spectrophotometer. The effect of mole ratio of styrene to acrylonitrile, reaction time and temperature, initiator concentration, CR content and solvents on graft copolymerization were examined. It was observed that the grafting efficiency increased with [ST]/[AN] mole ratio and reaction time. The grafting efficiency increased with increasing initiator concentration and CR content. The maximum grafting efficiency was obtained when the mole ratio of [ST]/[AN] was 1.5 and reaction was made at 40hrs, and $70^{\circ}C$ using chloroform/toluene mixed solvent. The thermal properties, light resistance and flammability of ACS were compared with those of ABS and AES. It was found that flame retardancy of related polymers increased in the order ACS>ABS>AES. The thermal stability of ACS was greatly improved when compared with ABS or AES. Morphology of ACS was also investigated by using a transmisson electron microscope(TEM).

• Membrane Journal
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• v.18 no.1
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• pp.84-93
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• 2008

Poly(vinylidene fluoride) has received much attention in the last several years for the lithium secondary batteries. In this study, to enhance the porosity, PVdF was prepared by phase inversion method using as an additive, PEG (poly(ethylene glycol)), with N,N-dimethylformamid as a solvent. The pores are generated during the solvent and non-solvent exchange process in the coagulation bath filled with non-solvent (distilled water). The surface and cross-section of the membranes were observed with a scanning electron microscopy (SEM). The mechanical property of the membrane was determined by using an universal testing machine (UTM) and thermal property was verified by heat shrinkage. Uniformed sponge structure of PVdF-PEG membrane for the lithium secondary batteries was prepared with 10 wt% of PEG concentration in the PVdF-PEG solution. Porosity, elongation and tensile strengh of the membrane were 87%, 75.45%, and 275. 27 MPa respectively.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.11
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• pp.6000-6007
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• 2013

Cr(VI)-heterocyclic complex[Cr(VI)-isoquinoline] was synthesized by the reaction between of heterocyclic compound(isoquinoline) and chromium trioxide, and characterized by IR and ICP analysis. The oxidation of benzyl alcohol using Cr(VI)-isoquinoline in various solvents showed that the reactivity increased with the increase of the dielectric constant(${\varepsilon}$), in the order : cyclohexene$CH_3$, m-Br, m-$NO_2$). Electron- donating substituents accelerated the reaction, whereas electron acceptor groups retarded the reaction. The Hammett reaction constant(${\rho}$) was -0.69(308K). The observed experimental data have been ratiolized. The hydride ion transfer causes the prior formation of a chromate ester in the rate-determining step.

• Membrane Journal
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• v.23 no.2
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• pp.112-118
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• 2013

Polyancrylonitrile nanofiber membrane (PAM) was prepared by using the electrospinning method with a solution of polyacrylonitrile (PAN) in DMF. The pore-diameter of PAMs and the number of PAM's layer were controlled for the microfiltration (MF) application. In addition, in order to improve the water-flux, AN-PEGMA copolymers have been synthesized via free radical polymerization with poly (ethylene glycol) methyl ether methacrylate and azobisisobutylronitrile (AIBN), and then PAN/AN-PEGMA nanofiber membranes (PAM/APM) were prepared by electrospinning with a mixture of PAN (9 wt%) and AN-PEGMA (3 wt%) in DMF (88 wt%). The prepared membranes were investigated with FT-IR and E.D.S. It was confirmed through scanning electron microscope (SEM), porometer, and porosity analysis that the porous membrane with a uniform diameter (400~600 nm) and a uniform pore characteristics (0.5~0.4 ${\mu}m$) was prepared. For the MF application, water-flux measurements were investigated and then the result was shown that the water permeability value of PAM/APMs introduced AN-PEGMA copolymers was relatively higher than that of the PVdF commercial membrane. From these results, PAN nanofiber membranes prepared by electrospinning could be utilized as a MF membrane.

• Applied Chemistry for Engineering
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• v.18 no.6
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• pp.568-574
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• 2007

Crack-free dried gel monoliths of the composition $Li_2O1{\cdot}7Al_2O_3{\cdot}8.6SiO_2$ have been prepared as a precursor of transparent glass-ceramic by the hydrolysis and polycondensation of mixed metal alkoxides in solutions containing N,N-dimethylformamide as the drying control chemical additive, alcohols, and water. It was investigated that activation energy for gelation according to the variation of water concentration ranged from 13 to 14 kcal/mol. Only when the amount of water for gelation was 3 times higher than the stoichiometric amount, monolithic dry gels were successfully prepared after drying at $70{\sim}75^{\circ}C$ and at a rate of 0.1~0.3%/h. The specific surface area, the pore volume, the average pore diameters of dried gel at $180^{\circ}C$ were about $239.40m^2/g$, 0.001~0.03 mL/g, and $145.62{\AA}$, respectively. It showed that the dried monolithic gel had a porous body. The DTA curve had the first exothermic peak around $800^{\circ}C$ and the 2nd peak around $980^{\circ}C$, which may correspond to crystallization of the gel.

• Applied Chemistry for Engineering
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• v.19 no.4
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• pp.413-420
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• 2008

Over the past decade, there have been significant advancement in the field of electrospinning area. This study has focused on preparing yarn using polycarbonate (PC) nanofibers including modified multi-walled carbon nanotube (mMWNT) by solution electrospinning process using the mixture of solvents consisting of tretrahydronfuran (THF) and N,N-dimethylformamide (DMF). In order to enhance the dispersion, MWNT was chemically modified. TEM analysis for the prepared PC/mMWNT nanofibers reveals that mMWNT was well-dispersed into the PC nanofiber matrix. Also with increasing contents of mMWNT, thermal stability of PC/mMWNT nanofibers was improved than that of PC nanofibers. Moreover when 3 to 5 wt% of mMWNT was added, the nanofibers showed good electrical properties expecting antistatic effect, ranging 109.1~109.5 ${\Omega}$. It was confirmed that the multi-filament fibers using PC/mMWNT had $60{\sim}100{\mu}m$ in diameter and 4~5 cm in length.

• Applied Chemistry for Engineering
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• v.5 no.4
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• pp.616-623
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• 1994

Conductive Polypyrrole films have been synthesized by electrochemical method in nucleophilic solvent such as N, N-dimetylformamide(DMF), dimethylsulfoxide(DMSO). The effect of protic acid as supporting electrolyte to decrease the nucleophilicity of the solvent was studied. Cyclic voltammetry, I-t transients were carried out to investigate the electrodeposition of conductive polypyrrole film on platinum electrode. Three peaks of 0.65V, 0.85V, and 1.2V vs. $Ag/AgNO_3$ indicated oxidation of monomer, oxidation of pyrrole to the platinum electrode and decomposition of polypyrrole film, respectively. With the I-t transients, nucleation process was confirmed and from obtained linear fits of I vs.t2resembles the metal film formation, and 2.15-2.26 of n-value could be calculated. As concentration of pyrrole or prolic acid was increased, the conductivity of polypyrrole film increased linearly. Tensile strength and elongation were investigated for comparing the mechanical properties and also SEM was performed for morphology investigation.

• Applied Chemistry for Engineering
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• v.28 no.5
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• pp.597-600
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• 2017

$(C_{10}H_8N_2H)_2Cr_2O_7$ was synthesized by reacting 4,4'-bipyridine and chromium (VI) trioxide. The structure of the product was characterized with FT-IR (infrared spectroscopy) and elemental analysis. The oxidation of benzyl alcohol using $(C_{10}H_8N_2H)_2Cr_2O_7$ in various solvents showed that the reactivity increased with the increase of the solvent dielectric constant, in the order of DMF (N,N'-dimethylformamide) > acetone > chloroform > cyclohexane. In the presence of DMF, an acidic catalyst such as $H_2SO_4$ $(C_{10}H_8N_2H)_2Cr_2O_7$ oxidized benzyl alcohol (H) and its derivatives ($p-OCH_3$, $m-CH_3$, $m-OCH_3$, m-Cl, $m-NO_2$). Electron donating substituents accelerated the reaction rate, whereas electron acceptor groups retarded the reaction rate. Hammett reaction constant (${\rho}$) was -0.70 (308 K). The observed experimental data were used to rationalize the hydride ion transfer in the rate determining step.