• Membrane and Water Treatment
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• v.5 no.2
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• pp.109-122
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• 2014

Polyvinylidene fluoride (PVDF) hollow fiber membrane is widely used for water treatment. However, the weak mechanical strength of PVDF limits its application. To enhance its tensile strength, a double-layer composite hollow fiber membrane, with PVDF and polyetherimide as the external and inner layers, respectively, was successfully prepared through phase inversion technique. The effects of additive content, air gap distance, N,N-dimethyl-acetamide content in the inner core liquid, and the temperature of external coagulation bath on the membrane structure, permeation flux, rejection, tensile strength, and porosity were determined. Experimental results showed that the optimum preparation conditions for the double-layer composite hollow fiber membrane were as follows: PEG-400 and PEG-600, 5 wt%; air gap distance, 10 cm; inner core liquid and the external coagulation bath should be water; and temperature of the external coagulation bath, 40 C. A single layer PVDF hollow fiber membrane (without PEI layer) was also prepared under optimum conditions. The double-layer composite membrane remarkably improved the tensile strength compared with the single-layer PVDF hollow fiber membrane. The permeation flux, rejection, and porosity were also slightly enhanced. High-tensile strength hollow fiber PVDF ultrafiltration membrane can be fabricated using the proposed technique.

• Membrane and Water Treatment
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• v.13 no.4
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• pp.173-181
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• 2022

Polyvinylidene fluoride (PVDF) flat sheet hydrophobic membranes were prepared using 16 wt% PVDF in Dimethyl acetamide (DMAc) by phase inversion technique for desalination application using Membrane Distillation (MD). In this work, the effect of coagulation mediums such as ethanol and water as well their synergistic behavior on the fabricated PVDF membrane morphology was studied using SEM. Moreover, other characteristics required for the membrane distillation applications namely porosity, hydrophobicity and tensile strength were measured using the gravimetric method, sessile drop method and universal testing machine respectively. It was observed that the membrane morphology paradigm shifted from the finger-like structure to the sponge-like structure on increasing the ethanol concentration in coagulant. The porosity of the fabricated membrane was under the required MD range and found to be 57.3% at 16 weight % of PVDF in DMAc solvent under a pure ethanol coagulant bath. Moreover, the top surface contact angle ranges from 85° to 115° on increasing the bath concentration from CBC 0 to CBC 100 at 16 weight % of PVDF in DMAc solvent.

• Journal of the Korean Ceramic Society
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• v.39 no.11
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• pp.1063-1068
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• 2002

Polyimide/silica(PI/silica) hybrid materials having physical or chemical bonds between the PI and silica network were prepared using sol-gel process through hydrolysis and polycondensation of tetraethoxysilane with the polyamic Acid(PAA) or end-capped PAA solution. PAA solution was synthesized by ring opening reaction of pyromellitic dianhydride and oxydianiline monomers in dimethyl acetamide solution. End-capped PAA solution was synthesized by the addition of 3-aminopropyltriethoxysilane in PAA solution. PI/silica hybrid samples were characterized by infrared spectroscopy, differential thermogravimetry, X-ray diffractometry, scanning electron microscopy, and tensile tester. It has been demonstrated that the properties of hybrid samples were affected by the silica content and the bond type between PI and silica.

• Analytical Science and Technology
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• v.27 no.6
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• pp.339-346
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• 2014

The author assessed the availability of urine reference material for proficiency test provided for laboratories in occupational health. N-methylacetamide is the biomarker of exposure to N,N-dimethyl acetamide, which was used as the substitute for hepatotoxic N,N-dimethylformamide (DMF). N-methylacetamide (NMAC) urine samples of 3 different levels covering the 0.2~2 times of the exposure limit were tested. Stability test up to 180 days (0, 7, 30, 60, 180 days) at 4 different temperatures (-60, -20, 5, $25^{\circ}C$) and homogeneity test were performed for these samples. New analytical condition by GC/MSD using SIM mode (m/z 58, 59) and DB-624 column was investigated for better selectivity, sensitivity and resolution. Urinary NMAC samples showed good homogeneity for 3 levels. These samples also showed good stability up to 180 days. The data of stability and homogeneity of urinary DMAC confirmed the basis of including this item into Korean proficiency test for occupational health laboratories since 2008.

• Macromolecular Research
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• v.11 no.4
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• pp.260-266
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• 2003

Ethylene vinyl acetate (EVA)/clay nanocomposites were synthesized by blending a solution of ethylene vinyl acetate copolymer containing 12% vinyl acetate abbreviated as EVA-12 in toluene and dispersion of dodecyl ammonium ion intercalated montmorillonite (l2Me-MMT) in N,N-dimethyl acetamide (DMAc). X-ray patterns of sodium montmorillonite ($Na^+$-MMT) and 12Me-MMT exhibited $d_{001}$ peak at $2{\theta}=7.4^{\circ}$ and $2{\theta}=5.6^{\circ}$ respectively; that is, the interlayer spacing of MMT increased by about 0.39 nm due to intercalation of dodecyl ammonium ions. The XRD trace of EVA showed no peak in the angular range of $3-10^{\circ}(2{\theta})$. In the XRD patterns of EVA/clay hybrids with clay content up to 6 wt% the basal reflection peak of 12Me-MMT was absent. leading to the formation of delaminated configuration of the composites. When the 12Me-MMT content was 8 wt% in the EVA-12 matrix, the hybrid revealed a peak at about $2{\theta}=5.6^{\circ}$, owing to the aggregation of aluminosilicate layers. Transmission electron microscopic photograph exhibited that an average size of 12-15 nm clay layers were randomly and homogeneously dispersed in the polymer matrix, which led to the formation of nanocomposite with delaminated configuration. The formation of delaminated nanocomposites was manifested through the enhancement of mechanical properties and thermal stability, e.g. tensile strength of an hybrid containing only 2 wt% 12Me-MMT was enhanced by about 36% as compared with neat EVA-12.

• Membrane Journal
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• v.11 no.3
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• pp.116-123
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• 2001

Polyimide-silica hybrid membranes were prepared and the effect of silica content on the structural properties and the gas transport properties was studied. The hybrid membranes were obtained by the sol-gel process starting from 1,2,4,5-benzenetetracarboxylic dianhydride(PMDA), 4,4`-diamino- diphenyl oxide(ODA) and tetraethoxysilane(TEOS) in N,N` dimethylacetatmide (DMAc) solvent. The structural characterizations of the membrane were performed by FT-IR, EDX, TGA and SEM. The gas permeation experiments with ${N_2}, {O_2}, {H_2}, {CO_2}and ${CH_4}$ were carried out at the temperature of $25^{\circ}C$ and in the range of pressure from 3atm to 7atm. the hybrid membranes showed higher thermal stability than PI membranes. The silica patricles were uniformly embedded in the polyimide matrix and the size of silica particles increased with increasing silica content. The permeability coefficients of ${N_2}, {O_2}, {H_2}, {CO_2}and ${CH_4}$ increased with increasing silica content but the diffusion coefficients might appear to be a result of a solubility enhancement. In spite of the permeability enhancement, an increase in the selectivities of ${H_2}/{N_2}, ${H_2}/{O_2} and ${H_2}/{CO_2} was observed.

• Journal of Food Hygiene and Safety
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• v.16 no.2
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• pp.125-132
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• 2001

The present study was conducted to investigate biological degradability of phosphamidon and profenfos. In the biodegradation test of two pesticides by the modified river die-away method from May 20 to July 29, 1999, the biodegradation rate was determined in Nakdong (A) and Kumho(B) River. The residual percentages of phosphamidon were 74.9%, 68.8% and 62.7% in control, A and B samples 7 days after applicaton, respectively. Biodegradation constants and half-lives of phosphamidon were 25.1%, 21.9% and 11.9% in control, A and B samples 7 days after application. Biodegradation constants and half-lives of profenofos were 0.0005 and 58.4 days in A, 0.0013 and 21.6 days in B, respectively. The biodegradation rates of phosphamidon and profenofos were higher in the Kumho River (B) than in the Nackdong River(A). The strains of microorganisms for the degradation of phosphamidon and profenofos were identified as Klebsiella pneumoniae, Aeromonas hydrophila and Acinetobacter calcoaceticus, all Gram-negative bacteria. In order to identify biodegradate products, the extracts of cultivates were analyzed by GC/MS. The mass spectra of biodegradate roducts of phosphamidon were at m/z 153 and 149, those of the profenofos were at m/z 208 and 240, respectively. It was suggested that the biodegradate metabolites of phosphamidon were O, O-dimethyl phosphate(DMP) and N, N-diethylchloroacetamide, those of profenofos were 4-bromo-2-chlorophenol and O-ethyl-S-propyl phosphate.

• Polymer(Korea)
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• v.29 no.2
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• pp.177-182
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• 2005

Montmorillonite (MMT) modified with siloxane diamine was reacted with a reactant obtained from 4,4'-diphenyl methane diisocyanate (MDI) and polyester type polyol, $Nippollan4010(\bar{M}_n2000)$. Finally, polyurethane (PU)/MMT composites were prepared by using 1,4-butane diol as a chain extender in $25\;wt\%$ solution of N,N-dimethyl acetamide (DMAc). It was expected that these nanocomposites had superior exfoliation property to that of MMT dispersed polyurethanes produced by simple mixing due to insertion of siloxane main chain to the silicate interlayer of MMT. Extent of reaction and formation of final products were analysed by using FT-IR spectroscopy. Dispersion into the PU and intercalation of MMT were identified by applying X-ray diffraction (XRD) and transmission electron microscopy (TEM). Tensile data were acquired by universal test machine (UTM). Thermal stability and variation of surface energy were characterized by thermal gravimetric analysis (TGA) method and measurement of contact angle on the synthesized composites, respectively. As the results the organo-MMT modified with siloxane diamine in the PU composites has an intercalated structure relatively well-expanded rather than a completely exfoliated structure. The tensile strengths and the moduli for the PU/organo-MMT composites were drastically enhanced in comparison to those of $PU/Na^+-MMT$ composites.

• Journal of the Korean Chemical Society
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• v.32 no.6
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• pp.557-566
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• 1988

The causes of failure in the deketalization of rigid ${\beta}$-aminoketals were separately investigated by examining the deketalization of 3 ketals, 2-ethylenedioxy-l-acenaphthenylamine (2), N-(2-ethylenedioxy-l-acenaphthenyl)acetamide(13) and trimethyl-2-ethylenedioxy-1-acenaphthenylammonium iodide(14), and by examining the deketalization of non-rigid ${\beta}$-aminoketal, 2-amino-l-ethylenedioxyacetophenone(19) and non-rigid aliphatic acetals, dimethylaminoformaldehyde dimethylacetal (20) and 2-aminoactaldehyde dimethyl acetal(21). While compounds 2 and 14 were not able to be hydrolyzed in the various acidic conditions 13 was easily deketalized. The result indicated the importance of electrostatic repulsion in the possible dicationic intermediates as a factor of failure in the deketalization. The observations of easy deketalization of compounds 19, 20 and 21 indicated that the structural characters of rigid $\beta-aminoketals$ are also important factors in the hydrolysis of ${\beta}$-aminoketals.

• Journal of Animal Science and Technology
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• v.54 no.2
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• pp.95-101
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• 2012

The objective of this study was to examine the effect of amides as a cryoprotectant for semen cryopreservation in Korean Jeju Black Bull. The semen was cryopreserved with extenders containing 5% dimethyl acetamide (DMA), 5% dimethyl formamide (DMF), 5% methyl formamide (MF) or 7% glycerol. Post-thawed sperm were evaluated for sperm motility, viability, acrosome integrity and membrane integrity. Post-thawed sperm motility was significantly higher (p<0.05) in glycerol and DMF ($64.00%{\pm}9.62$ and $59.00%{\pm}5.48$, respectively) than DMA and MF ($50.00%{\pm}3.24$ and $44.00%{\pm}4.18$, respectively). Sperm viability wassignificantly higher (p<0.05) in glycerol and DMF ($58.25%{\pm}7.35$ and $53.05%{\pm}3.77$, respectively) than others. However, for sperm motility and viability, there were no differences among glycerol and DMF. Also, swelling sperm ratio by hypo-osmetic selling test (HOST) was significantly increased (p<0.05) in glycerol and DMF treatments ($45.12%{\pm}25.08$ and $44.95%{\pm}8.58$, respectively). The percentage of capacitated sperm assessed by CTC staining, F pattern was lower (p<0.05) in DMF than others. B pattern was increased (p<0.05) in DMA, DMF and MF when compared with glycerol. AR pattern ratio was decreased (p<0.05) in glycerol and DMF when compared with DMA and MF. These results suggested that amides performed better and could be used as a cryoprotectant for semen freezing of Korean Jeju Black Bull.