• Journal of the Korean Institute of Gas
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• v.16 no.6
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• pp.115-122
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• 2012

Polyurethane foams were synthesized with different contents and kinds of catalysts to know change of properties under various NCO index. UTM(universal testing machine), DSC(differential scanning calorimetry), SEM(scanning electron microscope) and FT-IR(Fourier transform spectroscopy) were used for studying the PUF's physical properties change. Compressive strength of PUF increased with increasing contents of catalyst. Glass transition temperature(Tg) and compressive strength of PUF using PC-8 and 33LV catalyst, increased with increasing NCO index at the aging. According to the results of Infrared spectral analysis, reduction of NCO peak was found in gelling catalyst, because unreacted NCO reacted with polyurethane. Although Tg and compressive strength of PUF using TMR-2, unchanged with increasing NCO index at the aging, because trimerization of isocyanate.

• Bulletin of the Korean Chemical Society
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• v.31 no.7
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• pp.1988-1992
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• 2010

4-Amino-1,2,4-triazole copper complex (4-ATzCu) was synthesized, and its thermal behaviors, nonisothermal decomposition reaction kinetics were studied by DSC and TG-DTG techniques. The thermal decomposition reaction kinetic equation was obtained as: $d\alpha$ / dt =$10^{22.01}$ (1-$\alpha$)[-ln(1-$\alpha$)]$^{1/3}$ exp($-2.75\times10^4$ /T). The standard mole specific heat capacity of the complex was determined and the standard molar heat capacity is 305.66 $J{\cdot}mol^{-1}{\cdot}K^{-1}$ at 298.15 K. The entropy of activation $({\Delta}S^{\neq})$, enthalpy of activation $({\Delta}H^{\neq})$, and Gibbs free energy of activation $({\Delta}G^{\neq})$ are calculated as 171.88 $J{\cdot}mol^{-1}{\cdot}K^{-1}$ 225.81 $kJ{\cdot}mol^{-1}$ and 141.18 $kJ{\cdot}mol^{-1}$, and the adiabatic time-to-explosion of the complex was obtained as 389.20 s.

• Applied Chemistry for Engineering
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• v.4 no.4
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• pp.814-822
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• 1993

To improve the solubility and adhesion strength of diamine-quinone polymers, urethane group was introduced into the polymer backbone. Urethane group containing polymeric diamines(UDA) were prepared firstly by the decarboxylation of the NCO group in NCO terminated prepolymer obtained from the reaction of MDI and 1.6-hexandiol. The reaction mole ratio of NCO/OH was changed from 1.2 to 2.1 to increase the molecular weight of diamine. From the addition reaction of UDA and p-benzoquinone in THF or DMSO solvent, five kinds of urethane group containing diamine/quinone polymers(PUAQ) were prepared according to the diamine used. IR, NMR, UV-visible spectroscopy and GPC were used to characterize the molecular structure and molecular weight of UDAs and PUAQs. Thermal analysis of polymer by DSC and TGA were carried out according to the molecular weight differency. Also solubility test of UDA and PUAQ with 10 different solvents were carried out to predict the coacting property of the polymers.

• Culinary science and hospitality research
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• v.7 no.3
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• pp.263-273
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• 2001

This study was to investigate the effect of 5~20% soybean flout(SBF) and/or 0.5~5% calcium on the quality of bread. pH of bread was increased with increasing an amount of SBF and calcium. pH of bread was higher than that of dough. The scores of specific volume and sensory evaluation for the bread quality were shown higher and increased its relative volume in the group of added both of 5~15%, SBF and 0.5~2%, calcium Endothermic peak for a thermal property of bread was increased with increasing the storage time of bread. The bread staling was progressed rapidly in control and calcium added groups only. with increasing an amount of SBF, L values of bread was decreased, but a and b values were increased. However, L, a and b values were shown no difference in the group of calcium added only. Therefore, the optimum blending ratios of SBF and calcium for the quality of bread were 5~10%, SBF and 0.5~1% calcium, respectively.

• Korean journal of food and cookery science
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• v.13 no.5
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• pp.627-634
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• 1997

The purpose of this study is to examine the effect of protein content on the physicochemical properties, gelatinized characteristics and textural properties of cowpea precipitate gels stored for 24 hrs and 48 hrs at room temperature. The contents of protein, total fat, and ash ranged from 0.35%∼1.38%, 0.54%∼0.64%, and 0.21%∼0.25%, respectively. The X-ray diffraction patterns were all Ca-type, showing no difference according to the protein content. Protein content did not make any difference in the blue values of cowpea precipitate. The blue value of cowpea precipitate powder as protein content was decreased. The water-binding capacity of cowpea precipitate powder increased as the protein content increased. Swelling power and solubility of cowpea precipitate powder increased as protein content decreased. The transmittance of cowpea precipitate powder was not different according to the protein content. The initial pasting temperature of cowpea precipitate powder by differential scanning calorimetry (DSC) and rapid visco analyser (RVA) showed no differences according to the protein content. In sensory evaluation, the color and clarity of cowpea precipitate gels stored for 24 hrs and 48 hrs at room temperature as the protein content increased, and the hardness, cohesiveness, springiness, acceptability were greater when the gels were stored for 48 hrs. Instrumental analyses using a rheometer showed that the hardness, gumminess, and chewiness of cowpea precipitate gels stored for 24 hrs, which was increased as the high protein content increased. For the gels stored for 48 hrs, all other factors are significantly different except cohesiveness as the protein content increased.

• Polymer(Korea)
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• v.24 no.1
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• pp.48-57
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• 2000

Polycaprolactone (PCL) and thermoplastic starch (TPS) blends were prepared. Mechanical properties, thermal property, water absorption, biodegradability by composting and surface morphology of PCL/TPS blends were investigated. The compositions of PCL/TPS blends were 90/10, 80/20, 70/30, 60/40, 50/50, 40/60, 30/70, 20/80, and 10/90. Strength and elongation at break decreased as the content of TPS increased, while modulus increased. DSC thermogram of TPS showed two glass transition temperatures (T$_{g}$ ) at 23$^{\circ}C$ and 126$^{\circ}C$. And TPS proved to be an amorphous polymer because there was no endothermic peak due to the melting of starch crystal. The unchanged melting temperatures and T$_{g}$ 's of PCL/TPS blends revealed that PCL and TPS were not miscible. All of the blends were found to be mechanically compatible but phase separated in each other. After 45 days composting, the biodegradability of PCL was 44% and that of PCL/TPS blends increased as the contents of TPS increased.

• Journal of Korea Foundry Society
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• v.31 no.1
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• pp.26-30
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• 2011

For the fabrication of bulk near-net-shape Ti-Ni-Cu shape memory alloys, consolidation of Ti-Ni-Cu alloy powders are useful because of their brittle property. In the present study, $Ti_{50}Ni_{30}Cu_{20}$ shape memory alloy powders were prepared by gas atomization and martensitic transformation temperatures and microstructures of those powders were investigated as a function of powder size. The size distribution of the powders was measured by conventional sieving, and sieved powders with the specific size range of 25 to $150\;{\mu}m$ were chosen for this examination. XRD analysis showed that the B2-B19 martensitic transformation occurred in the powders. In DSC curves of the as-atomized $Ti_{50}Ni_{30}Cu_{20}$ powders as a function of powder size, only one clear peak was found on each cooling and heating curve. The martensitic transformation start temperature($M_s$) of the $25-50\;{\mu}m$ powders was $31.5^{\circ}C$. The $M_s$ increased with increasing powder size and the difference of $M_s$ between $25-50\;{\mu}m$ powders and $100-150\;{\mu}m$ powders is only $1^{\circ}C$. The typical microstructure of the rapidly solidified powders showed cellular morphology and very small pores were observed in intercellular regions.

• Journal of Adhesion and Interface
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• v.3 no.3
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• pp.15-21
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• 2002

The modified polyethylene(m-PE) films were prepared from aqueous dispersions which were synthesized by reacting poly(ethylene-co-methylacrylate) with aqueous KOH and ammonia solution to attach -COOK, $CONH_2$, and COOH as pendent groups in the polyethylene backbones. Thermal, tensile and heat-seal properties were measured to investigate the effect of the pendent groups. Endothermic peaks on DSC curves were affected by the thermal history of the samples and a melting peak was observed at around $86^{\circ}C$ on the second heating curve while three melting peaks were shown on the first heating curve. A minimum value of tensile strength was shown at 70 mole% of COOK based on pendent groups. Tensile modulus increased with increasing the amide content in pendent groups. The m-PE films were heat-sealed at lower temperature than LDPE films and showed a minimum heat seal strength at around 70 mole% COOK content in pendent groups.

• Journal of Electrical Engineering and Technology
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• v.13 no.2
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• pp.918-927
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• 2018

Based on the actual operating environment of transformer, the aging tests of nitrile butadiene rubber (NBR) were conducted systematically under four conditions: in air, in transform oil, under compression in air and under compression in transform oil to studythe effect of high temperature, transform oil and compression stress simultaneously on the thermal aging behaviors of nitrile butadiene rubber and predict the lifetime. The effects of liquid media and compression stress simultaneously on the thermal aging behaviors of nitrile butadiene rubber were studied by using characterization methods such as IR spectrosc-opy, thermogravimetric measurements, Differential Scanning Calorimetry (DSC) measurements and mechanical property measurements. The changes in physical properties during the aging process were analyzed and compared. Different aging conditions yielded materials with different properties. Aging at $70^{\circ}C$ under compression stress in oil, the change in elongation at break was lower than that aging in oil, but larger than that aging under compression in air. The compression set or elongation at break as evaluation indexes, 50% as critical value, the lifetime of NBR at $25^{\circ}C$ was predicted and compared. When aging under compression in oil, the prediction lifetime was lower than in air and under compression in air, and in oil. It was clear that when predicting the service lifetime of NBR in oil sealing application, compression and media liquid should be involved simultaneously. Under compression in oil, compression set as the evaluation index, the prediction lifetime of NBR was shorter than that of elongation at break as the evaluation index. For the life prediction of NBR, we should take into account of the performance trends of NBR under actual operating conditions to select the appropriate evaluation index.

• Elastomers and Composites
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• v.42 no.3
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• pp.151-158
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• 2007

MWNTs have been widely investigated due to unique properties of such as good electrical conductivity and thermal stability in polymer composites industries. This paper established the procedure to fabricate PMMA/MWNT composites by a modular intermeshing co-rotating twin screw extruder with L/D ratio of 42. The electrical properties of PMMA/MWNT composites with different content of MWNT have been investigated. A sheet resistance percolation was observed at 4 wt% of MWNT for the melt processed composites. Sheet resistance of PMMA/MWNT composite film containing 4 wt% of MWNT was nearby $10^4{\Omega}/sq$ and this shows the possibility of potential application to EMI (Electronic Magnetic Interference) shielding materials. The characteristics of composites were analyzed by TGA, DSC, and SEM. In addition, MFI (Melt Flow Index) has been measured to analyze the rheological property.