• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.349-352
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• 2009

In this study, the relation between the performance degradation of SOFC single cell and the increase of polarization resistance for the cathode is investigated. $Pr_{0.3}Sr_{0.7}Co_{0.3}Fe_{0.7}O_3$(PSCF3737, $19.4{\times}10^{-6}K^{-1}$) and $Gd_{0.1}Ce_{0.9}O_2$ (CGO91, $12{\times}10^{-6}K^{-1}$) are used as a cathode and an electrolyte, respectively. The polarization resistance of cathode is increased due to the delamination caused by thermal expansion coefficient difference. The voltage drop with 10%/1000h decline rate occurs during long-term, when the interface between the cathode and the electrolyte is delaminated due to TEC difference.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.05a
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• pp.31-35
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• 2006

Degradation characteristics of filament-winded composites due to accelerated environmental aging have been evaluated under high temperature, water immersion and thermal impact conditions. Two kinds of laminated composites coated by an urethane resin have been used: carbon-fiber reinforced epoxy(T700/Epon-826, CFRP) and glass-fiber reinforced phenolic (E-glass/phenolic, GFRP). For tensile strength of $0^{\circ}$ composites, CFRP did high reduction by 25% under the influence of high temperature and water while CFRP showed little degradation. However for water-immersed $90^{\circ}$ composites both CFRP and GFRP showed high reduction in tensile strength. Bending strength and modulus of $90^{\circ}$ composites were largely reduced in water-immersion as well as high temperature environment. Urethane coating on the composite surface improved the bending properties by 20%, however hardly showed such improvement for water-immersed $90^{\circ}$ composites.

• Korea-Australia Rheology Journal
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• v.20 no.4
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• pp.245-251
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• 2008

Two polysiloxanes having different chemical structures were blended with polycarbonate (PC) under ultrasonic irradiation in solution. The polysiloxanes used were poly(methylphenyl siloxane) and vinyl-terminated poly(dimethyl siloxane). It was of primary interest to investigate the effect of polysiloxane structure on the rheological properties of PC/polysiloxane blends. It was found that a small amount (1.5 phr) of polysiloxanes greatly altered the melt viscosities and elasticity of PC. In particular, incorporation of poly(methylphenylsiloxane) led to a notable increase in elasticity with greater shear sensitivity of PC. The observed rheological behaviors of PC/polysiloxane blends were partly explained in conjunction with the tendencies found in ultrasonic degradation of polysiloxanes. Thermal stability and morphology in sonicated blends of PC/polysiloxane blends were also discussed.

• Journal of the Korean Chemical Society
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• v.16 no.2
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• pp.100-105
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• 1972

The thermal degradation of poly (${\alpha}$-methyl styrene) in several mixed solvents (toluene-n-butylalcohol, toluene-sec-butylalcohol, toluene-kerosene, toluene-methyl ethyl ketone) without hydroquinone, and in with the addition of the hydroquinone, was studied at temps. of $165^{\circ}{\sim}205^{\circ}C$. The velocity constant of degradation (k), and the activation energy (E) were calculated for each solvent. As results, k decreased with the increase of the volume-fraction of poor solvent in both systems, whereas E either showed no perceptible change or it increased with the volume-fraction of poor solvents. these results were discussed.

• Bulletin of the Korean Chemical Society
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• v.21 no.1
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• pp.69-74
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• 2000

Applicability of Thermal field flow fractionation (ThFFF) was investigated for the analysis of masticated natural rubber (NR) adhesives produced bya hot melt mastication process. An optimum ThFFF condition for NR analysis was found by using tetrahydrofuran (THF) as a solvent/carrier and a field-programming. Low flowrate (0.3 mL/min) was used to avoid stopping the flow for the sample relaxation. Measured molecular weight distribution was used to monitor degradation of rubber during the mastication process. Rubber samples collected at three different stages of the mastication process and were analyzed by ThFFF. It was found that in an anaerobic process rubber degradation occurs at the resin-mixing (compounding) zone as well as in the initial break-down zone, while in an aerobic process most of degradation occurs at the initial breakdown zone. It was also found that E-beam radiation on NR causes a slight increase in the NR molecular weight due to the formation of a branched structure.

• Elastomers and Composites
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• v.23 no.2
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• pp.125-133
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• 1988

The thermal degradation of polymethyl methacrylate(PMMA) blend namely polymethyl methacrylate-polycarbonate(PMMA-PC) blend and polymethyl methacrylate-polystyrene(PMMA-PS) blend were carried out by isothermal method under air at several heating temperature from 220 to $270^{\circ}C$. Molecular weight changes during the thermal decomposition were monitored by means of the viscosity average molecular weight($\bar{M}v$). The viscosity average molecular weight was determined by Gel Permeation Chromatography(GPC). The dominant process in the degradation of PMMA-PC and PMMA-PS blend were main chain scission randomly due to weak links that may be distributed along the polymer backbone and the initial rate which the bonds are broken is not sustained. The infra-red spectra of degraded PMMA-PS blend show that the presence of aromatic ketone band at $1685cm^{-1}$. However, the infra-red spectra of degraded PMMA-PC blend show that the presence of hydroperoxide band at $3450cm^{-1}$. Thus indicating that the weak links are attacked by oxygen from the air and produce hydroperoxide or ketone. The activation energies of PMMA-PC blend and PMMA-PS blend were 18.2 and 17.9 Kcal/mol, respectively.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.12
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• pp.1-6
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• 2004

In this study, heat and discharge treatments are arbitrary simulated for finding out the initiations and processes of surface degradation on the surface of polymer for using as a PCB substrate. Thermal-treatment changed the surface to the hydrophobic one with the increase of contact angle and surface potential decay, respectively. The XPS spectrum showed that the increased hydrophobicity in thermal treatment was originated from the continuous decrease of side-chains caused by secessions of oxygen groups and the increase of unsaturated double bond in carbon chains. Also, thermal-treatment caused the discoloration on the point of treated surface. These phenomena were attributed to the generation of ether group. In the chemical change by discharge treatment, a lot of side-chains occurred on the treated surface, and so the hydrophilicity increased as time elapsed.

• Preventive Nutrition and Food Science
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• v.20 no.2
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• pp.102-109
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• 2015

In order to investigate the thermal degradation of glucose and maltose solutions after high temperature and high pressure (HTHP) treatment, the samples were treated at temperatures of 110, 120, 130, 140, and $150^{\circ}C$ for 1, 2, 3, 4, and 5 h in an apparatus for HTHP treatment. Glucose and maltose solutions (20% w/w) were prepared by weighing glucose and maltose and adding distilled water in the desired proportion. Chromaticity, pH, organic acids, 5-hydroxymethylfurfural (HMF), free sugar contents, electron donating ability (EDA), and ascorbic acid equivalent antioxidant capacity (AEAC) were evaluated. With increasing heating temperatures and times, the L-, a-, and b-values decreased. The pH and free sugar contents decreased, and organic acids and HMF contents increased with greater temperatures and times. EDA (%) and the AEAC of the heating sugars increased with the increases in temperatures and times.

• Elastomers and Composites
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• v.24 no.1
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• pp.11-18
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• 1989

The thermal degradation of Poly(methyl methacrylate) (PMMA) and poly(acrylonitrile butadiene styrene)(ABS) terpolymer as well as their mixtures were carried out using the thermogravimetry and differential scanning calorimetry(DSC) in the stream of nitrogen and air with 50 ml/min at the various heating rate from 4 to $20^{\circ}C/min$ and temperature from 200 to $300^{\circ}C$ The values of activation energies of thermal degradation determined by TG and DSC in the various PMMA/ABS mixtures were $34{\sim}58Kcal/mol,\;35{\sim}54Kcal/mol$ in the stream of nitrogen. The values of activation energy of ABS20% mixture was appeared high in camparison with addition rule. According to increasing the composition of ABS, the temperatures of glass transition and initial decomposition temperature were increased. PMMA/ABS mixtures by the analysis of infrared spectrophotometer were decomposed by main chain scission in the stream of nitrogen.

• Food Science and Biotechnology
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• v.18 no.3
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• pp.717-723
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• 2009

Thermal degradation characteristics of sucrose was investigated. A 20% sucrose solution was heated to temperatures of $110-150^{\circ}C$ for 1-5 hr. Chromaticity, pH, organic acids, 5-hydroxymethylfurfural (HMF), free sugars, electron donating ability (EDA), and ascorbic acid equivalent antioxidant capacity (AEAC) of the heated sucrose solutions were evaluated. With increasing temperatures and times, the L-, a-, and b-values decreased; however, total color difference (${\Delta}E_{ab}$) increased. The pH and sucrose contents decreased, and fructose and glucose contents increased with increasing heating temperature and time. Organic acids, such as formic acid, lactic acid, and levulinic acid, and HMF contents increased with increasing heating temperatures and times. EDA (%) and the AEAC of the heated sucrose solutions increased with increasing heating temperature and time. The heated sucrose solution was more effective than unheated sucrose solution, having higher EDA (90 fold), and AEAC (13 fold).