• 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.

• Macromolecular Research
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• v.17 no.3
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• pp.149-155
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• 2009

The thermal decomposition behavior and degradation characteristics off our different thermotropic liquid crystalline polymers (TLCPs) were studied. The thermal decomposition behavior was determined by means of thermogravimetric analysis (TGA) at different heating rates in nitrogen and air. The order of the thermal stability was as follows: multi-aromatic polyester > hydroxybenzoic acid (HBA)/hydroxynaphthoic acid (HNA) copolyester > HNA/hydroxyl acetaniline (HAA)/terephthalic acid (TA) copolyester > HBA/Poly(ethylene terephthalate) (PET) copolyester. The activation energies of the thermal degradation were calculated by four multiple heating rate methods: Flynn-Wall, Friedman, Kissinger, and Kim-Park. The Flynn-Wall and Kim-Park methods were the most suitable methods to calculate the activation energy. Samples were exposed to an accelerated degradation test (ADT), under fixed conditions of heat ($63{\pm}3^{\circ}C$), humidity ($30{\pm}4%$) and Xenon arc radiation ($1.10\;W/m^2$), and the changes in surface morphology and color difference with time were determined. The TLCPs decomposed, discolored and cracked upon exposure to ultraviolet radiation.

• Journal of the Korean Ceramic Society
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• v.30 no.3
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• pp.181-188
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• 1993

The sintering and renitridation behaviors of ultrafine Si3N4 powder compacts, which were heavily oxidized and/or free-Si rich, were investigated with particular attentiion to microstructures. The specimens were heated without restoring to additives and pressure by controlling heating process attained a Xe image apparatus. The effect of particle size, free-Si contents, decomposition and renitridation, were investigated. When fired to 1$650^{\circ}C$ within 15 sec and then immediately held at 135$0^{\circ}C$ for 10min N2 atmosphere, significant densification took place in the limited region, in addition to decreasing oxygen contents to less than 0.3wt%. On the other hand, specimens decomposed due to overheating at the initial stage were rapidly renitridated at the relatively lower temperature of the holding stage. And, then, the activation energy for the renitridation was calculated to be 49kcal/mole.

• Journal of the Korean Ceramic Society
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• v.23 no.6
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• pp.71-75
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• 1986

The forming reaction processes of magnesium aluminate spinel by a thermal decomposition of sulfate hydrate were studied with DTA, TG. SEM and X-ray powder diffraction methods. The hydrous salt composed of the mixture of the two compounds of $MgSO_4$ $6H_2O$ and ${AL_2}({SO_4})_17H_2O_3$ in which both sulfates were crystalline. On heating the hydrous slat the crystalline magnesium and aluminum sulfate anhydride to amorphous alumina magnesium sulfate anhydride decomposed to amorphous magnesia and these amorphous oxides reacted completely each other to form a spinel at $1000^{\circ}C$ The apparent activation energy of forming reaction of spinel was 36.5 kcal/mole($900^{\circ}C$~$1000^{\circ}C$) The crystallite size of spinel obtained at $1000^{\circ}C$ after 1 h was 380$\AA$.

• Resources Recycling
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• v.24 no.5
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• pp.15-21
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• 2015

Waste plastic differs in its speed of combustion owing to its variety in composition as well as kinds of plastic. This study is aimed at examining the thermal weight analysis and determination of its kinetics in order to derive the design element in pyrolysis of RPF (Refused Plastic Fuel) as the plastic solid fuel. Based on the result of TGA (Thermogravimetric analysis), kinetic characteristics were analyzed by using Kissinger method which are the most common method for obtaining activation energy, and experimental conditions of TGA were set as follows: in a nitrogen atmosphere, gas flow rate of 20 ml/min, heating rate of $5{\sim}50^{\circ}C/min$, and maximum hottest temperature of $800^{\circ}C$. The method used for determining the property of waste plastic when thermally decomposed was thought feasible as the basic data in deciding the performance, design, and optimal operating condition of the reactor in the actual reactor.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.10a
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• pp.265-268
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• 2002

In this work, the blend system of epoxy and PMR-15 polyimide is investigated in terms of the cure behaviors and thermal stabilities. The cure behaviors are studied in DSC measurements and thermal stabilities are also carried out by TGA analysis. DDM (4, 4'-diamino diphenyl methane) is used as curing agent for EP and the content of PMR-15 is varied within 0, 5, 10, 35, and 20 phr to neat EP. As a result, the cure activation energy ($E_a$) is increased at 10 phr of PMR-15, compared with that of neat EP. From the TGA results of EP/PMR-15 blend system, the thermal stabilities based in the initial decomposed temperature (IDT) and integral procedural decomposition temperature (IPDT) are increased with increasing the PMR-15 content. The fracture toughness, measured in the context of critical stress intensity factor ($K_{IC}$) and critical strain energy release rate ($G_{IC}$), shows a similar behavior with $E_a$. This result is probably due to the crosslinking developed by the interactions between intermolecules in the polymer chains.

• Polymer(Korea)
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• v.27 no.3
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• pp.183-188
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• 2003

The dielectric constants of fluorine-containing epoxy resins, 2-diglycidylether of benzotrifluoride(FER)/4,4'-diamino-diphenyl methane (DDM) and diglycidylether of bisphenol-A (DGEBA)/DDM systems were evaluated by dielectric spectrometer. Glass transition temperature and thermal stability factors, including initial decomposed temperature, temperatures of maximum rate of degradation, and decomposition activation energy of the cured specimens were investigated by dynamic mechanical analysis and thermogravimetric analysis. For the mechanical properties of the casting specimens, the fracture toughness, flexural, and impact tests were performed, and their fractured surfaces were examined by scanning electron microscope. The dielectric constant of FER/DDM system was lower than that of commercial DGEBA/DDM system, and the mechanical properties of the cured specimens showed higher values than those of DGEBA/DDM system. This was probably due to the introduction of trifluoromethyl (CF$_3$) group into the side chain of the epoxy resins, resulting in improving the electric and mechanical properties of the epoxy cure system studied.

• Journal of the Korean Chemical Society
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• v.8 no.2
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• pp.88-91
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• 1964

A rapid and simple method is described here for the determination of scandium in monazite by neutron activation analysis. The sample is irradiated for 20 hours at the neutron flux of $10^{12}$ thermal neutrons/$cm^2$/sec in the TRIGA MARK Ⅱ reactor, after which the sample is decomposed by fusion with concentrated sulfuric acid. The scandium-46 together with scandium carrier are separated from the irradiated sample by precipitating with ammonia, and are extracted by solvent extraction of the thiocyanate complex into ether. The induced radioactivity is measured by gamma scintillation spectrometry using the Multichannel Pulse Height Analyzer connected with 2"${\times}$2" NaI(Tl). The chemical yield is determined gravimetrically by precipitating scandium with mandelic acid. In order to check the efficiency of scandium separation and the errors from interfering activities of the other elements, scandium was separated by the cation exchange resin column, and the results from both samples were compared each other, which showed that the chemical procedure used in this work was as selective as the ion-exchange method with respect to scandium separation. The scandium contents in Korean monazite were found to be about 12 p. p. m.

• Korean Chemical Engineering Research
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• v.54 no.3
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• pp.299-304
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• 2016

Characteristics of self-propagating reaction for the preparation of ZnO powder from precursors composed of nitrate and citrate compounds were examined. The ratio of C/N was maintained in range of 0.7~0.8 to initiate the self-propagating reaction between the reducing citrate and oxidizing nitrate groups. The samples were decomposed thermally by using TGA. The sudden decomposition occurred in the range of X > 0.5 in a very short time with a very sharp decrease of mass, indicating that the self-propagating reaction would occur. Friedman, Ozawa-Flynn-Wall and Vyazovkin methods were employed to predict the activation energy, reaction order and frequency factor of the reaction rate in the rate determining step of X < 0.5 range. The activation energy increased with increasing fractional conversion in the range of 46~130 (kJ/min). The reaction order decreased in the range of 2.9~0.9, while the frequency factor increased in the range of 85~278 ($min^{-1}$), respectively, with increasing the rate of temperature increase.

• Journal of the Korean Ceramic Society
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• v.24 no.5
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• pp.453-460
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• 1987

β'-sialon(Z=2.7) specimens with <30%wt. graphite as a reducing agent were decomposed at 1350°up to 1,450℃ under the atmosphere of 90% N2-10%H2. The decomposition of β'-sialon was calculated from the change in Z-value, and the formation of new minerals was identified from X-ray diffraction patterns. The decomposition reactions of sialon were considered to yield a stable sialon close to β-silicon nitride and some aluminum compounds according to the following equations; β'-sialon(s)＋C(s)＋N2(g)→β2-sialon(metastable)＋β3-sialon(stalbe phase) β2-sialon(s)＋C(s)＋N2(g)→β3-sialon(s)＋AlN(s)＋α-Al2O3(s)＋15R(s)＋SiO(g)＋Al2O(g)＋CO(g) Z-value; β2( 3.5)>β'( 2.7)>β3( 0.5) The decomposition rate of sialon was controlled by two mechanisms ; One was characterized by the interface area of contact, corresponding to an apparent activation energy of 50.5Kcal/mol in the initial stage, and the other by the diffusion, corresponding to that of 104.3Kcal/mol in the final stage of the decomposition.