• Title, Summary, Keyword: Kissinger method

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Thermal Degradation Kinetics of Antimicrobial Agent, Poly(hexamethylene guanidine) Phosphate

  • Lee, Sang-Mook;Jin, Byung-Suk;Lee, Jae-Wook
    • Macromolecular Research
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    • v.14 no.5
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    • pp.491-498
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    • 2006
  • The thermal degradation of poly(hexamethylene guanidine) phosphate (PHMG) was studied by dynamic thermogravimetric analysis (TGA) and pyrolysis-GC/MS (p-GC). Thermal degradation of PHMG occurs in three different processes, such as dephosphorylation, sublimation/vaporization of amine compounds and decomposition/ recombination of hydrocarbon residues. The kinetic parameters of each stage were calculated from the Kissinger, Friedman and Flynn-Wall-Ozawa methods. The Chang method was also used for comparison study. To investigate the degradation mechanisms of the three different stages, the Coats-Redfern and the Phadnis-Deshpande methods were employed. The probable degradation mechanism for the first stage was a nucleation and growth mechanism, $A_n$ type. However, a power law and a diffusion mechanism, $D_n$ type, were operated for the second degradation stage, whereas a nucleation and growth mechanism, $A_n$ type, were operated again for the third degradation stage of PHMG. The theoretical weight loss against temperature curves, calculated by the estimated kinetic parameters, well fit the experimental data, thereby confirming the validity of the analysis method used in this work. The life-time predicted from the kinetic equation is a valuable guide for the thermal processing of PHMG.

Slow Cook-Off Test and Evaluation for HTPE Insensitive Propellants (HTPE 둔감추진제 완속가열 시험평가)

  • Yoo, Ji-Chang;Kim, Chang-Kee;Kim, Jun-Hyung;Lee, Do-Hyung;Min, Byung-Sun
    • Journal of the Korean Society of Propulsion Engineers
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    • v.14 no.6
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    • pp.31-37
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    • 2010
  • This study was carried out to investigate the thermal decomposition and execute EIDS slow cook-off test for the propellant ingredients and 2 kinds of HTPE propellants. The thermal analysis of the propellant ingredients used in this study showed that the thermal stability of these materials decreases in the following order : AP > HTPE > AN > BuNENA. In addition, propellant HTPE 002 containing AN showed that an endothermic process at around $125^{\circ}C$ corresponding to the solid phase change(II$\rightarrow$I) of AN was followed by the exothermic process of BuNENA/AN mixture up to $200^{\circ}C$. In EIDS slow cook-off tests, HTPE 001 and HTPE 002 reacted at around $250^{\circ}C$ and $152^{\circ}C$ respectively, and both of them showed sudden temperature increase curves at $115^{\circ}C$. The critical temperatures, $T_c$, of thermal explosion for the propellants HTPE 001 and HTPE 002, were obtained from both the non-isothermal curves at various heating rates and Semenov's thermal explosion theory. Kissinger's method that was used to calculate $T_c$ was also employed to obtain the activation energies for thermal decompositions.

Kinetic Studies of Pyrolysis and Char-$CO_2$ Gasification on Low Rank Coals (저급탄의 열분해 및 촤-$CO_2$ 가스화 반응의 속도론적 연구)

  • Kang, Suk-Hwan;Ryu, Jae-Hong;Park, Soo-Nam;Byun, Yong-Soo;Seo, Seok-Jung;Yun, Yong-Seung;Lee, Jin-Wook;Kim, Yong-Jeon;Kim, Joo-Hoe;Park, Sam-Ryong
    • Korean Chemical Engineering Research
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    • v.49 no.1
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    • pp.114-119
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    • 2011
  • Thermogravimetric analysis(TGA) was carried out for pyrolysis and char-$CO_2$ gasification of low rank Indonesian ABK coal and China lignite. The pyrolysis rate was successfully described by a two-step model adopting the modified Kissinger method. The shrinking core model, when applied to char-$CO_2$ gasification gave initial activation energy of 189.1 kJ/mol and 260.5 kJ/mol for the ABK coal and China lignite, respectively. Thus, the char-$CO_2$ gasification has been successfully simulated by the shrinking core model. In particular, the activation energy of char-$CO_2$ gasification calculated in this work is similar to the results on the anthracite coal, but considerable difference exists when other models or coal types are used.

Study on the Non-isothermal Crystallization Kinetics of Branched Polypropylene (분지형 폴리프로필렌의 비등온결정화 거동 연구)

  • Yoon, Kyung-Hwa;Shin, Dong-Yup;Kim, Youn-Cheol
    • Polymer(Korea)
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    • v.36 no.2
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    • pp.245-250
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    • 2012
  • Branched polypropylenes (PP) with long chain branch were prepared by solid state reaction with three different branching agent of 0.3 wt% content. The chemical structures, non-isothermal crystallization behavior and complex viscosity of the branched PP were investigated by FTIR, DSC, optical microscope, and dynamic rheological measurement. The chemical structure of the branched PP was confirmed by the existence of =C-H stretching peak of the branching agent at 3100 $cm^{-1}$. There was no distinct change in melting temperature in case of PP-D-0-3 and PP-F-0-3, but PP-H-0-3 indicated a decrease in melting temperature. The decrease in melting temperature was interpreted by the fact that the degradation reaction of PP was more dominant than branched reaction, and confirmed by a decrease in complex viscosity. The non-isothermal crystallization behavior of the branched PP was analyzed using by Avrami equation. The Avrami exponent of PP was 3, and the values of the branched PP with DVB and FS were below 3. The activation energy of PP calculated by Kissinger method was 25 kJ/mol, and there were no big difference in activation energies of the branched PPs compared to PP.

An Investigation on the Crystal Growth Studies and Emission line shape in $Er^{3+}$-doped Sodium Tellurite Glasses

  • Joshi, Purushottam;Jha, Animesh
    • Ceramist
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    • v.10 no.3
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    • pp.67-74
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    • 2007
  • Crystallisation kinetics of the erbium doped soda-tellurite glasses were studied using the differential thermal analysis (DTA) and differential scanning calorimetery (DSC) techniques. The DTA curves in the temperature range of 350 K to 650 K were obtained from isochronal heating rates, chosen in the range of 2 to 20 K/min. DSC isothermal curves were used to calculate the fraction of crystals formed on reheating. The apparent activation energies for devitrification were derived by measuring the shifts in the values of $T_g$ and $T_x$ with heating rates, using the Kissinger method. The derived values of apparent activation energies for isochronal and isothermal methods varied in the range of $190-204\;{\pm}\;5\;kJ\;mol^{-1}$. The X-ray powder diffraction analysis of heat treated and transparent samples showed the presence of nano-scale size sodium-tellurite crystals. These crystallites were found to have a strong influence on the full width of half maxima of the transition in $Er^{3+}:\;^4I_{13/2}{\rightarrow}^4I_{15/2}$, which extended from 70 nm in the vitreous materials to 132 nm in glass-ceramic materials.

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Fabrication and Characterization of Porous Nickel Membrane for High Precision Gas Filter by In-situ Reduction/Sintering Process (In-situ 환원/소결법을 이용한 다공성 니켈 멤브레인 가스필터의 제조 및 평가)

  • Kim, Nam-Hoon;Song, Han-Bok;Choi, Sung-Churl;Choa, Yong-Ho
    • Journal of Korean Powder Metallurgy Institute
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    • v.16 no.4
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    • pp.262-267
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    • 2009
  • Disk type porous nickel membrane was fabricated by in-situ reduction/sintering process using compacted NiO/PMMA (PMMA; Polymethyl methacrylate) mixture at $800^{\circ}C$ in hydrogen atmosphere. The porosity (49$\sim$58%) of these membrane was investigated as an amount of PMMA additive. The thermal decomposition and reduction behavior of NiO/PMMA were analyzed by TG/DTA in hydrogen atmosphere and the activation energy for the hydrogen reduction of NiO and thermal degradation of PMMA was calculated as 61.1 kJ/mol, evaluated by Kissinger method. Finally, the filtering performance and pressure drop were measured by particle counting system.

Cure Behavior of a DGEBF Epoxy using Asymmetric Cycloaliphatic Amine Curing Agent (비대칭 고리형 지방족 아민 경화제를 이용한 DGEBF 계열 에폭시의 경화 거동)

  • Kim, Hongkyeong
    • Korean Chemical Engineering Research
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    • v.46 no.1
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    • pp.200-204
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    • 2008
  • The curing kinetics of diglycidyl ether of bisphenol F (DGEBF) with an asymmetric cycloaliphatic amine curing agent were examined by thermal analysis in both isothermal and dynamic curing conditions. From the residual curing of the samples partially cured in isothermal condition and from the dynamic curing with various heating rates, it was found that there exist two kinds of reactions such as at low temperature and at high temperature regions. It was thus also found that the cure parameters obtained from the isothermal curing kinetic model hardly estimate experimental results for a degree of cure larger than 0.6. The activation energies and frequency factors of these two kinds of reactions were obtained from the dynamic curing experiments with various heating rates. From the curing analysis, it was verified that the total cure kinetics for low degrees of cure is dominated by the cure reaction in the low temperature region.

Structural evolution and kinetic study of high isotacticity poly(acrylonitrile) during isothermal pre-oxidation

  • Zhang, Li;Dai, Yongqiang;Kai, Yi;Jin, Ri-Guang
    • Carbon letters
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    • v.12 no.4
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    • pp.229-235
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    • 2011
  • Isotactic polyacrylonitrile (PAN) with triad isotacticity of 0.53, which was determined by $^{13}C$ NMR, using dialkylmagnesium as an initiator, was successfully synthesized. Isothermal treatment of iso-PAN was conducted in air at 200, 220, 250 and $280^{\circ}C$. Structural evolutions and chemical changes were studied with Fourier transformation infrared and wide-angle X-ray diffraction during stabilization. A new parameter $CNF={I_{2240cm}}^{-1}/ ({I_{1595cm}}^{-1}+f^*{I_{1595cm}}^{-1})$ was defined to evaluate residual nitrile groups. Crystallinity and crystal size were calculated with X-ray diffraction dates. The results indicated that the nitrile groups had partly converted into a ladder structure as stabilization proceeded. The rate of reaction increased with treatment temperature; crystallinity and crystal size decreased proportionally to pyrolysis temperature. The iso-conversional method coupled with the Kissinger and Flynn-Wall-Ozawa methods were used to determine kinetic parameters via differential scanning calorimetry analysis with different heating rates. The active energy of the reaction was 171.1 and 169.1 kJ/mol, calculated with the two methods respectively and implied the sensitivity of the reaction with temperature.

Thermal Characteristics of Polyvinylchloride in Combustion Reaction Using TGA (TGA를 이용한 폴리염화비닐의 연소반응에서의 열적 특성 연구)

  • Seo, Su-Eun;Kang, Yun-Jin;Min, Cho-Young;Bae, Dong-Chul;Kang, Kyung-Sik
    • Journal of the Korea Safety Management & Science
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    • v.11 no.3
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    • pp.217-226
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    • 2009
  • The combustion reaction of polyvinylchloride(PVC) was investigated using a thermogravimetric technique under an air atmosphere condition at several heating rates from 10 to $50^{\circ}C$/min. To obtain information on the kinetic parameters, the dynamic thermogravimetric analysis curve and its derivative were analyzed by a variety of analytical methods such as Kissinger, Friedman, Chatterjee-Conrad, Ozawa and Coats-Redfern methods. The combustion reaction of PVC proceeded in two steps; the first step was caused by the dehydrochlorination process in PVC, and the second step by the combustion of polyene. The comparative works for the kinetic results obtained from various methods should be performed to determine the kinetic parameters, because there are tremendous differences in the calculated kinetic parameters depending upon the mathematical method taken in the analysis.

Effects of Impact Velocity on Crystallization and Activation Energy of Cu-based Bulk Metallic Glasses in Kinetic Spray Coating (저온 분사 코팅 공정에서 충돌속도에 따른 CuNiTiZr 벌크 비정질 소재의 활성화 에너지와 결정화 거동 분석)

  • Yoon, Sang-Hoon;Bae, Gyu-Yeol;Kim, Jung-Hwan;Lee, Chang-Hee
    • Journal of the Korean institute of surface engineering
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    • v.41 no.6
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    • pp.301-307
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    • 2008
  • In this paper, nanocrystallization of CuNiTiZr bulk metallic glass (BMG) subjecting to a kinetic spraying, dependent on impact velocity, was investigated by numerical and experimental approaches. The crystallization fraction and nucleation activation energy of initial feedstock and as-deposited coating were estimated by DSC and Kissinger method, respectively. The results of numerical modeling and experiment showed that the crystalline fraction and nucleation activation energy in BMG coatings were depended on kinetic energy of incident particle. Upon impact, the conversion of particle kinetic energy leads to not only decreasing free energy barrier but also increasing the driving force for an amorphous to crystalline phase transformation. The nanocrystallization of BMGs is associated with the strain energy delivered by a plastic deformation with a high strain rate.