Kissinger Model Research Articles

비등온 열중량분석법을 이용한 급속 반탄화 참나무 목분의 열적 특성과 활성화 에너지 연구

This study investigated thermal properties and activation energy () of torrefied oak wood powders treated with various torrefaction times (0, 5, 7.5, 10 min) by using non-isothermal thermogravimetric analysis at heating rates of 10, 20, to check the feasibility of rapidly torrefied oak wood powders as a fuel. As the torrefaction time increases, onset of thermal decomposition temperature, lignin content, and the amount of final residue of torrefied oak wood powders were accordingly increased with reduced hemicellulose content. was determined by using Friedman and Kissinger models and respective R-square values were over 0.9 meaning very good availability of calculated values. The values of the samples were decreased with the increase of torrefaction time and the lowest value ob served in the torrefied oak wood powders treated for 7.5 min showed high feasibility of rapidly torrefied oak wood powder as a biomass-solid refuse fuel.

E-Smoking Liquids as Precursors for Liquid Nitroesters

Currently, E-smoking cigarettes are widely used and occur within all classes of society. This work investigated the use of E-smoking liquids for the synthesis of Nitroglycerin (NG) and 1,2-Propylene Glycol Dinitrate (PGDN), both considered as nitroester liquid high explosives. Two kinds of E-smoking liquids (10 mL) were investigated: nicotine free and with nicotine (10 mg/mL). Quantitative analysis of the glycerin and propylene glycol (PG) present in the E-smoking liquids was carried out by gas chromatography-mass spectrometry (GCMS), with calculation of the accuracy and precision parameters. The percentage of glycerin was (10-13 wt.%) and percentage of propylene glycol was (40-70 wt.%) The synthesis of pure NG and pure PGDN were performed with laboratory grade glycerin and propylene glycol and compared to the samples obtained from the E-smoking liquid. Differential Scanning Calorimetry (DSC) was used for the determination of the activation energy and the heat of decomposition for each synthesized explosive, using the Ozawa and Kissinger models. The brisance index was assessed by the witness plate test and compared with some conventional explosives (TNT and C4). Finally, the influence of nicotine (less than 2 wt.%) on the synthetic process and the detonic properties of the explosive mixture was studied.

Amorphous Sulfadoxine: A Physical Stability and Crystallization Kinetics Study.

Poor aqueous solubility of drugs and the improvement thereof has always been a challenge for the pharmaceutical industry. With this, one of the focuses of the pharmaceutical research scientist involves investigating possible metastable forms of a given drug to be incorporated into solid dosage forms. The rationale being, the improved solubility offered by the metastable solid-state forms of drugs. Solubility remains a major challenge for formulation scientists, especially with antimicrobial agents where the emergence of resistance is directly dependent on the concentration and duration of the parasite exposed to the drug. Sulfadoxine-pyrimethamine combination therapies are still the recommended treatments for uncomplicated Plasmodium falciparum malaria. The aim of this study was to prepare an amorphous form of sulfadoxine and to investigate the stability and recrystallization behavior thereof. The amorphous form was prepared by the well-known quench cooling of the melt. The physico-chemical properties and stability of amorphous sulfadoxine were studied using hot-stage microscopy (HSM), scanning electron microscopy (SEM), x-ray powder diffractometry (XRPD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), as well as microcalorimetry. The recrystallization kinetics were studied isothermally by applying the Johnson-Mehl-Avrami model and non-isothermally by applying the Kissinger model. The physical stabilization of the amorphous form was investigated using physical mixtures of amorphous sulfadoxine with polyvinylpyrrolidone-25 (PVP-25). It was proved that sulfadoxine is a good glass former with relative high physical stability; however, water acts as a strong plasticizer for amorphous sulfadoxine, detrimentally affecting the stability during exposure to high moisture conditions.

Evaluation of thermal stability and isochronal crystallization kinetics in the Ti40Zr25Ni8Cu9Be18 bulk metallic glass

The thermal stability of Ti40Zr25Ni8Cu9Be18 bulk metallic glass was studied by differential scanning calorimetry (DSC). Under non-isothermal heating process, the results indicate that the Ti40Zr25Ni8Cu9Be18 bulk metallic glass show two crystallization processes. X-ray diffraction (XRD) was conducted at room temperature and annealed temperature to examine the phase nature. Several theoretical models were used to analyze the apparent activation energies for characteristic temperatures (i.e. the glass transition temperature, the onset temperature of the crystallization, etc.). The results show that the apparent activation energies for characteristic temperatures in the Ti40Zr25Ni8Cu9Be18 bulk metallic glass by Kissinger model, Flynn–Wall–Ozawa model, Augis–Bennett model and Gao–Wang model are in good agreement with each other. The average values of the Avrami exponent n in the first and the second crystallization processes for the Ti40Zr25Ni8Cu9Be18 bulk metallic glass are around 1.41 and 2.47, respectively. The apparent activation energies are determined by different isoconversion methods, the values are close to each other in both crystallization processes.

Non-Isothermal Crystallization Behaviors of Ethylene Vinyl Acetate Copolymer and Ethylene Vinyl Acetate Copolymer-Graft-Maleic Anhydride

Maleic anhydride (MAH) was melt-grafted on ethylene-vinyl acetate copolymer (EVA) with a grafting degree of 6.3%. Through studying the crystal structure of the resulting EVA-g-MAH, the MAH groups had little influence on crystal structure. According to the Owaza model analysis of the non-isothermal crystallization kinetics of EVA-g-MAH and EVA, the MAH groups had a large blocking effect on crystallization. However, the Mo model showed that the crystallization rate of EVA-g-MAH was slightly faster than EVA. The crystallization activation energy was calculated by the Takhor and Kissinger models, and both results indicated that EVA had a larger effective energy barrier than EVA-g-MAH.

Polystyrene with trifluoromethyl units: Monomer reactivity ratios, thermal behavior, flammability, and thermal degradation kinetics

ABSTRACTChemical modification based on incorporation of flame retardants (FR) into the polymer backbone was used in order to reduce polystyrene flammability. 3‐(trifluoromethyl)styrene (StCF3) and 3,5‐bis(trifluoromethyl)styrene (St(CF3)2) were applied as reactive FR. Copolymers were synthesized with different feed ratios and it gave series of copolymers with various amounts of StCF3 and St(CF3)2 (5–50% mol/mol of St). Glass transition temperature (Tg) and thermal stability of obtained (co)polymers were determined from differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), respectively. Kinetic parameters such as the thermal decomposition activation energy (E) and frequency factor (A) were estimated by Ozawa and Kissinger models. Pyrolysis combustion flow calorimeter (PCFC) was applied as a tool for assessing the flammability of the synthesized (co)polymers. Relative reactivity ratios were determined by applying the conventional linearization Jaacks method (rSt = 1.34, rStCF3 = 0.54), (rSt = 0.47, rSt(CF3)2 = 0.13). The results suggest that incorporation of fluorinated styrenes into PSt enchance flame retardance. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42839.

Thermal crystallization of an Al88Ni6Sm6 metallic glass

This work essentially deals with the first stages of crystallization of melt spun Al1−(x+y)NixSmy metallic glasses. Specific emphasis is given to the microstructural and kinetics aspects of primary crystallization because of the high specific strength of this class of materials in the partially crystallized state. The nanometric size of the crystalline particles is measured either by direct transmission electron microscopy or by indirect X-ray diffractometry. The Kissinger model as well as the Friedman model free method is used to estimate the local activation energies and the results obtained with both kinds of approaches are compared. A sustained attention is also paid to the nature of the crystallization phenomenon at the origin of the second exothermic peak in differential scanning calorimetry. This result is indeed the subject of controversy in the literature data concerned by Al–Ni–Sm alloys.

Pyrolysis kinetics of recycled polyesters

Purpose – The purpose of this paper is to study the non-isothermal degradation kinetics of recycled polybutylene terephthalate, polytrimethylene terephthalate and polyethylene terephthalate using thermogravimetric analysis (TGA) in a nitrogen atmosphere. Design/methodology/approach – To achieve this goal, the author utilized standard kinetic models, such as Coats-Redfern and Kissinger equations, for analysis of the TGA data. Findings – When applied to the TGA data, the Kissinger model resulted in a coefficient of determination (R2) value greater than 0.99. Originality/value – This study describes the maiden application of the Kissinger model to obtain the pre-exponential factor (A) and activation energy (E) for different polyester systems used in the textile industry.

ZnO nanoparticles favours heterogeneous nucleation in PET–ZnO nanocomposites

The structural and chemical properties with non-isothermal crystallization kinetics of PET–ZnO nanocomposites have been reported in this article. ZnO nanoparticles have been synthesized via chemical route with average diameter 19 nm which made confirm by transmission electron microscopy and X-ray diffractometer (XRD) techniques. PET–ZnO nanocomposites have been prepared by solution casting method. The structural and chemical changes occurred in poly (ethylene terephthalate) after inclusion of ZnO nanoparticles have been studied with the help of XRD and Fourier transform infrared spectroscopy, respectively. It was observed from differential scanning calorimeter that ZnO nanoparticles work as nucleating agent for heterogeneous nucleation in PET matrix under non-isothermal crystallization process. The combined Avrami and Ozawa models have been proved adequate to explain non-isothermal crystallization kinetics of PET–ZnO nanocomposites, and also, ZnO nanoparticles have been caused to reduce crystallization activation energy in pristine PET as per the applied Kissinger model.

Novel cordierite nanopowders of new crystallization aspects and its cordierite-based glass ceramics of improved mechanical and electrical properties for optimal use in multidisciplinary scopes

Nanocrystalline α-cordierite Mg2Al4Si5O18 powders have been synthesized via a novel and facile co-precipitation method using MgCl2.6H2O, NaAlO2, Na2SiO3.5H2O as starting materials. XRD, SEM, HR-TEM and EDS techniques were employed to investigate the phase structure and crystal morphology of the synthesized powders at various annealing temperatures. The kinetics of cordierite crystallization was studied under non-isothermal conditions using Differential Thermal Analysis (DTA). The apparent activation energy (Ea) of μ-cordierite crystallization, calculated by modified Kissinger model was equal 286.1 K J mol−1 and comparable with the literature. The dielectric measurements revealed that the cordierite ceramic samples sintered at 1300 and 1350 °C could be successfully applied for electronic packaging under the microwave and radiowave frequency regions, respectively.

Investigation of the thermal behaviour and decomposition kinetics of kaolinite

AbstractPrevious work on the structural and thermal properties of various types of kaolinite have led to different conclusions, rendering comparison of analytical results difficult. The objectives of the present study were to investigate the thermal behaviour of kaolinite and to carry out a kinetic analysis of the decomposition of kaolinite at high temperatures. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and thermogravimetry-differential scanning calorimetry (TG-DSC) were used to study the mechanism of the thermal decomposition. The modified Coats–Redfern, Friedman, Flynn–Wall–Ozawa and Kissinger decomposition models were used to determine the decomposition mechanism of the kaolinite sample. The dehydroxylation of kaolinite occurred at ∼600°C with the formation of metakaolin, which then transformed into either γ-alumina or aluminium-silicon spinel together with amorphous silica. The results of the XRD and FTIR analyses indicated that the γ-alumina, or aluminium-silicon spinel and amorphous silica phases, transformed into mullite and α-cristobalite, respectively, after decomposition at 900°C. Good linearity was observed with the modified Coats–Redfern, Flynn–Wall–Ozawa and Kissinger models from room temperature to 1400°C and the range of the activation energy determined was 120–180 kJ/mol.

Thermal and kinetic parameters of 30Li2O–55B2O3–5ZnO–xTiO2–(10−x)V2O5 (0 ≤ x ≤ 10) glasses

In the present investigation, the effects of titanium and vanadium concentration on the thermal properties have been studied for 30Li2O–55B2O3–5ZnO–xTiO2–(10−x)V2O5 (0 ≤ x ≤ 10) glasses. To understand the crystallization mechanics, activation energy has been calculated using two different approaches, i.e., Kissinger model and Augis and Bennett model. Using the derivative differential thermal analysis, the inflection point temperature (Tf) and crystallization constants ky(T) and kf(T), for different heating rates, have also been obtained for all the glasses. Furthermore, kinetic parameters such as fluctuation free volume (fg) and change in bulk thermal expansion coefficient (αf) have been calculated for all the glass samples. The replacement of V2O5 by TiO2 induces phase separation in glasses.

Vulcanization of EPDM rubber compounds with and without blowing agents: Identification of reaction events and TTT-diagram using DSC data

Vulcanization of industrial-like ethylene propylene diene termonomer rubber compound is studied using a differential scanning calorimetry (DSC). The analysis starts with DSC information to obtain the total transformation heat, followed by an isothermal-dynamic temperature ramp that captures diffusion-controlled reaction kinetics. The vulcanization is modeled by an auto-catalytic Kamal–Sourour model, complemented with a Kissinger model for the prediction of one energy of activation, DiBenedetto's equation for the glass transition temperature, and adjusted reaction constants to include diffusion mechanisms. Two rubber formulations, with and without blowing agents, containing crosslinking agents, primary and secondary accelerators, activators, promoters, and processing aids are studied. The identification and separation of multiple reaction events, occurring during crosslinking of the compound without a blowing agent, is done through a 2k design of experiments. Time–temperature–transformation (TTT) diagrams are calculated, integrating the kinetic model, thereby delineating processability windows, providing avenues for optimization, design, and online processing control. According to the kinetics and the TTT diagrams, the blowing agent induces several differences to the vulcanization reaction: decreases reaction temperatures while increasing reaction heats. It eliminates the exothermic peak before vulcanization and decreases the fully cured resin's glass transition temperature. Therefore, the presence of the blowing agent drives a shift in the vitrification line, resulting in a reduced operational window. POLYM. ENG. SCI., 55:2073–2088, 2015. © 2014 Society of Plastics Engineers

Crystallization Kinetics of Polypropylene and Poly (butyl methacrylate-co-hydroxyethyl methacrylate) Blend

The crystallization kinetics of polypropylene and poly (butyl methacrylate-co-hydroxyethyl methacrylate) blend was investigated with differential scanning calorimetry. The isothermal crystallization analysis based on the Avrami theory indicated a heterogeneous nucleating effect from the copolymer. A systematic study of the nonisothermal crystallization kinetics was undertaken using the Avrami equation and its later modifications by Ozawa, Mo, and Zhang. The results demonstrated that the linear relationship failed in the different cooling rates because the Avrami method did not take into account that the crystallization temperature was lowered continuously. The Ozawa and Mo methods could be successful in describing the overall nonisothermal process of polypropylene and the blend. In addition, the nonisothermal crystallization energy values were estimated by the Kissinger and Freidman models. There are two mutually opposite effects on the crystallization behavior of the blend: nucleation ability and growth retardation.

Synthesis and Performance of a Novel Aromatic Amine Curing Agent for Epoxy Resin

A new curing agent(PBMI-DDE) for epoxy resin was synthesized from phthalide-containing bismaleimide(PBMI) and aromatic amine(DDE) according to the Michael addition reaction. The chemical structure of PBMI-DDE was characterized by1 H NMR spectroscopy and Fourier transform infrared spectroscopy(FTIR). The curing performance and kinetics of E-51/ PBMI-DDE was studied by DSC.Apparent activation energy evaluated according to Kissinger model or FWO model is 46.7 or 49.1 kJ/mol,respectively, and the calculated reaction order is 0.88 based on Crane method. The DMA and TGA results show that the cured resin possesses excellent thermostability with a glass transition temperature153℃ for the completely cured resin.

Crystallization and Glass Transition Kinetics of Na2s-P2s5-Based Super-Ionic Glasses

In the present study, sulfide glass xNa2S-(100–x)P2S5, 35 ≤ x ≤ 55 has been synthesized by the melt quenched technique. All the glass samples are characterized by x-ray diffraction (XRD), differential thermal analysis (DTA), dilatometery, and impedance spectroscopy. The XRD pattern of a sample showing a broad halo indicates its amorphous nature. Dilatometric study demonstrates that for x = 45 and x = 55 mol% Na2S samples exhibited higher thermal stability than x = 35, x = 40, and x = 50 samples. To understand the crystallization kinetics, DTA was carried out for x = 45 and 55 samples at different heating rates, viz. 10, 20, 30, and 40°C/min. Crystallization kinetics of synthesized glasses for x = 45 and 55 are calculated using Kissinger's model. The thermal expansion coefficient (TEC) of glasses for x = 45 and x = 55 is found to be almost comparable to β-alumina solid electrolyte, which is being used in rechargeable batteries.

Characterization of poly(amic acid)s and resulting polyimides bearing azobenzene moieties including investigations of thermal imidization kinetics and photoinduced anisotropy

Azobenzene-containing poly(amic acid)s and resulting polyimides were synthesized. Polymers differed in the polymer backbone structure and the position at which the azobenzene group was attached to the polymer chain. Polymers were characterized and evaluated using Fourier transform infrared, 1H NMR and UV-visible spectroscopies, X-ray diffraction, differential scanning calorimetry (DSC) and thermogravimetric analysis. Polyimides revealed glass transition temperatures in the range 160–265 °C, and thermal stability with decomposition temperatures in the range 336–444 °C. The thermal imidization kinetics of poly(amic acid)s was investigated by means of DSC. Kinetic parameters, such as the activation energy (E) and the frequency factor, were estimated using the Ozawa and Kissinger models. The values of E, determined using both methods, were in the range 142.52–200.92 kJ mol−1. The photoinduced optical anisotropy (POA) was studied in the obtained azopolymers using a holographic grating recording technique. Surface relief gratings, which appeared after light exposure, were observed using atomic force microscopy. For the first time to the best of our knowledge, photoinduced anisotropy in poly(amic acid)s was studied and compared with POA in their polyimide analogues. © 2014 Society of Chemical Industry

Amorphous <inline-formula> <tex-math notation="TeX">${\rm CoFe}_{2}{\rm O}_{4}$ </tex-math></inline-formula> Nanoparticles: Synthesis, Crystallization Process, and Magnetic Properties

Amorphous ${\rm CoFe}_{2}{\rm O}_{4}$ nanoparticles have been successfully synthesized by the chemical microwave-assisted method. The crystallization process and the hard magnetic properties of prepared nanoparticles were systematically investigated in terms of thermal analysis and in situ measurement of magnetization dynamics. The as-prepared sample was amorphous, which was confirmed by various techniques, such as high resolution transmission electron microscopy, with electron diffraction and X-ray diffraction. The thermal analysis using differential scanning calorimetry showed that crystallization from ${\rm CoFe}_{2}{\rm O}_{4}$ amorphous state to ${\rm CoFe}_{2}{\rm O}_{4}$ crystalline started at 290 $^{\circ}{\rm C}$ . Crystallization activation energy was determined using the Kissinger model with a value of 1.09 eV. A study of the temperature dependence of magnetization supported the crystallization process of cobalt ferrite nanoparticles. Magnetic measurement indicated that the as-prepared amorphous particles were superparamagnetic. Compared with the bulk material, the observed value of saturation magnetization of the annealed sample was significantly low (27 emu/g) due to its nanocrystalline nature.

Halogeno‐modified polystyrene: monomer reactivity ratios, thermal behaviour and flammability

AbstractChemical modification based on incorporation of flame retardants into polymer backbones was used in order to reduce flammability of polystyrene (PSt). The halogeno‐substituted styrenes: 4‐chlorostyrene (ClSt), 4‐bromostyrene (BrSt) and 2,3,4,5,6‐pentafluorostyrene (5FSt) were applied as reactive flame retardants. Homo‐ and copolymers of these halogeno‐substituted styrenes and styrene (St) were synthesized with various feed ratios using free radical bulk polymerization with azobisisobutyronitrile as a initiator. This yielded series of (co)polymers with various amounts of included ClSt, BrSt and 5FSt (5–50 mol% of modified St). Copolymer compositions were determined using 1H NMR spectroscopy. The relative reactivity ratios of the used comonomers were determined by applying conventional linearization methods. The Jaacks (J) method was used for systems including BrSt and ClSt monomers whereas the Fineman–Ross method was additionally used to confirm the values of reactivity ratios of St–5FSt. The reactivity ratios of comonomer pairs obtained from J plots were 0.75 and 0.38 (St–ClSt), 1.65 and 0.46 (St–BrSt), 0.44 and 0.42 (St–5FSt). Glass transition temperature and thermal stability of obtained (co)polymers were determined using differential scanning calorimetry and thermogravimetric analysis (TGA), respectively. The thermal degradation kinetic of PSt, PClSt, PBrSt and P5FSt was studied applying TGA. Kinetic parameters such as thermal decomposition activation energy (E) and frequency factor (A) were estimated using Ozawa and Kissinger models. The resulting activation energies estimated using these two methods were quite close. The values of activation energy (kJ mol−1) increased in the following order: PClSt (E(O) = 216.1) < PSt (E(O) = 219.9) < PBrSt (E(O) = 224.7) < P5FSt (E(O) = 330.9). A pyrolysis combustion flow calorimeter was applied as a tool for assessing the flammability of the synthesized (co)polymers. © 2014 Society of Chemical Industry

The nonisothermal crystallization behavior of polyamide-6,6/mobile crystalline material hybrid composites prepared by in situ polymerization

A new kind of polyamide-6,6/mobile crystalline material (PA66/MCM-41) hybrid composites were prepared by in situ polymerization. The crystal structural and physical properties of these composites were investigated by Fourier transform infrared and nitrogen adsorption/desorption measurements. The nonisothermal crystallization behavior of PA66/MCM-41 was studied through differential scanning calorimetry measurements. Ozawa, Mo, and Kissinger models were used to analyze the kinetics of the nonisothermal crystallization process. It was found that MCM-41 acting as a nucleating agent in composites accelerated the crystallization rate; the Ozawa method failed to describe the nonisothermal crystallization behavior of PA66/MCM-41 composites. However, the Mo model was able to describe the nonisothermal crystallization process fairly well.