Studies on multistep thermal decomposition behavior of polytriazole polyethylene oxide‐tetrahydrofuran elastomer

Polytriazole polyethylene oxide‐tetrahydrofuran (PTPET) is an energetic propellant elastomer that is prepared using glycidyl azide polymer and trifunctional alkynyl‐terminated polyethylene oxide‐tetrahydrofuran. Its thermal decomposition, determined using thermogravimetic analysis, showed two mass‐loss peaks largely related to the decomposition of azide groups and the main chain. Flynn‐Wall‐Ozawa and Kissinger‐Akahira‐Sunose methods were deployed to obtain kinetic triplet parameters of PTPET thermal decomposition by the traditional model‐free method; the Coats‐Redfern approach was used as the model‐fitting method. Kinetics analysis indicated that the mechanism of the two‐step reactions were the primary‐reaction of first order and the power‐law phase reaction of the 2/3 order. The first decomposition stage of PTPET had an activation energy (E_a) of 113 to 116 kJ/mol while the second was 196 to 210 kJ/mol. The thermal decomposition of PTPET with different heating rates and mechanisms showed good kinetic compensation effects, the gas products being further studied with TG‐FTIR.     

CoC2O4·2H2O在空气中的热分解动力学研究

纳米Co3O4具有尖晶石结构,Co3 占据八面体位,具有较高的晶体场稳定化能,在空气中低于800℃时十分稳定,是优良的催化材料[1]。Co3O4还可以作为高比能锂离子电池负极材料具有非常好的电化学活性,充放电容量高达960m A h·g-1。纳米Co3O4在紫外、可见及近红外区域都有良好的吸收效果,因此,在隐身技术、保温节能技术等领域具有潜在的应用前景。所以,Co3O4超细粉体的制备和应用研究具有十分重要的意义。我们合成了草酸盐先驱物制备纳米Co3O4用作隐身材料,因此对先驱物的热分解过程研究是十分必要的。热分析方法在了解先驱物热分解反应的物理…     

Thermal decomposition kinetics of potassium iodate

The thermal decomposition of potassium iodate (KIO₃) has been studied by both non-isothermal and isothermal thermogravimetry (TG). The non-isothermal simultaneous TG–differential thermal analysis (DTA) of the thermal decomposition of KIO₃ was carried out in nitrogen atmosphere at different heating rates. The isothermal decomposition of KIO₃ was studied using TG at different temperatures in the range 790–805 K in nitrogen atmosphere. The theoretical and experimental mass loss data are in good agreement for the thermal decomposition of KIO₃. The non-isothermal decomposition of KIO₃ was subjected to kinetic analyses by model-free approach, which is based on the isoconversional principle. The isothermal decomposition of KIO₃ was subjected to both conventional (model fitting) and model-free (isoconversional) methods. It has been observed that the activation energy values obtained from all these methods agree well. Isothermal model fitting analysis shows that the thermal decomposition kinetics of KIO₃ can be best described by the contracting cube equation.     

A Comparison of Catalytic Effect of Nano‐Mn3O4 derived from MnC2O4.2H2O and Mn(acac)3 on Thermal Decomposition of Ammonium Perchlorate

The formation and catalytic effect of Mn₃O₄ spinel nanoparticles on thermal decomposition of ammonium perchlorate (AP) were investigated and compared to two manganese precursors of MnC₂O₄ · 2H₂O and Mn(acac)₃. The catalytic effects of two coated precursors on AP thermal decomposition were measured by differential scanning calorimetric (DSC) and thermogravimetric analysis (TG). The MnC₂O₄ · 2H₂O@AP composite showed a decrease in the decomposition temperature of AP from 428.35 to 310.93 °C in one step, whereas for the Mn(acac)₃@AP composite, the thermal decomposition was seen in two steps at 288.04 and 323.875 °C. The kinetic triplet of activation energy (E_a), frequency factor (log A) and model of mechanism function [f(α)] of thermal decomposition for pure ammonium perchlorate,MnC₂O₄ · 2H₂O@AP and Mn(acac)₃@AP were investigated via two model‐free (FWO, KAS and Starink) and model‐fitting (Starink) methods at different conversions of α (α = 0.05–0.95). Also, the thermodynamic parameters were obtained via activation energy and frequency factor for different concentrations of catalysts.     

Thermal Behavior and Decomposition Kinetics of the Complexes of CuX2 （X=NO3, Br, CI and CIO4） with 3,3＇-Dimethyl-1 -（1 H-1,2,4-triazol-1-yl）-2-butanone

The thermal behaviors of the complexes of Cu(DMTZB)4X2 (DMTZB=3,3‘-dimethyl-1-(1H-1,2,4-triazol-1-yl)-2-butanone, X=NO3 or ClO4) and Cu(DMTZB)2 X2 (X=Br or Cl) in a nitrogen atmosphere were studied under the non-isothermal conditions by simultaneous TG-DTG-DSC, EDS and elemental analysis techniques. The resuits showed that their decomposition proceeded in three different ways mainly depending on the anions in the molecules. The heat effect associated with the decomposition step of DMTZB molecules was also different. The decomposition mechanisms and the kinetic parameters of DMTZB were determined and calculated by jointly using four methods, which showed that its pyrolysis was controlled by D3 mechanism but with different activation energies and pre-exponential factors for different complexes.     

Thermal behavior study and decomposition kinetics of salbutamol under isothermal and non-isothermal conditions

The thermal decomposition of salbutamol (β₂ — selective adrenoreceptor) was studied using differential scanning calorimetry (DSC) and thermogravimetry/derivative thermogravimetry (TG/DTG). It was observed that the commercial sample showed a different thermal profile than the standard sample caused by the presence of excipients. These compounds increase the thermal stability of the drug. Moreover, higher activation energy was calculated for the pharmaceutical sample, which was estimated by isothermal and non-isothermal methods for the first stage of the thermal decomposition process. For isothermal experiments the average values were E _act=130 kJ mol⁻¹ (for standard sample) and E _act=252 kJ mol⁻¹ (for pharmaceutical sample) in a dynamic nitrogen atmosphere (50 mL min⁻¹). For non-isothermal method, activation energy was obtained from the plot of log heating rates vs. 1/T in dynamic air atmosphere (50 mL min⁻¹). The calculated values were E _act=134 kJ mol⁻¹ (for standard sample) and E _act=139 kJ mol⁻¹ (for pharmaceutical sample).     

The influence of CaCO3 filler component on thermal decomposition process of PP/LDPE/DAP ternary blend

Polypropylene‐low density polyethylene (PP‐LDPE) blends involving PP‐LDPE (90/10 wt%.) with (0.06 wt%) dialkyl peroxide (DAP) and different amounts (5, 10, 20 wt%) of calcium carbonate (CaCO₃) were prepared by melt‐blending with a single‐screw extruder. The effect of addition of CaCO₃ on thermal decomposition process and kinetic parameters, such as activation energy and pre‐exponential factor of PP‐LDPE blend with DAP matrix, was studied. The kinetics of the thermal degradation of composites was investigated by thermogravimetric analysis in dynamic nitrogen atmosphere at different heating rates. TG curves showed that the thermal decomposition of composites occurred in one weight‐loss stage. The apparent activation energies of thermal decomposition for composites, as determined by the Tang method (TM), the Kissinger–Akahira–Sunose method (KAS), the Flynn–Wall–Ozawa method (FWO), and the Coats–Redfern (CR) method were 156.6, 156.0, 159.8, and 167.7 kJ.mol^?1 for the thermal decomposition of composite with 5 wt% CaCO₃, 191.5, 190.8, 193.1, and 196.8 kJ.mol^?1 for the thermal decomposition of composite with 10 wt% CaCO₃, and 206.3, 206.1, 207.5, and 203.8 kJ mol^?1 for the thermal decomposition of composite with 20 wt% CaCO₃, respectively. The most likely decomposition process for weight‐loss stages of composites with CaCO₃ content 5 and 10 wt% was an A_n sigmoidal type. However, the most likely decomposition process for composite with CaCO₃ content 20 wt% was an R_n contracted geometry shape type in terms of the CR and master plots results. It was also found that the thermal stability, activation energy, and thermal decomposition process were changed with the increase in the CaCO₃ filler weight in composite structure. Copyright © 2009 John Wiley & Sons, Ltd.     

Thermal study of TiO<Subscript>2</Subscript>–CeO<Subscript>2</Subscript> yellow ceramic pigment obtained by the Pechini method

TiO₂–CeO₂ oxides for application as ceramic pigments were synthesized by the Pechini method. In the present work the polymeric network of the pigment precursor was studied using thermal analysis. Results obtained using TG and DTA showed the occurrence of three main mass loss stages and profiles associated to the decomposition of the organic matter and crystallization. The kinetics of the degradation was evaluated by means of TG applying different heating rates. The activation energies (E _a) and reaction order (n) for each stage were determined using Horowitz–Metzger, Coats–Redfern, Kissinger and Broido methods. Values of E _a varying between 257–267 kJ mol^–1 and n=0–1 were found. According to the kinetic analysis the decomposition reactions were diffusion controlled.     

鬼臼毒素及其衍生物热分解反应的动力学研究

The thermal behavior and thermal decomposition kinetic parameters of podophyllotoxin （1） and 4 derivatives, picropodophyllin （2）, deoxypodophyllotoxin （3）, fl-apopicropodophyllin （4）, podophyllotoxone （5） in a temperature-programmed mode have been investigated by means of DSC and TG-DTG. The kinetic model functions in differential and integral forms of the thermal decomposition reactions mentioned above for first stage were established. The kinetic parameters of the apparent activation energy Ea and per-exponential factor A were obtained from analy- sis of the TG-DTG curves by integral and differential methods. The most probable kinetic model function of the decomposition reaction in differential form was （1- a）^2 for compounds 1-3,2/3·a^-1/2 for compound 4 and 1/2（1-a）·[-In（1-a）]^-1 for compound 5. The values of Ea indicated that the reactivity of compounds 1-5was increased in the order： 5〈4〈2〈1〈3. The values of the entropy of activation △S^≠, enthalpy of activation △H^≠ and free energy of activation △G^≠ of the reactions were estimated. The values of △G^≠ indicated that the thermal stability of compounds 1-3 with the samef（a） was increased in the order： 2〈3〈1.     

Thermal and electrical behavior of hybrid thermosets based on epoxy and maleimide resins cured with p-aminobenzoic acid

Two thermoset systems based on maleimides and diglycidyl ether of bisphenol A (DGEBA) cured with p-aminobenzoic acid were characterized in terms of thermal and electrical behavior. Thermal characterization has been undertaken by means of thermogravimetric analysis in nitrogen atmosphere up to 600°C using simultaneous thermogravimetric/Fourier transform infrared/mass spectrometry (TG/FT-IR/MS) analysis. In the first stage of thermal degradation, the global kinetic parameters [activation energy (E_a) and preexponential factor (log A₁ (s⁻¹))] were calculated using the isoconversional method of Friedman. The energies variation as well as the shape of the differential thermal analysis curves suggests that the thermal decomposition process occurred in multiple stages. The evolved gases analysis was conducted by simultaneous TG/FT-IR/MS coupled techniques. Dielectric relaxation spectroscopy characterization was also made.     

The Non‐Isothermal Decomposition Kinetics of NaNTO·H2O and the Relationship between its Structure and Properties

NaNTO·H₂O was prepared by mixing 3‐nitro‐1,2,4‐triazol‐5‐one (NTO) aqueous solution and sodium hydroxide aqueous solution. Its thermal decomposition and kinetics were studied under non‐isothermal conditions by DSC and TG/DTG methods. The kinetic parameters were obtained from analysis of the DSC and TG/DTG curves by the Kissinger method, the Ozawa method, the differential method and the integral method. The most probable mechanism function for the thermal decomposition of the first stage was suggested by comparing the kinetic parameters. The critical temperature of thermal explosion (T_b) was 240.93 °C. The theoretical investigation on the structure unit of the title compound was carried out by DFT‐B3LYP/CEP‐31G methods; atomic net charges and the population analysis were discussed.     

Preparation and thermal analysis of synthetic malachite CuCO3·Cu(OH)2

The synthesis of malachite CuCO₃·Cu(OH)₂ or Cu₂CO₃(OH)₂ was studied through titrations of copper(II) salt solutions with a solution of sodium carbonate at different temperatures. The precipitates were characterized by TG, IR and chemical analysis. The composition varies depending on thepH of the solution and the temperature. Purer malachite was synthesized by simple mixing of a solution of copper(II) nitrate or sulfate with a solution of sodium carbonate at 50°C.The kinetics of the thermal decomposition of synthetic malachite was described by eitherR ₃ orA _m(m=1.2–1.4) law, according to TG analysis, both isothermal and nonisothermal. The Arrhenius parameters determined using three different integral methods showed the kinetic compensation effect, which is correlated to the working temperature interval analyzed.The authors thank Mr. H. Takemoto for analyzing kinetics of the thermal decomposition of synthetic malachite.     

Non-isothermal decomposition kinetics of NiFe<Subscript>2</Subscript>O<Subscript>4</Subscript> nanoparticles synthesized using egg white solution route

The thermal decomposition kinetics of nickel ferrite (NiFe₂O₄) precursor prepared using egg white solution route in dynamical air atmosphere was studied by means of TG with different heating rates. The activation energy (E _α) values of one reaction process were estimated using the methods of Flynn–Wall–Ozawa (FWO) and Kissinger–Akahira–Sunose (KAS), which were found to be consistent. The dependent activation energies on extent of conversions of the decomposition reaction indicate “multi-step” processes. XRD, SEM and FTIR showed that the synthesized NiFe₂O₄ precursor after calcination at 773 K has a pure spinel phase, having particle sizes of ~54 ± 29 nm.     

Thermal behavior of drugs

Data on the thermal stability of drugs was required to obtain information for handling, storage, shelf life and usage. In this study, the thermal stability of two nonsteroidal anti-inflammatory drugs (NSAIDs) was determined by differential scanning calorimetry (DSC) and simultaneous thermogravimetery/differential thermal analysis (TG/DTA) techniques. The results of TG analysis revealed that the main thermal degradation for the naproxen and celecoxib occurs in the temperature ranges of 196–300 and 245–359 °C, respectively. The TG/DTA analysis of compounds indicates that naproxen melts (at about 158.1 °C) before it decomposes. However, the thermal decomposition of the celecoxib started about 185 °C after its melting. The influence of the heating rate (5, 10, 15, and 20 °C min⁻¹) on the DSC behavior of the both drug samples was verified. The results showed that, as the heating rate was increased, decomposition temperatures of the compounds were increased. Also, the kinetic parameters such as activation energy and frequency factor for the compounds were obtained from the DSC data by non-isothermal methods proposed by ASTM E696 and Ozawa. Based on the values of activation energy obtained by various methods, the following order for the thermal stability was noticed: naproxen > celecoxib. Finally, the values of ΔS ^#, ΔH ^#, and ΔG ^# of their decomposition reaction were calculated.     

Thermal decomposition kinetics of potassium iodate

The effect of gamma ray irradiation on the rate and kinetics of thermal decomposition of potassium iodate (KIO₃) has been studied by thermogravimetry (TG) under non-isothermal conditions at different heating rates (3, 5, 7, and 10 K min^?1). The thermal decomposition data were analyzed using isoconversional methods of Flynn–Wall–Ozawa, Kissinger–Akahira–Sunose, and Friedman. Irradiation with gamma rays increases the rate of the decomposition and is dependent on the irradiation dose. The activation energy decreases on irradiation. The enhancement of the rate of the thermal decomposition of KIO₃ upon irradiation is due to the combined effect of the production of displacements and extended lattice defects and chemical damage in KIO₃. Non-isothermal model fitting method of analysis showed that the thermal decomposition of irradiated KIO₃ is best described by the contracting sphere model equation, with an activation energy value of ~340 kJ mol^?1.     

Study on thermal decomposition of calix[6]arene and calix[8]arene

Thermal decomposition kinetics of calix[6]arene (C6) and calix[8]arene (C8) were studied by Thermogravimetry analysis (TG) and Differential thermal analysis (DTA). TG was done under static air atmosphere with dynamic heating rates of 1.0, 2.5, 5.0, and 10.0 K min⁻¹. Model-free methods such as Friedman and Ozawa–Flynn–Wall were used to evaluate the kinetic parameters such as activation energy (E _a) and pre-exponential factors (ln A). Model-fitting method such as linear regression was used for the evaluation of optimum kinetic triplets. The kinetic parameters obtained are comparable with both the model-free and model-fitting methods. Within the tested models, the thermal decomposition of C6 and C8 are best described by a three dimensional Jander’s type diffusion. The antioxidant efficiency of C6 and C8 was tested for the decomposition of polypropylene (PP).     

Compatibility and decomposition kinetics studies of prednicarbate alone and associated with glyceryl stearate

In this work, TG/DTG and DSC techniques were used to the determination of thermal behavior of prednicarbate alone and associated with glyceryl stearate excipient (1:1 physical mixture). TG/DTG curves obtained for the binary mixture showed a reduction of approximately 37 °C to the thermal stability of drug ( T_{\textdm/\textdt = 0 \textDTG}^\textMax T_{{{\text{d}}m/{\text{d}}t = 0\,{\text{DTG}}}}^{\text{Max}} ). The disappearance of stretching band at 1280 cm⁻¹ (ν_as C–O, carbonate group) and the presence of streching band with less intensity at 1750 cm⁻¹ (ν_s C–O, ester group) in IR spectrum obtained to the binary mixture submitted at 220 °C, when compared with IR spectrum of drug submitted to the same temperature, confirmed the chemical interaction between these substances due to heating. Kinetics parameters of decomposition reaction of prednicarbate were obtained using isothermal (Arrhenius equation) and non-isothermal (Ozawa) methods. The reduction of approximately 45% of activation energy value (E _a) to the first step of thermal decomposition reaction of drug in the 1:1 (mass/mass) physical mixture was observed by both kinetics methods.     

Thermal studies on polymorphic structures of tibolone

Tibolone polymorphic forms I (monoclinic) and II (triclinic) have been prepared by recrystallization from acetone and toluene, respectively, and characterized by different techniques sensitive to changes in solid state, such as polarized light microscopy, X-ray powder diffractometry, thermal analysis (TG/DTG/DSC), and vibrational spectroscopy (FTIR and Raman microscopy). The nonisothermal decomposition kinetics of the obtained polymorphs were studied using thermogravimetry. The activation energies were calculated through the Ozawa’s method for the first step of decomposition, the triclinic form showed a lower E _a (91 kJ mol⁻¹) than the monoclinic one (95 kJ mol⁻¹). Furthermore, Raman microscopy and DSC at low heating rates were used to identify and follow the thermal decomposition of the triclinic form, showing the existence of three thermal events before the first mass loss.     

Researches on Thermal Decomposition Kinetics of Composite Modified Double-base Propellants

The thermal decomposition kinetics of composite modified double‐base (CMDB) propellants with a series of contents of hexogeon (RDX) was investigated by using parameters of T_eo, T_i, T_p, T_f, T_b, T_a, E, lg A and ΔH, which were obtained from using a CDR‐4P differential scanning calorimeter (DSC) and Perkin‐Elmer Pyris 1 thermogravimetric analyzer (TG) analyses with heating rates of 5, 10, 15 and 20 K/min. Reliable activation energy was calculated using Flynn‐Wall‐Ozawa method before analyzing the thermal decomposition mechanism. TG‐DTG curves were treated with Malek method in order to obtain the reaction mechanisms. The obtained results show that the thermal decomposition mechanisms with the conversion from 0.2 to 0.4 was f(α)?1/2α, and with the conversion from 0.5 to 0.7 was f(α)?(1/4)(1?α)[?ln(1?α)]^?3.     

Thermoanalytical behaviour of carbaryl and its copper(II) and zinc(II) complexes

Non-isothermal techniques, i.e. thermogravimetry (TG) and differential scanning calorimetry (DSC), have been applied to investigate the thermal behaviour of carbaryl (1-naphthyl-N-methylcarbamate = 1-Naph-N-Mecbm) and its complexes, M(1-Naph-N-Mecbm)₄X₂, where M = Cu, X = Cl, NO₃ and CH₃COO and M = Zn, X = Cl. Carbaryl and Zn(1-Naph-N-Mecbm)₄Cl₂ complex exhibit two-stage thermal decomposition while the copper(II) complexes exhibit three and four-stage decomposition in their TG curves. The nature of the metal ion has been found to play highly influential role on the nature of thermal decomposition products as well as energy of activation ‘E*’. The presence of different anions does not seem to alter the thermal decomposition patterns. The complexes display weak to medium intensity exothermic and endothermic DSC curves, while the free ligand exhibits two endothermic peaks. The kinetic and thermodynamic parameters namely, the energy of activation ‘E*’, the frequency factor ‘A’ and the entropy of activation ‘S*’ etc. have been rationalized in relation to the bonding aspect of the carbaryl ligand. The nature and chemical composition of the residues of the decomposition steps have been studied by elemental analysis and FTIR data.