Non-isothermal Thermogravimetry Research Articles

Thermal stability and Kinetic Study of rigid and plasticized Poly(vinyl chloride)/Poly(methylmethacrylate) blends

The thermal stability and kinetic parameters for degradation of rigid and plasticized poly(vinyl chloride)/poly (methylmethacrylate) blends have been investigated by using nonisothermal thermogravimetry in a flowing atmosphere of air. For that purpose, blends of variable composition from 0 to 100 wt% were prepared in the presence (15, 30, and 50 wt%) and in the absence of di‐(‐2‐ethyl hexyl) phthalate as plasticizer. Measurements were carried out in the temperature range of 30–550°C and at various heating rates (5, 10, 20, and 40°C/min). The kinetic parameters (Ea and A) were determined by applying the integral Kissinger method. Results indicate that these parameters and the thermal stability of the blends are dependent on the blend composition and the amount of plasticizer present. J. VINYL ADDIT. TECHNOL., 21:102–110, 2015. © 2014 Society of Plastics Engineers

Thermal Decomposition Study of Ferrocene [(C5H5)2Fe

A single-step thermal decomposition of ferrocene [(C5H5)2Fe] using nonisothermal thermogravimetry (TG) has been studied using single- as well as multiple-heating rate programs. Both mechanistic and nonmechanistic methods have been used to analyze the TG data to estimate the kinetic parameters for the solid state reaction. Two different isoconversional methods (improved iterative method and model-free method) have been employed to analyze the TG results to find out whether the activation energy of the reaction depends on the extent of decomposition and to predict the most probable reaction mechanism of thermal decomposition as well. A comparison of the activation energy values for the single-step thermal reaction of ferrocene estimated by different methods has been made in this work. An appraisal on the applicability of single-heating rate data for the analysis of single-step thermal decompositions over the recommendations by the International Confederation for Thermal Analysis and Calorimetry (ICTAC) is made to look beyond the choice.

On the degradation kinetics of poly(ethylene terephthalate) (PET)/poly(methyl methacrylate) (PMMA) blends in dynamic thermogravimetry

Abstract A thermal degradation model was developed for blends of Poly(ethylene terephthalate) (PET)/Poly(methyl methacrylate) (PMMA) subjected to non-isothermal (dynamic) thermogravimetry at four heating rates (5, 10, 15 and 20 °C/min). The model developed enabled the assessment of pre-exponential factor (A) and apparent activation energy (Ea) for each polymer individually in the blend after developing a mathematical expression based on an integral solution, which was related to both polymer fractions and their blending characteristics in the form of kinetic parameters. The unique approach presented in this study showed that the apparent activation energy of PET (Ea1) in the blend (240–270 kJ/mol) is always higher than PMMA's apparent activation energy (Ea2, 140–170 kJ/mol), which is attributed to the degradation mechanism of the blend and the latter being of a lower melting point hence degrading faster. It was also observed that the activation energy of both polymers increased with PET composition and decreased with higher heating rates, which can be attributed to PET acting as an inhibitor to PMMA in the blends.

Preparation and characterization of poly(3-hydroxybutyrate)/ Cloisite25A nanocomposites

Abstract Poly(3-hydroxybutyrate)/Cloisite25A (PHB/25A) nanocomposites were prepared by solution-intercalation method. The intercalation of PHB chains between the layers of Cloisite25A was observed by X-ray diffraction (XRD). Differential scanning calorimetry (DSC) and non-isothermal thermogravimetry (TG) analysis were performed to study the thermal properties, crystallization and the thermal degradation of the prepared nanocomposites. DSC analysis indicates that Cloisite25A acts as a nucleating agent and increases the crystallization rate of PHB, but due to intercalation reduces its overall degree of crystallinity. TG analysis shows that addition of Cloisite25A enhances the thermal stability of PHB.

Thermal decomposition mechanism of p-tert-butyl-calix[n]arenes

Thermal decomposition of p-tert-butyl-calix[n]arene was studied using thermo gravimetry (TG) and differential thermo gram (DTG) methods. Non-isothermal TG was done under static air atmosphere with 1, 2.5, 5.0 and 10.0K/min. Model-free methods such as Friedman and Flynn Wall Ozawa (FWO) were used to evaluate the kinetic parameters such as activation energy and exponential factors. The probable thermal decomposition mechanism was proposed by analyzing the quenched intermediate p-tert-butyl-calix[n]arene samples with FTIR, mass, 1H NMR, 13C NMR cross polarization magic angle spectrometry (CP-MAS), EPR spectroscopy and elemental analysis. The thermal stability of the polyolefins was checked with p-tert-butyl-calix[n]arene as an antioxidant additive.

Fire safety evaluation of expanded polystyrene foam by multi-scale methods

Microscale thermal analysis, bench scale cone calorimetric and real scale burning tests were conducted to evaluated fire safety performance of expanded polystyrene (EPS) foam. Simultaneous thermal analysis was used to study the thermal degradation of the foam in nitrogen, air, and oxygen environments at four heating rates. An endothermic effect is observed only in nitrogen environment, while two exothermic effects are observed in oxygen and air environments. In the nitrogen environment, the onset temperature of the endothermic effect and the endothermic peak temperature are much higher than that of the exothermic processes observed in air and oxygen environments. The Flynn–Wall–Ozawa method is utilized to analyze the degradation kinetics of the non-isothermal thermogravimetry. The activation energies calculated for an air environment, in a conversion range α = 20–70 %, are lower than those for an oxygen environment. The temperature range for this conversion range is 275–371 °C. The enthalpies of the first exothermic effect exceed that of the oxygen environment by 10–45 %. Bench scale cone calorimetric tests were carried out at incident heat flux of 25, 35, and 50 kW m−2 with two sets of cone equipment. Heat release rate, ignition time, effective heat of combustion, and critical heat flux required for ignition is obtained. In real scale burning tests, the EPS boards were ignited in sandwich structures. Fire spread speeds were derived from temperature measurement inside sandwich structure.

UV initiated oxidation and chemiluminescence from aromatic–aliphatic co-polyesters and polylactic acid

The chemiluminescence of UV irradiated aromatic–aliphatic polyesters (Ecoflex and PBAT) and polylactic acid (PLA) was examined in nitrogen and oxygen atmospheres during the non-isothermal temperature runs in the interval from 40 to 250 °C and isothermally from 150 to 190 °C. The non-isothermal thermogravimetry and FTIR spectroscopy have been used for the characterization of differences in original samples. The temperature maxima of peroxidic peaks in nitrogen scaling their stability were compared and found to be in the order PBAT < Ecoflex < PLA. Their positions on the temperature scale that correlate well with the melting temperature of the respective polymer have been discussed. With prolongation of the UV irradiation period, the intensity of peroxidic peaks increased. On the other hand, the effect of pre-irradiation on non-isothermal runs of chemiluminescence measured in oxygen was not as distinct as for measurements in nitrogen. The deconvolution of the non-isothermal chemiluminescence runs in nitrogen revealed two kinds of peroxides in irradiated samples.

Thermal decomposition kinetics of rigid polyurethane foam and ignition risk by a hot particle

ABSTRACTRigid polyurethane foam, one kind of building insulation material used in China, is prone to being ignited by hot particles from fireworks or welding processes and has been the fuel for some catastrophic fire accidents. Thermal decomposition has long been recognized to play an important role in the ignition and fire‐spreading processes of materials, and thus, it is important to understand the behavior and kinetics of material decomposition. In this study, the characteristics of the thermal decomposition of polyurethane foam were investigated in an air atmosphere with nonisothermal thermogravimetry and differential scanning calorimetry (DSC). Model‐free (isoconversional) methods and model‐fitting methods were used to study the decomposition kinetics. The results reveal that the decomposition process of polyurethane foam in air presented three main stages: the loss of low‐stability organic compounds (bond fission of the weakest link in the chain), oxidative degradation of organic components, and oxidative degradation of residue material. A scheme containing three consecutive reactions was proposed to describe the decomposition process, and good agreement was found between the experimental and simulated curves. The heat during decomposition was calculated from DSC measurement. On the basis of the kinetics and heat of decomposition, the critical conditions for a hot particle to ignite polyurethane foam was evaluated, and this was helpful for the understanding the ignition risk of polyurethane foam. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39359.

Investigation on Thermal Decomposition Kinetics of Ulipristal Acetate (Form B)

Non-isothermal thermogravimetry analysis was applied to study the thermal decomposition kinetics of ulipristal acetate (form B). According to the experimental result, ulipristal acetate (form B) decomposed included three steps. Based on different kinetics function of corresponding thermal decomposition mechanisms and experimental data of ulipristal acetate (form B), decomposition mechanisms of three steps of ulipristal acetate (form B) were analyzed by differential method. According to fitting results of different mechanism functions, decomposition mechanisms of three steps of ulipristal acetate (form B) were determined, and three corresponding thermal decomposition dynamic functions were also obtained.

Study on the Thermal Stability of Polyphenylene Sulfide Filter Media by Non-Isothermal Thermogravimetry

In order to study the thermal stability of PPS (polyphenylene sulfide) filter media, by means of non- isothermal thermogravimetry, thermal degradation kinetics behavior of two kinds of PPS filter media were analyzed. The kinetic parameters of PPS filter media were obtained according to Friedman method. Thermal stability of PPS filter media was discussed. It was found that the initial decomposition temperature and activation energy of N3 sample are all higher than B1 sample, the thermal stability of N3 sample is better than B1 sample, and kinetic analysis can be used as an important method to evaluate the thermal stability of filter media.

Nonisothermal kinetics analysis of the dehydration of ziprasidone hydrochloride monohydrate by thermogravimetry

In the current work the kinetics of dehydration of ziprasidone hydrochloride monohydrate was studied by nonisothermal thermogravimetry. Ziprasidone hydrochloride monohydrate was heated from 30 to 150° with a heating rate of 5° per min under nitrogen gas atmosphere and weight loss data were collected. Powder X-ray difraction was used to characterize the solid before and after dehydration. The well accepted Coats-Redfern model fitting approach was applied to the thermogravimetry data for the kinetic analysis. Thirteen solid state reaction models were studied; among them one-dimensional diffusion model was found to be the best fit model for this reaction with an excellent correlation 0.9994. The Arrhenius parameters, activation energy, and pre-exponential factor were determined, the values were found to be 28 k.cal/mol and 9.53×1013 sec−1, respectively.

Combustion Process’s Kinetics Study of Biomass and its Cellulose Based on Biomaterials in Material Engineering

The combustion characteristics of some biomass samples, such as rice straw and its cellulose, were investigated. Non-isothermal thermogravimetry, where the sample was heated in air and the temperature of which increased at a linear rate of 10°C/min, 20°C/min, 30°C/min, was used to investigate combustion process of the biomass samples. The differences in the TG-DTG-DSC curves of the samples were determined and discussed in detail. Results showed that combustion process can be described in terms of first order reaction.

CoTiO3 via cobalt oxalate–TiO2 precursor. Synthesis and characterization

Abstract Purely trigonal ilmenite type powder; CoTiO3 was successfully synthesized through the thermal decomposition of CoC2O4·2H2O–TiO2 precursor. The decomposition course was followed using differential thermal analysis–thermogravimetry measurements and the intermediate decomposition products as well as the titanate product were characterized using X-ray diffraction, Fourier transform infrared, transmission electron microscopy techniques. Thermal analysis study indicated that, the intermediate decomposition product; Co3O4 decomposed endothermically into CoO at 963 °C with instantaneous formation of CoTiO3. X-ray diffraction of the powder calcined at 950 °C showed characteristic lines for Co2TiO4 besides secondary phase of rutile-TiO2, which are disappeared by rising the calcination temperature to 1000 °C. Transmission electron microscopy image of CoTiO3 powder exhibit weak agglomerated particles with heterogeneous morphology in both shape and dimensions. Type II adsorption isotherm estimated using Brunauer–Emmett–Teller procedure indicated a very high specific surface area of 29.7 m2 g− 1. Electrical properties of CoTiO3 measured as a function of temperature and frequency showed a semiconducting behavior at high temperatures with conduction activation energy of 0.73 eV. Kinetic analysis of the non-isothermal thermogravimetry curves, using different computational methods, illustrated that the random nucleation and growth mechanisms are the predominant one.

Thermal behavior and decomposition kinetics of Formex-bonded explosives containing different cyclic nitramines

Thermal behavior and decomposition kinetics of Formex-bonded PBXs based on some attractive cyclic nitramines, such as 1,3,5-trinitro-1,3,5-triazinane (RDX) and 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX). Actually, cis-1,3,4,6-tetranitrooctahy droimidazo-[4,5-d]imidazole (BCHMX) and 2,4,6,8,10,12-hexanitro-2,4,6,8,10, 12-hexaazaisowurtzitane (CL-20), was investigated by means of nonisothermal thermogravimetry (TG) and differential scanning calorimetry (DSC). It was found that the mass loss rate of PBXs involved in this research depends greatly on heating rate and the residue of the decomposition of these PBXs decreases with the heating rate. The onset of the exotherms was noticed at 215.4, 278.7, 231.2 and 233.7 °C with the peak maximum at 235.1, 279.0, 231.2 and 233.7 °C for RDX-Formex, HMX-Formex, CL-20-Formex, and BCHMX-Formex, respectively. Their corresponding exothermic changes were 1788, 1237, 691, and 1583 J g−1. It was also observed that the dependence on the heating rate for onset temperatures of HMX- and BCHMX-based PBXs was almost the same due to their similar molecular structure. In addition, based on nonisothermal TG data, the kinetic parameters for thermal decomposition of these PBXs were calculated by isoconversional methods. It was shown that the Formex base has great effects on the activation energy distribution of nitramines. It was further found that the kinetic compensation effects occurred during the thermal decomposition of nitramine-based PBXs, and they almost have the same compensation effects due to similar decomposition mechanism.

Permethylated β-cyclodextrin/pesticide complexes: X-ray structures and thermogravimetric assessment of kinetic parameters for complex dissociation

The X-ray crystal structures of the inclusion complexes formed between three pesticides (two organophosphorus insecticides and one chloroacetanilide herbicide) and permethylated β-cyclodextrin (TRIMEB) are reported. The complexes TRIMEB–fenitrothion (1), TRIMEB–fenthion (2) and TRIMEB–acetochlor (3) are members of a commonly occurring isostructural series. The mode of inclusion of the two organophosphate insecticides is very similar, while the acetochlor molecule, which is structurally quite distinct from the two insecticide molecules, adopts a somewhat different position within the TRIMEB cavity. In addition to the structural elucidation of these complexes, their thermal behaviour was investigated using isothermal and non-isothermal thermogravimetry. The isothermal results showed that the dissociation of the guest molecules from the TRIMEB cavities can best be described by two mechanisms, namely a first-order reaction model and a three-dimensional diffusion model. Both the isothermal and non-isothermal methods allowed the determination of the activation energies of the guest loss process for each complex.

Dehydroxylation kinetics of lizardite

The thermally induced dehydroxylation of lizardite and its phase transformation to forsterite were studied by high-temperature X-ray diffraction (H T -XRD), thermogravimetry (TGA) and Fourier-transformed infrared spectroscopy (FTIR). Primary sample characteristics like chemical composition and crystallographical structure were determined by combined (HR)TEM-EDX, electron-microprobe analyses (EMPA) as well as conventional X-ray diffraction (XRD). Isothermal H T -XRD and non-isothermal TGA data were treated with the classical Avrami-Erofe’ev method and more advanced isoconversional methods in order to obtain kinetic data of a multi-step decomposition reaction. A highly precise activation energy E a versus reaction progress (α) dependency based on non-isothermal TGA data of lizardite is provided and associated mechanisms are discussed. Here, the main focus is on recently published ab initio calculations from the phase transformation of other phyllosilicates. Moreover, the calculated overall apparent activation energy is compared with discrepant data from the literature and discussed. Especially, the usability of overall activation energies of multi-step decomposition reactions is critically discussed. The presented and discussed reaction steps of water formation from different hydroxyl species in lizardite can be used to improve ab initio calculations, especially the pre-selection of reacting hydroxyl species in hydrous sheet like minerals.

Combustion characteristics of sodium-free pyrolytic char from hazelnut shell

Hazelnut shell is a woody biomass with high sodium content that leads severe fouling problems in combustion systems. Thus, hazelnut shells were pyrolysed under nitrogen to eliminate sodium, and then the burning characteristics of the obtained sodium-free pyrolytic char were investigated up to 900°C by non-isothermal thermogravimetry. Inorganic and the morphological properties of original biomass and the char were investigated via Inductively Coupled Plasma (ICP) and Scanning Electron Microscopy (SEM) techniques. Also, inorganic phases in the pyrolytic char were determined by X-Ray Diffractometry (XRD). The pyrolytic chars were burned up to 900°C by heating rates of 5, 10, 20, 30, 40, and 50°C/min under dry air flow. It was found that the pyrolysis process almost eliminated sodium, and a sodium-free char that has higher calorific value compared to the parent biomass was obtained. The reactivity of the char during combustion did not show any decrease as conversion proceeds. It was also found that char burning reactivity was higher at low heating rate conditions. Also heating rate has an influence on burning of char in such a way that the increasing heating rate shifted the temperatures of maximum burning rates to higher temperatures.

Kinetics of the Dehydroxylation of Serpentine

There has been increasing interest in carbon dioxide sequestration in mineral form, because there are large deposits of silicate minerals in peridotite and basalt that have the potential for this option. We examined the dehydroxylation of natural serpentine ore, considered to be a candidate for mineralization of CO2. In this study, serpentine and dehydroxylated serpentine have been characterized using different techniques and the dehydroxylation kinetics of serpentine has been investigated by non-isothermal thermogravimetry. The results indicated that the thermal decomposition of magnesium serpentine [Mg3Si2O5(OH)(4)] proceeds via the removal of physisorbed water and, subsequently, the hydroxyl group. Kinetic modeling of the dehydroxylation shows that the reaction follows a three-dimensional diffusion-controlled mechanism in the particles. The effect of the heating rate and particle size on the dehydroxylation reaction has been investigated, and the results are found to be consistent with diffusion-controlled kinetics. The gas solid heat-transfer resistance is shown to influence the results at a high heating rate and large particle size.

Thermoplastic polyurethane/(organically modified montmorillonite) nanocomposites produced by in situ polymerization

A series of polyurethane nanocomposites were synthesized from thermoplastic polyurethanes (with different hard segment ratios) and two types of organically modified montmorillonites (OMMT) - Cloisite ® 10A and Cloisite ® 20A. The thermal behavior was examined by non-isothermal thermogravimetry (TG, DTG), Differential Scanning Calorimetry (DSC) and Dynamic-Mechanical Thermal Analysis (DMTA). The results of X-ray analyses showed that the OMMT pro- duced the intercalated polyurethane nanocomposites. It has been proven that the thermal stability and tensile properties of these new systems were higher when the organoclay was present within the polymer matrix. Moreover, these properties depend on both the OMMT loading and the type of gallery cations of the organically modified montmorillonites.

Experimental Study on Coal Pyrogenation Characteristic and Dynamic Model of Reaction

The study effort was in progress through a thermogravimetric analyzer which export experimental data for construction pyrogenation dynamic model when import varied coal grain diameter in non-isothermal thermogravimetry method. This paper chiefly introduces a study on coal pyrogenation process with different altering parameter like temperature rise rate, grain diameter of coal that has been proved to affect in a big way in the whole work. The experimental research represents that there are four stages of the coal thermal decomposition, taking volatile release feature index as basic characteristic reflection to establish a thermogravimetry dynamic model.