Kinetic study of the pyrolysis of neoprene

Kinetics of neoprene thermal decomposition has been performed under dynamic conditions at different heating rates, between 5 and 80 °C/min in a TG apparatus. The same kinetic model has been applied simultaneously to runs performed at different heating rates and different atmospheres allowing a good correlation of the weight loss data. A mechanism based on three independent reactions has been used to model the thermal decomposition. The first reaction is of an order close to two, and the other two reactions are of order below one, similar to other plastic materials. Different alternatives for the mathematical treatment for fitting TG data were considered. The accuracy of the calculated kinetic parameters was studied by means of a sensibility analysis.     

Thermogravimetric and kinetic analysis of the decomposition of solid recovered fuel from municipal solid waste

The thermal decomposition of a solid recovered fuel has been studied using thermogravimetry, in order to get information about the main steps in the decomposition of such material. The study comprises two different atmospheres: inert and oxidative. The kinetics of decomposition is determined at three different heating rates using the same kinetic constants and model for both atmospheres at all the heating rates simultaneously. A good correlation of the TG data is obtained using three nth-order parallel reactions.     

Kinetics of pyrolysis and combustion of pine needles and cones

A wide kinetic study has been carried out under different conditions in TG and TG–MS for each material, at different operating conditions. Runs were carried out at three different atmospheres: N₂, N₂:O₂ 4:1 and N₂:O₂ 9:1. In addition to the dynamic runs carried out at constant heating rate, other runs were performed in an isothermal regime (constant heating rate until the set temperature is reached and then the set temperature is maintained constant).In addition, a study of the thermal decomposition for both materials was also carried out in a dynamic run using TG–MS in order to observe the evolution of the major compounds and to discuss the information that could be obtained.From the overall analysis of the data, schemes of reactions and kinetic values were calculated by integration of the differential equations and minimizing the squared differences between the experimental and calculated values. It is important to emphasise that the same set of parameters is proposed for the runs for each material, and depends on neither the heating rate in dynamic runs nor whether the run is carried out in a dynamic or isothermal mode.     

Kinetics of tetrabromobisphenol A pyrolysis. Comparison between correlation and mechanistic models

Brominated flame retardants are well recognized as being highly effective flame retardants. 4-4′-Isopropylidenebis(2,6-dibromophenol), commonly known as tetrabromobisphenol A, is the brominated flame retardant with the largest production volume and is used to improve fire safety, mainly of laminates in electrical and electronic equipment. A kinetic study of the pyrolysis of TBBA has been carried out to obtain decomposition parameters under different operating conditions and taking into account that TBBA is a compound with a high boiling point and that vaporization occurs simultaneously to decomposition. Dynamic runs and dynamic + isothermal run at different heating rates and using different masses of sample were correlated simultaneously. All TG runs were fitted with a unique set of kinetic parameters that is able to explain all the experiments. Moreover, a simplified detailed kinetic model has been developed and the kinetic parameters obtained satisfactorily reproduce the thermal decomposition of TBBA.     

Kinetic study of the pyrolysis and combustion of tomato plant

A kinetic study of the thermal decomposition of tomato plant has been carried out under different conditions by TG and TG–MS. A total of 24 experiments were performed in a nitrogen atmosphere (pyrolysis runs) and also in an oxidative atmosphere with two different oxygen concentrations (10% and 20% oxygen in nitrogen). Dynamic runs and dynamic + isothermal runs have been carried out to obtain many data of decomposition under different operating conditions.A scheme of five independent reactions for pseudocomponents has been proposed for the pyrolysis process, although only three fractions have probed to be significant, comparing the weight fractions of volatiles evolved with the hemicellulose, cellulose and lignin content of the plant. For the combustion runs, four new reactions have been added: two competitive oxidation reactions for the cellulose and lignin, and two combustion reactions of the carbonaceous residue obtained from pyrolysis. The kinetic parametres have been calculated by integration of the differential equations and minimizing the differences between the experimental and calculated values. It is important to emphasize that the same set of parameters has been proposed for the pyrolysis and combustion runs, and which do not depend on either the heating rate in dynamic runs or whether the run is carried out in a dynamic or isothermal mode. The influence of the oxygen pressure has been also discussed.     

Kinetic model of the decomposition of a PET fibre cloth in an inert and air environment

The kinetics of the global thermal decomposition of a PET fibre cloth have been studied in three different atmospheres with nitrogen, 20 and 10% oxygen, using thermogravimetric analysis (TGA) between room temperature and 1050 K. Three different heating rates were used at each atmosphere condition. Moreover, several isothermal experiments in nitrogen and 20% oxygen have been carried out. For the pyrolysis of an old PET fibre cloth, the kinetic model comprises three independent reactions. The combustion kinetic model considers that pyrolysis of two fractions of the initial material occurs regardless of the oxygen concentration and then a combustion of the forming char and the third fraction starts. One set of parameters can explain all the isothermal and dynamic experiments at the three different heating rates used.     

Analysis of the vaporization process in TG apparatus and its incidence in pyrolysis

An analysis of the evaporation process of n-hexadecane in a thermogravimetric apparatus was carried out. n-Hexadecane represents a typical example of a high boiling point compound and its study is interesting for understanding those processes where vaporization takes place in parallel with pyrolysis during thermal treatment. The process has been studied under different operating conditions: nitrogen and air atmospheres, and isothermal and dynamic runs with three different heating rates from 5 K/min to 20 K/min. The experimental data were satisfactorily correlated to a n-order model with zero process order and the same apparent activation energy for all runs, but the exponential factors of the different runs depended on the initial mass and the heating rate. The experimental results were compared with those predicted considering the diffusion process inside the crucible, taking into account the vapor pressure and the diffusion coefficient of n-hexadecane. A parameter, product of these two variables, can be estimated from a single TG run, so the vaporization process in other equipment and/or operating conditions can also be estimated.     

Applicability of bi-pseudo component separated-stage model for decomposition of lignocellulosic materials in air at multiple heating rates

In our previous research (Liu et al., J Anal Appl Pyrol 63:303–325, 2002), the pseudo bi-component separated-stage model (PBSM) was suggested for the kinetic analysis on the decomposition of lignocellulosic materials in air at relatively lower heating rates. As a continuing work, this paper is intended to investigate the applicability of PBSM at different heating rates by experimental analyses. Decomposition of oil tea wood has been studied by means of non-isothermal thermogravimetric analysis in air atmosphere at 10–25 K min⁻¹ heating rates. A two-step parallel reaction kinetic model is used to optimize the kinetic parameters of these materials in air. Meanwhile, an improved PBSM is developed to describe the thermal degradation process of oil tea wood. Furthermore, a comparison between the kinetic results of parallel model and PBSM reveals realistic applicability of PBSM. It is concluded that the PBSM has relatively high accuracy for the first decomposition step in the lower temperature range, while fails to predict the thermal decomposition behavior in the char oxidative process which occurs in the higher temperature range.     

Non-isothermal degradation of a thermoset powder coating in inert and oxidant atmospheres

This paper studies the thermal stability of an epoxy powder coating. The study was carried out in a thermobalance at various heating rates and in different atmospheres: nitrogen, air and oxygen. Degradation in air and oxygen leads to a kinetic process which is clearly different from degradation in an inert atmosphere. To characterise each process, the DTG signal peaks were separated and kinetic parameters were associated to each by means of the isoconversional method and other standard methods. The results obtained were compared with the experimental results. This revised version was published online in July 2006 with corrections to the Cover Date.     

Integration of block copolymer-wrapped single-wall carbon nanotubes into a trifunctional epoxy resin. Influence on thermal performance

Novel nanocomposite materials were prepared by incorporating block copolymer-wrapped single-wall carbon nanotubes (SWCNTs) into a trifunctional epoxy resin. The work was focused on the study of the influence of the SWCNTs and the block copolymer based on ethylene oxide and propylene oxide, Pluronic F68, on the thermal and thermo-oxidative cleavage reactions of the resin. A nanocomposite sample containing 2 wt% Pluronic-wrapped SWCNTs was prepared and its behaviour compared with that of Pluronic/epoxy and SWCNT/epoxy composites. Their thermal performance in both oxidative and inert atmospheres was evaluated by different techniques including thermogravimetric analysis (TGA), mass spectrometry and infrared spectroscopy. A kinetic study of the TGA data in both atmospheres based on the Vyazovkin’s advanced isoconversional method showed differences in the activation energies. Infrared spectroscopy of residues extracted at various steps during dynamic heating indicated a common degradation mechanism for all samples, and improved thermo-oxidative performance in the nanocomposite containing Pluronic-wrapped SWCNTs.     

Thermal behavior of ara?a oil (Psidium cattleianum Sabine)

The ara?á is a well-known fruit, which belongs to the Myrtaceae family, Psidium cattleianum Sabine species, frequently found in the southern region of Brazil. The extraction of ara?a oil was carried out from seeds, and the fatty acid profile of this oil indicates the predominant presence of linoleic acid (81.38%). Thermogravimetry, derivative thermogravimetry, and differential scanning calorimetry (DSC) were used to characterize this oil. In addition, this oil was evaluated by DSC from 25 to ?60?°C, where the crystallization behavior was verified. Details concerning thermal decomposition as well as data of kinetic parameters of these stages have been described here. The kinetic behavior of the thermal decomposition was evaluated from several heating rates with mass samples of 5 and 20?mg in open crucibles under nitrogen and synthetic air atmospheres.     

The thermal decomposition of ammonium metavanadate

On heating, ammonium metavanadate (AMV) decomposes in several atmospheredependent stages. An important decomposition intermediate, ammonium hexavanadate (AHV), may also be prepared by wet-chemical methods and the kinetic parameters for the thermal decomposition of AMV and of the AHV preparation have been obtained. The kinetic study has been supplemented by surface-area measurements and by electron microscopic examination of the surfaces of reactant, intermediate and product crystallites. On the basis of the type of decomposition curve, the measured activation energies, and the effects of oxygen and water vapour on the decomposition rate, it has been concluded that in vacuum and in inert atmospheres the evolution of ammonia is the rate-determining step, while in oxidizing atmospheres evolution of water is rate determining. Comparison of the kinetic parameters with thermodynamic data for the decomposi. tion has led to suggestions as to the nature of the activated complexes involved.     

Thermal degradation and their kinetics of biodegradable poly(butylene succinate-co-butylene terephthate)s under nitrogen and air atmospheres

In this study, thermal degradation and their related kinetics have been investigated mainly by means of thermal gravimetrical analyzer (TGA) under the dynamic nitrogen and air atmospheres for the chemically prepared biodegradable aliphatic-aromatic copolyesters of poly(butylene succinate-co-butylene terephthalate) (PBST). To further shed new lights on the comonomer molar composition and experimental condition dependences of thermal degradation kinetics, the as-known Friedman model was at first applied to quantitatively evaluate the kinetic parameters in terms of activation energy (E), degradation reaction order (n) and the frequency factor (Z). The results clearly demonstrated that thermal stabilities of these PBST copolyesters were substantially enhanced with the incorporation of more rigid butylene terephthalate comonomer, and tended to be much better in nitrogen than in air. Furthermore, the Friedman, Freeman-Carroll and Chang models were concurrently employed to quantitatively evaluate the thermal degradation kinetic parameters of the PBST copolyesters in nitrogen at different heating rates of 1, 2 and 5 K/min. It was found that the thermal degradation kinetic parameters for the PBST copolyesters were strongly dependent on the heating rate and calculating models. In addition, life-time parameters of the biodegradable PBST copolyesters were first calculated to predict the maximum usable temperatures, and this would be useful for practical application of these new bio-based green plastics.     

1,3-二硫杂环戊烯-2-硫酮-4,5-二巯基的不对称二硫纶金属(Cd,Zn)配合物的热行为和热分解反应动力学

用TG-DTG-DTA联用技术研究了两种1,3-二硫杂环戊烯-2-硫酮-4,5-二巯基的不对称二硫纶金属(Cd,Zn)配合物在动态氮气气氛中的热行为,通过应用EDS技术和元素分析方法对热分解过程中各步反应中间体的组成进行了探索,并结合其物质结构进行了讨论。协同使用四种热分析动力学方法获得了各步反应的热分解动力学参数,并推断了它们的最可能分解反应机理。     

Thermal behavior and decomposition kinetics of composite solid propellants in the presence of amide burning rate suppressants

The employment of burning rate suppressants in the solid rocket propellant formulation is long known. Different research activities have been conducted to well understand the mechanism of suppression, but literature about the action of oxamide (OXA) and azodicarbonamide (ADA) on the thermal decomposition of composite propellant is still scarce. The focus of this study is on investigating the effect of burning rate suppressants on the thermal behavior and decomposition kinetics of composite solid propellants. Thermogravimetric analysis (TG) and differential thermal analysis have been used to identify the changes in the thermal and kinetic behaviors of coolant-based propellants. Two main decomposition stages were observed. It was found that OXA played an inhibition effect on both stages, whereas the ADA acts as a catalyst in the first stage and as coolant in the second one. The activation energy dependent on the conversion rate was estimated by two model-free integral methods: Kissinger–Akahira–Sunose (KAS) and Flynn–Wall–Ozawa (FWO) based on the TG data obtained at different heating rates. The mechanism of action of coolants on the decomposition of solid propellants was confirmed by the kinetic investigation as well.     

Thermal behavior of coffee oil (Robusta and Arabica species)

Coffee seeds are a source for obtaining oil which is used in the candy, soluble coffee, and cosmetics industries. The main purpose of this study was the investigation of the lipid profile and thermal behavior of the roasted and in nature coffee oil of Arabica and Robusta species, using thermogravimetry, differential thermal analysis, derivative thermogravimetry, differential scanning calorimetry (DSC), and modulated DSC. Details concerning the thermal decomposition as well as data of the kinetic parameters have been described here. The kinetic studies were evaluated from several heating rates with a sample mass of 10 mg in open crucible under nitrogen atmospheres. The obtained data were evaluated with the isoconversional kinetic method, where the values of activation energy (E _a/kJ mol^?1) were evaluated in function of the conversion degree (α). In addition, this oil was evaluated by modulated DSC from 25 to ?60 °C, where the transition phase behavior was verified.     

Thermal Decomposition and Melting of A New Carboxyindole Derivative

GV150526A is a novel 2-carboxyindole derivative, recently synthesized by GlaxoWellcome, which is used in treatment or prevention of CNS disorders resulting from neurotoxic damage. It has been prepared in three forms, F1, F2 and F3, having significantly different hydration/dehydration behavior and/or diffraction patterns. Here, we extend the thermal analysis of these polymorphs above 200°C, where all forms are fully dehydrated and the main thermal phenomena are decomposition and melting. Simultaneous TG/DSC measurements have been repeated in wet and dry nitrogen atmospheres over a wide range of heating rates. Form F3 displays a qualitatively different behavior relative to F1 and F2. This fact is interpreted as an evidence of a mechanism of decomposition which sets F3 apart from F1 andF2. The thermal data are summarized by simple heuristic equations and few ‘apparent’enthalpies. This revised version was published online in August 2006 with corrections to the Cover Date.     

Influence of the heating rate on the temperature profiles and on the conversion rate of powdery cellulose and pine sawdust

An experimental study of the thermal decomposition of powdered cellulose and pine sawdust has been performed. The influence of the heating rate on the temperature profiles in the sample and on the solid conversion rate has been studied. A mathematical model without adjustable parameters has been used to calculate the temperature at different points in the solid bed and the average total solid conversion. The experimental results have been compared with those calculated by the model. A good agreement has been obtained for sawdust. Some differences are observed for cellulose at high heating rates, and the influence of the thermal conductivity and the reaction heat on the results has been analysed.     

Kinetic analysis of the complex process of poly(vinyl alcohol) pyrolysis using a new coupled peak deconvolution method

A peak deconvolution procedure used for the analysis of data corresponding to simultaneous overlapping processes begins with separation of individual processes using functions such as Gaussian, Lorentzian, Weibull, and Fraser–Suzuki (FS) followed by application of kinetic analysis methods to the separated peaks. We propose a coupled peak deconvolution procedure to link the parameters of the FS functions of similar peaks in two DTG curves obtained at different linear heating rates, so that the coordinates of each peak can be obtained in a constrained manner. The proposed technique is a kinetic deconvolution method rather than a pure mathematical deconvolution technique. To analyze individual peaks in our study, the non-parametric kinetic and Freidman’s isoconversional methods have been applied to determine kinetic triplet of each process. This technique has been tested with both simulated and experimental data. Using this technique, the effects of molecular weight and degree of hydrolysis of polyvinyl alcohol (PVA) samples on reaction mechanism and activation energy of thermal degradation were studied. The presence of acetate group in the PVA samples causes thermal stability, decreases the rate of main reactions, and increases the activation energy. The results of this study may help tailor heat-resistant materials with proper choice of polymer characteristics.     

Thermal behaviour and slow molecular mobility in two isomers of biphenylmethanol

This research was aimed to investigate the role of clay on the combustion and kinetic behavior of crude oils in limestone matrix. For this purpose, simultaneous TG (thermogravimetry) and DTA (differential thermal analysis) experiments were performed at three different heating rates as 10–15 and 20°C min^–1, respectively. A uniform trend of decreasing activation energies was observed with the addition of clay. It was concluded that clays surface area affects the values of Arrhenius constant, while it is the catalytic properties of clay, which lower the activation energies of all the reactions, involved in the combustion process.