Derivative Thermogravimetry Curves Research Articles

Thermal degradation kinetics of poly(propylene carbonate) obtained from the copolymerization of carbon dioxide and propylene oxide

AbstractThe kinetics of the thermal degradation of poly(propylene carbonate) (PPC) were investigated with different kinetic methods with data from thermogravimetric analysis under dynamic conditions. The apparent activation energies obtained with different integral methods (Ozawa–Flynn–Wall and Coats–Redfern) were consistent with the values obtained with the Kinssinger method (99.93 kJ/mol). The solid‐state decomposition process was a sigmoidal A3 type in terms of the Coats–Redfern and Phadnis–Deshpande results. The influence of the heating rate on the thermal decomposition temperature was also studied. The derivative thermogravimetry curves of PPC confirmed only one weight‐loss step. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 947–953, 2003

Thermoanalytical study of the complexes of 4-dimethylaminocynnamylidenepyruvate with manganese (II), cobalt (II), nickel (II), copper (II), zinc (II) and lead (II), in the solid state

Solid state compounds M-4-DMCP, where 4-DMCP is 4-dimethylaminocinnamylidenepyruvate and M represents Mn (II), Co (II), Ni (II), Cu (II), Zn (II) and Pb (II) were prepared. These compounds were studied by thermoanalitycal techniques: thermogravimetry (TG), derivative thermogravimetry (DTG), differential scanning calorimetry (DSC), X-ray diffraction powder patterns and complexometric titration with EDTA. From the results obtained by the complexometric titration with EDTA, TG, DTG and DSC curves, was possible to establish the hydration degree, stoichiometry and thermal stability of the prepared compounds.

Thermoanalytical study of the complexes of 4-dimetilaminocinnamylidenepiruvate with manganese (II), cobalt (II), nickel (II), cupper (II), zinc (II) and lead (II), in the solid state

Solid state compounds M-4-DMCP, where 4-DMCP is 4-dimethylaminocinnamylidenepyruvate and M represents Mn (II), Co (II), Ni (II), Cu (II), Zn (II) and Pb (II) were prepared. These compounds were studied by thermoanalitycal techniques: thermogravimetry (TG), derivative thermogravimetry (DTG), differential scanning calorimetry (DSC), X-ray diffraction powder patterns and complexometric titration with EDTA. From the results obtained by the complexometric titration with EDTA, TG, DTG and DSC curves, was possible to establish the hydration degree, stoichiometry and thermal stability of the prepared compounds.

Study by thermogravimetry of the evolution of ettringite phase during type II Portland cement hydration

Thermogravimetry (TG) and derivative thermogravimetry (DTG) have been used by the authors as very effective tools to study hydration steps of cements used for solidification/stabilization of tanning wastes. The present paper presents a method which was applied to separate the peaks shown by DTG curves of type II Portland cement pastes, analyzed at different times during the first 4 weeks of setting. Through a specific software a more detailed study of the evolution of the cement hydration may be done, which allows the measurement of the amount of hydrated water present in tobermorite gel as well as in ettringite, which are the main phases formed from the original components of the cement. The number of moles of water present in the ettringite phase calculated by the method is in very good agreement with the values found in the literature, validating the method to calculate the same parameter in tobermorite gel. In the latter case the water content decreases significantly during the first day of hydration, then remains at a constant value over the rest of the analyzed period.

Thermal analyses of poly(3‐hydroxybutyrate), poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate), and poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate)

AbstractThermal analyses of poly(3‐hydroxybutyrate) (PHB), poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) [P(HB–HV)], and poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate) [P(HB–HHx)] were made with thermogravimetry and differential scanning calorimetry (DSC). In the thermal degradation of PHB, the onset of weight loss occurred at the temperature (°C) given by To = 0.75B + 311, where B represents the heating rate (°C/min). The temperature at which the weight‐loss rate was at a maximum was Tp = 0.91B + 320, and the temperature at which degradation was completed was Tf = 1.00B + 325. In the thermal degradation of P(HB–HV) (70:30), To = 0.96B + 308, Tp = 0.99B + 320, and Tf = 1.09B + 325. In the thermal degradation of P(HB–HHx) (85:15), To = 1.11B + 305, Tp = 1.10B + 319, and Tf = 1.16B + 325. The derivative thermogravimetry curves of PHB, P(HB–HV), and P(HB–HHx) confirmed only one weight‐loss step change. The incorporation of 30 mol % 3‐hydroxyvalerate (HV) and 15 mol % 3‐hydroxyhexanoate (HHx) components into the polyester increased the various thermal temperatures To, Tp, and Tf relative to those of PHB by 3–12°C (measured at B = 40°C/min). DSC measurements showed that the incorporation of HV and HHx decreased the melting temperature relative to that of PHB by 70°C. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 90–98, 2001

Pyrolysis kinetics of waste PVC pipe

The pyrolysis kinetics of waste PVC pipe was investigated with a thermal gravimetric analysis system at heating rates of 5, 10, and 30°C/min in a nitrogen atmosphere. Freeman-Carroll method was employed to evaluate kinetic parameters. Two dominant peaks were observed on derivative gravimetric curves, hypothetically suggesting a two-stage apparent reaction model. The first-stage reaction was likely to be represented by stoichiometric reaction to yield volatiles (mainly HCl) and intermediates. The second-stage reaction might be described by thermal degradation of intermediates competitively into gas, liquid, and solid by-products. Quasi-isothermal operations were introduced to verify the reaction types of the first and second reaction. The generation reaction of intermediates achieved at lower temperatures was carried out independently with their decomposition reaction at higher temperatures. The effects of additives on the pyrolysis kinetics of waste PVC pipe seem to be significant, especially on the first-stage reaction. The first-stage reaction was retarded. A merged peak at low temperatures was observed on the derivative thermogravimetry (DTG) curve instead of two peaks usually observed for that of pure PVC resin. The first peak on the DTG curve of pure PVC resin may shift more, resulting in the complete overlap of two peaks. The quantity of evolved HCl was likely to decrease because of interaction of metal components of stabilizers with either HCl or active chlorine atom or both. The final residual fraction increased as a result of pyrolysis of organic forms of additives to yield extra char. On the other hand, the second-stage reaction kinetics demonstrates a similar pattern to that of pure PVC resin, implying that the effects of additives may be less significant in comparison with that at the first-stage reaction.

High-resolution thermogravimetric analysis of poly(trimethylene terephthalate) with different molecular weights

Poly(trimethylene terephthalate) samples with different molecular weights and poly(ethylene terephthalate) were investigated by high-resolution thermogravimetry in nitrogen at an auto-stepwise heating rate. The auto-stepwise heating-rate approach consists of two steps. The sample is heated at an initial rate until a weight change begins, and then is heated further at a step rate until the end of this weight change. The two-step sequence of heating is repeated for each weight change encountered. Both the beginning and the end of the weight change are defined as the step on and the step off criteria, of which the corresponding weight-loss rates are decided by the operator. Experiments were performed from ambient temperature to 600°C at an initial heating rate of 50 K/min and three step-heating rates of 0.5 K/min, 1.0 K/min, and 2.0 K/min. The step on (off) criterion used was 2%/min (1%/min). The thermogravimetry and derivative thermogravimetry curves of poly(trimethylene terephthalate) samples obtained from auto-stepwise heating-rate mode indicated a degradation of multiple weight-loss stages. The first small weight-loss stage (weight loss 2∼4%) was highly sensitive to molecular weight. The temperature at the maximum weight-loss rate of this stage increased significantly with molecular weight. The weight loss during this step decreased steadily with increasing molecular weight, and was in good agreement with the value predicted on the basis of complete volatilization of the 1,3-propanediol unit and carbon dioxide devaluated from chain ends and the residual catalysts. For the poly(trimethylene terephthalate) samples with high molecular weight the first small weight-loss stage diminished. Molecular weight also affected the major decomposition process (weight loss 83∼90%). The temperature at the maximum weight-loss rate of the major stage increased slightly with increasing molecular weight. The influence of step-heating rate on the thermal decomposition characteristics was preliminarily investigated. Additionally, the difference among various themogravimetric analysis algorithms was discussed.

High-resolution thermogravimetric kinetics of liquid crystalline poly(p-oxybenzoate-co-ethylene terephthalate)

Thermotropic liquid crystalline poly(p-oxybenzoate (B)-co-ethylene terephthalate (E))s with four B/E monomer ratios were subjected to high-resolution thermogravimetry at a variable heating rate in nitrogen and air. The thermogravimetry curves, the derivative thermogravimetry curves, the second derivative thermogravimetry curves and heating rate curves are discussed. The thermal degradation temperature, the maximum weight-loss rate, char yield at elevated temperature, and kinetic parameters of the polyesters are presented with the variation of B/E monomer ratio and compared with those obtained with traditional thermogravimetry at a constant heating rate. The degradation process of the copolyesters was usually divided into three stages, i.e., the first major stage and the latter two minor stages in nitrogen or the first and third major stages and the second minor stage in air. Of four copolyesters, the B/E (70/30) copolyester exhibited the largest degradation activation energy of 276kJ/mol in nitrogen and 244kJ/mol in air, the largest decomposition order of 2.4 in air, the largest Ln (frequency factor) of 43min−1 in nitrogen and 39min−1 in air.

KINETIC STUDY ON PYROLYSIS OF EXTRACTED OIL PALM FIBER Isothermal and non-isothermal conditions

Pyrolysis of extracted oil palm fibers under isothermal and non-isothermal conditions was carried out in a thermogravimetric analyzer. Isothermal curves showed that increasing pyrolysis temperature resulted in a faster pyrolysis and a higher conversion of oil palm fibers into gaseous products. Raw material sizes (below 1.0 mm) had insignificant effects on the isothermal pyrolysis, but the fibers with a size fraction of 1.0 to 2.0 mm resulted in a lesser conversion. Two-step reactions were found in the non-isothermal pyrolysis as evidenced by the presence of two peaks in the derivative thermogravimetry curves. Raw material sizes had no obvious effects on the temperature at which the maximum rate of pyrolysis occurred, but affected the rate of sample mass loss. For the low and high temperature regimes, a three-dimensional diffusion mechanism and a first-order of reaction mechanism respectively were used to describe the non-isothermal pyrolysis kinetics of extracted oil palm fibers.

Thermal, oxidative and radiation stability of polyimides I. Bismaleimidoethane and different diamine-based polyimides

The syntheses of 1,2-ethane-bis-maleamidoacid, N,N′-1,2-bis-maleimidoethane (BME), and polyimide resins based on BME and four different diamines are given. The thermal and thermooxidative stability of the resins was studied by thermogravimetry (TG) following parameters such as temperatures for defined weight loss and initial decomposition rate, i.e. shape of TG and first derivative TG curves. Samples have been irradiated and their radiation stability evaluated on the basis of the thermal and thermo-oxidative behavior of the irradiated samples. The thermal behaviors have been analyzed and the resin based on the diamine with the benzene ring showed the best thermal stability. Radiation in the applied dose range showed an increase of thermal stability.

High-resolution thermogravimetric kinetics of thermotropic liquid crystalline dioxynaphthalene copolymers

Four types of thermotropic liquid crystalline aromatic copolymers containing oxybenzoate, ethylene terephthalate or 2,6-naphthalate, 2,7-dioxynaphthalene or 1,5-dioxynaphthalene terephthalate units were subjected to high-resolution thermogravimetry at a variable heating rate in nitrogen and air. The thermogravimetry curves, the derivative thermogravimetry curves, the second derivative thermogravimetry curves and heating rate curves for the copolymers are discussed. The thermal degradation temperature and kinetic parameters for the copolymers were presented and compared with those obtained with traditional thermogravimetry at a constant heating rate. The degradation process of the copolymers was considered. Three copolymers with 2,7-dioxynaphthalene and 1,5-dioxynaphthalene of 5 mol% exhibit the same initial degradation temperature of 454°C and the same temperatures of 458°C, 470°C and 520°C for the maximum weight-loss rates of 9.8%/min, 10%/min, and 4.7%/min in nitrogen but slight differences in the degradation temperatures and the maximum weight-loss rates with variation of the copolymer composition in air. The thermostability of the 2,7-dioxynaphthalene copolymers is slightly higher in nitrogen than in air. The copolymers show degradation activation energies of 208–308 kJ/mol in nitrogen and 158–258 kJ/mol in air.

High-resolution thermogravimetry of poly(4-vinylpyridine-co-divinylbenzene)

Poly(4-vinylpyridine) crosslinked with 2 mol% divinylbenzene, i.e. poly(4-vinylpyridine-co-divinylbenzene), has been investigated by high-resolution thermogravimetry (TG) to ascertain its thermal stability and degradation kinetics in nitrogen and air at a variable heating rate. Experiments have been performed at a resolution of 4.0 and an initial heating rate of 50°C/min from room temperature to 900°C. The TG and derivative TG curves indicate a three stage decomposition. The poly(4-vinylpyridine-co-divinylbenzene) exhibits higher degradation temperature but lower kinetic parameters in nitrogen than in air. The results are compared with those of other authors derived using traditional TG at constant heating rates. The temperature, activation energy, reaction order, and natural logarithm of frequency factor of the thermal degradation for the poly(4-vinylpyridine- co-divinylbenzene) in nitrogen are 322°C, 78 kJ/mol, 0.6, and 12 min −1 respectively.

High-resolution thermogravimetry of cellulose esters

Cellulose dinitrate (CDN), cellulose diacetate (CDA), and cellulose triacetate (CTA) were subjected to high-resolution thermogravimetry (TG) at a variable heating rate in air. The TG curves, the derivative TG curves, the second derivative TG curves, and heating rate curves are discussed. The thermal degradation temperature and kinetic parameters are presented and compared to those obtained with traditional TG at a constant heating rate. The degradation process of the cellulose esters is speculated. Among the three cellulose esters, CDN exhibits the lowest degradation temperature of (213°C) but the largest degradation activation energy of (237–269 kJ/mol). © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 573–578, 1999

Characterization of monumental carbonate stones by thermal analysis (TG, DTG and DSC)

Abstract Thermogravimetry (TG), derivative thermogravimetry (DTG) and differential scanning calorimetry (DSC), were found to be suitable instrumental techniques for the study of monumental rocks because they need small amounts of sample and provide extensive qualitative and quantitative information. From DTG curves, the calcite/dolomite ratio in the samples as well as the differences between limestones and dolomites can be quantitatively determined. DSC curves are adequate for the identification of the degradation products in the monumental stones since they are usually salts (sometimes hydrates) which present first-order processes under 600°C. This technique makes it possible to carry out quantitative and semiquantitative analysis of the degradation of monumental rocks since it provides data about its mineralogic composition.

Characterization of thermal reaction by peak temperature and height of DTG curves

A relationship between the peak temperature and height in derivative thermogravimetry (DTG) curves was explored to seek their specific combination for addressing the uniqueness of a thermal reaction. The functional relationship between the peak temperature and height was closely related to the activation energy and reaction order, but rarely affected by the preexponential factor and heating rate. Determining peak temperature and height at a heating rate was enough to characterize a thermal reaction of first-order kinetics or known reaction order, but was insufficient to specify a reaction without knowing the shifting pattern of either peak temperature or peak height with heating rate. The peak temperature and height varied with the heating rate according to the kinetic parameters. The shifting pattern of the peak temperature with the heating rate was related to the activation energy, while that of the peak height was confined by the reaction order together with the activation energy.

Analytical techniques estimating kinetic parameters for pyrolysis reaction of scrap tire rubbers

Analytical techniques using derivative thermogravimetry (DTG) and thermogravimetry analysis (TGA) were developed to estimate kinetic parameters for complex decomposition reactions of a heterogeneous substance like scrap tire rubbers. Two methods using non-isothermal techniques were proposed: (1) subtraction method and (2) method utilizing peak properties in a DTG curve. The former method is a reliable tool to determine the kinetic parameters of decomposition reaction of each compositional component, but it may run into a difficulty provided that tire components demonstrate similar thermal stability, thus leading to a complete superposition of peaks in a DTG curve. The subtraction method, however, can be applied after manipulating heating rate, since overlapped peaks can be separated by increasing or decreasing heating rate. Although the peak temperature and height (rate) in a DTG curve in the latter method were closely related to kinetic parameters of a single reaction, they can be rarely utilized to estimate the kinetic parameters of complex reactions because of disturbance arising from peak superposition.

Reactivity of the submicron molybdenum ferrites towards oxygen and formation of new cation deficient spinels

Valence states of molybdenum and iron ions and their cationic distribution on both octahedral (B) and tetrahedral (A) sites of the spinel structure of molybdenum-substituted magnetites, Fe 3− x Mo x O 4, obtained by two ways (samples synthesized by w et process or ground samples synthesized by the ceramic route) and which are oxidized in cation deficient spinels, have been performed by derivative thermogravimetry (DTG), X-ray diffraction, IR and XPS spectrometries. It has been demonstrated that in the case of the samples synthesized by wet processes, the Fe 2+ B, Mo 3+ B, MO 4+ B, Fe 2+ A, Mo 4+ A ions are successiv ely oxidized into Fe 3+ B and Mo 6+ A ions below 530°C. For the samples synthesized by the ceramic method, only the Fe 2 B, Mo 3+ B, Mo 4+ B and Fe 2+ A oxidations have been observed. In these both cases, a quantitative analysis based on the discrepancy in reactivity of these different oxidizable cations has been used to determine the distribution of cations between the sublattices. As a result of the oxidation of all the oxidizable cations, the molybdenum defect ferrites may have a very high number of vacancies. These may reach 0.71 for x=0.5. The possibility to oxidize the Fe 2+ B and Mo 3+ B ions selectively, permits on the one hand to confirm the desummations of the DTG curves, and on the other hand to study the oxidation kinetics of these two ions. It has been also possible to show that the profile of the experimental DTG peaks obtained after desummation is comparable to the DTG peaks calculated from the isothermal kinetic parameters. Finally, the study of the cationic distribution of the oxidized phases has shown that the Mo 6+ ions, initially in tetrahedral coordination can remain in octahedral site as the octahedral sites are also occupied by Fe 2+ or Co 2+ ions.

Improved Quantitative Determination of Elastomers in Tire Rubber by Kinetic Simulation of DTG Curves

Abstract A method of identifying and quantifying elastomers and processing oil in tire rubber, called DTG curve simulation method, is proposed. This method is based on DTG (derivative thermogravimetry) analysis of the straight elastomers NR, BR and SBR, which produces a series of decomposition rate data and pairs of kinetic constants. DTG curves of binary elastomer systems NR/SBR, NR/BR and BR/SBR are measured. The samples are qualitatively identified following the shape of their DTG curves. Quantitative determination is achieved by DTG curve simulation using a least squares method. When correct elastomers and proper compound ratio are chosen, minimum simulation error is achieved leading to effective identification. Satisfactory results were obtained when applying the method to elastomer mixtures of known composition and to tire rubbers of unknown composition. The study advanced the capability of the TG-DTG technique for quantitative determination of elastomers and blends.

Weight Loss Behavior of Straight-Chain Saturated Fatty Acids

Weight loss and characterization of straight chain saturated fatty acids (even-numbered fatty acids : 8 kinds, odd-numbered fatty acids : 7 kinds) were studied by dynamic programmed thermogravimetry (TG), derivative thermogravimetry (DTG) and differential scanning calorimetry (DSC).1) Initial weight losses and weight loss curves of straight chain fatty acids under air and under nitrogen shifted only to the higher-temperature side with increase in carbon number. Weight loss patterns were simple and essentially the same to each other. The DSC curve of each fatty acid under air differed markedly from that under nitrogen. The curves of fatty acids under nitrogen shifted to the endothermic side. Under air, the DSC curves of fatty acids ranging from heptanoic to tridecanoic acids, also shifted to the endothermic side. However, the curves of fatty acids having carbon numbers exceeding that of tetradecanoic acid shifted to the exothermic side.2) GLC analysis of volatile and residual substances at the temperature corresponding to 25 % weight loss on TG indicated to the weight loss of fatty acid until to possibly be due primarily to evaporation of the fatty acid. However, the residual rate after the peak temperature of DTG increased with carbon number, this being particularly evident in the case of exposure to the air flow. Weight loss in the air flow is thus shown to be accompanied by decomposition.3) The peak temperature of DTG curve was closely correlated to fatty acid boiling point. However, the regression line in the air flow was situated on the lower-temperature side than that in the case of the nitrogen flow, due to accompanying decomposition.

Pyrolysis Behavior and Themostability of Branched-Chain and Hydroxylated Straight-Chain Fatty Acid Moleculars

The weight loss behaviors and thermostability of four iso and anteiso branched-chain fatty acids, and four hydroxylated straight-chain saturated fatty acids in air and nitrogen flows were studied by thermogravimetry (TG) and derivative thermogravimetry (DTG). The branched acids showed a simple weight loss pattern in their TG and DTG curves in both air and nitrogen flows, whereas a more complicated pattern was observed for the hydroxy fatty acids. The TG and DTG curves of the fatty acids shifted to the higher-temperature side with an increase in the number of carbon atoms. The weight loss was found to be caused mainly by evaporation accompanied with a small degree of decomposition. Thermostability of the hydroxy fatty acids evaluated with initial temperature of weight loss was shown to be superior to that of the straight- and branced-chain fatty acids.