Thermogravimetric analysis

Waterlogged archaeological woods (Pinus pinaster, Ulmus cf. minor and Fagus sylvatica L.) were consolidated by using Colophony, Rosin 100, and a mixture of Poly(ethylene) glycol (PEG) 3000 and Poly(propylene) glycol (PPG) 425. The efficiency of the consolidants was estimated by determining the content entrapped into the cavity of degraded wood. For this purpose, thermogravimetry was demonstrated to be a reliable tool. In the case that the polymeric mixture was used for impregnation, it was also possible to discriminate the amount of PEG 3000 from that of PPG 425 captured by the wood capillaries. Regardless of the wood nature, all the consolidants were present in treated samples in large amount (at least 70% w/w). Thermogravimetric results were in agreement with those calculated by using the wood degradation degree and composition of the consolidant mixture. One of the advantages of using this technique consists into requiring very small amounts (a few mg) of sample against the grams necessary for the conventional experiments.     

Thermogravimetric analysis of cellulose

An application of TGA technique to elucidate the chain reaction mechanism of cellulose pyrolysis is discussed. The mathematical expressions for isothermal kinetics are modified for use with temperature-programmed kinetics. It is shown that in temperature-programmed kinetics, the initial reaction should theoretically be a pseudo zero-order type, whereas the latter part should be a pseudo first-order type. Experimental data from the present study and from the literature are in good agreement with the theory. Energies of activation for the initiation and the propagation steps of cellulose pyrolytic reactions are analyzed from TG data. Various cellulose samples, such as adsorbent cotton, vibratory ball-milled absorbent cotton, mercerized commercial yarn, mercerized and treated commercial yarn, dewaxed-kiered cotton, and microcrystalline cellulose are included in this study. A basic problem which is associated with all thermogravimetric kinetic expressions is also discussed.     

Thermogravimetric analysis of carbide slag

Potential of carbide slag as transesterification catalyst is validated. Combined with X-ray fluorescence for ingredient determination, X-ray diffraction for textural phase analysis, scanning electron microscope for surface morphology observation and Hammett indicator for basic strength mensuration, thermal event of carbide slag is investigated through thermogravimetric analysis to estimate the potential of this calcium-based industrial waste as transesterification catalyst. Further, kinetic parameters are calculated through model-free method, where the experiments are conducted at temperature heating rates of 5, 10, 15, and 20 K min^?1. As for activation energy and reaction order, Vyazovkin method and Avrami theory are respectively mentioned. Meanwhile, catalytic performance of carbide slag is labeled by transesterification efficiency and calcium hydroxide is conditionally mentioned for comparison. In conclusion, potential of carbide slag as transesterification catalyst is adequately validated.     

Thermogravimetric analysis of forest understory grasses

Forest understory grasses are of significance in the initiation, establishment and maintenance of fire, whether used as a management tool or when occurring as wildfire. The fundamental thermal properties of such grasses are critical to their behavior in fire situations and have been investigated in the current work by the application of thermogravimetric analysis (TGA). TGA was performed in nitrogen and air, over a range of heating rates, allowing for the determination of activation energies and temperatures associated with the degradation of hemicelluloses and cellulose. Of particular interest is the behavior of Imperata cylindrica (cogongrass) an invasive species in the southern United States, which has been found to result in elevated temperatures during fires in forested ecosystems. The results from TGA for this species are in accord with these observations from the field.     

Thermogravimetric analysis of Mediterranean plant species

Twelve dominant Mediterranean plant species were subjected to thermogravimetric analysis (TGA) in air medium, in order to study their thermal degradation process and assess their potential combustibility as natural fuels. Statistically significant differences were observed among the values of the pyrolytic parameters of the species analyzed. The mean volatilization rate values resulted in meaningful ranking of the species into vegetation types of similar combustibility, as verified by observations during actual wildfires. The use of TGA as a method for assessing the combustibility of individual plant species seems justified.     

Thermogravimetric analysis of chitins of different origin

In this work the thermal properties of chitins of different origin were compared using a thermogravimetric technique. The α_s-α_r method, which makes possible a comparison of the thermal resistances of materials with similar thermostability, was used. The basic range of thermal conversion was determined. In this range, the thermal resistance depends on the chitin origin. The value of activation energy was calculated. No influence on the average molecular mass, crystallinity and the degree of acetylation on the thermal resistance was observed. On the other hand, it was found that the thermal stability depends on the size and perfection of crystallites as well as on the crystalline form of the chitin.     

Thermogravimetric analysis of PVC/ELNR blends

The thermal behaviour of a series of solution-cast blends of polyvinyl chloride/epoxidised liquid natural rubber (ELNR) of different mole percentage of epoxidation has been examined using thermogravimetric analysis. Thermal degradation is found to occur through a two-step route in which the first step corresponds to the dehydrochlorination of PVC to form a polyene and the second step is attributed to the decomposition of the ELNR and the polyene. Introduction of 20 and 50 mol% of epoxy group into the liquid NR is found to enhance the thermal stability of PVC. Probable mechanisms of degradation have been suggested on the basis of the kinetic analysis of the degradation studies. It is found that the mechanism is influenced by the epoxy content of the blend system. Activation energy for the degradation and the entropy change have also been reported.     

Thermogravimetric study of cobalt(II)-halide complexes in a molten nitrate eutectic

The temperatures and stoichiometries of reaction of cobalt(II) nitrate, chloride and bromide have been established by analysis, infrared, X-ray diffractometry and thermogravimetric analysis. Tricobalt tetraoxide and nitrogen dioxide were produced together with oxygen and nitrite from the first two reactants, but with nitric oxide and bromine from the third reactant. Reaction pathways are suggested. Addition of potassium chloride caused a large (150–200°) increase in temperature of maximum reaction rate, which was ascribed to the formation of chloro “complexes”. No stabilisation was observed on addition of potassium bromide, though broadening of the weight loss maxima when chloride and bromide were present suggested the formation of mixed complexes.     

Thermogravimetric analysis of PVC/NR-b-PU blends

Thermal stability of solution-cast blends of poly(vinylchloride) and NR-b-PU block copolymers of three different chain extender diols was studied by thermogravimetry. Thermal degradation of individual components and their blends were investigated with special reference to blend ratio. As the block copolymer content in the blends increased their thermal stability was also found to increase. Enhanced thermal stability of PVC is believed due to the favorable interaction with PVC and the PU hard segments of the block copolymer. DTG curves were used for the determination of different stages involved in the degradation. Activation energy for degradation was determined from Coats–Redfern plot.     

Thermogravimetric analysis of a polycyanurate thermosetting material

The thermal degradation of a fully cured polycyanurate thermosetting material was examined by monitoring the mass loss at various temperatures ranging from 200 to 220C. The effect of the copper naphthenate catalyst, generally used to facilitate curing, is also studied. A decrease in weight is observed with increasing time at elevated temperatures in the systems containing copper naphthenate, with the onset of degradation occurring sooner with higher concentrations of the copper compound. The apparent activation energy for degradation is 220±30 kJ mol^–1.The support of the National Science Foundation in the form of an equipment grant (CTS 9500318) is gratefully acknowledged.     

Thermogravimetric analysis of teeth for forensic purposes

Journal of Thermal Analysis and Calorimetry - The objectives of this study were to characterize the thermal decomposition of human teeth and to evaluate the decomposition of organic matter,...     

Thermogravimetric analysis of polymers with indanic structure

The thermal stability of polycarbonates, polythiocarbonates, and polyesters derived from a diphenol with an indanic structure, was studied and compared with the corresponding polymers derived from a diphenol with the same number of carbon atoms but no forming the indanic ring, showing that polymers with an indanic structure degrade at lower temperature due the rigidity of the indanic ring respect to those with an aliphatic structure. Also, the kinetic parameters of the thermal decomposition were determined by using the Arrhenius relationship and a computer program. In the considered range, all the polymers studied degraded in a single stage and theE values increase when the bulk of the side group increases and the rigidity decreases.

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Zusammenfassung Die stabilität gegen Warme von Polycarbonaten, Polythiocarbonaten und polyestern gewinnen aus einem Diphenol mit einer indan Struktur wird studiert und vergleicht mit denjenigen von analogen Polymeren gewinnen auseinem Diphenol mit der gleichen nummer von Kohlenstoffatomen ohne Bildung von einem Indanring. Diese Versuche zeigen, daß die Polymere mit einer Indanstruktur bei tiefer Temperatur ais diejenige mit einer alifatischen Struktur degradieren auf Grund der Streng des Indanringes. Die kinetische Parametern der Zersetzung gegen Warme der Polymeren wurden durch die Arrhenius Gleichung und ein Komputerprogram in dem angesehenden Bereich bestimmt. Alle Polymere durch einen Schritt zerfallen. Die E-Werte zunehmen, wenn die große der Seitegruppe zunimmt und die Strenge abnimmt.

     

Thermogravimetric study of polyacrylamide with evolved gas analysis

Dried samples of polyacrylamide in an He atmosphere have been subjected to thermogravimetric analysis in the 30–600°C range, and the evolved gases were monitored by FTIR. Water, ammonia, and small quantities of carbon dioxide are released in the first stages of decomposition (220–340°C), where the polymer chains remain intact and the reaction occurs on the pendant amide groups. In the second stage of decomposition (340–440°C), the majority of the weight loss occurs, and main chain breakdown occurs, releasing carbon dioxide, water, nitrile compounds, and imides. Trapping of the gases in this stage and analysis by GC–FTIR and GC–MS reveals the presence of more than 20 decomposition products, and confirms that a large proportion of these can be assigned to glutarimide and its substituted analogs. Imidization and dehydration reactions on the amide groups, as well as free radical breakdown of the main chains, with inter- and intramolecular hydrogen transfer, can account for many of the products of the decomposition. © 1993 John Wiley & Sons, Inc.     

Thermogravimetric analysis on gasification reactivity of Hailar lignite

Comparative studies on the Hailar lignite pyrolysis/gasification characteristics at N₂/CO₂ atmosphere and the influence of inherent mineral matters, external ash and pyrolysis temperature on its reactivity during gasification at CO₂ atmosphere were conducted by non-isothermal thermogravimetric analysis, FTIR, and X-ray diffraction (XRD) analysis. Thermogravimetric test results show that the atmosphere of N₂ or CO₂ almost has no effects on the pyrolysis behavior, and the gasification reaction under CO₂ atmosphere occurs over 943?K at the heating rate of 40?K?min^?1. The external ash prepared at 1173 and 1223?K shows a certain catalytic effect on promoting the gasification reaction, although the inherent mineral matters of Hailar lignite are found in stronger catalytic effects on gasification than the external ash. The lignite gasification reactivity decreases with increasing pyrolytic temperature between 1073 and 1273?K.     

Thermogravimetric analysis of co-combustion of biomass and biochar

The co-combustion of biomass and biochar was investigated by thermogravimetric analysis. Several thermal parameters and mean reactivity index (R _M) for different blends were used to evaluate co-combustion features. As the biomass content increased from 30 to 90 mass%, volatile releasing temperature (T _v), burnout temperature (T _b), and the temperature at the maximal peak (T _max) generally reduced, while average mass loss rates (R _a) and R _M increased, the maximum mass loss rate (R _max) initially decreased and then increased. Results showed that biochar additions enhanced biomass fuel reactivity over weighted average in main combustion region. Besides, blends with 10–30 mass% of biochar behaved better than those with higher biochar ratio. Synergy exists between the two components and better combustibility is feasible by co-firing biochar with biomass.     

Thermogravimetric analysis of photodegraded acrylic coated lime wood

A series of experiments were carried out to investigate the photodegradation of lime wood (Tilia cordata Mill.) coated with acrylic copolymer during artificial UV/Vis light irradiation for 600 h. Photodegradation of the Paraloid B72 films and Paraloid B72 treated lime wood samples was evaluated by thermogravimetry throughout the irradiation period of 100 h. The results obtained indicate a shifting of the DTG maxima to lower temperatures, which may be related to a decrease in the stability of the copolymer and wood during photodegradation. The decrease of weight loss with increasing time of exposure was observed, while the global kinetic parameters for the main peak increases when increasing exposure time of wood to the UV light. Even when the surface of the wood was covered with a thin layer of acrylic resin, some photodegradation reactions of the wood surface occurred. The modifications in the wood structure may be influenced by the newly formed structures from acrylic resin photodegradation.     

Thermogravimetric analysis of polymers for assessing thermal degradation

Experimental techniques and theoretical analyses of thermogravimetry as applied to the thermal decomposition of polymers are reviewed. It is concluded that little useful mechanistic information can be derived simply by measuring weight loss during heating. Stability assessments can be based on apparent A and E values determined by isothermal analysis. However, such parameters will apply only within the temperature range defined by the conditions of data collection.