Structural analysis of photodegraded wood by means of FTIR spectroscopy

We report on the detailed analysis of chemical modifications and structural changes in the cellulose and lignin of Populus tremula (a hardwood) and Buxus sempervirens (a softwood), as a result of photodegradation in a Xenon test chamber. The results obtained by means of FTIR spectroscopy indicate that lignin is the most sensitive component to the degradation process for both woods examined. On a structural level, the virtual elimination of the amorphous cellulose was observed for both types of wood. The crystallised cellulose I component, which accounts for the whole crystalline phase, undergoes minor structural changes, this effect being more important in the case of Populus tremula that was less degraded than Buxus Sempervirens.     

Thermogravimetric analysis of wood, holocellulose, and lignin from five wood species

Thermogravimetry has been widely applied to the study of wood and cellulose materials. There is a general agreement that decomposition of hemicellulose, cellulose, and ligning take place in a relatively narrow range of temperature, partially overlapping. There is no a definitive demonstration of which thermal feature corresponds to each component. In this study, three hardwood and two softwood species were considered: Castannea sativa, Eucaliptus globulus, Quercus robur, Pinus pinaster, and Pinus sylvestris. Thermogravimetric analysis of wood powder, ethanol-extracted wood, holocellulose, and lignin, obtained from those species revealed some important differences between hardwood and softwood holocelluloses and an important role of the ethanol-extractives, which explain the different behavior observed in both kinds of wood. FTIR spectra obtained from the evolved gases helped to clarify some degradation steps.     

Thermogravimetric study of the pyrolysis of waste wood

A thermogravimetric study of the pyrolysis of three different types of waste wood (forest wood, old furniture and used pallets) is carried out in a TGA equipment using dynamic and isothermal techniques. Isothermal runs were carried out at two temperature levels, one between 225° and 325°C (low range) and the other, between 700° and 900°C (high range). Results show a good agreement between the kinetic parameters obtained from either dynamic or isothermal techniques. It must be remarked that the own chemical composition of each type of wood together with the compounds added to the wood for each application, play a fundamental role in the kinetic behavior of their thermal decomposition.     

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 and kinetics modeling of isothermal carbonization of olive wood in inert atmosphere

The kinetics of olive wood carbonization is investigated by means of isothermal thermogravimetric analysis method. Measurements were carried out in a thermobalance for different fixed temperatures between 498 and 648 K. A two-stage semi-global kinetic model consisting of four sequential steps was proposed to derive kinetic parameters. The olive wood is classified in three pseudo-components. For the first two, similar thermal degradation mechanisms take place in a single reaction step. For the third, the thermal degradation takes place in two consecutive steps. The isothermal conditions allow the kinetic constants (activation energy and pre-exponential factors) to be estimated by means of the analytical solution of the mass conservation equations. An overall good agreement was obtained with activation energy values available in the literature.     

Degradation of lime wood painting supports: Evaluation of changes in the structure of aged lime wood by different physico-chemical methods

In the present work, aged lime wood from painting supports, differing in terms of the provenance, conservation status, wood ages and of storage conditions (microclimate in churches or rooms) was analysed, applying analytical pyrolysis as the main method. Analytical pyrolysis combined with gas chromatography/mass spectrometry has shown a great potential as a fast, sensitive and good reproducible analytical tool to characterize the structure of a variety of natural polymers. The attraction of the application of analytical pyrolysis for the investigation of objects having the artistic value is connected with the use of minor amounts of samples for analysis. Carbohydrates and lignin compounds released under Py-GC/MS were analysed, and carbohydrate/lignin (C/L) and syringyl/guaiacyl (S/G) ratios were determined. On the basis of the results obtained, it can be concluded that, with ageing of lime wood the carbohydrates moiety decreases significantly as the result of degradation of hemicelluloses, namely, slow hydrolysis of O-acetyl groups of xylan with the release of acetic acid. The increase in the free radical concentration in aged wood in comparison with the reference sample, observed by ESR-spectroscopy, confirms the relative increase in the lignin content and the degradation of lignin–carbohydrate complexes. The S/G ratio did not show any preference in the degradation of S or G lignin of aged lime wood. The main trends in changes in parameters of the porous structure of the objects under investigation are in conformity with the alteration in the composition of wood complex. Summing up the data of Py-GC/MS and ESR-spectroscopy, it may be concluded that, for 180- and 270-year aged wood samples, some tendency for the alteration of the lignin matrix is observed, namely, an increase in condensity, accompanied by the development of polyconjugated systems.     

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 cobalt sulfate

Morpholine is a base of moderate strength, comparable with that of ammonia, and capable of forming -onium-type salts. Extensive studies [1,2] have been made on the thermal stability of ammonium perchlorate because of its technological use as an oxidant in solid state rocket propellants. The preparation, characterization and thermal behaviour of morpholinium perchlorate are reported in this note. The study was followed by XRD, IR, TG, DTA and mass spectral techniques.     

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 and kinetic methods to date wood finds. First results

Fresh (larch and fir, in its white and red varieties) and ancient wood samples (dating respectively to the 13th, 15th and 17th centuries) were subjected to thermogravimetric analysis (TG and DTG). The resulting thermogravimetric data were then used to construct archeometric curves for the wood varieties tested. In a preliminary approach, it was attempted to correlate the onset temperature of the thermogravimetric step corresponding to cellulose decomposition with the age (expressed in centuries) of the samples, although the results obtained were anything but brilliant. More encouraging results were obtained by examining the relationship between wood sample age and the value of the (percent cellulose/percent lignin) ratio computed from the thermogravimetric data. Lastly, a procedure for processing data obtained from the TG curves was applied to a kinetic analysis of the processes that take place when wood samples are subjected to a temperature regime with a constant heating rate, obtaining values for the activation energy of the TG step corresponding to the decomposition of cellulose. Also using these data it was attempted to construct archeometric curves, obtaining results that varied quite significantly according to the wood species tested.     

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.     

Ceramic nanoparticles coated with polymers based on acrylic derivatives

Ceramic nanoparticles are synthesized by a microwave plasma process and coated with a polymer layer generated in situ by photopolymerization. Acrylic and methacrylic monomers are the most suitable precursors for polymer coatings. In the case of coatings derived from MMA, only a small quantity of the polymeric material is soluble in organic solvents. GPC analysis of the dissolved part reveals the predominance of oligomers. According to FT-IR spectra, a substantial number of MMA-ester groups is transformed into carboxylates, providing strong adhesion of the polymer to the ceramic core insoluble in THF. Composites with PTFE-analog coating exhibiting enhanced thermal and chemical stability are obtained from the condensation of perfluorinated alkanes on metal oxide nanoparticles.     

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 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 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 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 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.