Showing papers in "Journal of Thermal Analysis and Calorimetry in 2010"
TL;DR: In this article, the hydration kinetics and the hydrated phase assemblages of the main hydraulic phase ye'elimite with calcium sulfate were studied by isothermal conduction calorimetry, thermogravimetric analysis, X-ray diffraction analysis and thermodynamic modelling.
Abstract: Calcium sulfoaluminate (CSA) cements, which represent a CO2-friendly alternative to conventional Portland cements, are produced by blending CSA clinker with gypsum and/or anhydrite. The hydration kinetics and the hydrated phase assemblages of the main hydraulic phase ye’elimite (calcium sulfoaluminate) with calcium sulfate were studied by isothermal conduction calorimetry, thermogravimetric analysis, X-ray diffraction analysis and thermodynamic modelling. Two calcium sulfates with different reactivities (gypsum and anhydrite) were applied. It was found that the pure phase without any calcium sulfate addition exhibits very slow hydration kinetics during the first 10 h. The hydration can be accelerated by the addition of calcium sulfate or (less effective) by increasing the pH of the aqueous phase. The amount of the calcium sulfate determines the ratio between the hydration products ettringite, monosulfate and amorphous aluminium hydroxide. The reactivity of the added calcium sulfate determines the early hydration kinetics. It was found that the more reactive gypsum was better suited to control the hydration behaviour of ye’elimite.
241 citations
TL;DR: In this article, a Tetradecanol/Ag nanowires composite PCM containing 62.73 wt% (about 11.8 vol%) of Ag nanometres showed remarkably high thermal con- ductivity (1.46 W m -1 K -1 ) and reasonably high phase change enthalpy (76.5 J g -1 ).
Abstract: One of the greatest challenges in the applica- tion of organic phase change materials (PCMs) is to increase their thermal conductivity while maintaining high phase change enthalpy. 1-Tetradecanol/Ag nanowires composite PCM containing 62.73 wt% (about 11.8 vol%) of Ag nanowires showed remarkably high thermal con- ductivity (1.46 W m -1 K -1 ) and reasonably high phase change enthalpy (76.5 J g -1 ). This behavior was attributed to the high aspect ratio of Ag nanowires, few thermal conduct interfaces, and high interface thermal conductivity of Ag nanowires in the composite PCM. These results indicated that Ag nanowires might be strong candidates for thermal conductivity enhancement of organic PCMs.
234 citations
TL;DR: In this article, the effect of the slag on the hydration process is still not entirely known, and little research concerning the separation of both reactions can be found in the literature.
Abstract: The hydration of ordinary Portland cement (OPC) blended with blast-furnace slag (BFS) is a complex process since both materials have their own reactions which are, however, influenced by each other. Moreover, the effect of the slag on the hydration process is still not entirely known and little research concerning the separation of both reactions can be found in the literature. Therefore, this article presents an investigation of the hydration process of mixes in which 0–85% of the OPC is replaced by BFS. At early ages, isothermal, semi-adiabatic and adiabatic calorimetric measurements were performed to determine the heat of hydration. At later ages, thermogravimetric (TG) analyses are more suitable to follow up the hydration by assessment of the bound water content w
b. In addition, the microstructure development was visualized by backscattered electron (BSE) microscopy. Isothermal calorimetric test results show an enhancement of the cement hydration and an additional hydration peak in the presence of BFS, whilst (semi-)adiabatic calorimetric measurements clearly indicate a decreasing temperature rise with increasing BFS content. Based on the cumulative heat production curves, the OPC and BFS reactions were separated to determine the reaction degree Q(t)/Q
∞
(Q = cumulative heat production) of the cement, slag and total binder. Moreover, thermogravimetry also allowed to calculate the reaction degree by w
b(t)/w
b∞. The reaction degrees w
b(t)/w
b∞, Q(t)/Q
∞ and the hydration degrees determined by BSE-image analysis showed quite good correspondence.
148 citations
TL;DR: In this article, the microstructural and crystallographic aspects of the thermally induced transformation of goethite (α-FeOOH) into hematite were analyzed for a complete characterization of the changes brought about by the thermal treatments.
Abstract: This study deals with some microstructural and crystallographic aspects of the thermally induced transformation of goethite (α-FeOOH) into hematite (α-Fe2O3), occurring at about 300 °C. Powder specimens of goethite have been annealed in air at different temperatures, ranging from 200 °C up to 1,000 °C. The resulting products have been analyzed for a complete characterization of the changes brought about by the thermal treatments, using a multianalytical approach, based on: thermogravimetry, differential thermal analysis, transmission electron microscopy, Raman spectroscopy, and X-ray diffraction. At lower temperatures, the transition to hematite produces no important changes in size and shape of the original goethite grains. Recrystallization, and partial sintering, occurs only at temperatures in excess of 800 °C. The relevant evolution of pores present in both phases has been also considered, as it may provide important indications on the actual formation mechanism of hematite.
145 citations
TL;DR: In this paper, a novel benzoxazine monomer (Bz-C) based on agrochemical renewable resource, cardanol (byproduct of cashew nut tree, Anacardium occidentale) was synthesized.
Abstract: A novel benzoxazine monomer (Bz-C) based on agrochemical renewable resource—cardanol (by-product of cashew nut tree, Anacardium occidentale) was synthesized. Bz-C, a liquid monomer, was used as reactive diluent for the solventless synthesis of bisphenol-A benzoxazine monomer (Bz-A). Benzoxazine monomer based on cardanol and bisphenol-A in 3:1, 1:1 and 1:3 blend ratio were prepared by this method. The resins had Brookfield viscosity at 316 K in the range of 145–81,533 mPa s. The resins were characterized by 1H-NMR, FTIR and elemental analysis. Curing characteristics were studied by DSC analysis. Thermal stability of cured resins was found to improve with increase in Bz-C content in the blends.
109 citations
TL;DR: In this paper, thermal analysis (thermogravimetry and differential thermal analysis) was used with scanning electron microscopy technique to investigate the hydration mechanisms and the microstructure of Portland cement-fly ash-silica fume mixes.
Abstract: Thermal analysis (thermogravimetry and differential thermal analysis) was used with scanning electron microscopy technique to investigate the hydration mechanisms and the microstructure of Portland cement-Fly ash-silica fume mixes. Calcium silicate hydrate (C–S–H), ettringite, gehlenite hydrate (C2ASH8), calcium hydroxide (Ca(OH)2) and calcium carbonate (CaCO3) phases were detected in all mixes. In the mixes with the use of silica fume addition, there is a decrease in Ca(OH)2 with increasing silica fume content at 5 and 10% compared to that of the reference Portland-fly ash cement paste and a corresponding increase in calcium silicate hydrate (C–S–H).
97 citations
TL;DR: In the past 35 years, the emphasis of the activities has been doing and stimulating of fundamental research; managing research toward improvement and development of polymer systems and industrial applications of polymers; and providing analytical support by utilization and development for characterization techniques and methods as mentioned in this paper.
Abstract: In the past 35 years, the emphasis of the activities has been doing and stimulating of fundamental research; managing research toward improvement and development of polymer systems and industrial applications of polymers; and providing analytical support by utilization and development of characterization techniques and methods. Throughout, the research activities concerned the study of molecular structure, crystallization and melting, morphology, and thermal properties of polymeric systems, and to study and understand the relations between these topics. With respect to Thermal Analysis & Calorimetry (TA&C), quantitative research has been realized in the field of crystallization of polymers of which a choice of recent work is discussed.
96 citations
TL;DR: In this article, the adsorption of MCPA and 2,4-D on the activated carbon Filtrasorb 300 was studied, and the experimental equilibrium data were analyzed by the Langmuir-Freundlich isotherm taking into account the energetic heterogeneity of adsorbing system.
Abstract: The adsorption of MCPA and 2,4-D on the activated carbon Filtrasorb 300 was studied. The adsorption isotherms of herbicides from aqueous solutions were measured over a wide range of solute concentrations and at different temperatures. The experimental equilibrium data were analyzed by the Langmuir–Freundlich isotherm taking into account the energetic heterogeneity of adsorption system. The effect of temperature and herbicide properties on its uptake was discussed. The thermal analysis was applied in order to find the differences in herbicide interactions with carbon surface. The kinetic dependences were measured and the relations between solute properties and adsorption rate were discussed.
94 citations
TL;DR: In this paper, a model based on dimensionless groups is proposed to predict the viscosity of nanopar- ticle suspensions, nanofluids, and the model is in good agreement with experi- mental determined viscosities data for alumina-water nan ofluids.
Abstract: This article presents a model, based on dimensionless groups, to predict the viscosity of nanopar- ticle suspensions, nanofluids. This empirical model expresses the viscosity of a nanofluid as a function of the following: viscosity of the base liquid, particle volume fraction, particle size, properties of the surfactant layer, and temperature. According to this model, viscosity changes nonlinearly with nanoparticle loading. Compared to other models, the new model is in good agreement with experi- mentally determined viscosity data for alumina-water nanofluids.
86 citations
TL;DR: In this article, the authors compared six calculation procedures based on single TG curves and iso-conversional method, as well as 27 mechanism functions for the PTFE degradation process.
Abstract: The thermooxidative degradation kinetics of poly(tetrafluoroethene) (PTFE) in air flow has been studied at different heating rates (6, 10, 12 and 15 K min−1) by non-isothermal differential thermal analysis (DTA). Six calculation procedures based on single TG curves and iso-conversional method, as well as 27 mechanism functions were used. The comparison of the results obtained with these calculation procedures showed that they strongly depend on the selection of proper mechanism function for the process. Therefore, it is very important to determine the most probable mechanism function. In this respect the iso-conversional calculation procedure turned out to be more appropriate. In the present work, the values of apparent activation energy E, pre-exponential factor A in Arrhenius equation, as well as the changes of entropy ΔS
≠, enthalpy ΔH
≠ and free Gibbs energy ΔG
≠ for the formation of the activated complex from the reagent are calculated. All calculations were performed using programs compiled by ourselves.
81 citations
TL;DR: In this paper, the phase change temperature and fusion heat of binary gas hydrates for cold storage in air-conditioning system were investigated and a broader and more developed view was proposed that adding appropriate amount of hydrate with lower phase-change temperature to hydrate mixture with higher one can make the mixture more suitable for storage.
Abstract: In order to study the thermal properties of new type environment-friendly binary hydrate for cold storage in air-conditioning system, tests have been carried out by DSC comprehensively on the phase-change temperature and fusion heat of TBAB hydrate, THF hydrate, and TBAB–THF hydrate mixture. The results show a good trend that TBAB–THF hydrate has the superiority for more proper phase-change temperature and increased fusion heat. A broader and more developed view is that adding appropriate amount of hydrate with lower phase-change temperature to hydrate with higher one can make the hydrate mixture more suitable for cold storage (especially for 278–281 K); some hydrates with lower phase-change temperature can even make the fusion heat of mixture hydrate increased greatly. Several new environmental working pairs for binary gas hydrates have been listed to help to promote the application.
TL;DR: In this article, isothermal titration calorimetry has been used to determine the stoichiometry, formation constants and thermodynamic parameters (ΔG o, ΔH, ΔS) for the formation of the citrate complexes with the Mn2+, Co2+, Ni2+ and Zn2+ ions.
Abstract: Isothermal titration calorimetry has been used to determine the stoichiometry, formation constants and thermodynamic parameters (ΔG
o, ΔH, ΔS) for the formation of the citrate complexes with the Mn2+, Co2+, Ni2+ and Zn2+ ions. The measurements were run in Cacodylate, Pipes and Mes buffer solutions with a pH of 6, at 298.15 K. A constant ionic strength of 100 mM was maintained with NaClO4. The influence of a metal ion on its interaction energy with the citrate ions and the stability of the resulting complexes have been discussed.
TL;DR: In this paper, the combined calorimetry/chemical shrinkage test showed good reproducibility and revealed the different hydration behavior of sealed samples and open samples, i.e., samples exposed to external water during hydration.
Abstract: Isothermal calorimetry and chemical shrinkage measurements are two independent techniques used to study the development of hydration in cementitious systems. In this study, calorimetry and chemical shrinkage measurements were combined and simultaneously performed on hydrating cement paste samples. Portland cement pastes with different water to cement ratios and a cement paste containing calcium sulfoaluminate clinker and anhydrite were studied. The combined calorimetry/chemical shrinkage test showed good reproducibility and revealed the different hydration behavior of sealed samples and open samples, i.e., samples exposed to external water during hydration. Large differences between sealed and open samples were observed in a Portland cement paste with low water to cement ratio and in the calcium sulfoaluminate paste; these effects are attributed to self-desiccation of the sealed pastes. Once the setup is fully automatized, it is expected that combined calorimetry/chemical shrinkage measurements can be routinely used for investigating cement hydration.
TL;DR: In this article, the thermal degradation behavior of I2O5 mixed with micron and nanometer scale aluminum (Al) particles was examined in an argon environment on both particle scales revealing a non-reaction for micron Al and a complex multistep reaction for the nanometer-scale Al.
Abstract: Owing to increasing threats of biological attacks, new methods for the neutralization of spore-forming bacteria are currently being examined. Thermites may be an effective method to produce high-temperature reactions, and some compositions such as aluminum (Al) and iodine pentoxide (I2O5) also have biocidal properties. This study examines the thermal degradation behavior of I2O5 mixed with micron and nanometer scale aluminum (Al) particles. Differential scanning calorimetry (DSC) and thermogravimetric (TG) analyses were performed in an argon environment on both particle scales revealing a non-reaction for micron Al and a complex multistep reaction for the nanometer scale Al. Results show that upon I2O5 decomposition, iodine ion sorption into the alumina shell passivating Al particles is the rate-controlling step of the Al–I2O5 reaction. This pre-ignition reaction is unique to nano-Al mixtures and attributed to the significantly higher specific surface area of the nanometric Al particles which provide increased sites for I− sorption. A similar pre-ignition reaction had previously been observed with fluoride ions and the alumina shell passivating Al particles.
TL;DR: In this article, a polyaddition reaction using toluene diisocyanate (TDI), 2,2-di(hydroxy-methyl) propionic acid, soy-based polyols with different hydroxyl values, plus 2-hydroxyethyl methacrylate (HEMA) as chain termination agent, triethylamine as neutralization agent, and DBTDL as catalyst.
Abstract: Waterborne polyurethane coatings were prepared by a polyaddition reaction using toluene diisocyanate (TDI), 2,2-di(hydroxy-methyl) propionic acid, soy-based polyols with different hydroxyl values, plus 2-hydroxyethyl methacrylate (HEMA) as chain termination agent, triethylamine as neutralization agent, and DBTDL as catalyst. Six soybean oil-based polyols were used in this study with hydroxyl values of 100, 115, 128, 140, 155, and 164 mg KOH g−1, respectively. The molar ratio of polyol hydroxyl to DMPA was varied from 1.6 to 2.6. The storage stability of the waterborne polyurethane coatings was greater than 6 months. The thermal properties of the coating films were investigated by TG and DCS. The results show that the soy-based polyurethane films decomposed in three stages. The glass transition temperatures, T
g, of the soy-based polyurethane films increased with the hydroxyl number of the soy-based polyol.
TL;DR: In this article, the authors compared the pyrolysis of cellulose in cotton fibers compared to micro-crystalline cellulose (Avicel, PH 105) using the model-free method.
Abstract: Thermal decomposition of cellulose has been widely studied for the past several years. It has been reported that the source of cellulose and its composition greatly affect its pyrolysis. One of the most widely used analytical tools for the study of cellulose pyrolysis is thermogravimetric (TG) analysis. Several model-fitting methods have been employed to study cellulose pyrolysis kinetics. An alternative to the model-fitting approach is the so-called model-free method developed by Vyazovkin. This isoconversional technique calculates the activation energy as a function of the degree of the conversion. In this article, the pyrolysis of cellulose in cotton fibers compared to microcrystalline cellulose (Avicel, PH 105) was investigated. TG curves were acquired as a function of the heating rates (4, 5, 8, 10, and 16 °C min−1) and the model-free method was used to analyze the data. Activation energies of cotton fibers and Avicel were obtained, and compared to the data reported in the literature. In addition, models for isothermal decomposition were calculated and compared with experimental data at the same temperature.
TL;DR: In this article, the effects of vegetable oil transesterification and vegetable oil-1-butanol-diesel blends on fuel properties, cetane number (CN) and thermal characteristics were experimentally investigated.
Abstract: Vegetable oil derived fuels for diesel engines are becoming important as alternative to petroleum diesel fuels due to their environmental friendliness and availability. Ignition quality in compression ignition (CI) engines is influenced by thermal characteristics and fuel properties. In this study, the effects of vegetable oil transesterification and vegetable oil–1-butanol-diesel blends on fuel properties, cetane number (CN) and thermal characteristics were experimentally investigated. Methyl esters (biodiesel) and 10% vegetable oil–10% 1-butanol–80% diesel blends were prepared from croton oil (CRO), coconut oil (COO) and jatropha oil (JAO). CN was measured in a CFR F-5 engine, and a thermogravimetric analysis (TG), as well as the determination of fuel properties of vegetable oils, biodiesels and blends was carried out. It can be observed for vegetable oils that they possess low volatility characteristics, low CN and high viscosity different from those of biodiesels, blends and diesel fuel. It was observed that biodiesels and blends exhibit similarities with diesel in the fuel characteristics, CN and TG curves.
TL;DR: In this paper, the thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA) of bio-composite fibers were used to study the properties of wood pulp-polypropylene composite fibers.
Abstract: Bio-composite fibers were developed from wood pulp and polypropylene (PP) by an extrusion process. The thermo-physical and mechanical properties of wood pulp-PP composite fibers, neat PP and wood pulp were studied using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). The thermal stability of bio-composite fibers was found to be significantly higher than pure wood pulp. An understanding into the melting behaviour of the composite system was obtained which would assist in selecting a suitable temperature profile for the extruder during processing. The visco-elastic properties of bio-composite fibers were also revealed from the study. The generated bio-composite fibers were also characterized using Fourier transform infrared spectroscopy (FTIR) to understand the nature of chemical interaction between wood pulp reinforcement and PP matrix. The use of maleated polypropylene (MAPP) as a compatibilizer was investigated in relation to the fiber microstructure. Changes in absorption peaks were observed in FTIR spectra of bio-composite fibers as compared to the pure wood pulp which indicated possible chemical linkages between the fiber and polymer matrix.
TL;DR: In this article, the authors established a reaction kinetic model on thermal decomposition properties via differential scanning calorimetry (DSC) by well-known kinetic equations and kinetic model simulation.
Abstract: Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) is a typical highly energetic material that has been widely used in national defense industries since the 1940s. The aim of this study was to establish a reaction kinetic model on thermal decomposition properties via differential scanning calorimetry (DSC) by well-known kinetic equations and kinetic model simulation. Furthermore, the aim also was to compare kinetic algorithms for thermal decomposition energy parameters under various conditions. Experimental results highly depended on the reliability of the kinetic concept applied, which is essentially defined by the proper choice of a mathematical model of a reaction. In addition, the correctness of the methods is used for kinetics evaluation.
TL;DR: In this paper, a white calcium bentonite (CaB) taken from Camlidere (Ankara, Turkey) region was heated at various temperatures between 100 and 1100°C for 2.h.
Abstract: A white calcium bentonite (CaB) taken from Camlidere (Ankara, Turkey) region was heated at various temperatures between 100 and 1100 °C for 2 h. The mineralogy of the CaB was determined as calcium smectite (CaS), metahalloysite (MH), opal-A (OA), opal-CT (OCT), quartz (Q), feldspar (F), and calcite (C) using the X-ray diffraction patterns of the natural CaB and its heated samples. Besides the XRD patterns, the thermogravimetry, differential thermal analysis, and low-temperature nitrogen adsorption (N2-AD) data show that the CaS lose adsorbed and hydration water up to 300 °C, dehydroxylation takes place between 300 and 750 °C, and then the 2:1 layer structure completely collapses above 900 °C. The activation energies for the dehydration and dehydroxylation were calculated as 7636 and 48838 J mol−1, respectively, from the TG data using Coats and Redfern method. The specific surface area (S) and specific micro–mesopore volume (V) obtained from N2-AD data were 44 m2 g−1 and 0.100 cm3 g−1 for the natural CaB. S and V reach their maxima of 105 m2 g−1 and 0.155 cm3 g−1, respectively, at 300 °C, remain approximately constant as the temperature increases up to 700 °C and then decrease almost in parallel with each other, reaching their minima at 900 °C. This indicates that the S and V values increase gradually during dehydration and dehydroxylation of the CaS.
TL;DR: In this paper, a quantitative method based on thermal analyses has been used for the determination of the chemical composition of the C-S-H gel together with the degree of hydration and quantitative evolution of all the components of the pastes.
Abstract: This research is part of a European project (namely, CODICE project), main objective of which is modelling, at a multi-scale, the evolution of the mechanical performance of non-degraded and degraded cementitious matrices. For that, a series of experiments were planned with pure synthetic tri-calcium silicate (C3S) and bi-calcium silicate (C2S) (main components of the Portland cement clinker) to obtain different calcium–silicate–hydrate (C–S–H) gel structures during their hydration. The characterization of those C–S–H gels and matrices will provide experimental parameters for the validation of the multi-scale modelling scheme proposed. In this article, a quantitative method, based on thermal analyses, has been used for the determination of the chemical composition of the C–S–H gel together with the degree of hydration and quantitative evolution of all the components of the pastes. Besides, the microstructure and type of silicate tetrahedron and mean chain length (MCL) were studied by scanning electron microscopy (SEM) and 29Si magic-angle-spinning (MAS) NMR, respectively. The main results showed that the chemical compositions for the C–S–H gels have a CaO/SiO2 M ratio almost constant of 1.7 for both C3S and C2S compounds. Small differences were found in the gel water content: the H2O/SiO2 M ratio ranged from 2.9 ± 0.2 to 2.6 ± 0.2 for the C3S (decrease) and from 2.4 ± 0.2 to 3.2 ± 0.2 for the C2S (increase). The MCL values of the C–S–H gels, determined from 29Si MAS NMR, were 3.5 and 4 silicate tetrahedron, for the hydrated C3S and C2S, respectively, remaining almost constant at all hydration periods.
TL;DR: In this paper, thermal properties of industrial hydrolysis lignin (HL) obtained from bio-ethanol production plants were investigated by thermogravimetry and differential scanning calorimetry.
Abstract: Thermal properties of industrial hydrolysis lignin (HL) obtained from bio-ethanol production plants were investigated by thermogravimetry and differential scanning calorimetry. Thermal decomposition of HL was observed in two stages suggesting coexisting carbohydrates. Glass transition temperature (T
g) was observed in a temperature range from 248 to 363 K. T
g values were lower than that of other industrial lignins, such as kraft lignin or lignosulfate. Enthalpy relaxation was observed as sub-T
g, which is not as prominent as other industrial or laboratory scale isolated lignins. T
g of HL decreased in the presence of water and saturated at water content (W
c) of 0.18 (mass of water/mass of dry HL). The amount of bound water calculated from melting enthalpy of water and W
c was ca. 0.18. Thermal decomposition and molecular motion of as obtained industrial HL are affected by coexisting carbohydrates.
TL;DR: The carboxylato-cu(II) complexes of type [Cu2(RCOO)4] and their benzothiazole adducts were submitted to measurements relating to spectral (IR, UV-Vis, and thermal properties (TG, DTA, DSC) as mentioned in this paper.
Abstract: The carboxylato–Cu(II) complexes of type [Cu2(RCOO)4] and their benzothiazole adducts [Cu2(RCOO)4bt2] (bt = benzothiazole, R = CH3(CH2)n−2, n = 12, 14, 16, 18) form the main objectives of this study The studied carboxylato–Cu(II) complexes are formed from dimeric units to polymeric chains (chromofor CuO5) The structural changes are due to coordination of ligand (benzothiazole) The polymeric chains of carboxylato–Cu(II) complexes degraded to discrete centrosymetric tetracarboxylate-bridged dimmers (chromofor CuO4N) These prepared compounds [Cu2(RCOO)4] and [Cu2(RCOO)4L2] were submitted to measurements relating to spectral (IR, UV–Vis) and thermal properties (TG, DTA, DSC)
TL;DR: In this paper, the morphological structure and thermal stability of continuous basalt fiber were analyzed using CH-2 projection microscope, scanning electron microscope (SEM) and thermogravimetry (TG).
Abstract: Thermal insulation and fire protection have been a point of interest and discussion for several decades. Due to its excellent performances, basalt fiber has been widely used in the fields of thermal insulation and fire protection. The morphological structure and thermal stability of continuous basalt fiber were analysed using CH-2 projection microscope, scanning electron microscope (SEM) and thermogravimetry (TG). In order to evaluate the thermal radiation protective performance when exposed to fire environment, the spectral reflectances of nonwoven fabrics with different thicknesses were evaluated by ultraviolet-visible-near infrared (UV–Vis–NIR) spectrophotometer analysis. The jointly analysis of TG and UV–Vis–NIR spectrophotometer revealed that the basalt fiber exhibits good thermal stability, and the nonwoven fabrics present excellent thermal protective performance.
TL;DR: In this article, the process of oxygen chemisorption on coal in the temperature range ≈150-300 °C was studied under different experimental conditions using TG-DSC apparatus.
Abstract: The process of oxygen chemisorption on coal in the temperature range ≈150–300 °C was studied under different experimental conditions using TG-DSC apparatus. As changing experimental conditions, oxygen flow (20 or 200 cm3 min−1), material of crucible (α-Al2O3 or Pt–Rh alloy), and initial sample mass (2–13 mg) were examined with respect to reliability and reproducibility of the parameters derived from TA curves. As parameters quantifying coal oxidation, temperatures of minimal Tmin and maximal Tmax sample mass, mass changes (mass loss WH below Tmin and mass increase WO above Tmin), heat evolution during oxygen chemisorption QO (related to the coal mass increase), and kinetic parameters (activation energy E and frequency factor A) were evaluated. Values of Tmax, E, and A were found to lie in very close intervals independently on experimental conditions (95% confidence intervals were Tmax = 270.2 ± 0.7 °C, E = 81 ± 3 kJ mol−1, log10A = 5.9 ± 0.3 s−1). Thus, these parameters can be used as actual characteristics of oxygen chemisorption stage of coal oxidation irrespective on conditions of TA measurements. Opposite, parameter QO was confirmed to depend clearly on initial sample mass. The dependence is different for crucible materials used; however, it tends to the same value (≈50 kJ g−1) with increasing sample mass. Further, precision of values WH, WO, and Tmin determined from TG was found to be poor. This fact complicates evaluation of the effect of experimental conditions. Finally, the effect of oxygen flow on all above parameters was found to be negligible. Its influence (if any) was hidden by common experimental errors.
TL;DR: In this paper, the effect of the organoclay on the thermal degradation of polyolefins (polyethylene and polypropylene) was evaluated using X-ray diffraction (XRD) and elemental analysis.
Abstract: The results presented by a number of researchers indicate that the introduction of montmorillonite into polymer matrix results in an increase of thermal stability of polymer nanocomposites. The main purpose of this study was to evaluate the effect of the organoclay on the thermal degradation of polyolefins (polyethylene and polypropylene). Polyolefin-clay nanocomposites were prepared by melt compounding of polyolefins and montmorillonite clay organically modified with 4,4′-methylenebisaniline (MBA) (from 1.5 to 5 wt%). Changes in the surface of montmorillonite and the dispersion of organoclay in the polymer matrix were evaluated using X-ray diffraction (XRD) and elemental analysis. The thermal stability of the clay and nanocomposites were analysed by differential scanning calorimetry (DSC) and thermogravimetric analysis (TG). The XRD results show that almost complete exfoliation of the silicate layers took place and nanocomposite structure was obtained for all new materials. The thermal stability of the PE and PP/clay nanocomposites can be improved in the case of loading above 5 wt%.
TL;DR: The results of these studies suggest age dependence of blood serum denaturation transition, and suggest chronic obstructive pulmonary disease patients with severe stage of COPD are more vulnerable to this process.
Abstract: Differential scanning calorimetry (DSC) has been applied for studies of blood serum from patients sick with chronic obstructive pulmonary disease (COPD). The denaturation of serum proceeds as endothermic process over the temperature range 45–85 °C. Distinct changes in the shape of DSC curves have been observed for serum from patients with severe stage of COPD (treated with inhaled corticosteroids) relative to serum from healthy individuals. The first moment of the thermal transition with respect to the temperature axis shifts from the normal value of 63.9 ± 0.3 to 65.3 ± 0.7 °C and to 67.6 ± 1.6 °C for early and advanced stages of disease, respectively. The results of our studies suggest age dependence of blood serum denaturation transition.
TL;DR: In this article, N-methyl pyrrolidone evaporation from photo-crosslinked polyacrylate was monitored thermogravimetrically at temperatures ranging from 323 to 398 K.
Abstract: Kinetics of N-methyl pyrrolidone evaporation from swollen photo-crosslinked polyacrylate was monitored thermogravimetrically at temperatures ranging from 323 to 398 K. Crosslink density dependence of evaporation kinetics was investigated in photo-crosslinked polyacrylates with crosslinked density ranging from ≈1.2 × 102 to ≈1.7 × 104 mol m−3 and number of main chain atoms between crosslinks ranging from ≈70 atoms to ≈6 atoms, respectively. As was shown, evaporation kinetics was controlled by the solvent diffusion in polymer. Activation energies of evaporation (diffusion) were deduced from the rate measurements at different temperatures. Apparent activation energy of evaporation decreased from 48.7 to 31.1 kJ mol−1 with crosslink density increase. Activation energy of pure N-methyl pyrrolidone evaporation was 50.6 kJ mol−1. Decrease of the rate of solvent diffusion and unexpected decrease of diffusion activation energy with increase of crosslink density of swollen polymer matrix was explained by decrease in polymer chain segments mobility, as indicated by Eyring’s approach to diffusion in polymers.
TL;DR: In this paper, the thermal stability of two nonsteroidal anti-inflammatory drugs (NSAIDs) was determined by differential scanning calorimetry (DSC) and simultaneous thermogravimetery/differential thermal analysis (TG/DTA) techniques.
Abstract: Data on the thermal stability of drugs was required to obtain information for handling, storage, shelf life and usage. In this study, the thermal stability of two nonsteroidal anti-inflammatory drugs (NSAIDs) was determined by differential scanning calorimetry (DSC) and simultaneous thermogravimetery/differential thermal analysis (TG/DTA) techniques. The results of TG analysis revealed that the main thermal degradation for the naproxen and celecoxib occurs in the temperature ranges of 196–300 and 245–359 °C, respectively. The TG/DTA analysis of compounds indicates that naproxen melts (at about 158.1 °C) before it decomposes. However, the thermal decomposition of the celecoxib started about 185 °C after its melting. The influence of the heating rate (5, 10, 15, and 20 °C min−1) on the DSC behavior of the both drug samples was verified. The results showed that, as the heating rate was increased, decomposition temperatures of the compounds were increased. Also, the kinetic parameters such as activation energy and frequency factor for the compounds were obtained from the DSC data by non-isothermal methods proposed by ASTM E696 and Ozawa. Based on the values of activation energy obtained by various methods, the following order for the thermal stability was noticed: naproxen > celecoxib. Finally, the values of ΔS
#, ΔH
#, and ΔG
# of their decomposition reaction were calculated.
TL;DR: In this paper, the surface area of clinoptilolite-rich tuffs from Gordes and Bigadic regions of western of Anatolia and their exchanged forms (K+, Na+, Mg2+ and Ca2+) were characterized by TG/DTG-DTA, DSC and XRF methods and the surface areas were also determined for both tuffs.
Abstract: Turkey clinoptilolite-rich tuffs from Gordes and Bigadic regions of western of Anatolia and their exchanged forms (K+, Na+, Mg2+ and Ca2+) were characterized by TG/DTG-DTA, DSC and XRF methods and the surface areas were also determined for both tuffs. TG-DTG and DTA curves of all clinoptilolite samples were measured in the temperature range 30–1000 °C. All clinoptilolite samples had major, rapid mass losses between 30 and 200 °C, with slower and less significant mass losses at higher temperatures. The mass loss of the Natural-G is 9.54% while that of the Natural-B sample is 10.50%. Water content increases in the order of K < Na < Ca < Mg for Bigadic clinoptilolite samples and in the following sequence K < Na < Mg < Ca for Gordes clinoptilolite samples. One mass loss step for all clinoptilolite samples was observed using differential scanning calorimeter (DSC) in the range of 30–550 °C.