Authors:A. Leite, L. Maia, R. Paz, E. Araújo, and H. Lira
The aim of this work was to obtain membranes from polyamide 6/montmorillonite clay nanocomposites through the phase inversion
technique. The nanocomposites and membranes from polyamide 6/montmorillonite clay were characterized by X-ray diffraction
(XRD), Scanning Electron Microscopy (SEM), Thermogravimetry (TG) and Differential Scanning Calorimetry (DSC). Microporous
and asymmetric membranes were successfully obtained from nanocomposites and the results showed that the salts were incorporated
by intercalation between the organoclay layers and, apparently that the nanocomposites and membranes were thermally more stable
than the pure polyamide.
Authors:L. Cides, A. Araújo, M. Santos-Filho, and J. Matos
the present work, the thermal decomposition of glimepiride (sulfonylurea hypoglycemic
agent) was studied using differential scanning calorimetry (DSC) and thermogravimetry/derivative
thermogravimetry (TG/DTG). Isothermal and non-isothermal methods were employed
to determine kinetic data of decomposition process. The physical chemical
properties and compatibilities of several commonly used pharmaceutical excipients
(glycolate starch, microcrystalline cellulose, stearate, lactose and Plasdone)
with glimepiride were evaluated using thermoanalytical methods. The 1:1 physical
mixtures of these excipients with glimepiride showed physical interaction
of the drug with Mg stearate, lactose and Plasdone. On the other hand,
IR results did not evidence any chemical modifications. From isothermal experiments,
activation energy (Ea)
can be obtained from slope of lntvs. 1/T at a constant
conversion level. The average value of this energy was 123 kJ mol–1.
For non-isothermal method Ea
can be obtained from plot of logarithms of heating rates, as a function of
inverse of temperature, resulting a value of 157 and 150 kJ mol–1,
respectively, in air and N2 atmosphere, from the first
stage of thermal decomposition.
Authors:H. Polli, L. Pontes, A. Araujo, Joana Barros, and V. Fernandes
The degradation kinetics of the ABS terpolymer (acrylonitrile-butadiene-styrene) was investigated by means of thermogravimetric
analysis. The samples were heated from 30 to 900°C in nitrogen atmosphere applying three different heating rates: 5, 10 and
20°C min−1. The Vyazovkin model-free kinetic method was used to calculate the activation energy (E) of the degradation process as a function of conversion and temperature. Between 20 and 80% of conversion, E was calculated
and the figures were: for ABS GP, E is 204.5±11.5 kJ mol−1 (medium value); for ABS HI, E is 239.0±9.8 kJ mol−1; for ABS HH, E is 242.4±5.4 kJ mol−1.
Authors:A. Garrido Pedrosa, M. Souza, S. Lima, Dulce Melo, A. Souza, and A. Araújo
bifunctional catalysts were synthesized using impregnation and polymeric precursor
methods. After the synthesis process the samples were calcined at 600, 700
and 800C and characterized by X-ray diffraction, nitrogen adsorption
and temperature programmed reduction study by thermogravimetry. DTG-TPR profiles
showed between three and five reduction events at different temperatures attributed
to platinum reduction and to different stages of tungsten species reduction.
A comparative study of the synthesis method influence on the DTG-TPR curves
Authors:A. M. Garrido Pedrosa, M. J. B. Souza, D. M. A. Melo, and A. S. Araujo
The thermo-programmed reduction study of Pt/WOx–ZrO2 materials prepared with different tungsten loading were performed by thermogravimetry. The samples were synthesized by impregnation method and calcined at 600, 700 and 800°C. The characterizations of both un-calcined and calcined materials were carried out using different techniques: thermal analysis (TG and DTA), X-ray diffraction (XRD) and thermo-programmed reduction (TPR). TG and DTA analysis of un-calcined were used to determination of calcination temperatures of the samples. XRD diffractograms were useful to help us in the determination of phase presents. TPR profiles showed between three and four events at different temperatures attributed to platinum reduction and the different stages of tungsten specie reduction.
Authors:J. Santos, M. Conceiçăo, M. Trindade, A. Araújo, V. Fernandes, and A. Souza
The lanthanidic complexes of general formula Ln(C11H19O2)3 were synthesized and characterized by elementary analysis, infrared absorption espectroscopy, thermogravimetry (TG) and differential
scanning calorimetry (DSC). The reaction of thermal decomposition of complexes has been studied by non-isothermal and isothermal
TG. The thermal decomposition reaction of complexes began in the solid phase for Tb(thd)3, Tm(thd)3 and Yb(thd)3 and in the liquid phase for Er(thd)3 and Lu(thd)3, as it was observed by TG/DTG/DSC superimposed curves. The kinetic model that best adjusted the experimental isothermal thermogravimetric
data was the R1 model. Through the Ozawa method it was possible to find coherent results in the kinetic parameters and according
to the activation energy the following stability order was obtained: Tb(thd)3>Lu(thd)3>Yb(thd)3>Tm(thd)3>Er(thd)3
Authors:A. Garrido Pedrosa, P. Pimentel, D. Araújo Melo, H. Scatena, F. Borges, A. Souza, and L. Zinner
Ln(TFA)3⋅3AZA (Ln=La, Sm, Er; TFA=trifluoroacetate and AZA=2-azacyclononanone)compounds were synthesized and characterized by microanalytical procedures, IR spectroscopy, X-ray powder
diffraction, and thermal analysis. A kinetic study using La, Sm and Er thermogravimetric curves was carried out aiming to
proposing a mechanism for the thermal decomposition of such complexes.