Authors:M. Souza, Marta Conceição, M. Silva, L. Soledade, and A. Souza
Statins are a group of lipoproteins that
are used in medicine to treat the high cholesterol level. The effectiveness
of statins in reducing the cholesterol level is significant and in long time
scale the reduction of the cholesterol level helps to avoid the incidence
of degenerative diseases. Simvastatin and lovastatin are belonging to the
‘statins’ family, one of the pharmacologic groups used in the
control of dislipidemy. The objective of this work is the thermal stability
and kinetic study of the active forms of simvastatin and lovastatin.
Thermal data indicated that lovastatin and simvastatin are stable up
to 190 and 170°C in air and up to 205 and 203°C in nitrogen, respectively.
For melting temperatures DSC curves showed good correlation with the literature
data. Comparing the activation energies of the statins at heating rate of
10°C min–1, lovastatin is more stable
than simvastatin under the applied experimental conditions.
Authors:M. Bernardi, E. Leite, E. Longo, M. Conceiçăo, and A. Souza
The color efficiency of ceramic glaze blue pigments obtained by the Pechini method was presented in this work. The fired pigments
and enameled samples were characterized by thermogravimetry (TG) and differential thermal analysis (DTA), XRD, UV-VIS-NIR
spectroscopy and CIE-L*a*b* color-measurements. The pigments obtained by the Pechini method present a better solubility in
the molten glazes than the pigments obtained by the mechanical mixture of the precursor oxides.
Authors:E. Medeiros, R. Tocchetto, L. Carvalho, M. Conceição, and A. Souza
In this work, the influence of attapulgite concentration on the nucleating efficiency of isotactic polypropylene (iPP) and
on the kinetics of non-isothermal crystallization were ascertained.The study was conducted by DSC. The nucleating efficiency
was determined according to the procedure described by Fillon and the kinetics of non-isothermal crystallization was determined
using Ozawa's method using cooling rates of 2, 5 and 10C min−1.Our results indicate that both the relative crystallinity and the crystallization temperature increase with filler content
and that a maximum occurs at 2% mass/mass filler content. Both parameters decrease with increasing cooling rates. The Ozawa's
exponent tended to increase with temperature and filler content.
Authors:M. Conceição, A. Melo, N. Narain, I. Santos, and A. Souza
The thermogravimetric procedures applied to quality control of foods attain the global analysis of quality of the product,
through the determination of quality parameters and the thermal stability of products. The kinetic parameters such as order
of reaction, apparent activation energy, pre-exponential factors and the thermal decomposition rate constant were determined
for the samples of corn and its derivatives by applying isothermal thermogravimetry, utilizing the Arrhenius law. This method
presented excellent results as verified with the coherence and data adjustment. The rate constant values showed the expected
performance from the chemical point of view.
Authors:R. Filho, P. Franco, E. Conceição, and M. Leles
A formulation of nifedipine tablets was prepared in the present research. The tablets were conditioned in amber-colored glass
containers and placed in a climatized room at 40°C and relative humidity of 75% for 180 days. Differential scanning calorimetry
(DSC) and thermogravimetry (TG) were used in order to evaluate the thermal properties of nifedipine, the excipients and two
well-known nifedipine degradation products. The results demonstrated that there is no evidence on the interaction between
nifedipine and excipients, or degradation products.
Authors:R. Filho, P. Franco, E. Conceição, and M. Leles
A new formulation of nifedipine tablets was prepared. The tablets were conditioned in amber-colored glass containers and placed
in a climatized room at 40 °C and relative humidity of 75% for 180 days. Differential scanning calorimetry (DSC) and Thermogravimetry
(TG) were used in order to evaluate the thermal properties of nifedipine, the excipients and two well-known nifedipine degradation
products. There is no evidence of interaction between nifedipine and excipients or degradation products. High performance
liquid chromatography (HPLC) was used in the dosage of nifedipine tablets before and after acclimatized exposure. Results
show that DSC and TG offer important data for a more detailed assessment of the stability of a pharmaceutical formulation.
Authors:C. Xavier, C. Costa, S. Crispim, M. Bernardi, M. Maurera, M. Conceiçăo, E. Longo, and A. Souza
The pigments used in ceramic applications are of nature predominantly inorganic and they should be thermally stable, insoluble
in glazing, resistant to the chemical and physical agents' attacks. This work aimed at the synthesis by the polymeric precursor
method of ZrO2-based inorganic pigments, doped with Fe, Ni, Co, Cr and Cu cations. The fired pigments were characterized by thermogravimetry
(TG), differential thermal analysis (DTA) and X-ray diffraction (XRD). Among the metals used to zirconium-doping, the best
result was achieved with the cations Cu, which presented the monophase pigment, even as 20 mol% of dopant. Up to the temperature
of 1000C the pigments presented a good thermal stability.
Authors:M. Fook, A. Souza, M. Trindade, M. Conceiçăo, J. Santos, S. Prasad, V. Fernandes, and S. Crispim
The high-density polyethylene, thermoplastic widely-used in the production of industrial domestic utilities, was collected
in two situations: virgin high-density polyethylene (JV 060) and post-consumption high-density polyethylene (with features
of low-density polyethylene). After collecting the samples, they were submitted to natural aging with the quantification of
the incident solar radiation for 180 days. The samples were characterized by melt flow index, differential scanning calorimetry,
tensile strength, rupture load, elongation at break and infrared. The results showed that after 180 days of exposure the virgin
high-density polyethylene presented physical properties similar to the post-consumption polyethylene.
Authors:M. Silva, M. Conceiçăo, M. Trindade, A. Souza, C. Pinheiro1, J. Machado, and P. Filho
The thermodynamic and kinetic parameters of the thermal decomposition of Zn(S2CNR2)2 complexes (R=CH3, C2H5 and n-C3H7) were determined with the dynamic thermogravimetric method. Superimposed TG/DTG/DSC curves show that thermal decomposition
reactions for chelates with R=C2H5 and n-C3H7 occur in the liquid phase, at temperatures far away from their melting points, whereas for the complex with R=CH3 the thermal decomposition begins at a temperature closer to its melting point, suggesting a rather complex decomposition
Authors:A. Souza, M. Tavares, D. Melo, M. Conceição, J. Espinola, and C. Airoldi
The thermal decomposition reactions of crystalline chelates of general formula Ln(thd)3 (Ln=La,Pr, Nd, Sm and Gd; thd=2,2,6,6-tetramethyl-3,5-heptanedione) have been studied by isothermal thermogravimetry. Several models were proposed initially
to calculate the kinetic parameters by isothermal method, thus the time reduced method was used to define the best kinetic
models. The Avrami–Erofeev (Am=2, 3 and 4) and R1 and R2 models presented good agreement with experimental data, as well as, linear correlation coefficient
(r) and standard deviation (s).