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Abstract  

The thermal decomposition of salbutamol (β2 — selective adrenoreceptor) was studied using differential scanning calorimetry (DSC) and thermogravimetry/derivative thermogravimetry (TG/DTG). It was observed that the commercial sample showed a different thermal profile than the standard sample caused by the presence of excipients. These compounds increase the thermal stability of the drug. Moreover, higher activation energy was calculated for the pharmaceutical sample, which was estimated by isothermal and non-isothermal methods for the first stage of the thermal decomposition process. For isothermal experiments the average values were E act=130 kJ mol−1 (for standard sample) and E act=252 kJ mol−1 (for pharmaceutical sample) in a dynamic nitrogen atmosphere (50 mL min−1). For non-isothermal method, activation energy was obtained from the plot of log heating rates vs. 1/T in dynamic air atmosphere (50 mL min−1). The calculated values were E act=134 kJ mol−1 (for standard sample) and E act=139 kJ mol−1 (for pharmaceutical sample).

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Abstract  

The kinetics of the thermal decomposition of ammonium perchlorate at temperatures between 215 and 260°C is studied, in this work, by measuring the sample mass loss as a function of time applying the isothermal thermogravimetric method. From the maximum decomposition rate – temperature dependence two different decomposition stages, corresponding to two different structural phases of ammonium perchlorate, are identified. For the first region (215–235°C), corresponding to the orthorhombic phase, the mean value of the activation energy of 146.3 kJ mol–1, and the pre-exponential factor of 3.43⋅1014 min–1 are obtained, whereas for the second region (240–260°C), corresponding to the cubic phase, the mean value of the activation energy of153.3 kJ mol–1, and the pre-exponential factor of 4.11⋅1014 min–1 are obtained.

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Possibilities of applying the Piloyan method of determination of decomposition activation energies

Part III. Derivatives containing two picryl groups in the molecule, and melamine derivatives

Journal of Thermal Analysis and Calorimetry
Author: S. Zeman

Via the Piloyan method, activation energiesE were determined for polynitroaromatic compounds containing two picryl groups, and for melamine derivatives. At the same time the initial temperatures of exothermic decompositionT D were determined by means of non-isothermal DTA. Linear relationship were derived betweenE ·T D −1 and published kinetic data obtained from the study of HNB, HNAB, DIPS, DIPSO, HNS and TPM by isothermal manometry. On the basis of the derived relationship, as well asE andT D values from DTA measurements, kinetic data were calculated for DPA, KDPA, DMHNB, DPM, DPE and TMPM with the manometric method.

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