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  • Author or Editor: S. Lerdkanchanaporn x
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Abstract  

Ibuprofen has been subjected to a TG/DTA study over the temperature range of 30 to 350°C in a flowing atmosphere of nitrogen. The heating rate and the flow rate were varied. The DTA shows a melting at around 80°C and boiling point range from 212 to 251°C depending upon the heating rate. The mass loss in the TG data confirms the evaporation of Ibuprofen between them.p. and the normalb.p. Evaporation is limited to the surface area, which is a constant in the crucible holding the sample. The DTG plot shows clearly a zero order process which is consistent with the process of evaporation. The enthalpy of vaporization (Δvap H) calculated by Trouton's rule is found to be in the range of 42.7–46.1 kJ mol−1. TheE act for the zero order reaction is in the range of 81.8–87.0 kJ mol−1 and is calculated by use of the derivative method. The value ofE act is about twice that for ΔH vap in Ibuprofen and differs from other compounds, whereE act ≈Δ H vap. It is suggested that the Ibuprofen molecule is existing as a dimer in the liquid state and dissociates to a monomer in the vapor state.

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Journal of Thermal Analysis and Calorimetry
Authors: S. Lerdkanchanaporn, D. Dollimore, and K. Alexander

Abstract  

In a previous publication, the thermogravimetric (TG) analysis of ascorbic acid was considered. Simultaneously with the production of the TG data, time-temperature plots were also generated on the work station which allowed the process to be classified as exothermic or endothermic and identified the energy change with the reaction sequence. This aspect is investigated in the present study. To maximize the energy change, the model mixtures were assessed at a mass ratio of 1∶1. The analytical implications of this approach are explored. To avoid complications in this kind of analysis, the present study is restricted to the behavior of binary systems heat treated in nitrogen.

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