Kinetic investigation on thermal decomposition of organophosphorous compounds |
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Authors: | M R Sovizi K Anbaz |
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Institution: | (1) Faculty of Material and Manufacturing Technologies, Malek Ashtar University of Technology, P.O. Box 16765-3345, Tehran, Iran;(2) Department of Chemistry, Imam Hossein University, Tehran, Iran |
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Abstract: | In this paper, the thermal behaviours of two organophosphorous compounds, N,N-dimethyl-N′,N′-diphenylphosphorodihydrazidic (NDD) and diphenyl amidophosphate (DPA), were studied by thermogravimetery (TG), differential
thermal analysis (DTA) and differential scanning calorimetery (DSC) techniques under non-isothermal conditions. The results
showed that NDD melts about 185 °C before it decomposes. NDD decomposition occurs in two continuous steps, in the 190–410 °C
temperature range. First thermal degradation stage for NDD results a broad exothermic peak in the DTA curve that is continued
with a small exothermic peak at the end of decomposition process. On the other hand, applying TG-DTA techniques indicates
that DPA melts about 150 °C before it decomposes. This compound decomposes in the temperature range of 230 to 330 °C in two
steps. These steps are endothermic and exothermic, respectively. Activation energy and pre-exponential factor for the first
step of decomposition of each compound were found by means of Kissinger method and were verified by Ozawa–Flynn–Wall method.
Activation energy obtained by Kissinger method for the first stage of NDD and DPA decompositions are 138 and 170 KJ mol−1, respectively. Finally, the thermodynamic parameters (ΔG
#, ΔH
# and ΔS
#) for first step decomposition of investigated organophosphorous were determined. |
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Keywords: | |
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