Thermal properties of TEX decomposition or sublimation

Abstract

TEX is a thermostable compound and less sensitive to external stimuli. It sublimates and decomposes at high temperature. The influence of DSC and TG measurement conditions and substance mass on the thermal decomposition of TEX was determined. It was observed that substance mass, pan type and fulfillment degree of pan influence the thermal decomposition and kinetic parameters of TEX decomposition. Sublimation of the sample was the main observed process; thermal decomposition was the secondary process during the heating of TEX in open pans. With increasing substance mass, the participation of thermal decomposition of TEX increased. Uncontrolled thermal decomposition was observed for larger mass of a sample. The sublimation and decomposition processes were confirmed by FT-IR method. Thermal decomposition was the main process observed during heating the sample of TEX in hermetic pans. Sublimation of a sample was marginal. The sublimation effect decreased with increasing the degree of fulfillment pan. The kinetic parameters were determined with the Friedman's isoconversional method. The conversion, mass of sample and the type of pan caused the large changes in the values of kinetic parameters. The apparent activation energy varied from 128 to 355 kJ mol -1 and logA varied from 9.95 to 30.64 in initial step (a = 0.02) for different condition of measurements. The low values of apparent activation energy (about 130 kJ mol -1 ) were associated with sublimation process and the high values (about 340 kJ mol -1 ) with the decomposition process.

Origin of PYX thermal stability investigation with calorimetric and spectroscopic methods

“…The obtained values of the kinetic parameters determined in TG measurements may also be influenced by the high vapor pressure of intermediate decomposition products or PYX. The influence of measurement conditions on the determination of kinetic parameters has already been described in the literature [8]. The determined kinetic parameters for the initial PYX thermal decomposition step are in line with those obtained using the Russian manometric method [10].…”

“…The results indicate that the kinetic parameters are dependent on all of the subsequent and parallel reactions. Therefore, the obtained value of the activation energy is henceforth referred to as the apparent activation energy ( a E a ) [7,8,21]. In accordance with to ICTAC recommendations [7], the apparent activation energy a E a was determined with the Friedman isoconversion method [22].…”

“…Such information for PYX is available [5]. Many parallel and subsequent reactions run during HEM decomposition and that is why the values of kinetic parameters may substantially change with the conversion degree of the progress [6][7][8]. Thermal explosion may occur even in a low conversion degree [9], so the determination of kinetic parameters at the initial stage of decomposition is significant.…”

Comparison between Glass and Stainless-Steel Vessels in Differential Scanning Calorimetry Estimation

“…Nevertheless, these effects have not been studied in detail; most researchers tend to use their own preferred vessel for thermal risk assessment. Judging from recent research trends, pressure vessels seem to be the most commonly used in studying the relationship between the thermal reactivity and explosiveness of a chemical substance [4] [5] [6] [7] [8]; however, chemicals have also been examined using an aluminum pan [9] [10] [11], alumina vessel [12], and glass capillary tube [13].…”

The influence of substituents position on products of dinitrotoluene isomers initial thermal decomposition

“…No complex studies containing particular analysis of all DNT isomers with the same analytical technique were performed. It is unfavorable because changing of the method may influence the thermal decomposition process [21]. That is why thermal stability parameters and decomposition products cannot be compared on the basis of the existing literature.…”