Untitled

The variation of the parameters of front processes of thermal decomposition of condensed systems in the vicinity of the limit of thermodynamic stability

“…In so doing, the rate of decrease in mass is higher than that predicted by the Arrhenius equation corresponding to low temperatures [5][6][7]. An especially abrupt increase in the rate of transformation was observed at temperatures close to T l ; this is due to the weakening of intermolecular interaction (IMI) with increasing volume of CS, because the deformations of chemical (valence) bonds are negligible.…”

“…These conditions are observed in the "thermal probe" method [3,4,10] and other contact TA methods [5][6][7], which enables one to investigate the kinetics of decomposition of CS at high temperatures inaccessible for many other standard TA methods. The conductive heating is characterized by higher rates of sample temperature increase compared to the convective method of delivering heat to crucibles in conventional TA methods.…”

“…Interest in this problem is caused by the practical importance of the results of investigations in various fields of modern engineering such as aviation, rocketry, chemical technology, and so on. Many a mathematical model of propagation of heat and, in particular, of front processes in nonvolatile thermally unstable CS fail to include the possibility of loss of thermodynamic stability at high temperatures attained as a result of rapid (10 3 to 10 5 K/s) heating and at high values of energy input [3][4][5][6][7]. The region of variation of CS temperature in simulation is taken to be unlimited (as in the gas phases): 0 < T < ∞.…”

“…This omission is largely caused by the absence of reliable methods of experimental determination of the limit of phase state (LPS), because the numerical determination of the conditions of thermodynamic stability of CS from equations of state [8,9] is characterized by low accuracy. The advent in the 1980s of methods of pulsed heating such as the "thermal probe" method [3,4] and contact methods of thermal analysis (TA) [5,6] enabled one to actually determine the position of LPS by the temperatures of attainable superheating T l of volatile and nonvolatile CS including polymer systems [4][5][6][7]10]. The development of TA methods opened up prospects for the construction of physical and mathematical models of front processes in view of temperature constraints (T < T l ).…”