Thermal behavior and decomposition kinetics of composite solid propellants in the presence of amide burning rate suppressants

Abstract

The employment of burning rate suppressants in the solid rocket propellant formulation is long known. Different research activities have been conducted to well understand the mechanism of suppression, but literature about the action of oxamide (OXA) and azodicarbonamide (ADA) on the thermal decomposition of composite propellant is still scarce. The focus of this study is on investigating the effect of burning rate suppressants on the thermal behavior and decomposition kinetics of composite solid propellants. Thermogravimetric analysis (TG) and differential thermal analysis (DTA) have been used to identify the changes in the thermal and kinetic behavior of coolant-based propellants. Two main decomposition stages were observed. It was found that OXA played an inhibition effect on both stages, whereas the ADA acts as a catalyst in the first stage and as coolant in the second one. The activation energy dependent on the conversion rate was estimated by two model-free integral methods: Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO) based on the TG data obtained at different heating rates. The mechanism of action of coolants on the decomposition of solid propellants was confirmed by the kinetic investigation as well.

A Promising Energetic Polymer from Posidonia oceanica Brown Algae: Synthesis, Characterization, and Kinetic Modeling

“…Before the discussion of the computed E a and A , it is interesting to note that activation energy represents the barrier of energy to overcome the initiation of the decomposition reaction of the energetic material. Thus, higher value of activation energy means slower reaction rate and the process becomes more difficult to occur, whereas the pre‐exponential factor is an indication of the quickness and the frequency of the decomposition reaction, revealing that the elevated value of the activation energy corresponds to the higher value of the pre‐exponential factor . This behavior, attributed to the kinetic compensation effect can be clearly verified for our investigated nitrated samples, as depicted in Figures and .…”

“…On the other hand, in order to well highlight the compensation effect, the decimal logarithm of frequency factor calculated by both TAS and VYA/CE (β = 5, 10, 15, and 20 °C min −1 ) were plotted as function of activation energy, and the values of the compensation parameters ( a and b ) are displayed in Table 5 . A great linear correlation was found with linear correlation coefficients higher than 0.99990, confirming the kinetic compensation effect …”

“…These lower relative deviation values are probably due to the different approximations applied in the programs . Furthermore, it is worthy to note that several authors pointed out that the kinetic parameter results with maximum relative deviation less than 10% between the employed kinetic approach confirmed the reliability and the consistency of the executed calculations and the good predictive power of the used kinetic method …”

“…As can be clearly checked, the Arrhenius parameters evaluated by the different used isoconversional kinetic methods present comparable trend and close values, except those computed based on it‐FWO approach, which shows slightly lower values of Arrhenius parameters than those obtained by TAS, it‐KAS, and VYA/CE, while keeping the same evolution. This finding was expected since it‐FWO equation employs only the first approximation of the temperature integral …”

“…Besides that, kinetics behavior studies of energetic materials such as NC and MCCN could be an excellent complementary approach, which can provide reliable information about their decomposition and to estimate the influence of their exothermic degradation on the potential hazard in their preparation, storage, and use . Kinetic parameters (activation energy, pre‐exponential factor, and mathematical reaction mechanism) from non‐isothermal data can be computed by isoconversional and non‐isoconversional procedures .…”