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Ammonium perchlorate (AP) is the most abundant ingredient in many solid rocket motors and presents a thermal runaway hazard. The addition of metal oxides (MOs) can alter motor performance but may affect decomposition behavior. In this work, a total of 14 MOs, mostly transition metal oxides, were mixed with AP and subjected to isothermal thermogravimetric analysis (TGA). MOs commonly incorporated into AP-based propellants can alter AP decomposition rates, the extent of reaction, and the particle size of the AP itself. Partially decomposed AP showed significant changes in terminal particle size. There is an inverse correlation between MO lattice energy and peak reaction rates of AP/MO mixtures. The objective of this work is not to provide definitive details of mechanisms, but rather to report observations and interactions with a wide variety of MOs, often ones that were not previously reported. The findings have implications for the safe storage of AP and the development of insensitive motors. [ABSTRACT FROM AUTHOR]

Abstract To date, research on the low temperature (< 240 °C) decomposition of ammonium perchlorate (AP) has typically presented decomposition data either as mass loss curves or Avrami equation fits. Neither approach measures true decomposition reaction rates, which should be a fundamental and early consideration in understanding the chemistry underlying AP decomposition. In addition, concern for low temperature AP decomposition usually occurs in confined environments where unvented product gases may react in a heterogeneous manner with the pristine AP material. In this work, we show evidence that decomposition gas products play a role in promoting the decomposition of solid AP, which suggests that heterogeneous reactions are a major driving force behind these decomposition reactions. A simple heterogeneous chemistry model is proposed to describe the growth and evolution of pores as AP decomposes. The model qualitatively predicts a size dependence on maximum decomposition rates with respect to particle size using kinetic information derived from literature. The experimental data and model provide some insight into decades-old questions surrounding the unique decomposition behavior of AP. An understanding of the role that heterogeneous reactions play in AP decomposition may be used to develop gas scavenging strategies that can protect AP-based propellants from thermal threats. [ABSTRACT FROM AUTHOR]