Thermal decomposition and combustion characteristics of HTPB-coarse AP composite solid propellants catalyzed with Fe₂O₃

ABSTRACT

Many factors and their mutual interactions induce complexity in the combustion of hydroxyl-terminated polybutadiene (HTPB)–ammonium perchlorate (AP)–ferric oxide (Fe₂O₃) composite solid propellant (CSP). Among them, we investigated exothermicity of coarse AP decomposition for thermal decomposition and high-pressure combustion of HTPB-AP. Thermal decomposition of coarse AP was characterized by high twin-peak exothermicity, while HTPB-AP decomposed in single-stage at 329°C. Coarse AP improved thermal decomposition due to significant first-stage exothermicity. High exothermicity and predominance of coarse AP dominate thermal decomposition of CSP. Fe₂O₃ catalyzed decomposition of AP by shifting second exothermic peak to lower temperature and releasing more heat. Fe₂O₃ increased the burning rate of HTPB-AP and the highest burning rate was achieved for 1 wt % nano-Fe₂O₃ of average size 4 nm. Similar results for milli- (average size 200 μm) and micro-Fe₂O₃ (average size 2 μm) were recorded at higher concentrations. Exothermicity of coarse AP and catalytic activity of Fe₂O₃ on AP speed up subsurface processes and help in the enhancement of burning rates.

KEYWORDS:

• Ammonium perchlorate
• Burning rate
• Ferric oxide
• Thermal decomposition

Acknowledgments

The authors thank Dr C.R. Chodankar, Dr N. Yadav, and the staff of Rocket Propulsion Laboratory, Department of Space Engineering and Rocketry, Birla Institute of Technology, Ranchi, for their help during the course of work.

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Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.