Effect of Organic Fluoride on Combustion Agglomerates of Aluminized HTPB Solid Propellant

Hydroxyl-terminated polybutadiene (HTPB) based propellants containing fixed aluminum content (18 wt %) and different amounts of organic fluoride (OF) additive were studied. Explosion heat of propellant samples and particle size distribution of the solid combustion products were experimentally measured to generally assess the effect of the organic fluoride compounds on propellants. Heats of explosion decreased approximately by 9.5 %, from 7209 (±259) to 6525 (±146) kJ kg⁻¹, with the increase in OF content from 0 % to 6 %, and the volume fraction of particles size above 10 μm was sharply decreased. In addition, scanning electron microscope images showed the solid combustion products to be well separated, the titration analysis results also gave the amount of unburned metallic aluminum decreased. These results indicated that OF as an additive would be helpful to reduce agglomeration in the combustion products of aluminized HTPB propellants. Furthermore, a mechanism for suppression of agglomerate size can be postulated based on the X-ray diffraction analysis data that addition of OF promotes increased content of γ-Al₂O₃ (aluminum oxide) in the solid combustion products.