Enhanced combustion characteristics of fuel-rich propellant based on Al−Mg via GAP-IPDI energetic thermoplastic polymer

In this work, the energetic thermoplastic polymers were synthesized with different ratios of energetic prepolymer glycidyl azide (GAP) and isophorone diisocyanate (IPDI), and used as the binder to prepare fuel-rich propellants based on Al−Mg. The results showed that energetic thermoplastic polymer enabled the fuel-rich propellant a faster flame spread, greater flame strength, and a stronger injection effect of metal droplets. The weight loss (Δm) of the propellants increased with GAP content, while the weight loss rate (D_max) increased similarly. The Δm increased from 7.92 % to 9.86 % and D_max from −0.23 % ⋅ °C⁻¹ to −0.35 % ⋅ °C⁻¹ in the range 100–256.5 °C. The propellant with the highest GAP content (85GAP-Prop) had the lowest apparent activation energy (150.77 kJ ⋅ mol⁻¹). The average pressure rate of 85GAP-Prop burning in a closed bomb reached 7.67 MPa ⋅ s⁻¹ and the maximum instantaneous pressure rate could reach 16.52 MPa ⋅ s⁻¹, significantly higher than the other propellants. The combustion products analysis indicated that the higher GAP content in the GAP-IPDI energetic thermoplastic polymer more significantly reduced the agglomeration of Al particles and improved the loosening of the combustion products. The rapid combustion gas generation characteristic and energy release of energetic thermoplastic polymer enhanced the combustion characteristics of the fuel-rich propellant based on Al−Mg, which promoted dispersion level between the metal droplets. This work provides insight into the combustion principles and performance improvements of fuel-rich propellant based on Al−Mg.