Decomposition and combustion of HTPB-based composite propellants containing intercalated HMX crystals with desired high energy but low burn rate

Two types of qy-HMX (insensitive HMX with improved energy density, numbered 1 and 2) have been used and studied as an ingredient of HTPB-based composite propellants (CPs), and the decomposition and combustion performances have been investigated. It has been shown that the main exothermic peak temperature of blank CPs containing 21 wt% of qy-HMX-1 is 258.9 °C, which is 4.7 °C higher than that of HMX-containing one, indicating improved thermostability. The corresponding heat of explosion for blank qy-HMX-2-based CPs was measured to be 5830 J∙g⁻¹, which is 300 J∙g⁻¹ higher than that of HMX-based one. Interestingly, the qy-HMX-2-based CPs has higher energy density than corresponding CL-20-based ones, but it has much lower burn rate under the same pressure, e.g. 4.38 mm∙s⁻¹ at 3 MPa for the former vs. 9.03 mm∙s⁻¹ for the latter. Under the effect of typical conventional catalysts such as nano-CuO and nano-Fe₂O₃, the qy-HMX-1-based CPs showed increased heat of explosion and higher burn rate. In addition, the particle sizes of condensed combustion products (CCPs) of CPs containing qy-HMX-2 are much smaller than that of HMX-based one, where the Al₄C₃ was produced as its unique CCPs ingredient.