Interaction Mechanism of Composite Propellant Components under Heating Conditions

Abstract

To examine the interactions between two binder systems—hydroxyl-terminated polybutadiene (HTPB) and hydroxyl-terminated block copolyether prepolymer (HTPE)—as well as between these binders and ammonium perchlorate (AP) at various temperatures for their susceptibility to varying degrees of thermal damage treatment, the thermal characteristics and combustion interactions of the HTPB and HTPE binder systems, HTPB/AP and HTPE/AP mixtures, and HTPB/AP/Al and HTPE/AP/Al propellants were studied. The results showed that the first and second weight loss decomposition peak temperatures of the HTPB binder were, respectively, 85.34 and 55.74 °C higher than the HTPE binder. The HTPE binder decomposed more easily than the HTPB binder. The microstructure showed that the HTPB binder became brittle and cracked when heated, while the HTPE binder liquefied when heated. The combustion characteristic index, S, and the difference between calculated and experimental mass damage, ΔW, indicated that the components interacted. The original S index of the HTPB/AP mixture was 3.34 × 10−8; S first decreased and then increased to 4.24 × 10−8 with the sampling temperature. Its combustion was initially mild, then intensified. The original S index of the HTPE/AP mixture was 3.78 × 10−8; S increased and then decreased to 2.78 × 10−8 with the increasing sampling temperature. Its combustion was initially rapid, then slowed. Under high-temperature conditions, the HTPB/AP/Al propellants combusted more intensely than the HTPE/AP/Al propellants, and its components interacted more strongly. A heated HTPE/AP mixture acted as a barrier, reducing the responsiveness of solid propellants.

Keywords

• composite propellant
• thermal damage treatment
• thermal weight loss
• interaction
• combustion characteristics