Study on the synthesis and interfacial interaction performance of novel dodecylamine-based bonding agents used for composite solid propellants

An effective pathway was explored to design and select proper bonding agents that could effectively improve the interfacial interactions between bonding agents and solid particles, with three novel synthesized alkyl bonding agents, dodecylamine-N,N-di-2-hydroxypropyl-acetate (DIHPA), dodecylamine-N,N-di-2-hydroxypropyl-hydroxy-acetate (DIHPHA) and dodecylamine-N,N-di-2-hydroxypropyl-cyano-acetate (DIHPCA), as examples. Molecular dynamics simulation was applied to compare unit bond energies of these bonding agents with the [110] crystal face of ammonium perchlorate (AP) and the [120] crystal face of hexogen (RDX). The infrared test was used to characterize the interfacial interactions of these bonding agents with AP or RDX. XPS test was applied to calculate the adhesion percentage of the bonding agents on the surface of precoated AP or RDX particles. All of the above results indicated that these three bonding agents have strong interfacial interactions with AP or RDX in the order of DIHPCA > DIHPHA > DIHPA. The prepared three bonding agents were used in HTPB/AP/RDX/Al propellants, and their effects on tensile strength (σ), elongation under maximum tensile strength (ε_m), elongation at breaking point of the propellant (ε_b) and adhesion index (Φ) of the propellant were studied. The results show that the bonding agents improve the mechanical properties of the propellant in the order of DIHPCA>DIHPHA>DIHPA. The methods found from theoretical design, materials synthesis, and mechanistics studies up to practical application show effective guiding significance for choosing the proper bonding agent and improving the interfacial interactions between the solid particles and binder matrix.