Synthesis of two novel neutral polymeric bonding agents to enhance the mechanical properties of composite solid propellants

Currently, only a few bonding agents can be utilized efficiently in nitramine filler material-based solid rocket energetic binder systems. Herein, we demonstrate the synthesis and specific characterization of two kinds of neutral polymeric bonding agents (NPBA-1 and NPBA-2) and their application in composite propellants consisting of the nitramine octogen (HMX) and glycidyl azide polymer (GAP). The as-obtained NPBAs were well-coated on the surface of HMX and RDX due to their functionalized groups, and they significantly affected the viscosity of the uncured propellant mixtures and possessed obviously enhanced mechanical properties in the cured AP/HMX/GAP propellant mixtures, even at low concentrations (down to 0.001 wt% of the whole propellant). In addition, because of the existence of an epoxy group and no hydroxyl functionalities, NPBA-2 exhibited improved mechanical strength and glass transition temperature as compared to NPBA-1, which has plenty of reactive hydroxyl groups. The as-synthesized epoxy-modified NPBAs are essential for obtaining NEPE propellants with high bonding and mechanical properties.