Mechanical and combustion properties of fluoroalkylsilane surface-functionalized boron/HTPB composite

Abstract

Boron (B) and hydroxyl‑terminated polybutadiene (HTPB) composites have been studied as potential solid fuels for air-breathing propulsion systems. One of the challenges facing the B/HTPB composites is the weak interfacial interaction between B and HTPB, which leads to the agglomeration of B particles within the HTPB matrix and deteriorates the mechanical properties and combustion efficiency. The slow oxidation kinetics of B also limit B/HTPB combustion. Herein, we explored functionalizing the B surface with fluoroalkylsilane (F-B) to improve the interaction between B and HTPB while simultaneously providing fluorine as a more potent oxidizer than air. We found that F-B particles, compared to pristine B particles, have a more uniform particle distribution, aggregate into smaller sizes, interact with HTPB more strongly, and consequently relieve stress softening. The F-B/HTPB composite also burns faster in oxygen with less ejection of B particles due to the supply of fluorine nearby B particles. These findings highlight the effectiveness of using interfacial chemistry to modify the mechanical and combustion properties of solid composite fuels, which can apply to other energetic solid composites.