Perfluoroalkyl-Functionalized HTPB Improves the Mechanical and Combustion Performance of Boron/HTPB Composites as Solid Fuel

Solid composites comprising boron (B) and hydroxyl-terminated polybutadiene (HTPB) are attractive potential fuels for air-breathing propulsion systems. However, a notable challenge for B/HTPB composites is the sluggish oxidation kinetics of B that hinders the combustion efficiency. Addition of fluoropolymers in the composites has been found to improve the combustion efficiency but reduce the mechanical performance. Herein, we covalently grafted fluoroalkyl side chains onto HTPB (F-HTPB) to introduce fluorocarbon to B/HTPB composites without macroscopic phase separation and compared with composites using hydrocarbon grafted HTPB, pristine HTPB, and blended fluorocarbon. We found that B/HTPB composites using F-HTPB exhibited the best combined mechanical performance and flame propagation rate compared with the other formulations. These findings demonstrate that functionalizing HTPB with fluorocarbon side chains is a promising strategy to improve the mechanical and combustion properties of solid composite fuels.