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

Solid composites comprising boron (B) and hydroxyl-terminated\npolybutadiene\n(HTPB) are attractive potential fuels for air-breathing propulsion\nsystems. However, a notable challenge for B/HTPB composites is the\nsluggish oxidation kinetics of B that hinders the combustion efficiency.\nAddition of fluoropolymers in the composites has been found to improve\nthe combustion efficiency but reduce the mechanical performance. Herein,\nwe covalently grafted fluoroalkyl side chains onto HTPB (F-HTPB) to\nintroduce fluorocarbon to B/HTPB composites without macroscopic phase\nseparation and compared with composites using hydrocarbon grafted\nHTPB, pristine HTPB, and blended fluorocarbon. We found that B/HTPB\ncomposites using F-HTPB exhibited the best combined mechanical performance\nand flame propagation rate compared with the other formulations. These\nfindings demonstrate that functionalizing HTPB with fluorocarbon side\nchains is a promising strategy to improve the mechanical and combustion\nproperties of solid composite fuels.