The advantageous mechanism of membrane emulsification method in THV-GAP synergistic modification of nano-sized boron to promote its ignition and combustion

Abstract

Boron (B) powder has received significant attention in propellant applications because of its high gravimetric and volumetric calorific values, but the oxide layer on the surface hinders its complete combustion. To solve this issue, tetrafluoroethylene hexafluoropropylene vinylidene@glycidyl azide polymer@B (THV@GAP@B) composites were obtained using the solvent evaporation (SE) and membrane emulsification (ME) methods. The THV@GAP@B sample prepared by the ME method possesses more uniform surface coverage and more uniform distribution of THV and GAP, whereas the THV@GAP@B sample prepared by the SE method exhibits local nonuniform coverage and more exposed particle surfaces. ME also reduces the characteristic particle size by suppressing excessive secondary agglomeration. Thermal analysis and combustion experiments demonstrate that the THV@GAP@B sample prepared by the ME method facilitates the reaction between the decomposition products of the modification layer and B particles due to the more sufficient interfacial contact, thereby promoting oxide-layer removal and rapid low-temperature oxidation of B. Compared with raw nano-sized boron (n-B), the THV@GAP@B samples prepared by both modification methods shorten the ignition delay time, and the THV@GAP@B sample prepared by the ME method exhibits the strongest flame radiation intensity and the most vigorous and complete combustion. Combustion product analysis further confirms that the THV@GAP@B sample prepared by the ME method shows the lowest diffraction intensity of residual B and more pronounced oxidation products (B 2 O 3 and H 3 BO 3 ), indicating the highest burnout degree. This study provides guidance for selecting preparation methods for the synergistic modification of B powder using fluoropolymers and energetic binders, as well as for their application to B-containing propellants.