Effect of hydroborate iron additives (BH-Fe) on the properties of composite solid rocket propellants

Abstract

Several industrial - and research - types of hydroxy-terminated polybutadiene (HTPB) - based composite solid propellants with and without hydroborate iron additives (BH-Fe) were experimentally prepared. In general, they feature the same nominal composition, but different mass fraction of BH-Fe particles are investigated as burning catalysts and contrasted to a conventional formulation without BH-Fe particles, which are taken as reference. Strand burning rates and the associated combustion flame structures of propellants were analyzed. The mechanical sensitivity and microstructure surface of the formulations were compared to that of a referenced propellant already certified as steady. The results show that the BH-Fe powders are of irregular shapes, which tend to disperse or not stick together easily into cold clots. The BH-Fe powder are insensitive for friction and impact stimuli (0%, >125.0 cm) and all the propellant formulations containing different mass fraction of BH-Fe particles were sensitive to impact and friction (96 %, 10.0 cm), which is a bit sensitive to the referenced formulation without BH-Fe particles (92 %, 30.2 cm). The hydroborate iron additives (BH-Fe) can affect the combustion behavior and change the burning rate effectively. The burning rate can be increased more than 12.1 % for 3 % of BH-Fe particles replaced common Al powder in the formulations. The burning rate and pressure exponent values depend little on the formulation of the mass fraction of BH-Fe powder. A change of part mass fraction of BH-Fe particles may boost the burning rate a bit higher than that of the common Al powder, and the pressure exponent was increased little from 0.30 to 0.31 at the experimental pressure range.