A Viscometric study of mixtures with Hydroxyl-terminated polybutadiene (HTPB) and short chain diols used in the formulations of solid composite propellants

Abstract

Hydroxyl-terminated polybutadiene (HTPB) is widely used in the formulations of solid propellants used in rocket motors. Furthermore, in general, chain extenders and short chain diols, such as 1,4-butanediol and 1,2-propanediol, can also be used in propellant formulations to improve mechanical properties, especially tensile strength. However, the incorporation of these diols can result in a considerable increase in the viscosity of the mixture during the processing of propellants. Thus, the present study evaluated the compatibility of these diols with the HTPB prepolymer, through a viscometric study, with the aim to determine the order of addition that results in greater homogeneity for the mixture. It was concluded that 1,4-butanediol, due to its larger chain size, has better compatibility with HTPB resin than 1,2-propanediol. On top of that, it was found that when the resin is added first, it results in mixtures with greater compatibility.

Key words
Chain extenders; propellant; solid propulsion; viscometry