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.
Highlights
Solid composite propellants are considered as a material with solid particles, an oxidizer, such as ammonium perchlorate (AP), and a metallic fuel, normally aluminum powder, and with additives, such as plasticizer, antioxidant, and bonding agent, incorporated in an elastomeric matrix that acts as a binder providing a rubber-like elasticity to the grains (Shusser 2012)
When adding hydroxyl-terminated polybutadiene (HTPB) resin first, the viscosity was increased, in relation to the pure resin, for concentrations above 55 % in mass basis. This phenomenon suggests that 1,4-butanediol is considered a good solvent for HTPB resin (Lucas et al 2001), when it is used in this order of addition and from this concentration, because there was an increase in viscosity in the final mixture in comparison to the pure resin
The analysis proposed in this work proves to be useful to evaluate the interaction between the studied diols and HTPB resin, to predict their rheological behavior and to determine their potential to be used in formulations of solid composite propellants
Summary
Solid composite propellants are considered as a material with solid particles, an oxidizer, such as ammonium perchlorate (AP), and a metallic fuel, normally aluminum powder, and with additives, such as plasticizer, antioxidant, and bonding agent, incorporated in an elastomeric matrix that acts as a binder providing a rubber-like elasticity to the grains (Shusser 2012). Polyurethane binder systems, formed by a hydroxyl-functional prepolymers, such as hydroxyl-terminated polybutadiene (HTPB) and diisocyanate curing agent are extensively used in composite solid propellants, due to convenient reaction conditions (Amtower 2006). They are used in the formulations of composite propellants and explosive materials as PBX type – Plastic explosive, acting as an agglomerant and providing a suitable mechanical behavior for the grain, especially tensile strength. The tensile mechanical characteristics of HTPB-based binder have been modified by increasing the hard segment content in the matrix, when short chain diol is used. It is possible to increase the tensile strength of the polymeric matrix based on cured polyurethanes, obtained through the reaction
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call