EFFECT OF TEMPERATURE ON THE RHEOLOGICAL BEHAVIOR OF HYDROXYL TERMINATED POLYBUTADIENE PROPELLANT SLURRY

Hydroxyl terminated polybutadine (HTPB) based composite solid propellants have gained prominence in advanced missiles and launch vehicles including the Space Shuttle's Inertial Upper Stage (IUS) motor (1). To achieve a blow-hole free well performing casting, the knowledge of the processability characteristics and rheological behavior of the propellant slurry are of vital interest. In our earlier communication (2) we had discussed the effect of compositional aspects, namely solid loading, oxidizer particle size distribution, and aluminum content on the rheology of HTBP propellant. For an optimized solid loading with corresponding oxidizer particle size distribution and aluminium content, the effect of temperature on the processability and the pot life are studied and reported in this paper. This study establishes the fact that the HTPB slurry shows a complex rheological behavior having thixotropy and yield stress. The thixotropic index and yield stress show minimum values at an optimum temperature. This optimum temperature shifts to lower values as time elapses. Activation energies have been calculated for the cure reaction based on yield stress and viscosity. It is observed that the activation energy values reach asymptotic levels after about three hours of curative addition.