An empirical model for the viscosity buildup of hydroxy terminated polybutadiene based solid propellant slurry

Abstract The Polar Satellite Launch Vehicle (PSLV) makes use of hydroxy terminated polybutadiene (HTPB) based solid propellant in the booster stages, strap‐ons, and the third stage. An empirical model that describes the change in viscosity of various formulations of propellant slurry with time and temperature has been developed as an extension of the Andrade equation. The model incorporates constants that account for the viscosity of the slurry caused by the combined effect of the continuous binder phase, dispersed particulate solids, and progress of crosslinking between reactive species of the binder and curators. The correspondence between predicted viscosity buildup and measured values obtained during casting of motors is verified and found satisfactory. A method of tailoring some constants, so as to make them batch‐specific, is explained. Several practical applications are described. The model serves as a predictive tool for evaluating the potlife and rheological behavior of the slurry during production of large solid motors. The experimental method and approach used for data analysis can be used for other slurries that are similar in composition to propellant slurry.