Composite propellants based on hydroxyl terminated polybutadiene/ aluminium powder/ammonium perchlorate (HTPB/Al/AP) are commonly used in solid rocket motors (SRM) in defence and space applications. The solid propellant is a polymeric matrix with high solid loadings of metallic fuel and oxidiser along with some additives. Due to high solid loading, the propellant slurry becomes highly viscous and thus becomes difficult to process. In the case of trimodal distribution of the oxidiser, the effect of viscosity becomes more pronounced and it is difficult to mix and cast the propellant under vacuum owing to its high viscosity. In this paper, rheology of the propellant slurry containing oxidiser in trimodal distribution has been studied and an attempt has been made to find the effect of mixing parameters such as oxidiser addition sequence, mixing temperature and plasticiser concentration on the propellant properties and in improving the ease of processing. The study shows that the processability and pot life can be improved by optimising mixing parameters.

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