(kJ mol-1) 33.1 29.6 33.1

The pseudoplasticity indexes calculated from the Power Law equation are plotted as a

It is observed that the PI is higher at higher temperature. This indicates that at higher temperature the PU-IIp becomes more non-Newtonian. Interestingly, the PI decreases at 40°C and 60 °C with cure time, whereas at 50 °C, it is almost consistent within the pot life of 3 hours, usually required for casting of the propellant slurry into the rocket case. However, the viscosity index decreased initially with temperature, and afterwards, it increased with the cure time. This is attributed to the increase in cross linking, caused by PU reaction. The flow behaviour of HTPB propellant slurry assumes to have great importance as this is the cause of many grain defects in large scale motor. To make a logical decision regarding propellant mixing and casting, not only the effect of temperature and time on viscosity of
