Effect of Process Parameters on Pot Life of Solid Propellant Composite Based on Hydroxyl-Terminated Polybutadiene: A Short Review

Effect of process parameters on pot life of composite solid propellant based on hydroxyl- terminated polybutadiene (HTPB) is an important issue in the production of medium and large scale grains. In this article, the prolonging of pot life of composite solid propellant based on HTPB was studied through process control of parameters such as: mixing temperature, casting temperature, NCO/OH ratio (r), mixing speed and time, presence of micro or nano-sized aluminum and ammonium perchlorate (AP) and feeding sequence of solid loading. In literature, it is reported that increases in casting temperature result in curing progress and subsequently increases the slurry viscosity. Therefore, it is preferred to increase the pot life by reducing the casting temperature in adjusting the curing process. The curing rate is increased by increasing the NCO/OH ratio, which can be attributed to the growth of molecular weight, branching and more crosslinking of the polymer chain. It is reported that viscosity build up is transformed from linear plot to exponential, when (μAPf:μAPc) ratio is exceeded than 1:4. Moreover, by acquiring a 1:2 ratio of (μAPf:μAPc), viscosity is increased which makes casting difficult. By studying the increases in feeding rate it is shown that the pot life is mainly determined by feeding rate of (Al+2APc+2APf) for (μAPf:μAPc) ratio of 1:2 and 1:3 and to feeding rate of (APc+APf+APc+APf+2Al) for (μAPf:μAPc) ratio of 1:4.