Rheological Modification of a Composite Solid Propellant via Maleic Anhydride Addition

Viscosity is one of the important parameters in design and production of composite solid propellants. Propellants with low end of mix (EoM) viscosity and longer pot-life have suitable condition for casting process. Several factors control the rheology behavior of propellants. In some cases, it may be necessary to apply some additives in order to optimize the rheology of the formulation. In this research, the effect of adding 0.013 to 0.029% by weight of maleic anhydride (MA), as a pot-life extender, was investigated on rheological properties of a HTPB/DDI based composite solid propellant containing 88% solid loading. Results showed that the formulation containing 0.025% by weight of MA compared to other samples showed lower EoM viscosity. EoM viscosity enhanced by either increase or decrease in MA concentration related to this formulation. The viscosity of samples decreased due to shear stress and rotational motion of the viscometer spindle until a specific time and then will increase by progress in cure reaction in binder system. Furthermore, viscosity reached to ascendant step in relatively longer time by adding MA concentration. Furthermore, having increased amount of MA, the viscosity increases over a relatively longer period of time.