An Overview of the Rheological Behavior and Characterization of Energetic Formulations: Ramifications on Safety and Product Quality

The characterization of the flow and deformation behavior (rheology) of energetic materials is a significant challenge. This challenge stems first from the ubiquitous viscoplasticity and the concomitant wall slip of concentrated suspensions of energetic formulations, which involve either a gel phase (for example, solvated nitrocellulose) or high degrees of solid fill (most energetic formulations attempt to approach the maximum packing fraction of the solid phase). The rheological behavior of such suspensions is very sensitive to the microstructure of the suspension during processing, as well as myriad of factors including the migration of the binder and the particles, mixing history, and entrainment of air into the suspension. Although difficult, one needs to generate a detailed understanding of the flow and deformation behavior of various energetic formulations to eliminate or minimize the hazards associated with their processing using both batch and continuous technologies and in assuring an acceptable product quality. In the following, an overview of the various factors, which are important in the rheological characterization of energetic formulations, is provided along with their ramifications on the safety of the processing of the energetic formulation and various determinants of quality.