Continuous processing and shaping using a fully intermeshing co-rotating twin screw extruder

Different types of continuous processors can be used for the processing of energetic materials, that is, continuous shear roll mills, single screw extruders, single screw kneaders, and twin screw extruders. The application of continuous manufacturing of energetics has been explored extensively since the late 1950s for a broad range of energetic products, including solventless and solvated propellants, cast cure and pressed explosives, and pyrotechnics. There are advantages and disadvantages associated with each processing platform. The continuous shear roll mills [1,2] are generally used for wet systems and have limited control on the temperature distribution of the energetic formulation. The single screw extrusion systems have only limited distributive mixing capabilities and no dispersive mixing ability (see Chapter 9). Continuous kneaders are based on a single screw that not only rotates but also oscillates within a barrel with kneading teeth [3]. Such kneaders have kneading teeth installed at the barrel and screw surfaces to enable the application of relatively high shearing stresses to the energetic formulation within the gaps formed by the kneading teeth at the barrel and screw surfaces. Thus, single screw kneaders are effective processors for dispersive mixing operations. However, they are handicapped by the presence of a single screw (no self-cleaning mechanism), and they lack geometric flexibility.