【正文】 附錄ATwin Screw Extrusion Processing of Energetic MaterialsABSTRACT The continuous processing of various energetic formulations is a challenge thatrequires the apriority characterization of the rheological behavior of the energetic formulation, mathematical modeling of the process, a good understanding ofthe structure development aspects and ways of verifying and characterization ofmicrostructural distributions of energetic grains. These steps facilitate the generation of a detailed understanding of the flow and deformation behavior and thethermomechanical history that the energetic material will experience in thecontinuous processor. Such work, done prior to the actual continuous processingof the live materials, eliminates or minimizes the subsequent risk associatedwith the precarious trial and error procedures and experimental studies that areprevalent in other industries~ However, the determination of the physical, rheological and processability characteristics of energetic formulations under variousrelevant sets of operating conditions of the extrusion process, the development,the fabrication and the installation of instrumentation for the characterization ofspecific material properties, the data analysis and the determination of materialparameters, and the mathematical modeling of the thermomechanical history ofthe energetic formulations in the extruder and the die are not straightforward.The challenges include the slip at the wall of the viscoplastic suspensions, possible segregation of the binder and the migration of the particles in the transverseto flow direction, the important role played by air, the formation of flow instabilities and associated surface and bulk distortions of extrudates, the formationof hot spots, the important role played by the distributive and dispersive mixingof the ingredients as affected by the deformation history and the specific energyinput in the extruder. The quantitative characterizations of the degree of mixedness of live propellants and explosives and the particle size and the defect density distributions of the crystalline particles of the energetic materials are alsonecessary to link the processing history in the extruder to the mechanical andburn rate properties of the processed energetic grains. In this paper some ofthese challenges are reviewed to contribute towards the improved safety of thetwin screw extrusion process and better control of the quality of the energeticgrams. Key words: Extrusion, energetics, twin screw, continuous processingI. INTRODUCTION: Various Government organizations and defense contractors are engaged in thedevelopment of advanced energetic positions for use in a wide variety ofapplications. Many of these formulations are intended to be processed viacontinuous processing techniques, most monly the fully intermeshing corotating twin screw extrusion process. Continuous processing allows better control of the microstructure and hence the consistency of the energetic product inparison to batch processes. The principal factor is the significantly greatersurface to volume ratio of the continuous processor in parison to the batchprocessor. However, the energetic materials involve very sensitive ingredients,the processability of which in a suspension is always precarious and requirestrict exposure limits in temperature, residence time and stress. Furthermore, thescale up of the processing operation is also not straight forward due to therheological behavior of the positions and the processability and the physicalproperties of the energetic formulations being principally affected by the veryhigh degree of solid fill of the formulations, which by design needs to approachthe maximum packing fraction of the solid phase. The mathematical modelingtechniques for continuous processing need to take into consideration theirextremely high degree of fill which imparts various solid like characteristics tothe energetic formulations including the development of viscoplasticity and wallslip over and above various phenomena specific to highly filled formulations,including the interlocking of the particles, migration, of the binder in thedirection of the pressure gradient, and the extensive roles played by theentrained air etc. In the following a summary of what we have learned is reviewed and typicalresults are presented.II. RHEOLOGICAL BEHAVIORThe rheological behavior and processability of dilute to concentrated suspendsions have been the subject of numerous investigations. Information on thedependence of the shear viscosity material function on the filler content, particlesize, particle size distribution, particle shape and orientation in the flow field aresummarized in various reviews (17). Until the 198039。s investigations of the flowand deformation behavior of concentrated suspensions have been restricted tosolid concentrations, which are below sixty four percent by volume. The majority of these studies have utilized the C