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2019
Conference Paper
Titel
Coating of ammonium salt particles by fluidized bed processes
Abstract
The application of ammonium salts as ammonium dinitramide (ADN) and phase stabilized ammonium nitrate (PSAN) in solid propellants is challenging. Ammonium based particles can show poor interactions with surrounding composite matrices, often exhibit unsuitable mechanical properties, low chemical stability or require adjustment of their energetic properties like for example burning behavior or impact and friction sensitivity. Fluidized bed coating is a process technology facilitating the modification of such materials by the particle encapsulation with thin homogenous coating layers. The fluidized bed process can thereby be operated to achieve a gentle coating avoiding fragmentation of brittle materials and to minimize particle agglomeration or aggregation during the modification. Improvement of particle properties can be realized by their encapsulation with polymeric systems which alter particle interactions, mechanical stability and decelerate the solubility behavior in respective fluids. Embodied in this work is the investigation of the modification of ammonium dinitramide and phase stabilized ammonium nitrate by their encapsulation in two-component polymeric systems with a fluidized bed process. The work focused on the process development and optimization in order to achieve thin homogenous coating layers avoiding particle agglomeration and fragmentation. Thereby, a significant improvement of the fracture strength could be shown. Particularly, the influence of the particle modification on the fracture behavior could be characterized with a specific fracture strength analysis system and compared with the mechanical properties of the initial materials.