|M.Sc Student||Zelner Yefa Moshe Michael|
|Subject||Energetic Thioethers and Disulfides: Simple Preparation|
|Department||Department of Chemistry||Supervisor||Professor Yoav Eichen|
|Full Thesis text - in Hebrew|
Many applications of energetic materials, such as explosive and propellant devices, require the material to be processed in its liquid-state for packaging and molding into the needed shape. This requires that the melting point of the material would be far from its initiation point for the process to be safe. Classic energetic materials such as TNT can be casted and processed in the liquid-state. Furthermore, modern applications currently under development enable the printing of these energetic materials from the liquid-state, so that the process will go in one step from the material to the device; one example of such a technique is the Fused Deposition Modeling, FDM. However, modern energetic materials, such as RDX and other nitrogen-rich materials, undergo initiation prior to or close to the melting point, and are therefore unsuitable for processing in a liquid state.
Fused deposition modeling, FDM, is a manufacturing technology, which utilizes 3D printing for modeling, prototyping, and production applications. Typically, a pump pushes the material into the heated nozzle at a controlled rate. The material liquefies and is then deposited by an extrusion head. FDM relies on an ‘additive’ principle by laying down material in layers.
The research focused on the development of a simple, safe and inexpensive method for the preparation of new and known energetic materials, based on the veteran TNT skeleton, that can be processed safely in the liquid state. The physical and chemical properties of the synthesized materials were characterized. Finally, layers were successfully printed using the materials developed to reach proof of concept.
Reaction between thiourea and halo-nitro-aromatic materials was studied. Inexpensive starting materials react in one phase and under mild conditions to produce high-energy nitro-aromatic sulfides and disulfides, which can be purified without the need for expensive chromatography. We investigated the family of nitro-aromatic sulfides and disulfides that was produced by the explored reaction. The energetic density was characterized for most of the synthesized materials and showed good energetic properties. All of the materials were shown to form high density crystal structures and some of them exhibit polymorphism. Some of the materials were tested for friction and shock sensitivity and were shown to be more inert than other ‘triggered’ explosives such as TNT. Most of the materials have a wide temperature window between the melting point and the initiation point, which makes the material safe to process in liquid state. Furthermore, they have high melting temperatures, which makes them undergo a phase transition in room temperature to solid phase.
In summary, these safety and process features make the materials suitable for their application in areas requiring casting and injection, and therefore suitable for processing by FDM. In light of the results we made prototype prints for some of the materials developed using an FDM-like method . We therefore achieved proof of concept by printing layers using the materials we had produced and characterized, as we had planned.