N141-017 TITLE: Environmentally Friendly Alternative Synthesis and Process to Manufacture Cost-Effective Hexanitrohexaazaisowurtzitane (CL-20)

TECHNOLOGY AREAS: Air Platform, Materials/Processes, Weapons

ACQUISITION PROGRAM: PMA 259

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OBJECTIVE: Develop and demonstrate a viable alternate synthesis route for Hexanitrohexaazaisowurtzitane (CL-20) with efforts directed to lowering production costs for CL-20 bulk use.

DESCRIPTION: CL-20 is the most energy-dense explosive material. CL-20 surpasses current state of the art nitramines, cyclotetramethylene-tetranitramine (HMX) and cyclotrimethylene-trinitramine (RDX) in performance by up to 20 percent as an explosive and has a better oxidizer to fuel ratio as a propellant ingredient. In the correct configuration, particle size, and morphology, CL-20 shows similar or even improved impact, shock, and thermal responses than RDX and HMX, but with significant performance improvement. There is a significant increase in interest for CL-20 in a wide variety of applications. However, CL-20�s potential as a large-scale replacement for the widely used RDX and HMX is limited due to its cost-prohibitive nature. The United States� (US) primary domestic source of CL-20 has been using the benzylamine synthesis route to prepare the tetra-acetyldiamino isowurtzitane (TADA) precursor. This source was given exclusive right to the CL-20 work approximately 14 years prior with the belief that they would be able to increase production and reduce cost, allowing this material to be utilized as a tool for our warfighter capability. In all actuality, the reverse has occurred with reduced production and increased cost. The source originally purchased this precursor from a non-US source at a fairly hefty price, which resulted in initial CL-20 costs of $550/lb. The non-US source stopped supplying the material. As it stands, no firm manufacturing replacement has been identified domestically. This continues to hamper the ability of CL-20 to be produced at a reasonable cost and production rate, thus resulting in ever increasing costs which stand currently at $950/lb. CL-20�s production process suffers from several economic and environmental disadvantages resulting in a low number of US-based suppliers. As such, discovery of novel applications for this material and the continued development of promising applications have been limited. The synthesis route needs to redefine or tailor alternate synthesis routes, using pharmaceutical methods and/or other approaches, in order to improve and advance these efforts towards a final environmentally friendly and cost effective solution.

Novel synthetic routes to CL-20 that will significantly reduce the cost associated with this material are of great interest. Specifically seeking novel synthetic routes to CL-20 that avoid starting reagent benzylamine, (thus eliminate chlorine waste streams), and costly transition metal catalysts (palladium and platinum). The approach to designing a lower-cost process begins with the use of inexpensive commodity chemicals and no more than four synthetic steps during processing. Proposals which incorporate widely used and inexpensive commodity chemicals as starting materials while featuring fewer synthetic steps will be given priority. Strong considerations will also be given to the alternate chemistry proposing environmentally-friendly. A successful development should reduce the cost of CL-20 to around $150/lb or lower, and upon transition to industrial scale would provide even greater cost savings making CL-20 competitive with RDX and HMX, the current explosive and propellant nitramines. Once, cost becomes competitive with RDX or HMX, a variety of programs would benefit enormously in performance and sensitivity as an alternate to the other nitramines.

In the development of alternate synthesis routes, characterization of chemical structure, thermal, and physical properties using widely accepted chemistry and scientific methods and techniques is required to validate precursor and intermediates developed and utilized in the alternate synthesis pathway to CL-20 end product. Final characterization and verification of the CL-20 end product is required to validate the feasibility of the alternate synthesis route.

PHASE I: Design and determine feasibility of a concept for an alternate synthesis route of CL-20. Prepare a minimum of 5-grams of a novel direct precursor to CL-20 at laboratory scale. Characterize the key thermal and physical properties of all intermediates and potential hazard sensitivity.

PHASE II: Using results from Phase I, develop and optimize laboratory process for production of minimum 100-gram scale of new precursor to CL-20. Demonstrate the production of CL-20 from this precursor at multi-gram scale, Verify the structure, thermal stability and potential hazard sensitivity. Validate that the laboratory synthesis exhibits a lower cost than the current state-of-the-art process.

PHASE III: Complete and transition a scale-up process design and data package that has demonstrated production and reproducibility for lower-cost commercial production of CL-20 with direct scale-up to be demonstrated in conjunction with Naval Air Warfare Center Weapons Division (NAWCWD).

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: As a low-cost alternative oxidizer, CL-20 could be utilized as a high energy material in solid rocket boosters for satellites or space travel. CL-20 could be used for specialize gun propellant and also as a method for demolition as a 'cutter' in detonation cords.

REFERENCES:
1. Chapman. R. D., & Hollins, R. A. (2008). Benzylamine-Free, Heavy-Metal-Free Synthesis of CL-20 via Hexa(1-propenyl)hexaazaisowurtzitane. Journal of Energetic Materials, 26(4), 246-273. doi:10.1080/07370650802182385

2. Mandal, A. K., Pant, C. S., Kasar, S. M., & Soman, T. (2009). Process Optimization for Synthesis of CL-20. Journal of Energetic Materials, 27, 231-246. doi:10.1080/07370650902732956

3. Mason, M. H., Hall, K., & Mason, S. L. "Shock Insensitive Plastic Bonded Explosive," 56th JANNAF Propulsion Meeting/39th Structures and Mechanical Behavior/35th Propellant and Explosives Development and Characterization/26th Rocket Nozzle Technology/24th Safety and Environmental Protection/17th Nondestructive Evaluation Joint Subcommittee Meeting, Las Vegas, Nevada, April 2009.

4. Clubb, J., Chan, M., Turner, A., and Meyers, G. "Development of High Energy � High Density Propellant for Phase III IHPRPT Applications," 34th Propellant & Explosives Development and Characterization Subcommittee/23rd Safety & Environmental Protection Subcommittee Joint Meeting, Reno, Nevada, August 2007.

5. Herve, G., Jacob, G., & Gallo, R. (2006). Preparation and Structure of Novel Hexaazaisowurtzitane Cages. Chemistry - A European Journal, 12(12), 3339. doi:10.1002/chem.200501032

6. Gore, G. M. 2006. Synthesis and Scale-up of Hexanitro-Hexaazaisowurtzitane (CL-20). Pune, India: Energetic Materials Division, High Energy Materials Research Laboratory.

7. Xiong, Y., Chen, S., Jin, S., & Shi, Y. (2006). Hydrolysis and Nitration Reaction of Tetraacetylhexaazaisowurzitane. Chinese Journal of Energetic Materials, 3, 168-170. http://caod.oriprobe.com/articles/10612028/Hydrolysis_and_Nitration_Reaction_of_Tetraacetylhexaazaisowurzitane.htm

8. Sysolyatin, S. V., Lobanova, A. A., Chernikova, Y. T., & Sakovich, G. V. (2006). Methods of Synthesis and Properties of Hexanitrohexaazaisowurtzitane. ChemInform, 37(9). doi:10.1002/chin.200609257.

9. Nair, U. R., Sivabalan, R., Gore, G. M., Geetha, M., Asthana, S. N., & Singh, H. (2005). Hexanitrohexaazaisowurtzitane (CL-20) and CL-20-Based Formulations (Review). Combustion, Explosion, and Shock Waves, 41(2), 121-132. doi:10.1007/s10573-005-0014-2

10. Balas, W., Nicolich, S., Capellos, C., Hatch, R., Akester, J., & Lee, K. E. (2003). CL-20 PAX Explosives Formulation, Development, Characterization, and Testing (NDIA 2003 IM/EM Technology Symposium). Orlando, FL. http://www.dtic.mil/ndia/2003insensitive/nicolich.pdf

KEYWORDS: RDX, HMX, Synthesis, CL-20, explosive, Scale-up

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