TECHNOLOGY AREA(S): Materials/Processes, Weapons

ACQUISITION PROGRAM: PEO IWS 11, Rolling Airframe Missile

The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), 22 CFR Parts 120-130, which controls the export and import of defense-related material and services, including export of sensitive technical data, or the Export Administration Regulation (EAR), 15 CFR Parts 730-774, which controls dual use items. Offerors must disclose any proposed use of foreign nationals (FNs), their country(ies) of origin, the type of visa or work permit possessed, and the statement of work (SOW) tasks intended for accomplishment by the FN(s) in accordance with section 3.5 of the Announcement. Offerors are advised foreign nationals proposed to perform on this topic may be restricted due to the technical data under US Export Control Laws.

OBJECTIVE: Develop elastomeric polymer binder systems with controllable chain-extension and cure chemistries that are suitable for formulating advanced energetic oxidizer, fuel, and explosives ingredients using conventional and emerging manufacturing techniques such as microfluidics engineering and additive manufacturing (AM).� A capability for small batch production is desired for transition to follow-on energetic formulations development.

DESCRIPTION: In cast cure energetic formulations, the polymer binder system is the key enabling technology for establishing critical properties including mechanical response, thermal degradation, insensitive munitions (IM) compliance, particle adhesion, and chemical stability relating to aging/safe life. Currently, the rocket motor and warhead design and manufacturing communities have access to a severely limited set of polymer binder systems. The most prominent�hydroxyl-terminated polybutadiene (HTPB)�is not chemically compatible with potentially high-performing oxidizers such as ammonium dinitramide (ADN), often requires the use of specialized �bonding-agent� chemical additives for proper particle-binder adhesion, and utilizes decades-old, toxic, isocyanate-based cure chemistry that provides inadequate cure control for emerging AM techniques. Historic development and availably of HTPB-based formulations coupled with resistance to invest in and qualify new energetic formulations led to its wide-spread use; however, the emergence of new polymer/soft chemistry technology, new energetic ingredients, current IM requirements, and new manufacturing techniques warrant development of new, �off-the-shelf� binder systems for advanced energetic formulations. The focus of this SBIR topic is to design and produce polymer binder systems where polymer backbone and cure chemistries allow for tailored/on-demand curing and enhanced composite formulation energy density (energetic chemical moieties and/or increased solids fill), while maintaining critical energetic formulation properties (i.e., multi-ingredient compatibility and adhesion, favorable IM response, low toxicity, high elongation, long-term stability, low modulus, and low glass transition temperature). HTPB will serve as a baseline binder system for comparison. The emphasis of the effort will be polymer backbone and cure chemistry development, leading to resultant binder system evaluation in terms of cure and crosslink control, multi-ingredient/oxidizer compatibility, thermal stability, mechanical properties, processability via AM and conventional mixing/casting methods, and composite formulation energy density. These new binder cure motifs (i.e., chemically-, thermally-, light-activated), and polymer backbone chemistries (e.g., co-block, energetic functional groups) will be combined to enhance critical formulation properties, and scaled appropriately for functional formulation development, testing, and transition to the energetic material manufacturing communities. Such binder systems will provide a much needed, broader commercial ingredient base to enable emerging advanced energetic materials technology. Results of this effort are expected to facilitate improved tactical rocket motor and warhead formulations with maximum energy content and enhanced IM response, amenable to emerging AM methods. This work would also help alleviate single-source and poor binder-performance related issues currently being experienced by the rocket motor community with regard to HTPB.

Work produced in Phase II may become classified. Note: The prospective contractor(s) must be U.S. owned and operated with no foreign influence as defined by DoD 5220.22-M, National Industrial Security Program Operating Manual, unless acceptable mitigating procedures can and have been implemented and approved by the Defense Security Service (DSS). The selected contractor and/or subcontractor must be able to acquire and maintain a secret level facility and Personnel Security Clearances, in order to perform on advanced phases of this project as set forth by DSS and the Office of Naval Research (ONR) in order to gain access to classified information pertaining to the national defense of the United States and its allies; this will be an inherent requirement. The selected company will be required to safeguard classified material IAW DoD 5220.22-M during the advanced phases of this contract.

PHASE I: Demonstrate the capability to design and synthesize new, novel elastomer polymer binder systems with properties as described above. At least five polymer systems should be developed at a reasonable scale (10 � 100 grams) for associated thermal and mechanical properties evaluation by methods including Differential Scanning Calorimetry (DSC) and Instron stress-strain experimentation. Chemical stability, in addition to multi-ingredient compatibility will be assessed by methods such as Vacuum Thermal Stability (VTS) as outlined in MIL-STD-286C or equivalent [Ref 3]. This should include nitramine explosives, metal fuels, and strong oxidizers such as ammonium dinitramide and ammonium perchlorate.

PHASE II: Down-select from successfully demonstrated polymer systems from Phase I and provide in a reasonable scale (hundreds of grams) for extensive binder gum-stock and formulation studies to include particle/binder adhesion, formulation mechanical properties, formulation aging characterization, and formulation performance testing (e.g., burn rate, energy release, etc.), in addition to a demonstration in a novel AM process that emphasizes cure/crosslink chemistry control. Testing will be defined prior to Phase II depending on success of Phase I efforts and which type of formulation (propellant vs. explosive) is chosen for Phase II scale up, formulation, and performance assessment activities. Pursue efforts to partner with appropriate DoD points of contact (POCs) for IM program insertion.

It is probable that the work under this effort will be classified under Phase II (see Description section for details).

PHASE III DUAL USE APPLICATIONS: Conduct a tactical rocket motor formulation, manufacture, and testing demonstration with a DoD or industry partner as needed, using the most promising binder system candidate in the rocket motor formulation. This demonstration should be with a formulation comparable to a HTPB analog rocket motor baseline with the goal of demonstrating superior thermal, chemical, aging, performance, and other properties by utilizing the advanced binder system. Commercial applications of technologies developed under this topic would be polymers for applications which experience a wide range of temperatures such as automotive industry or even commercial space launch.

REFERENCES:

1. Kubota, N. Propellants and Explosives. Weinheim: WILEY-VCH Verlag GmbH & Co. KGaA, 2007. http://www.getanewgun.com/Pyrotechnic/Pyrotechnic_Books/Propellants_and_Explosives_Thermochemistry_and_Combustion_by_Naminosuke_Kubota.pdf

2. Carraher, C E.� Polymer Chemistry. New York: Marcel Dekker, Inc., 2000.

3. MIL-STD-286C, MILITARY STANDARD: PROPELLANTS, SOLID: SAMPLING, EXAMINATION AND TESTING. 1991. http://everyspec.com/MIL-STD/MIL-STD-0100-0299/MIL-STD-286C_8618/

KEYWORDS: Polymer; Binder; IM; Propellant; Explosives; Hydroxyl-terminated Polybutadiene (HTPB); Ammonium Dinitramide; Cross-link