Enhancing Mechanical and Combustion Properties of Boron/Polymer Composites via Engineered Interfacial Chemistry
Abstract
Research Problem and ObjectivesSolid fuel ramjet (SFRJ) is of great interest for a wide range of naval applications. The performance of SFRJ is closely related to the mechanical and combustion properties of the fuel grain, which consists of reactive metals (e.g., boron) and polymeric binder (e.g., HTPB). The common practice to prepare the SFRJ fuel grain is to mix boron (B) and HTPB mechanically.However, HTPB has only two terminal hydroxyl groups (-OH, accounting for 1% in PB) to interact with the polar B surface, so negligible chemical interaction exists between B and HTPB. Consequently, B particles tend to agglomerate in HTPB, making B combustion even slower. In addition, the poor interaction between B and HTPB affects the mechanical properties of composites, limiting the B loading and causing potential cracks/hot spots. One potential solution to these challenges is to design interfacial chemistry between B and HTPB to enhance their interaction, which leads to better B particle dispersion and enhancedinterfacial mechanical properties. Simultaneously, we can introduce fluorinated functional groups at the interface to facilitate the removal of B2O3. Hence, our research objective is to study the effect of interfacial chemistry between B and HTPB on their mechanical and reactive properties. Our long-term goal is to enable efficient and safe application of B for SFRJ.Research Tasks and ApproachesTo achieve our objectives, we propose to carry out the following four research tasks: 1) developing synthetic recipes for functionalizing B particles with hydrophobic, hydrophilic, or fluorinated surfaces; 2) developing synthetic methods for modified HTPB and model PB-based binders; 3) developing mixing methods to prepare uniform B/PB composites with interfacial chemical bonding; 4) characterizing the mechanical and combustion properties of various B/PBcomposites and understanding the relationships between materials performance and interfacial and polymer chemistry. Our interdisciplinary team covers the required expertise on metal combustion (PI, Zheng) and polymer chemistry and materials (Co-PI, Xia). All the equipment needed is eitherin Zheng and Xia~s labs or in Stanford shared facilities.Expected Outcome and Impact on DODThe proposed research addresses several priorities of ONR energetic materials program. It will provide important experimental data and information to understand and model correlations between materials strength/reactivity with their energetic compositions and interfacial chemistry.In addition, the project will produce new synthetic routines for producing various functionalized metal particles and new multi-functional polymer binders. The success of the proposed project will lead to new SFRJ fuel grains with improved formulation properties (i.e., higher B loading, higher energy output, and less sensitive munitions). Such knowledge can be extended to other energeticapplications that share the similar needs to enhance the adhesion/interaction between metal particles and polymers.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Feb 07, 2019
- Source ID
- N000141912085
Entities
People
- Xiaolin Zheng
Organizations
- Office of Naval Research
- Stanford University
- United States Navy