Investigation of a Low-Toxicity Energetic Binder for a Solid Propellant: Curing, Microstructures, and Performance

Area of Science:

• Materials Science
• Polymer Chemistry
• Energetic Materials

Background:

• Energetic binders are crucial for propellant performance.
• Developing binders with improved mechanical properties and safety is an ongoing challenge.

Purpose of the Study:

• To synthesize and characterize a novel propellant binder based on branched glycidyl azide polymer (B-GAP) and dimer acid diisocyanate (DDI).
• To investigate the curing kinetics, microstructure evolution, and mechanical properties of the B-GAP/DDI binder.

Main Methods:

• Thermal analysis (DSC/TGA) was employed to study curing kinetics and thermal properties.
• A variance method was used to determine the reaction endpoint.
• Microstructure analysis and mechanical testing (tensile, dynamic mechanical analysis) were performed.

Main Results:

• The B-GAP/DDI binder exhibited an induction period, with thermal diffusion effectively describing the curing process via an autocatalytic model.
• The reaction endpoint was determined to be between 156-168 hours, with Shore A hardness stabilizing around 40.78.
• Cross-linking density reached 4.0 × 10^-4 mol·cm^-3, with significant hydrogen bonding (53.3% carbonyl participation).
• The binder demonstrated superior mechanical performance and a lower glass-transition temperature compared to the GAP/N100 binder.

Conclusions:

• The B-GAP/DDI binder offers a promising alternative with enhanced mechanical properties and a lower glass-transition temperature.
• The study elucidates the curing behavior and microstructure development, highlighting the role of hydrogen bonding.