Biphasic Architecture to Enable Structural Integrity and Enhanced Regression Behavior in Ethylene-α-Olefin Elastomer/Polyethylene Wax Fuel Blends

High Resolution Image Download MS PowerPoint Slide Ethylene-α-olefin elastomer (EAO)/polyethylene (PE) wax blends with various compositions were investigated as candidate materials for hybrid rocket fuel applications, focusing on correlating blends’ crystalline structure and thermomechanical properties to their combustion behaviors. The structural characterizations using grazing-incidence wide-angle X-ray scattering and X-ray diffraction revealed a composition-dependent evolution from predominantly out-of-plane oriented lamellar crystalline domains toward increasingly in-plane oriented crystalline domains as the content of PE wax increased. This structural evolution was accompanied by enlarged crystallite size and enhanced crystallinity in the blends, reaching an optimum value of 45.6% for the D30E70 (EAO: PE wax wt. ratio, 30:70) blend, as confirmed by differential scanning calorimetry. Furthermore, the thermogravimetric analyses showed a decreasing thermal stability, and dynamic mechanical analyses displayed progressively increased stiffness and reduced elastomeric response with the increasing PE wax content in the blends. The thermal conductivity of the D30E70 blend increased to 0.36 W m –1 K –1 from 0.26 W m –1 K –1 for pristine EAO, indicating improved internal heat transfer capability. The Mechanical tests demonstrated that tensile strength increased with PE wax loading, while the elastomeric EAO phase helped preserve ductility in the blends. The combustion and hot-fire evaluations revealed that the D30E70 blend exhibited the highest regression rate value of 0.78 mm s –1, while effectively suppressing thermal dripping observed in pristine PE wax. These findings suggest that the orientation of crystalline domains in EAO/PE wax blends is closely correlated with thermomechanical and combustion behavior, particularly regression rate. This approach offers an effective strategy to modulate regression rate through control of crystalline domain orientation.