Facile Sol-Gel Synthesis of PTFE@Al Core-Shell Powders for Enhanced Curing Depth in UV-Curing-Assisted Direct Ink Writing of Composite Solid Propellants

UV-curing-assisted direct ink writing (DIW) is an established additive manufacturing technique for composite solid propellants, facilitating the development aerospace propulsion systems. However, direct application to aluminum (Al)-containing propellant slurries leads to limited curing depth, attributed to the high UV absorbance of aluminum powder. To address this limitation, we propose a novel surface modification strategy in which aluminum powders are coated with polytetrafluoroethylene (PTFE), yielding PTFE@Al composite powders with a core-shell structure. UV absorbance measurements show that PTFE coatings reduce the absorbance of aluminum powder by approximately 63%. Scanning electron microscopy (SEM) confirmed the uniformity and integrity of the PTFE coatings. Thermogravimetric (TG) and differential scanning calorimetry (DSC) analyses indicate that PTFE coating significantly enhances the energy release of aluminum powder, achieving an exothermic heat output of 2.19 kJ·g -1 below 1400 °C-approximately three times that of uncoated aluminum. Furthermore, curing tests on formulations containing PTFE@Al powders demonstrated an approximate 15% increase in curing depth. These results demonstrate that PTFE@Al composite powders not only overcome the limitations of aluminum’s UV absorption but also significantly enhance photocuring efficiency and energetic output. This work presents an innovative material design strategy and a practical route for additive manufacturing of high-performance solid propellant grains.