Abstract:

The liner, which is a transition layer serving as a bridge between the main material of the solid propellant and the coating layer, can significantly enhance the bonding between the solid propellant and the coating, thereby ensuring the structural integrity and operational reliability of the solid propellant during storage and usage. Therefore, the spreading, penetration, and coverage of this transition layer on the surface of solid propellant directly affect the propellant’s service efficiency. So, the surface behavior of this transition layer on the propellant is worth studying. Improving the spreading uniformity of the transition layer on the propellant surface and ensuring adequate penetration can enhance its interaction with the propellant surface. In this work, the spreading and penetration of different transition layers on the surface of solid propellant were studied by dynamic contact angle measurement. The relationship between the composition of the transition layer and its spreading and penetration was analyzed by calculating the surface energy of different propellants and measuring the surface tension of transition layer. Accordingly, the composition of transition layer was optimized. The results showed that, the larger the surface energy of solid propellant, the better the spreading of transition layer on its surface. When the propellant exhibited a surface energy of 97.62 mJ/m², both the instantaneous contact angles of water and glycerol on its surface were smaller than those observed at the surface energy of 55.83 mJ/m². Furthermore, the composition of the transition layer had significant influence on its surface tension. By adjusting the composition, the surface tension of the transition layer could be reduced from 48.7 mN/m to approximately 24.8 mN/m. Therefore, the spreading and penetration of the transition layer on the propellant surface could be improved by modifying the propellant surface and regulating the composition of the transition layer, which would improve the interfacial bonding strength between the propellant and the cladding.

Key words: transition layer, propellant, dynamic contact angle, surface energy, spread and penetrate