Theoretical characterization of mesoscopic structure of PBT propellant based on liquid film thickness

Solid propellant slurry is a high solid content suspension, and its rheological properties are very complex. In order to solve the problem that it is hard to estimate the process propertie of 3,3-bis(azidomethyl) oxetane-tetrahydrofuran copolyether (PBT) solid propellant slurry, the concept of liquid film thickness in propellant was proposed by analyzing the mesoscopic structure of PBT solid propellant slurry, and the calculation method of liquid film thickness under different propellant packing grade ratios is given. Four kinds of filler particle size are used as examples, the theory of tight packing of tertiary particles was extended to multi-gradation. Furthermore, based on the theory of packing, the relationship between the liquid film thickness of the propellant and the particle size of the filler is obtained, that is, the liquid film thickness becomes thinner with the decrease of the particle radius and changes proportionally with the particle radius. In this work, the analysis method provides theoretical guidance for propellant formulation design, thereby reducing the number of experiments, shortening the propellant formulation development cycle, and reducing labor and material costs.