Research on crosslink density testing method of GAP propellant based on swelling method

Abstract In order to determine the crosslink density of GAP (Glycidyl Azide Polymer) propellants more accurately and conveniently, and to explore the relationship between the performance of GAP propellants and the crosslink density and gel fraction, this paper proposes several key factors that should be paid attention to when selecting solvents for the determination of the crosslink density of GAP propellants by equilibrium dissolution method. The values of the crosslink density of GAP are determined, while the dissolution time required for the determination of the crosslink density of GAP by the equilibrium dissolution method is given. The changes in GAP propellant crosslink density and gel fraction with aging and the relationship with its mechanical properties were explored. The results showed that the interaction parameters between solvent and adhesive and the solubility of components such as solid filler should be considered when selecting the solvent for equilibrium swelling, and the solvent selected should not dissolve out the solid filler in order to calculate accurately; trichloromethane was selected as the solvent for the determination of cross-linking density of GAP by comparing the swelling degree and the mass fraction of dissolved material, and the swelling time should be around 48 h at 25°C; the results of the determination of the crosslink density of the GAP propellant were in the range of 5.1666×10 −5 −5.5957×10 −5 mol·cm −3 ; the crosslink density and gel fraction of the GAP propellant did not change much with aging, and the changes in its mechanical properties due to aging should be considered in light of other factors such as dehumidification.