Improvement of the creep resistance of glycidyl azide polyol energetic thermoplastic elastomer-based propellant by nitrocellulose filler and its mechanism

To investigate the effects of nitrocellulose (NC) content on the creep properties of glycidyl azide polyol energetic thermoplastic elastomer (GAP-ETPE)-based propellant, creep behaviour was studied by rotary rheometer under various shear stress and temperatures. Experimental results showed that creep strain and creep rate of samples increase with the increasing shear stress level, and similar creep behaviour tendency was observed under elevated temperature. When filled with 1 and 2 wt% NC, the creep strain and creep rate of GAP-ETPE/NC-based propellant were significantly less than the unfilled state, indicating that the NC contents partly inhibited the mobility of the binder segment and improved the creep resistance of GAP-ETPE-based propellant. Moreover, the constitutive equations of the creep curves were obtained from the four-element mechanical model, and the fitting results coincided well with the experimental data. Among the fitting parameters, the elastic modulus of high elastic deformation, E₂, and the viscosity of Voigt units, η₂, were sensitive and promising for the evaluation of creep strain of the GAP-ETPE-based propellant. Finally, the creep resistance model was established and verified by Fourier transform infrared spectroscopy, glass temperature and physical crossing point density of GAP-ETPE/NC-based propellant. Upon analysis of the experimental data, we concluded that the creep resistance mechanism of GAP-ETPE/NC-based propellant came from NC altering the flow lines of the continuous phase and restricted chain mobility in the propellant, which improved the creep resistance.