Abstract:

The curing process of the NEPE(nitrate ester plasticized polyether) propellant was studied by means of the dynamic rheology method. The results indicated that the viscoelastic properties of the propellant slurry changes obviously in different curing stages, in the initial curing stage(viscous fluid state), where G′(storage modulus) and G″(loss modulus) increases slowly, G′ is less than G″; in the medium of the curing process, the propellant slurry is gelated, G′ and G″ increase significantly in the mean time, G′ is equivalent to G″ and higher than that; in the finial curing stage(viscoelastic state), where G′ and G″ increase to the maximum and level off, G′(~106 Pa) is obviously higher than G″(~105 Pa). It was experimentally show that tgel(gel time) of the propellant decreases as the curing temperature increases, while G′_gel(storage modulus at gel point) and G′_∞(storage modulus at the end of curing) change slightly, which are in the range of 622 Pa to 781 Pa and 831.1×10³ Pa to 868.3×10³ Pa, respectively. It was found that the crosslinking kinetic of the propellant in the initial curing stage is reaction controlled, and follows the first-order model. The curing of the propellant is in agreement with the Hsich kinetic model. k_c(reaction rate constant), t_gel and τ(characteristic relaxation time in the Hsich model) are used to calculate the apparent activation energy(ΔE_c, ΔE_g and ΔE_τ) of the curing of the propellant, which are 129.6, 122.1 and 120.6 kJ/mol, respectively.

Key words: Nitrate ester plasticized polyether propellant, Rheology, Curing, Crosslink, Model