Relaxation Properties of the Solid Propellant Based on Hydroxyl-Terminated Polybutadiene

Abstract

The polymer-based propellant is a typical viscoelastic material. Better understanding of the relaxation properties of the propellant in the storage conditions is of great importance for predicting the lifetime. Due to the component complexity of the composite propellants, the transformation relation between the relaxation modulus and the complex modulus may not be suitable for all kinds of propellants. In the present work, we focused on the transformation of the relaxation modulus and complex modulus for the HTPB propellant. The master curves for the relaxation modulus and the storage modulus of the aged/unaged HTPB propellants were obtained by performing the stress relaxation tests and DMA tests, respectively. It was found that there existed a great difference in the double logarithmic plot between relaxation modulus and storage modulus master curves. Moreover, the testing results for the relaxation modulus and the storage modulus were well fitted by an empirical transformation relation with three segment-related coefficients. These three coefficients were determined by using the unaged samples, and then were applied to estimate the relaxation modulus of the aged samples. A good agreement between the calculation and the experimental results was also found, revealing that the three coefficients were insensitive to the aging time.