Dynamic Mechanical Properties of a Modified Double-Base Propellant

The dynamic mechanical properties of a modified double-base propellant were studied over a wide temperature range from 173K to 373K at four different frequencies, 0.1Hz, 1Hz, 10Hz and 100Hz, using dynamic mechanical analyzer, and the storage modulus, loss modulus and loss tangent curves were obtained. The results showed that three material states, glassy state, viscoelastic state and rubbery state, were presented for modified double-base propellant and two relaxation transitions were observed: the secondary transition (β transition), occurred at about 240K, and the glass transition (α transition), occurred at about 314K Analysis results showed that the storage modulus maintained a near constant plateau and was slight affected by frequency at low temperature(<;240K), which meant the modified double-base propellant exhibited almost elastic characteristic at low temperature. With increasing temperature, the storage modulus decreased and became lowest at rubbery state, which was strongly influenced by frequency. Furthermore, loss modulus increased with increasing frequency and the peak of loss tangent curves decreases with increasing frequency; The α transition and β transition switched to higher temperature with increasing frequency, and the temperature locations of these relaxation transitions shifted approximately 7.5K and 4K respectively to high temperature per decade increase in frequency for α transition and the β transition. The Richeton model was employed to clarify the storage modulus of the modified double-base propellant, and the model parameters were obtained, which showed that the Richeton model provided reasonable results over a wide range of temperature at various frequencies.