Impact of initial grain temperature on the activation energy and the burning rate of cast double-base propellant

Ballistic properties of cast double-base propellants can be affected by the thermal treatment of the propellant grain before firing. In this work, we study the effect of initial grain temperature on both burning rate and activation energy of the double-base propellant. The burning rate of cast double-base propellant has been reported for different initial grain temperatures of -20 degrees C, +20 degrees C, and +50 degrees C. It has been noticed that the burning rate is increased with increasing the initial grain temperature. A reasonable elucidation for this behavior based on thermal investigation is represented. DSC and TGA thermal analysis were conducted to evaluate the effect of initial grain temperature on degradation process. Results from DSC were used to calculate the apparent activation energy related to each initial temperature using Kissinger and Friedman methods. The thermodynamic parameters of activation have been calculated. Tracing the activation energies of the cast double-base propellant over the initial temperature showed that the required activation energy, the enthalpy of activation, and the free energy of activation were decreased with increasing the initial grain temperature which might affect the propellant burning rate to be accelerated due to faster degradation process.