Prediction of Storage Life of Propellants having Different Burning Rates using Dynamic Mechanical Analysis
Propellants, visco-elastic in nature, show time and temperature dependent behaviour on deformation. Hence, the time–temperature superposition principle may be applied to the visco-elastic properties of propellants. In the present study, dynamic mechanical analyser (DMA) was used to evaluate the dynamic mechanical properties and quantify the storage life of four different propellants based on hydroxyl terminated polybutadiene, aluminium and ammonium perchlorate having different burning rates ranging from 5 mm/s to 25 mm/s. Each sample was given a multi-frequency strain of 0.01 per cent at three discrete frequencies (3.5 Hz, 11 Hz, 35 Hz) in the temperature range - 80 °C to + 80 °C. The storage modulus, loss modulus, tan delta and glass transition temperature (Tg) for each propellant samples have been evaluated and it is observed that all the propellants have shown time (frequency) and temperature dependent behaviour on deformation. A comparison of the log aT versus temperature curves (where aT is horizontal (or time) shift factor) for all four propellants indicate conformance to the Williams–Landel–Ferry (WLF) equation. The master curves of storage modulus (log É versus log ω plots) were generated for each propellant. A plot of É versus time for all propellants was generated up to 3 years, 6 years, and 10 years of time, respectively. The drop in the storage modulus below the acceptable limit with time may be used to predict the shelf life of the propellant.
Defence Science Journal, 2012, 62(5), pp.290-294, DOI:http://dx.doi.org/10.14429/dsj.62.2480
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