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1 Central European Journal of Energetic Materials

1 2007

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Applicability of Dynamic Mechanical and Thermal Methods in Investigation of Ageing Processes of Double Based Rocket Propellants

Matečić-Mušanić S., Sućeska M., Bakija S.

Central European Journal of Energetic Materials

2007

Vol. 4, nr 1-2

45-65

Ageing of double based rocket (DBR) propellants, as a consequence of chemical decomposition reaction, as well as physical processes (migration of low molecular constituents: plasticizers, etc.) has significant influence on their relevant properties (e.g. decrease of molar mass of nitrocellulose, decrease of stabiliser content, decrease of specimen mass, change of mechanical and thermal properties, etc.). The change of relevant properties of DBR propellants limits their safe and reliable service life. Even more, under certain conditions decomposition of a DBR propellant may become autocatalytic, which can lead to self-ignition of the DBR propellant. Because of that, it is very important to find out reliable methods for determination of propellant stability at a given moment of time, as well as to predict self-ignition probability under given conditions. In this work we studied dynamic mechanical and thermal properties of DBR propellants artificially aged for different period of time at 90 C, in order to detect and quantify changes in dynamic mechanical and thermal properties that can be used in the propellants stability assessment. Dynamic mechanical properties were studied by dynamic mechanical analysis (DMA), while thermal properties were studied using differential scanning calorimetry (DSC) and thermogravimetry (TGA). The obtained results showed that the ageing caused significant changes of DMA, DSC and TGA curves' shape. The changes are quantified by some of characteristic points on DMA, DSC and TGA curves. It was found out that the most sensitive parameters/characteristic points to the ageing process at DMA curves are: storage modulus at 25 C, storage modulus at softening region, peak width and height on loss modulus curve, glass transition temperature, loss modulus at viscoelastic region, tanδ maximum at viscoelastic region, while the most sensitive parameters at DSC and TGA curves are: peak height and width, heat of reaction, max. heat flow rate, mass loss at a given time, and rate of mass loss at a given time.