engleski

Influence of ageing on nitrocellulose thermal properties and hazard potential figures-of-merit

Thermal decomposition reactions in nitrocellulose, which is the basic component of homogeneous propellants, limit the safe use and safe storage time of propellants. The ageing of propellant is not only a quality problem, but a safety problem too. It is known that, under certain conditions, decomposition process may lead to the well known phenomenon of self-ignition. The probability of self-ignition increases with ageing of a propellant. In order to predict safe use and safe storage time, i.e. to predict the hazard potential figures-of-merit during ageing, one has to follow the changes of properties which are in connection with the decomposition reactions. The properties that are usually folowed include: mean molecular mass of nitrocellulose, decrease of stabiliser content, mass loss, gas formation, heat generation, etc. The influence of accelerated ageing on the changes of the heat capacity, activation energy, pre-exponential factor and heat of decomposition of a nitrocellulose propellant is studied in the papert. The study is performed by differential scanning calorimetry (DSC). The obtained results are used for the calculation of the time-to-thermal explosion, critical half thickness, and critical temperature, as parameters which indicate relative degree of hazard, applying equations derived from the thermal explosion theory. It is found out that with ageing, the activation energy, pre-exponential factor, and heat of decomposition decrease, while the heat capacity decreases. Consequently, the relative degree of hazard increases.

nitrocellulose; DSC; kinetics; heat capacity; hazard poten

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