engleski

Kinetics of nitroglycerine evaporation in double base rocket propellants

Double base propellants (DB) are composed of two basic compounds: nitrocellu-lose (NC) as matrix and nitroglycerine (NG) as blasting oil and plasticiser at the same time, and of additives such as stabilisers, burning catalysts, modifiers of bal-listic properties, etc. In the course of time, a number of chemical and physical processes such as stabilizer consumption, migration and evaporation of NG, decomposition of NG and NC, etc. take place in the propellant grain. Consequently, the physical, chemi-cal, thermal, ballistic and mechanical properties of the propellants change with time. This will result in the decrease of propellant’ s performances and reduction of propellant’ s safe service lifetime. Standard methods for the determination of propellant stability at a given moment of time are mostly based on following of stabiliser consumption. However, experience has shown that mechanical properties can be a crucial factor that limits DB propellant’ s safe service lifetime. Since the amount of NG in the propellant strongly influences the mechanical stability, the aim of this work was to study kinetics of evaporation of NG in a DB propellant. The kinetics was studied from isothermal and non-isothermal experi-ments carried out in a thermostat and using a TGA analyser. It was found out that the sample mass loss during the early stage of NG evaporation could be described by the potential kinetic model ( ), while the sample mass loss for the whole range of NG evaporation could be described by the nth-order kinetic model ( ). The non-isothermal TGA experiments were treated by the Flynn-Wall isoconversional method. The activation energy of evaporation of NG was calculated to be from 77 to 110 kJ/mol, while the pre-exponential factor ranges from 2.5• 107 to 2.5• 108 s-1.

activation energy; double based rocket propellant; kinetics of evaporation; nitroglycerine; thermogravimetry

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