Investigations into the copper chromite particle size effect on the combustion characteristics of poly(vinyl-chloride) plastisol propellants

Abstract

The investigation of the possibility to optimize ballistic behavior and consequently to obtain better performance without affecting the cost and safety aspect of plastisol propellants has been presented in this paper. Addition of specific additives and changes in particle size can be one of these solutions, which are continuously in research. The use of burn rate modifier and metallic fuel, with finer particle sizes, becomes mandatory, to enhance the catalytic effect on ammonium perchlorate and to offer additional high heat release. Moreover, the knowledge of the combustion characteristics and especially the burning rate depending on the combustion chamber pressure of the propellant are important conditions in the validation and successful design of a solid rocket motor. The first part of this work deals with the selection of the higher energetic catalyst among three of the most common of them, namely copper chromite, ferric oxide and ferrocene. The selection results in choosing copper chromite as the best burning catalyst. Then, we have studied the effect of its particle size on the thermoanalytical properties of poly(vinyl-chloride) plasticized propellants, by the determination of energetic and kinetic characteristics through the use of an adiabatic bomb calorimeter and a differential scanning calorimeter respectively. The kinetic parameters were determined by Ozawa and Kissinger methods and compared. Besides, the effect of particle size on the combustion properties has been also studied. The plot of the burning rate-pressure curves is used to determine the combustion laws using a strand burner in the typical Crawford bomb. Copper chromite and its particle size have been found to influence the decomposition and to enhance the burning rate of the plastisol propellants. In the second part, we have investigated the energetic effect of fine aluminum powder on the thermal decomposition of ammonium perchlorate and of plastisol propellant as a function of its concentration, both in the presence and the absence of 1 mass-% copper chromite in the basic propellant composition. Aluminum is chosen because of its effect to get high flame temperatures and increased performance.