Polarographic study on the evolution of the diphenylamine as stabiliser of the solid propellants

Differential pulse polarography (DPP) and square wave voltammetry (SWV) were investigated, in order to know the stability of solid propellants which contain diphenylamine. The simultaneous determination of N-nitrousdiphenylamine (NnDPA), 2-nitrodiphenylamine (2nDPA), 4-nitrodiphenylamine (4nDPA) and 2,4-dinitrodiphenylamine (2,4dnDPA) by DPP and SWV was proposed due to these nitro-derivatives appear during the stabilisation process from degradation of diphenylamine (DPA) used as stabiliser in propellant compositions. The proposed methods were successfully applied to the simple base solid propellant (with nitrocellulose as the only active component), with its stabiliser DPA. In all cases and with both the techniques, detection limits ≤0.01 ppm were obtained.When the usual LC procedure was applied to the real sample, no significant differences were found between the obtained results and those given by the electroanalytical techniques. In addition, the detection limits reached by the electrochemical methods were better than those obtained by LC.Moreover, the proposed procedure can be considered an objective test that would avoid the use of the classic stability tests and would allow one to determine the stability of propellants accurately, faster and cheaper than LC methods.