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Figure 2. Chromatogram of a partially burned propellant sample. Components: A, 4-nitrodiphenylamine; B, 2,4' dinitrodiphenylamine; C, N-nitrosodiphenylamine D, diphenylamine; and E, 2-nitrodiphenylamine.
from this lot had stabilizer levels below 0.14%. The questionable lot had stabilizer levels comparable to those of other lots tested with the same composition and grain size. Figure l b shows a sample chromatogram for propellant from a different lot indicating t h e low levels of 2,^-dinitrodiphenylamine present. A study was conducted to determine grain-to-grain variations within a propellant lot. Individual grains were cut into sections and analyzed for the percentage of stabilizer content. A statistical comparison of the means and standard deviations for a multiple of grains and grain sections indicated that there were no significant differences. In addition, partially burned propellant samples were analyzed for their percentage of stabilizer. This provided additional information concerning the stability of the propellant after thermal decomposition (burning) occurred. These samples contained equal or slightly lower amounts of stabilizer, 0.20%, w h e n compared w i t h t h e stored lots. Although additional degr a d a t i o n products were observed with t h e b u r n e d propellant (Figure 2), rapid decomposition of t h e stabilizer was not expected because diphenylamine and TV-nitrosodiphenylamine were still present in the sample. The total effective stabilizer was at a level acceptable to warrant use
Figure 3. Chromatogram of a fumed propellant sample. Components: A, 4-nitrodiphenylamine; B, 2,4'dinitrodiphenylamine; and C, 2-nitrodiphenylamine.
but, although composed primarily of diphenylamine and N-nitrosodiphenylamine, it contained higher levels of 2- a n d 4-nitrodiphenylamine. The partially burned propellant analysis indicated that the stabilizer remained at an effective level even during the burning process. One additional question remained unanswered. Was there a point when stabilizer was present but not at a sufficient concentration to prevent rapid fuming of the propellant? In other words, what is the stabilizer content, if any, when a propellant fumes? We tried to answer this question by analyzing t h e accelerated fumed samples. Once t h e s e p r o p e l l a n t s a m p l e s were fumed in the oven, they were removed and on the same day placed directly into acetonitrile. Assuming that they were unstable, we did not attempt to slice the grains but rather extracted whole grains for analysis. Our results showed that the diphenylamine and N-nitrosodiphenylamine were almost depleted. In addition, 2and 4-nitrodiphenylamine were present at levels averaging 0.05% in most samples and slightly higher in others. The most noticeable difference was that the 2,4'-dinitrodiphenylamine concentration was 0.20% or more. There was an abundance of
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