Thermal decomposition and combustion of nitrocellulose.

T derivation of a realistic theory of combustion and the understanding of the aging of nitrocellulose depend upon an adequate knowledge of the kinetic mechanism of thermal decomposition. This paper is directed towards understanding the initial bond-breaking step and how this results in the distribution of products observed under different experimental conditions. Schuyler has proposed a mechanism for the pyrolysis of nitrocellulose that is essentially the same as that presented earlier by Shafizadeh and Wolf rom and by Gelernter et al. It was assumed that the initial step involved the scission of the CO—N02 bond as is the weakest bond in nitrocellulose. If N02 split off from a nitrate ester group attached to a secondary carbon atom, then glyoxal and N02 were assumed to be the primary products. If scission of a nitrate ester group attached to a primary carbon atom occurred, then the primary products were assumed to be formaldehyde and N02. This scheme is the same as that advanced by Wolf rom. Consistent with the experimental findings of Phillips, Orlich, and Steinberg, it was assumed that loss of N02 led to the intermediate formation of a carbonyl group on the nitrocellulose residue. However, formic acid, C02, CO, and NO were also isolated as products in addition to glyoxal and formaldehyde. It was assumed that these products resulted from oxidation of formaldehyde and glyoxal by N02 in the vapor phase. A number of independent investigators have derived values for the parameters of the Arrhenius equation. The reported values of A and Ef the pre-exponential factor and activation energy, respectively, for the first-order thermal decomposition, are tabulated in Table 1. The agreement among the values determined by the different experimental techniques is very good. It is noteworthy that activation energy lies within the range of 43-46 kcal. The dissociation energy of the CO—NO2 bond is 36.4 to 39.5 kcal determined experimentally from the kinetics of thermal decomposition of simple nitrate esters in the vapor phase. Smith thought that the difference between the activation energies for the pyrolysis of nitrocellulose and that of the simple nitrate esters might be because the former was pyrolyzed in the solid state. He measured the rate of py-