Degradation behavior of nitrocellulose in imidazole aqueous solution

Abstract

Nitrocellulose (NC)-based materials can take years to degrade considerably in nature. One of the most promising NC waste treatment methods is inorganic base hydrolysis. In this work, the degradation mechanism of NC in an aqueous solution of imidazole, an organic base, had been constructed. The results showed that imidazole can cause denitration, ring opening, and oxygen bridge breaking in NC; eventually, NC was completely degraded. In this process, the denitration of vicinal nitrates generated nitrite and carbonyl groups, while the denitration of isolated nitrates produced nitrate and hydroxyl groups. The molar ratio of nitrite to nitrate in the reaction solution increased from 2.77 to 4.44 and finally decreased to 1.97 with time. The reaction rate of the nitrate group and oxygen bridge at the early stages of the reaction was as follows: vicinal nitrate's denitrification > isolated nitrate's denitrification > oxygen bridge breaking. Moreover, imidazole's diffusion rate gradually decreased as the reaction progressed, eventually balancing with the rate for complete degradation of NC. Meanwhile, the degree of crystallinity of remaining NC gradually increased, whereas the nitrogen content and relative number-average molecular weight of remaining NC gradually decreased from 13.52 % and 139,212 to 11.57 % and 3721; they ultimately maintained balance. The apparent morphology of NC fibers changed as cracks initially formed, then cracks progressively enlarged to produce fiber fragments, and eventually NC vanished entirely in the solution. The degradation of NC by imidazole potentially supports the one-step biochemical treatment of NC waste.