Effect of cotton linter and nitrification conditions on nitrogen content and its distribution uniformity of nitrocellulose

The effects of DP of the cotton linter, the nitrification time, and the HNO₃ concentration in nitric-sulfuric mixes on the nitrogen content and its distribution uniformity of nitrocellulose were investigated by a test instrument developed by Beijing Institute of Technology. It is the first time that the swelling degree of fibre is used as a analysis indicator. The results show that the DP of cotton linter has no significant effect on the nitrogen content, but the lower the DP is, the more uniform the nitrogen distribution of the resulting nitrocellulose is; As the nitration time extends, the nitrogen content gradually increases and reaches its maximum at the time of 30 mins, then it shows a slight downward trend; while the distribution index D_ξ of NC shows a contrary trend, it initially decreases with time and obtains its minimum at the time of 30mins, then become larger with further extension of nitration time. The nitrogen content of nitrocellulose increases with the HNO₃ concentration within the interested range, while the most uniform nitrogen distribution can only be obtained in a appropriate HNO₃ concentration value, too low or too high concentration of HNO₃ in nitric-sulfuric mixes result in wider nitrogen distribution. It is found from the investigation that the swelling degree of fiber is a direct indicator affecting the nitrogen distribution of nitrocellulose. The higher the swelling degree is, the better the distribution uniformity of nitrogen content is.