Reactions in the System Nitro-cellulose/ Diphenylamine with Special Reference to the Formation of a Stabilizing Product Bonded to Nitro-cellulose

• Main Author: Lindblom, Torbjörn
• Format: Doctoral Thesis
• Language: English
• Published: Uppsala universitet, Avdelningen för analytisk kemi 2004
• Subjects: Analytical chemistry; Nitro-cellulose; NC; Propellant; Stabilizer; Diphenylamine; DPA; Stability; Shelf-life; Chemometry; FTIR; HPLC; Microcalorimetry; Analytisk kemi
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-3989; http://nbn-resolving.de/urn:isbn:91-554-5868-8

The methods HPLC, microcalorimetry and FTIR together with chemometry, provide good analytical tools to follow the degradation of nitro-cellulose. The degradation products formed from diphenylamine (DPA) during storage can be followed with HPLC. FTIR, together with chemometry, also gives the precision needed for safety control of propellants. Nitro-cellulose (NC) containing DPA obtained a green colour already after 1 day storage at 70°C. About 10% of the stabilizer, and its derivatives, added were not extractable giving an extended time to autocatalysis. This time could be extended up to 70 days at 70°C for an extracted sample compared to about 3 days for non-stabilized NC. This was not shown before. Aged and extracted NC samples contained a non-extractable nitro compound. The most likely compound is 2,4´-dinitroDPA, probably bonded to NC via the amine nitrogen. The bonding to NC occurs after the formation of NNODPA. This is something not described before. Using another batch of nitro-cellulose to find out if a chemical bonding occurs gave inconclusive results as a blue NC was formed. Low molecular NC with high stability was obtained. A chemical bonding probably occurs when using NNODPA as a stabilizer, indicating NNODPA plays a key role. The use of FTIR/chemometry is a promising method to use when studying small chemical changes. The described methodology should be used to find out more about the compound(s) being bonded to NC.