Researches on the Efficiency of Diphenylamine Addition to Aged Nitrocellulose Propellants

It is well known that natural ageing of ammunitions during storage and service causes modification of mechanical, physico-chemical and ballistic characteristics. After long periods of time these modifications become so important that the ammunition does not longer perform according to its specifications and usage/storage are considered dangerous. It is also known that propellant charge is the most vulnerable part of these systems relative to natural ageing especially when energetic polymers are involved as energetic base. Among the energetic polymers used in propellant charges nitrocellulose (NC) is usually preferred but glycidylazidopolymers [1] and polyvinylnitrates [2] can also be used. Even when they are stored at normal temperature and humidity levels, nitrates will slowly decompose producing nitrous vapours and consuming the stabilizer. The mechanism of this decomposition process was detailed by Rychly et al. [3] and will not be discussed here. When stabilizer content decreases under some specific values the stability reserve of the propellant is no longer considered satisfactory and it must be disposed. Compared to all other ammunition parts simple base propellants have the shortest service life which is not usually longer than 35 years (when pass reception and all periodic tests). Romania, like other countries from eastern block, has to deal with large stocks of ammunitions produced in the last 50 years, many of them containing simple base propellants approaching the end of their service life. Among them, there are large quantities of aged simple base propellant produced in the first decade after the Second World War that suffered the so called process of “revival” which consisted in supplementary addition of stabilizer (diphenylamine DPA) and volatile solvents.