(441b) Environmentally Friendly Green Propellant for the Medium Caliber Training Rounds

The purpose of this effort is to provide a replacement for the medium caliber propellants that is more environmentally friendly to manufacture by eliminating toxic ingredients and removing solvents from the manufacturing process. Executive Order 12856 of 3 August 1993, paragraph 3-303, requires each Federal Agency to establish a plan and goals for eliminating or reducing the unnecessary acquisition of products containing extremely hazardous substances or toxic chemicals. Barium nitrate (BaN), Dibutyl phathalate (DBP) and diphenyl amine (DPA) are widely used in a multiplicity of propellants for medium caliber ammunition. Over the next five years, approximately 38,500 pounds of diphenyl amine (DPA), 44,000 pounds dibutylphthalate (DBP) and 10,000 pounds of barium nitrate (BaN) will be incorporated into medium caliber ammunition via the propellant. These materials are toxic, hazardous or carcinogenic. DBP currently used as a plasticizer in several medium caliber propellant formulations is a carcinogenic material. Plant operators continuously exposed to DBP are more likely to have liver, bile duct and bladder cancers. DPA, acting as a stabilizer in several propellants to prevent the deterioration of nitrocellulose, is a known toxin and contains a carcinogenic impurity (4-aminobiphenyl). This impurity can be absorbed into the body by inhalation of its aerosol, through the skin and by ingestion. BaN is a moderately poisonous heavy metal compound that is often used as an oxidizing agent to make the propellant easy to ignite. It can irritate the mucous membranes and the skin, producing dermatitis and eye, nose, and ear irritation. Contamination of training ranges by these ingredients jeopardizes sustained use. Also, any desired demilitarization or scrap disposal of these propellants is complicated by these compounds' undesirable environmental characteristics. In order to meet the 25mm M793 ballistic requirements, it was necessary to utilize various nitroester or nitratoethyl nitramine (NENA) plasticizers to achieve the correct propellant mechanical properties and energy level. The use of a single base production line was impossible because of these ingredients. Three propellants were formulated to be produce by solventless production line and a fourth propellant containing a NENA was initially produced using solvents, but possibly could be made solventless. The solventless production technique further enhances the mechanical properties given by solvent processing, to yield propellants with the best possible toughness characteristics. This paper will present the formulation development effort, characterization testing and gun firing results.