The use of multi-base gun propellants in artillery ammunition creates 0.3 pounds of solvent emissions for every pound of propellant used. At expected production rates of 3 million pounds per year, this represents the largest source of volatile organic compound (VOC) emissions due to gun propellant production.
This project seeks to demonstrate the feasibility of reducing or eliminating the emission of VOCs and solvents associated with the production of gun propellants through the use of thermoplastic elastomer (TPE) propellants.
New TPE propellant formulations were designed to permit solventless processing while simultaneously meeting performance and safety requirements. This required evaluating the most promising TPEs, determining the proper composition and molecular weight of the TPE, and optimizing the choice and amount of oxidizer used in the propellant. A solventless process was then demonstrated on a pilot plant scale. The manufacturability, safety, sensitivity, and performance properties of the propellant produced were evaluated in “proof-of-principle” tests.
Bis-azidomethyloxetane and azidomethylmethyloxetane (BAMO-AMMO) was chosen over Hytrel to be used as the binder propellant in processing development and demonstration and in gun firing trials. The Naval Surface Warfare Center-Indian Head Division (NSWC-IHD) successfully processed 10 pounds of BAT-5RDX (35%/65% BAMO/AMMO) TPE propellant from individual feed streams on the 40mm Twin Screw Extruder. The NSWCIDH also renewed the Interim Hazard Classification of BAMO-AMMO propellants being evaluated under this project. In addition, propellant grains of BAT-5RDX composition have been prepared at Thiokol by batch mixing followed by twin-screw extrusion processing. This project was completed in FY 1999.
Once the technology is fully developed and implemented, solvent emissions from triple-base gun propellant manufacture can be eliminated. This will include the elimination of approximately 500,000 pounds per year of VOC emissions, 400,000 pounds per year of other solvent emissions, as well as the elimination of scrap propellant. Cost saving will result from a reduction in the need for VOC elimination facility modifications, the elimination of solvent costs, and a decrease in energy costs associated with heating drying houses.