Manufacturing superfine AP by milling in a lab-scale resonant acoustic mixer (LabRAM)

A common practice to deisgn composite propellants with high burning rates is to use several sizes of the oxidizer (e.g., ammonium perchlorate, AP) to increase the total amount of solids that can be packed into the composite propellant system. Small AP particles (<= 15 mu m) are difficult to obtain from commercial vendors due to restrictions derived from increased explosion hazards for superfine AP (SFAP). An in-house SFAP manufacturing process was devised herein using resonant acoustic mixing (RAM). A 90-mu m AP feedstock was utilized to produce SFAP batches with average particle sizes of approximately 2 mu m. Scanning electron microscopy (SEM) was used to characterize particle size distributions. Ballistic testing was conducted with an 80% SFAP composite propellant formulation was burned over a pressure range of 500 to 3,000 psi (3.45 to 20.68 MPa) and a burning rate of 1 in/s (25 mm/s) at 1,000 psi (6.89 MPa) was achieved without optimizing the propellant with additives.