Applying Mechanically Activated Al/PTFE in CMDB Propellant

A novel reactive powder (aluminum/polytetrafluoroethylene, Al/PTFE 75/25 mass %) containing two kinds of PTFE (pre-sintering PTFE and fresh PTFE, P-PTFE and F-PTFE) was prepared by a two-step mechanical activation (MA) method. By introducing it into composite modified double base (CMDB) propellant, an attempt to improve the propellant performance of this mechanically activated Al/PTFE was made. Scanning electron microscopy (SEM) characterization indicated that F-PTFE in activated powders deformed to abundant fibers under uniform shear forces. These fibers significantly enhanced propellant tensile properties and show improved safety performance. Compared to blank CMDB propellant (without PTFE), the elongation at maximum strength for propellant with activated Al/PTFE inclusions was increased to 3.7 times at −40 °C and to 3.9 times at −70 °C, the friction sensitivity and impact sensitivity were reduced by 88.9 % and 20.4 %, respectively. P-PTFE in activated powders promoted the Al reaction activity, thereby reducing the propellant combustion agglomeration. The average diameter (D₅₀) of coarse products for propellant with activated Al/PTFE 75/25 mass-% was reduced by 82 % compared to that of blank CMDB propellant with spherical aluminum. This novel activated Al/PTFE shows increased propellant mechanical performance, decreased sensitivity and improved combustion efficiency of Al, which might expand the application field of CMDB propellants.