Aspects of the Tribology of the Plastic Bonded Explosive LX‐04

The dynamic coefficient of friction, μ_d, of the plastic bonded explosive (PBX) LX‐04 was measured on stainless steel, aluminum, Teflon and the explosive itself as a function of temperature between ambient and 135 °C at a rotational speed of 0.0025 rad/s⁻¹. An optical profilometer was used to analyze surface roughness. LX‐04 is a composite of the explosive 1,3,5,7‐tetranitroazacyclooctane (HMX) and Viton A in an 85/15 weight ratio. For LX‐04 on stainless steel, μ_d decreased from 0.38 at ambient to 0.18 at 95 °C, then was nearly constant to about 125 °C, where the coefficient began to increase again. The opposite behavior was observed for aluminum. Against Teflon μ_d was nearly constant from ambient to 65 °C at 0.43, and then decreased to 0.17 from 100 °C to 135 °C. Against LX‐04 itself the coefficient of friction averaged 0.64 at temperatures between 35 °C and 95 °C, but tended to increase during the measurement, probably due to adhesion of the Viton to itself. Above 95 °C the coefficient dropped off and became nearly constant again at 0.16 up to 135 °C. Measurements on stainless steel with the mock explosive RM‐04‐BR, a composite of cyanuric acid and Viton A, and with the same weight ratio as the actual explosive, compared reasonably well with the explosive itself.