Nitric Oxide Depth-Profiles of Aged Double-Based Gun Propellants

摘要

As part of a propellant/epoxy compatibility study, double-base perforated stick gun propellant was downloaded from tank rounds subjected to temperature/humidity cycling for one month. The propellant was analyzed by traditional HPLC methods and found to have experienced no significant depletion of stabilizer. Analysis by a new desorption-GC-MS method yielded depth-profiles of nitric oxide (NO) that indicated localized decomposition at propellant surfaces. Surfaces of the propellant that had been in direct contact with a layered material (glass-reinforced RTV rubber/RTV rubber/epoxy/composite sabot) showed NO levels well in excess of baseline measurements, and a level somewhat higher than that of exterior surfaces not in direct contact with the layered material. Nitric oxide 'enhancement' was observed as deep as 1-mm in from the exterior surfaces. Analysis of samples aged in the lab revealed that some of the NO generated by decomposing propellant diffuses into the silicone in the RTV rubber, thereby removing it from the autocatalytic degradation cycle and resulting in a decreased level of decomposition (as evidenced by NO levels at the core of the propellant). It was observed that uptake of NO by the silicone components was completely reversible. While the NO level at the core of the propellant was found to be lower for the samples exposed to the suspected incompatible material than for the control, elevated NO levels were found at depths up to 0.75 mm from the surface exposed to the suspected incompatible epoxy, confirming the existence of an incompatibility between the propellant and epoxy in the layered material.