| Abstract: | Slow multi‐sample thermal ramp aging experiments were performed on high viscosity lacquer grade nitrocellulose over the temperature range 30–80 °C. Nitrocellulose was used in the fibrous state, in solution and as the gelatinous nitro‐plasticized binder used to bind high explosive crystals (HMX) in a polymer‐bonded explosive (PBX) formulation. Samples were subjected to a slow, stable heating rate (dT/dt) of 10 °C per day with periodic sample withdrawal for analysis by triple detector size exclusion chromatography (SEC). Molecular weight and intrinsic viscosity data indicate inter‐chain recombination/aggregation for fibrous material or highly concentrated solutions, when dry. When in fibrous or gelatinous binder form, little degradation was observed, aside from apparent recombination/aggregation. As a concentrated solution complex behavior was noted; fast eluting peaks formed with increased temperature, accompanied by rapid molecular weight reduction and a marked decrease in light scattering peak area. Progressive dilution of nitrocellulose solutions and/or addition of very small quantities of water reduced the recombination/aggregation effects but did not appear to significantly affect the overall rate of nitrocellulose degradation. Activation energies for nitrocellulose chain scission have been estimated from the molecular weight and intrinsic viscosity data obtained by the thermal ramp method. |
