Role of water in degradation of nitroplasticizer

Abstract The role of water in degradation of nitroplasticizer (NP) was studied using a set of NP samples aged inside confined containers between room temperature and 70∘C with their water concentrations monitored during the aging course. For the first 42 days at the temperatures at 55∘C and below, simple Fickian diffusion dominates the monotonic decreases of the water concentrations with time. After about 60–80 days depending on temperatures, diffusion alone can no longer explain the water decreases, despite no significant NP degradation detectable using the FTIR spectroscopy. Starting at about 80–160 days, also depending on temperatures, the measured water concentrations fluctuated around mean values that decrease with increasing temperature, and the onset of NP degradation was detected using FTIR and TGA. It was found that NP contains an irreducible amount of water on the order of a few hundred ppms, which decreases with increasing temperature. Pristine NP does not exist with a water concentration lower than this amount. The diffusivity, the irreducible amount of water in NP, and the mean water production rate due to NP degradation are calculated from the water concentrations of the first aging stage and the mean water concentrations during the onset of NP degradation. They all change with the temperature following Arrhenius laws with different prefactors and activation energies. This study shows that trace water formation is an intrinsic property of the NP while it ages with the mechanistic details to be resolved.