Thermal behavior of glassy phase stabilized ammonium nitrate (PSAN) thin films

Ammonium nitrate (AN) is a high interest material because of its wide usage in propellants and explosives but can be difficult to handle from a formulation standpoint. It is soluble in many common solvents and has complex phase behavior. Here, we formulate phase stabilized AN (PSAN) films in a polymer matrix and characterize thermal and phase behavior using neutron reflectometry and ellipsometry. These techniques are highly sensitive to small changes in composition and density which occur during phase transitions. Our PSAN films are generally stable up to 160 °C, though we observe small material loss between 60 and 100 °C, which we attribute to solvent interactions with the PSAN. Crystallization of AN from supersaturated polymer is most common at thicker regions of the film, suggesting a critical nucleation thickness for the AN which can be avoided by making very thin films.