Transport and wetting of moisture adsorbed on the surfaces of high explosives

Water is an unavoidable chemical antagonist that can negatively impact the functional characteristics of organic high explosives (HEs). It is not well understood how moisture absorbs in and permeates through heterogeneous polycrystalline microstructures typical of most HEs. We use molecular dynamics (MD) to investigate how HE crystal surface orientation effects the wetting and transport behavior of adsorbed water. We find that water binds more strongly to crystal facets with many hydrophilic groups exposed, but all crystal surfaces considered exhibit a high degree of wettability. The impact of temperature and moisture content on the structure and dynamics of adsorbed water is also considered. Conditions where water might permeate the crystal lattice are identified using biased and unbiased MD. Our findings indicate plausible mechanisms for microstructural dependence on moisture sorption in organic HEs.