| dc.description.abstract | This research aims to explore novel, multi-component crystals based on
dinitramide salts as potential applications for environmentally benign propellants.
Crystal engineering was used in this study to create new oxidisers as a means of
enhancing the performance of existing energetic materials by changing the physical
and chemical properties of crystalline solids.
In the co-crystallisation studies, multi-component crystals based on ADN
were successfully synthesised incorporating guanidinium dinitramide (GDN) and
guanidinium nitrate (GN) via different crystallisation techniques including
evaporation, diffusion and mechanical grinding. The crystal structures of the multi-
component crystal were obtained by single-crystal X-ray diffraction and show that
the dinitramide is extensively hydrogen bonded. For ammonium dinitramide:
guanidinium dinitramide (ADN:GDN), the crystal density lies approximately midway
between the two co-formers and has a positive oxygen balance of 5.51%. The co-
crystal of ammonium dinitramide: guanidinium nitrate (ADN:GN) has a density that
surprisingly lies far from midway between the two co-formers and is closer to that of
ADN. The oxygen balance of ADN: GN is 0.00%.
The physicochemical and energetic properties, including density, thermal
expansion, thermal stability, hygroscopicity, impact sensitivity and calculated
energetic performance (e.g., detonation velocities and detonation pressures) of both
the multi-component crystals have been investigated. The syntheses of ADN:GDN
and of ADN:GN can be scaled-up using grinding techniques and resonant acoustic
mixing (RAM). ADN: GDN has a higher melting point (111 °C) higher than that of ADN
whereas ADN:GN has lower melting point at 89 °C. The detonation velocity was
calculated by using EXPLO-5 program based on densities, chemical composition, and
heats of formation. The detonation velocities and pressures of both co-crystals are is
higher than that of ADN. Humidity testing of ADN: GN and ADN:GDN was performed
using a humidity chamber at 55% RH and 25 °C. Both these materials are less
hygroscopic than ADN. Impact sensitivity testing using a BAM Fall Hammer gave an
impact sensitivity for ADN: GDN of 17 J compared to ADN (3-4 J).
The compatibilities of the multi-component crystals with various polymer
binders were studied. From these studies, ADN:GDN was compatible with hydroxyl-
terminated polybutadiene (HTPB) and polycaprolactone (PCL). ADN:GN had fair
compatibility with HTPB, but was compatible with PCL. Both compounds were
incompatible with polyethylene glycol (PEG). | en |
