Abstract:
Energetic, fluorinated, linear polyphosphazenes are currently under investigation
as potential, high-density binders for new, polymer bonded explosive
compositions. A series of such polymers was synthesised and the enthalpy of
combustion of each member of the series was measured by static bomb
calorimetry. This was performed after combusting appropriate secondary
thermochemical standards to model the combustion stoichiometry of the heteroatoms
nitrogen, fluorine and phosphorus. The water-soluble combustion products
were identified and quantified using 19F NMR spectroscopy and Ion
Chromatography. Since some of the combustion products are hydrolytically
unstable, it was found necessary to stabilise the initial combustion product
mixtures by using a buffer solution instead of pure water in the bomb, and then to
determine the composition of the stabilised product mixtures in order to obtain
meaningful values for the enthalpies of combustion and thence enthalpies of
formation. The thermochemical measurements themselves were made with pure
water in the bomb. The composition and structures of the various
polyphosphazenes were correlated with their energies of combustion and
enthalpies of formation. The latter were calculated using the latest CODATA
values of enthalpy of formation of the combustion products. The ‘combustion’ of
the polyphosphazenes under a nitrogen atmosphere was also investigated with the
view to calculating the enthalpies of detonation of each member of the series.
Three conference papers which include the results of this work have been
published and are included in Appendices C-E.
