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Bomb Calorimetric Correlation Study between Chemical Structure and Enthalpy of Formation for a Linear Energetic Polyphosphazene

Bellamy A. J., Contini A. E., Golding P.

Central European Journal of Energetic Materials

2013

Vol. 10, no. 1

3--15

Energetic polyphosphazenes constitute a novel class of insensitive binders which potentially outperform conventional carbon-based systems in terms of their energy-densities and glass transition temperatures. To facilitate the calculation of energetic performance for these materials, we report here on the use of bomb calorimetry to determine the standard enthalpies of combustion (ΔcH°) and formation (ΔfH°) of 2,2,2-trifuoroethan-1-oxy-/2,3-dinitratopropan-1-oxy-polyphosphazene (I) as the proportion of (energetic) 2,3-dinitratopropan-1-oxy substituents (% Energetic Substitution, % ES) is varied between 31% and 78%. Similar data is presented for the parent polymer bis(2,2,2-trifuoroethan-1-oxy)-polyphosphazene (II) (% ES = 0). ΔcH° was found to vary between -2275 kJ·mol-11for the parent polymer II (% ES = 0) and -3415 kJ·mol-1 for I with % ES = 78. The corresponding values for ΔfH° were -3184 kJ·mol-1 and -1566 kJ·mol-1. These data indicate that, as expected, the polymer heats of formation become more favourable – with respect to the energetic performance of the polymer – as the percentage of energetic side chain functionalities (% ES) increases.

Bomb Calorimetric Study of a Series of Energetic Linear Polyphosphazenes

Bellamy A. J., Contini A. E., Golding P., Trussell S. J.

Central European Journal of Energetic Materials

2005

Vol. 2, nr 4

23-31

Energetic linear polyphosphazenes are of potential interest as novel binders for energetic formulations. However, the presence of phosphorus in these materials renders their combustion chemistry significantly different to that of conventional binders. This paper explores the combustion chemistry of a series of energetic polyphosphazenes. The heat of combustion of each member of the series has been measured by bomb calorimetry, and the water-soluble combustion products have been identified and ąuantified using NMR Spectroscopy and łon Chromatography. Since some of the combustion products are hydrolytically unstable, it was 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 stabilized product mixtures in order to obtain meaningful values for the heats of combustion and thence heats of formation. The thermochemical measurements themselves were made with pure water in the bomb. The composition and structures of the various polyphosphazenes have been correlated with their heats of combustion and should enable polyphosphazenes with specific thermochemical properties to be identified. The 'combustion' of the polyphosphazenes under a nitrogen atmosphere has also been studied.