Effect of Ultraviolet Irradiation on Phase Transformations in HMX Polymorphs

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Abstract
1,3,5, 7-Tetranitro-1,3,5,7-Tetrazacyclooctane, commonly known as HMX in the explosives field, exists in four polymorphic forms.1 During a study of solid phase transitions in these polymorphs of HMX, utilizing Differential Thermal Analysis, we have found that prior irradiation with 2537 Å light causes the β to δ transformation to occur approximately 15°C below the transition point of unirradiated material. Also, a similar but smaller effect, i.e. a decrease of 5°, is observed after irradiation of β-HMX with 3100–3400 Å light which is in the region of the apparent absorption edge. Previous reports of similar effects were not found in the literature.