Flash differential scanning calorimetry has been used to cool
TNT at rates q ranging from 0.01K/s to 1000K/s, i.e., a range
of five orders of magnitude. We find three regimes of behavior
upon reheating are observed: q > 100K/s only a glass transition
is observed; 10K/s < q < 100K/s, glass transition, cold crystallization
and melting are observed; 0.1K/s < q < 10K/s, only melting
is observed with no glass transition or cold crystallization. For
the regimes where a glass transition is observed, we have been
able to determine the activation energy of vitrification Eg to be
approximately 290 ± 16 kJ/mol and the dynamic fragility index is
m ∼= 62 ± 6, similar to other small molecule organic liquids. For the
cooling rate between 10K/s and 1000K/s,the Tg (i.e., Tf) varies from
239.3K to 247.5K. These values are significantly lower than prior
estimates in the early TNT literature. Future work is planned to
investigate the influence of the vitrification path on cold crystallization
above the Tg as well as crystallization from the glassy state
itself.
Flash differential scanning calorimetry has been used to coolTNT at rates q ranging from 0.01K/s to 1000K/s, i.e., a rangeof five orders of magnitude. We find three regimes of behaviorupon reheating are observed: q > 100K/s only a glass transitionis observed; 10K/s < q < 100K/s, glass transition, cold crystallizationand melting are observed; 0.1K/s < q < 10K/s, only meltingis observed with no glass transition or cold crystallization. Forthe regimes where a glass transition is observed, we have beenable to determine the activation energy of vitrification Eg to beapproximately 290 ± 16 kJ/mol and the dynamic fragility index ism ∼= 62 ± 6, similar to other small molecule organic liquids. For thecooling rate between 10K/s and 1000K/s,the Tg (i.e., Tf) varies from239.3K to 247.5K. These values are significantly lower than priorestimates in the early TNT literature. Future work is planned toinvestigate the influence of the vitrification path on cold crystallizationabove the Tg as well as crystallization from the glassy stateitself.
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