“Casting TNT As an Explosive”, Thomas M. Klapötke2023-09-28 (science)⁠:

Few explosives are better-known to non-chemists than trinitrotoluene (TNT). Thomas M. Klapötke reflects on the enduring appeal of TNT and whether its starring role as an explosive is nearing its end.

…It is 160 years since the discovery of TNT in 1863 by Julius Wilbrand… the annual industrial production of TNT by Europe’s biggest producer NITRO-CHEM (based in Poland) has increased to 5,000 tonnes per year. Even so, it is still predominantly used by the military.

…Despite its lower performance, TNT is still widely used today, largely thanks to its low melting point (80℃) and much higher decomposition temperature (295℃), which make it an excellent melt-cast explosive³. Melt-cast explosives are a sub-class of secondary explosives that can be melted at moderate temperatures (80–100℃) and poured into a form to cool and solidify without decomposition or detonation occurring. Such a process is not possible with many of the aforementioned pure compounds…Even without best-in-class metrics, TNT’s utility propels its use into worldwide recognition.

However, the long reign of TNT as the melt-cast explosive par excellence may be reaching its end. Increasingly, the environmental impacts of not only TNT and its metabolites, but also of nitrated by-products in its production, have been a cause for concern⁶.

…One candidate vying to replace TNT is 2,4-dinitroanisole (DNAN or DNAs)…yet its explosive performance (detonation velocity = 5,960 m s⁻¹)⁵ is far below modern standards…Sabatini et al 2018 recently discovered one of the most promising possible TNT replacements, namely 5,5′-bis-(1,2,4-oxadiazole)-3,3′-bismethylene dinitrate (BODN).

…The field remains wide open for a successor to TNT, but before TNT becomes consigned to the history books, any challenger must fulfil stringent specifications: detonation velocity above 7,600 m s⁻¹, density above 1.76 g cm⁻³, melting point in the region of 80–100℃, but decomposing not below 180℃, low sensitivity to impact (>10 J), friction (>120 N) and electrostatic discharge (>700 mJ), as well as—crucially—an economic industrial-scale synthesis and much lower toxicity, mutagenicity and cytotoxicity than that of TNT3. Until then, TNT will continue its explosive reign.