PLX, or Picatinny Liquid Explosive, is a liquid binary explosive, a mixture of 95% nitromethane (NM) along with 5% ethylene diamine (EDA) as a sensitizer. Other amine compounds can be used instead of of ethylene diamine, such as triethylene tetramine or ethanolamine, but EDA has been found to be most effective. PLX is a fairly powerful high explosive, marginally exceeding the destructive yield of TNT.
PLX, when mixed, is a transparent liquid with a yellowish tint. Both ethylene diamine and nitromethane are very volatile, requiring the contents to be sealed if any storage is intended. Generally, for safety purposes, the contents are transported separately and mixed on site. PLX is known to have a velocity of detonation (VoD) of anywhere between 6,000 and 7,000 m/s, depending on diameter. Although greatly sensitized by the addition of EDA, PLX still requires a powerful blasting cap or a small booster charge to successfully detonate.
PLX was invented during World War II by the Picatinny Arsenal in New Jersey. It was originally designed to clear minefields by being spread via plane over the targeted area or poured from a safe distance and detonated by troops on the ground.
This explosive can also be gelled through the addition of nitrocellulose, ETN, or any number of soluble nitrate esters or gelling agents. This allows for powdered metals, such as aluminum or magnesium, to be suspended in the mixture. The metal powders act as fuel, increasing heat and energy output but lowering the brisance and VoD. The result is a more sustained blast wave and a "push and heave" effect, desirable for thermobaric purposes. Trzciński reports that 200 grams of a mixture of NM with PMMA as gelling agent and AlMg (45:55, mean particle size = 63 microns) as fuel, in a ratio of 67.2/2.8/30 by mass, has a peak overpressure of 120 kPa 2 m from the (open air) blast site, a 1.65 TNT equivalency in peak presure, and a 1.62 equivalency in shockwave impulse.