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PLX, or Picatinny Liquid Explosive, is a liquid binary explosive, a mixture of 95% nitromethane (NM) and 5% ethylene diamine (EDA). Other amine groups can be used in replacement of ethylene diamine, such as triethylene tetramine or ethanolamine. While the previously mentioned amines, as well as many others, sensitize NM quite well, ethylene diamine has been found to be most effective.
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 should be transported separately and mixed on site. PLX is known to have a VoD of anywhere between 6,000 - 7,000 m/s, depending on diameter. Although greatly sensitized by the addition of EDA, PLX still requires a powerful blasting cap if not a small booster charge to successfully detonate.
Uses and Discovery
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 the use of an addition powdered metal fuel such as aluminum or magnesium to be suspended in the mixture. The addition of metal powders increases heat/energy output but lowers brisance and VoD, creating a more sustained blast wave and a push and heave effect, desirable for thermobaric purposes. Trzcinski reports that a 200 g charge of NM/PMMA (gelling agent)/AlMg (45:55, mean particle size = 63 microns) 67.2/2.8/30 (by mass) has a peak overpressure of 120 kPa 2 m from the (open air) blast site, 1.65 TNT equivalency in peak presure and 1.62 equivalency in shockwave impulse. PLX is a fairly powerful High Explosive, marginally exceeding the destructive yield of TNT.
Sensitizing of Nitromethane
It is known that the amine groups (nitrogen atom bonded to carbon and or hydrogen exhibiting a valence pair of electrons) are responsible for the sensitization of nitromethane, chemical formula CH3NO2. It is thought that the amine weakens the C-N bond in the nitromethane, resulting in less energy being needed to break the bond, thus detonation.