PBX (explosive)

First developed in 1947 at Los Alamos Scientific Laboratory, plastic bonded explosives (PBX) were intended to make the high-explosive components of nuclear weapons have "adequate energy content, mechanical properties, sensitivity, and chemical stability required for stockpile[d] nuclear weapons. The first was PBX-9205, a mixture of RDX explosive and polystyrene binder. In the U.S. nuclear program, responsibility for PBX development later moved to Lawrence Livermore National Laboratory.

Key to a PBX is the polymer coating, in the range of 5-20% of the total weight, that bonds the explosive granules into a solid, stable mass. Plastic bonding decreases sensitivity to accidental explosion, but does not eliminate it, or pass the one-point safe criterion in weapons, unless the explosive(s) are designated as insensitive high explosives. Two main explosives were used in the late 1990s, RDX and TATB; only TATB is insensitive.

Choice of polymer, and of the bonding technique, involves both careful design, and continued verification through the production and storage phases. "Too brittle a PBX can sustain damage in normal handling and succumb to extreme temperature swings or thermal shocks, while too soft a PBX may be susceptible to creep and may lack dimensional stability or strength."

PBXs have other applications than the implosion systems of fission devices, although those are the most critical. They are used in slapper detonators that initiate the main implosion system. PBXs have been used for explosive welding and precision cutting. They can be used as rocket propellants, and the feasibility of their disposal through cryocracking is superior to that of other large solid rocket propellants.