Plastic explosive (or plastique) is a specialised form of explosive material. They are soft and hand malleable and may have the added benefit of being usable over a wider temperature range then the pure explosive. Plastic explosives are especially suited for explosive demolition as they can be easily formed into the best shapes for cutting structural members, and have a high enough velocity of detonation and density for metal cutting work. They are generally not used for ordinary blasting as they tend to be significantly more expensive than other materials that perform just as well in that field. Also, when an explosive is bound in a plastique, it's power is generally lower than when it is pure.
One of the earliest plastic explosives was Nobel 808, developed well before World War II and used extensively by SOE during that war. During and just after World War II a number of new RDX based explosives were developed, including Compositions C, C2, and eventually C3. Together with RDX these incorporated various plasticisers to decrease sensitivity and make the composition plastic.
C3 was very effective but proved to be too brittle in cold weather. In the sixties it was replaced by C4, also using RDX but with polyisobutylene and di(2-ethylhexyl)sebacate as the binder and plasticizer.
Varieties include C-4, PENO and Semtex.
Compare to Polymer-bonded explosive.