reduced the toxicity while increasing the concentration of RDX and improving safety of use and storage. It also opened the way to begin study of new non-explosive low-toxicity plasticisers (esters of dicarboxylic acid) and binder (branched polymers). Discovery Research on a replacement for C-2 was begun prior to 1950, but the new material, new generation of Composition C (number four, C-4), did not begin pilot production until 1956. Properties Since 1960 the mixture of C-4 has contained: 90.0–91.0% of cyclonite (RDX explosives) ~2.1% of polyisobutylene (short chain) ~1.6% of motor oil ~5.3% of di-(2-ethylhexyl)sebacate (dioctyl sebacate), sometimes it was replaced partly by similar compounds such as dioctyl adipate less than 0.6% of water (small amount of marker or odorising taggant) It is less volatile than C-3 and has less tendency to harden at low temperature. It has a density 1.48–1.60g/ml, does not become hard even at −55 °C (−67 °F), and does not exude at +77 °C (171 °F). C4 has a detonation velocity of 8092 m/s (26550 ft/s) at high density and velocity of 7550 m/s (24770 ft/s) at low density 1.48 g/ml. It is so successful that it remains in army service up to the current time without any significant changes. See also Composition C4 Composition B Composition H6 Plasticisers for energetic materials Polymer-bonded explosive RE factor Semtex References Explosives