||C-4 is made up of explosives, plastic binder, plasticizer and, usually, marker or taggant chemicals such as 2,3-dimethyl-2,3-dinitrobutane (DMDNB) to help detect the explosive and identify its source.
As with many plastic explosives, the explosive in C-4 is RDX (cyclonite or cyclotrimethylene trinitramine), which makes up around 91% of C-4 by weight. The plasticizer is diethylhexyl or dioctyl sebacate (5.3%) and the binder is usually polyisobutylene (2.1%).
Another plasticizer used is dioctyl adipate (DOA). A small amount of SAE 10 non-detergent motor oil (1.6%) is also added. /Wikipedia 01/06/09/