C4 explosives

C-4
Inserting blasting caps into blocks of C-4 explosive
Type	High-yield chemical explosive
Place of origin	United Kingdom
Service history
Used by	United States
Wars	Vietnam War War on Terror
Production history
Designed	1956
Produced	1956–current
Variants	PE-4, M112
Specifications (M112)
Weight	1.25 lb (0.57 kg)
Length	11 in (28 cm)
Width	2 in (5.1 cm)
Height	1.5 in (3.8 cm)
Filling	RDX
Filling weight	91%
Detonation mechanism	PETN-based detonating cord
Blast yield	High

C-4 or Composition C-4 is a common variety of the plastic explosive family known as Composition C. A similar British plastic explosive, based on RDX but with different plasticizer than Composition C-4, is known as PE-4 (Plastic Explosive No. 4). C-4 is composed of explosives, plastic binder, plasticizer to make it malleable, and usually a marker or odorizing taggant chemical.

C-4 has a texture similar to modeling clay and can be molded into any desired shape. C-4 is stable and an explosion can only be initiated by a shock wave from a detonator.

The Composition C-4 used by the United States Armed Forces contains 91% RDX ("Research Department Explosive", an explosive nitroamine), 5.3% dioctyl sebacate (DOS) or dioctyl adipate (DOA) as the plasticizer (to increase the plasticity of the explosive), 2.1% polyisobutylene (PIB, a synthetic rubber) as the binder, and 1.6% of a mineral oil often called "process oil." Instead of "process oil," low-viscosity motor oil is used in the manufacture of C-4 for civilian use.

The British PE4 consists of 88.0% cyclonite, 1.0% pentaerythrite dioleate and 11.0% DG-29 lithium grease (corresp. to 2.2% lithium stearate and 8.8% paraffin oil BP); a taggant (2,3-dinitro-2,3-dimethylbutane, DMNB) is added at a minium of 0.10% weight of the plastic explosive, typicaly at 1.0% mass. The newer PE7 consists of 88.0% cyclonite, 1.0% DMNB taggant and 11.0% of a plasticizer composed of low molecular mass hydroxyl-terminated polybutadiene, along with an antioxidant and an agent preventig hardening of the binder upon prolonged storage. The PE8 consists of 86.5% cyclonite, 1.0% DMNB taggant and 12.5% of a binder composed of di(2-ethylhexyl) sebacate thickened with high molecular mass polyisobutylene.