PETN or
Pentaerythritol Tetranitrate is an explosive used in a variety of
military and
civilian applications. It's primarily found in
Primacord, an explosive fuse that looks like
clothesline. PETN is not very shock sensitive, and is usually
detonated by an explosive
blasting cap. Traces of
PETN were supposedly found on pieces of
TWA flight 800, leading some to suspect that the
plane was brought down with a
bomb.
PETN is also used as a vasodilator to treat people who have chest pain. It's usually mixed with lactose.