The only kind of expletives I could identify were swear words. Here's a definition:
" Expletive is a single word or short phrase, usually interrupting normal syntax, used to lend emphasis to the words immediately proximate to the expletive. (We emphasize the words on each side of a pause or interruption in order to maintain continuity of the thought.) "

The site has many helpful descriptions and examples.
http://www.virtualsalt.com/rhetoric.htm