The stuff in disposable diapers is sodium polyacrylate. If you really want to use it it is sold separately by the bag. I would guess, but don't know, that it would be cheaper that way than buying diapers to rip up so you might want to do a price comparison. If you do a Google search on sodium polyacrylate msds you'll get some Material Safety Data Sheets for it which may help your decision whether or not to use it.
