In the case of pump packing and gaskets you have plenty of options. Synthetic fibers, PTFE (contrary to the previous post, in a filament yarn can be used to about 500 F), Polyamide and Aramid fibers, graphite, and metal based packing are all options. Of course other service factors will help narrow your search for the best product.
What else can you tell us about the application you have in mind? Or, call the your local packing salesperson. The major seal manufacturers have lines of packing as well as many smaller local companies. Call someone from Chesterton, John Crane, Flowserve, Anchor, Green Tweed, or Garlock.