Used primarily as a key intermediate in the synthesis of perfluorooctanesulfonic acid (PFOS) and other fluorinated compounds. Widely applied in the production of surfactants, surface treatments, and fire-fighting foams due to its ability to lower surface tension and resist heat, oil, and water. Also utilized in specialty polymers and coatings requiring extreme durability and chemical resistance. Its use has declined in recent years due to environmental persistence and toxicity concerns.