N-Phenyl-4-biphenylamine is primarily used as an antioxidant in the rubber and polymer industries. It helps in preventing the degradation of materials caused by oxidation, thereby extending their lifespan and maintaining their mechanical properties. This chemical is particularly effective in stabilizing synthetic rubbers and plastics, making it valuable in the production of tires, seals, and other rubber products exposed to high temperatures and oxidative environments. Additionally, it finds application in lubricants and oils, where it inhibits oxidation and reduces the formation of sludge and deposits, ensuring smoother operation and longer service life of machinery. Its use in these applications contributes to enhanced durability and performance of various industrial and consumer products.