Hydrogenated Polyisobutene (HPI) is a synthetic, high-purity saturated hydrocarbon polymer derived from the hydrogenation of polyisobutene, a homopolymer of isobutylene. As a versatile emollient and non-aqueous viscosity-increasing agent, it is widely used in cosmetics as an alternative to natural squalane and light mineral oils, prized for its stable, non-oxidizing nature and exceptional skin compatibility. Its chemical structure—saturated, highly branched, and cyclic-free—enables it to mimic the skin's natural sebum, delivering a feather-light, non-greasy silkiness while reinforcing the skin's barrier against moisture loss.