Polyduranide is a metallic material used for construction purposes during the 24th century.
In 2368, after the USS Enterprise-D had been hit by a quantum filament, an energy conduit ruptured and ignited the polyduranide inside a cargo bay bulkhead, causing a plasma fire. (TNG: "Disaster")
Baseball bats in the 2370s were composed of polyduranide. Kasidy Yates' brother's team, the Pike City Pioneers, played in a league that had decided to use wooden baseball bats instead. (DS9: "Family Business")
On a larger scale, the hulls of Trabe starships, later Kazon fighters, were composed of a polyduranide alloy, an alloy not used in the construction of Federation spacecraft. (VOY: "Initiations")
In 2374, Harry Kim asked Tom Paris to replicate some polyduranide golf clubs for him, for his rematch with Ensign Kaplan. (VOY: "Vis à Vis")