Vulcanization or vulcanisation is a chemical process for converting natural rubber or related polymers into more durable materials via the addition of sulfur or other equivalent curatives or accelerators. These additives modify the polymer by forming cross-links (bridges) between individual polymer chains. Vulcanized materials are less sticky and have superior mechanical properties. The term vulcanized fibre refers to cellulose that has been treated in a zinc chloride solution to cross-link the cellulose fibers.