Vulcanization is a chemical process used to harden rubber and improve its elasticity and strength. The process involves the formation of cross-links between sections of polymer chain, which results in increased rigidity and durability, as well as other changes in the mechanical and electrical properties of the material. Vulcanization is generally irreversible, and most rubber products are vulcanized as this massively improves their lifespan, function, and strength.

The most common vulcanizing methods depend on sulfur, which is a slow vulcanizing agent by itself. Accelerated vulcanization is carried out using various compounds that modify the kinetics of crosslinking; this mixture is often referred to as a cure package. The main polymers subjected to sulfur vulcanization are polyisoprene (natural rubber) and styrene-butadiene rubber (SBR), which are used for most street-vehicle tires.

Vulcanization techniques can vary, but they usually involve mixing crude rubber or other elastomeric materials with 5-30% sulfur or other agent (to elicit a cross-linking reaction) with an activator, accelerator, and retarder to form a cross-linked molecular network. Vulcanized rubber is much stronger than traditional rubber, can withstand greater pressure and stress, and is much more elastic, which is why many manufacturers prefer using vulcanized rubber in their products.

Some examples of products made from vulcanized rubber include rubber hoses, shoe soles, toys, erasers, hockey pucks, shock absorbers, conveyor belts, vibration mounts/dampers, insulation materials, tires, and bowling balls. Vulcanized rubber is used in a variety of different products, many of which are extremely common and which people use every day within their homes.