vulkanizasyon

Vulkanizasyon, or vulcanization, is a chemical process by which the polymer chains in rubber are cross-linked to form a three-dimensional network. The process increases elasticity, strength, heat resistance, and chemical stability, allowing rubber to return to its original shape after deformation. It is commonly achieved by heating natural or synthetic rubber with sulfur and accelerators, in the presence of activators and fillers. The term is often used in Turkish as vulkanizasyon.

History: The process was discovered by Charles Goodyear in 1839, when he heated rubber with sulfur. The name derives from Vulcan, the Roman god of fire, reflecting the heat-driven chemistry. Early methods were inconsistent, but improvements in catalysts and formulation enabled practical manufacturing.

Mechanism: Sulfur atoms form cross-links (polysulfide or disulfide bridges) between adjacent polymer chains, transforming the viscous polymer into a resilient network. The degree of cross-linking governs stiffness, elasticity, and heat resistance. Most rubbers use accelerators such as zinc oxide and organic accelerators to speed vulcanization and tailor properties; sometimes sulfur-donors are used. Peroxide vulcanization is an alternative that creates carbon–carbon cross-links, beneficial for certain weathering and heat performance. Special forms, such as dynamic vulcanization, are used to produce thermoplastic elastomers.

Process and parameters: Vulcanization typically occurs at 140–180°C, with curing times varying by formulation, thickness, and equipment. Under-curing yields tacky or weak material; over-curing can cause brittleness and loss of elasticity.

Applications: The technique underpins modern tire production and is widely used to manufacture belts, hoses, gaskets, seals, footwear soles, and many molded rubber goods.

Environmental aspects: Vulcanization consumes energy and involves additives that require handling and controls for emissions and worker safety. Recycling and alternative curing systems are areas of ongoing development.