Sulfurcured

Sulfurcured refers to elastomer materials that have been vulcanized by forming cross-links between polymer chains with sulfur. The process uses elemental sulfur and various accelerators and activators to create covalent sulfur-sulfur bonds between rubber molecules, typically natural rubber or synthetic polyisoprene, though other elastomers can be treated similarly. The resulting network transforms a pliable, tacky polymer into an elastic, heat- and abrasion-resistant material.

In practice, sulfur curing involves mixing the elastomer with elemental sulfur, accelerators, zinc oxide, stearic acid, and other additives, followed by heating to elevated temperatures. Cure time and temperature, as well as sulfur content, control the crosslink density: more sulfur and longer cures yield more cross-links, increasing modulus and heat resistance but reducing elongation and dynamic performance. Cross-links during sulfur vulcanization are primarily polysulfide bridges, whose length and abundance influence properties such as elasticity, strength, and temperature stability. Accelerators shorten cure time and help prevent premature vulcanization or scorching during processing.

Common applications of sulfur-cured elastomers include tires, belts, hoses, seals, and other rubber goods that require robust mechanical properties and durability. Compared with other curing methods, sulfur vulcanization provides a good balance of elasticity, resilience, and processability, making it a standard approach in many rubber systems. Limitations include potential aging due to sulfur–crosslink chemistry, sensitivity to processing conditions (scorch), and challenges related to recycling and devulcanization. The technology dates to the 19th century, with Goodyear’s vulcanization research establishing the foundation for modern sulfur-cured rubber.