Caoutchoucs

Caoutchoucs are natural rubbers obtained from the latex of tropical trees, most importantly Hevea brasiliensis. They are elastomeric polymers, dominantly cis-1,4-polyisoprene, with small amounts of proteins, lipids, and minerals that influence properties and allergenicity. The latex is tapped from trees, coagulated with acids, and processed into sheets or blocks, which are dried or smoked. Most caoutchoucs are vulcanized with sulfur or other agents to create cross-links between polymer chains, markedly improving strength, elasticity, and heat resistance.

Etymology and scope: The term caoutchouc comes from French, itself borrowed from indigenous South American languages. In English, the material is usually called natural rubber, with caoutchoucs referring to the natural variants. The category also includes different grades and forms derived from latex, such as block or sheet rubber.

Production and processing: After harvesting, latex is collected as a milky suspension, coagulated to form solid masses, then worked into sheets or blocks. Sheets may be dried, smoked, washed, and calendered. Vulcanization, typically with sulfur, introduces cross-links that stabilize the material and extend its usable temperature range and durability. Additives can modify properties for specific applications.

Uses and properties: The dominant application is tires, but caoutchoucs also serve in hoses, belts, seals, footwear, and medical gloves. Natural rubber offers excellent elasticity and grip, low heat buildup, and good abrasion resistance, but is susceptible to ozone and aging, and can provoke latex allergies in some people.

Global context: Production has shifted from historically Brazil to major Southeast Asian producers such as Thailand, Indonesia, and Malaysia, with ongoing concerns about sustainability, land use, and competition from synthetic rubbers.