Vulcanizing

Vulcanizing is a chemical process that converts natural rubber or related polymers into more durable materials by adding sulfur or other equivalent curatives or accelerators. This process involves heating the rubber with sulfur, typically at temperatures between 150 and 200 degrees Celsius. The sulfur molecules create cross-links between the polymer chains, which significantly alters the material's properties.

Before vulcanization, natural rubber is soft, sticky, and susceptible to temperature changes; it softens when heated and becomes brittle when cooled. Vulcanization makes the rubber stronger, more elastic, and resistant to abrasion and weathering. It also reduces its tackiness and susceptibility to aging. The degree of vulcanization can be controlled to achieve desired properties, from soft and flexible to hard and rigid.

The discovery of vulcanization is credited to Charles Goodyear in 1839. His accidental discovery, when rubber mixed with sulfur fell onto a hot stove, revolutionized the use of rubber. Before vulcanization, rubber had limited practical applications due to its instability. The process opened up a vast array of uses for rubber in industries ranging from automotive tires to footwear and industrial products. Modern vulcanization processes often involve accelerators and activators to speed up the reaction and improve the properties of the final product.