Vulcanization

VulcanizationMold1941

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Vulcanization is a chemical process for converting rubber or related polymers into more durable materials via the addition of sulfur or other equivalent curatives or accelerators. These additives modify the polymer by forming cross-links (bridges) between individual polymer chains. Vulcanized material is less sticky and has superior mechanical properties than its non-vulcanized counterpart. The term "vulcanization" is derived from Vulcan, the Roman god of fire. The process was discovered in 1839 by the American inventor Charles Goodyear, who found that heating natural rubber with sulfur improved its durability and elasticity.

History

The discovery of vulcanization marked a significant milestone in the industrial use of rubber. Before Goodyear's discovery, rubber products were susceptible to becoming sticky in hot weather and brittle in cold. Goodyear's accidental discovery occurred when he dropped a mixture of rubber and sulfur onto a hot stove, noticing the resulting material's improved properties. This discovery led to the widespread use of rubber in a variety of applications, including tires, seals, and gaskets.

Process

Vulcanization involves heating rubber with sulfur and accelerator chemicals. The process can vary in time and temperature depending on the specific properties desired in the final product. During vulcanization, sulfur atoms form cross-links between chains of the polymer of natural rubber. The amount of sulfur and the conditions of vulcanization significantly affect the properties of the final product, such as its elasticity, strength, and durability.

Types of Vulcanization

There are two main types of vulcanization: sulfur vulcanization and peroxide vulcanization. Sulfur vulcanization is the most common and involves the use of sulfur or sulfur-bearing compounds. Peroxide vulcanization, on the other hand, uses organic peroxides as the cross-linking agent and is used for polymers that do not react well with sulfur.

Applications

Vulcanized rubber has a wide range of applications due to its enhanced properties. It is used in the manufacturing of tires, hoses, belts, matting, and various molded and extruded goods. The automotive industry is one of the largest consumers of vulcanized rubber, particularly for tires.

Environmental and Health Considerations

The vulcanization process, particularly when using certain accelerators, can produce toxic by-products. There is ongoing research into finding safer and more environmentally friendly methods of vulcanization. Recycling vulcanized rubber is also challenging due to the cross-linked nature of the material, which resists many forms of degradation.

See Also

• Rubber
• Charles Goodyear
• Polymer
• Sulfur
• Elastomer