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How does sulfur vulcanization change the properties of synthetic rubber?
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major industrial polymers
Figure 1: The linear form of polyethylene, known as high-density polyethylene (HDPE).
Sulfur vulcanization is a chemical process that significantly improves the physical properties of synthetic rubber by creating a stable molecular network.1
When rubber is heated with sulfur, the sulfur atoms form chemical cross-links, or bridges, between the long-chain polymer molecules. This transformation provides several key benefits:12
- Enhanced Durability: The process increases the material's tensile strength and its resistance to abrasion and swelling.1
- Thermal Stability: By permanently tying the molecules together, vulcanization prevents the rubber from flowing or becoming soft and sticky when warm.2
- Improved Elasticity: The cross-links ensure the material remains elastic and resilient across a wider range of temperatures.12
- Prevention of Hardening: The addition of sulfur creates enough molecular irregularity to impede crystallization, which prevents the rubber from becoming hard and brittle at low temperatures.2
Because the molecules are covalently interlinked, the resulting solid will not dissolve in compatible solvents, making it a more robust and useful material for industrial applications.2