I. Sulfur: The Chemical Backbone of Vulcanization
The industrial importance of elemental sulfur in the rubber industry is derived from its unique ability to form cross-links between polymer chains, transforming raw elastomer into a durable, heat-resistant material.
1. The Molecular Mechanism (Sulfur Bridges)
In its raw state, rubber molecules are long chains that slide past each other easily. When sulfur is introduced under heat (140°C - 160°C), it breaks the double bonds in the rubber hydrocarbon. This creates sulfidic bridges (mono, di, or poly-sulfidic) that lock the chains together.
- Sulfur Content: Typically ranges from 1.5% to 3% for soft rubber.
- Reaction Speed: Accelerated by zinc oxide and fatty acids to ensure efficiency.
2. Advanced Vulcanization Systems
Not all sulfur vulcanization is the same. The ratio of Sulfur to Accelerators determines the aging properties of the rubber:
• Conventional Vulcanization (CV): High sulfur, low accelerator. Provides excellent initial physical properties but poor heat resistance.
• Efficient Vulcanization (EV): Low sulfur, high accelerator. Results in mainly monosulfidic links, providing superior heat and oxidation resistance.
3. Industrial Impact & Purity Hubs
Just like high-purity silica in the South Sinai Region, the purity of sulfur is critical. Impurities can lead to "blooming" (white powder on the surface) or weak spots in the tire structure.
Key Benefits of Optimized Sulfur Vulcanization:
| Property | Enhancement |
|---|---|
| Tensile Strength | Increased by 500% compared to raw rubber. |
| Elasticity | Remains stable across a wide temperature range. |
| Solubility | Reduced swelling in organic solvents. |
