What is the Continuous Vulcanization (CV) Tube: Peroxide, Sulfur, and Ozone?

Continuous Vulcanization (CV) using the steam curing method is an integral process for cross-linking polymer insulation in cables. By utilizing different cross-linking mechanisms—peroxide, sulfur, and ozone curing—the CV system achieves versatile applications across various industries. Below is a detailed exploration of these three curing systems integrated into the CV process.

1. Peroxide Curing in CV Systems

Peroxide curing is a common method used for cross-linking elastomers, such as rubber-based insulation, in cable production. The process relies on peroxide decomposition to generate free radicals that initiate cross-linking.

Mechanism

1. Initiation:
Peroxide (e.g., dicumyl peroxide, DCP) decomposes under high-temperature steam in the CV tube:
ROOR → 2·R
Free radicals form reactive sites on the polymer chain.

2. Propagation:
These radicals react with elastomer chains to create covalent bonds:
Rubber· + Rubber· → Rubber-Rubber (Cross-Linking)

Applications
- Power Cables: MV and HV cross-linked polyethylene (XLPE) insulated cables.
- Submarine Cables: Provides high thermal stability and mechanical strength.

Advantages
- Uniform cross-linking across the entire cable.
- High thermal resistance of the final product.
- Compatibility with large-scale manufacturing.

2. Sulfur Curing in CV Systems

Sulfur curing is widely used for elastomeric compounds, such as rubber-based insulation in flexible cables. This method forms sulfur bridges between polymer chains, enhancing elasticity and durability.

Mechanism

1. Activation:
Sulfur and accelerators react under heat, generating reactive sulfur species.
2. Cross-Link Formation:
Sulfur forms bridges (polysulfide links) between polymer chains:
Rubber + Sulfur → Rubber-S-S-Rubber

Applications
- Flexible Cables: Mining cables, automotive wiring, and industrial hoses.
- Abrasion-Resistant Products: Rubber sheathing and seals.

Advantages
- Excellent elasticity and mechanical strength.
- Cost-effective for elastomer-based materials.

Challenges
- Lower thermal resistance compared to peroxide curing.
- Residual sulfur by-products require proper management.

3. Ozone Curing in CV Systems

Ozone curing is an eco-friendly alternative to traditional cross-linking methods. It uses ozone gas (O₃) to initiate cross-linking reactions, particularly in elastomers with unsaturated bonds.

Mechanism
1. Ozone Reaction:
Ozone reacts with PE to form reactive intermediates, which initiate cross-linking:
PE + O₃ → PE-O₃ → PE-PE (Cross-Linking)

2. Cross-Link Formation:
Reactive intermediates decompose, creating covalent bonds between polymer chains.

Applications
- Environmental Coatings: Ozone-resistant materials for outdoor use.
- Specialty Wires: Non-toxic, residue-free cables for medical and sensitive applications.

Advantages
- No chemical cross-linking agents needed.
- Eco-friendly with no harmful residues.
- Operates at lower temperatures, making it suitable for heat-sensitive materials.

Challenges
- Limited to unsaturated polymers (e.g., natural rubber).
- Requires specialized ozone generation and handling systems.

As Result

The integration of peroxide, sulfur, and ozone curing in Continuous Vulcanization (CV) systems offers a versatile approach to cable manufacturing. Peroxide curing dominates power cable production due to its high thermal stability, sulfur curing is essential for flexible and durable rubber products, and ozone curing provides a sustainable alternative for eco-sensitive applications. By combining these methods, the CV process can cater to a wide range of industrial and environmental needs.