Do cables frequently fail in high-temperature or heavy-load environments? This is likely due to improper selection of the cross-linking process for the cable sheath material. Failing to choose the correct cross-linking method tailored to the cable's requirements and characteristics not only compromises cable performance but also jeopardizes the reliability and safety of the operating environment.
This article compares peroxide crosslinking and silane crosslinking technologies, analyzes their performance differences, and provides targeted selection recommendations based on voltage ratings, operating environments, and cost factors.
In cable manufacturing, scorch risks and extended crosslinking curing cycles are common concerns for manufacturers. Both crosslinking methods have distinct advantages and disadvantages in terms of process complexity, cost, and final performance—differences that directly determine cable quality.
Peroxide Crosslinking: Activates free radicals at high temperatures to achieve rapid and stable molecular bonding, imparting excellent heat resistance to cables.
Silane Crosslinking: Forms crosslinked structures under mild conditions via grafting reactions and moisture curing, minimizing scorch risk while retaining certain thermoplastic processing characteristics.
The process relies on organic peroxides decomposing at 160–200°C to generate free radicals. These radicals abstract hydrogen atoms from polymer chains, subsequently reorganizing into a three-dimensional crosslinked network that firmly locks molecular segments. This network structure enables the material to maintain melt resistance even above its average melting point.
During extrusion at 100–120°C, vinyl silanes are grafted onto the polymer backbone. Post-extrusion, air or moisture triggers hydrolysis of the silane groups. The resulting silanols condense into siloxane bonds within hours at 30–80°C, progressively forming a crosslinked network to achieve curing.
Requires processing at elevated temperatures of 170–200°C, followed by steam or hot water curing for a minimum of 30 minutes at the same temperature. This necessitates dedicated crosslinking extrusion equipment and curing lines at cable plants. Premature peroxide decomposition readily causes scorch marks, gel spots, or surface defects on extruded cables.
Can be extruded on standard thermoplastic production lines at 100–120°C. After forming, cables require curing for 6–48 hours in water baths or ambient air environments. Due to lower temperatures and absence of peroxide-generated odors, equipment requirements are relatively modest. However, extended curing times increase production duration and storage demands.
Widely used in medium- and high-voltage power cables, capable of sustained operation at 90°C and short-term overloads up to 250°C. Its high crosslink density and uniform network structure are particularly crucial for controlled electric field grading and water tree resistance.
Primarily used in medium- and low-voltage distribution cables, building wiring, and flexible cables. This method balances performance, cost, and equipment simplification, suitable for applications rated at 90°C continuous operation and 200°C short-term peaks.
Crosslinking methods directly impact cable durability.
Thermal stability, dielectric strength, and mechanical flexibility all depend on crosslink network density and chemical bond type.
Demonstrates exceptional thermal stability at elevated temperatures, maintaining over 80% dielectric strength even after decades of continuous operation at 90°C.
Though featuring slightly lower crosslink density, it offers outstanding flexibility with minimal scorch risk, ensuring reliable performance in medium- and low-voltage cable applications.
| Properties | Peroxide crosslinking | Silane crosslinking |
| Curing temperature | 160–200℃ | 30–80℃(grafting at 100–120℃) |
| Curing time | 30–60 minutes | 6–48 hours |
| Equipment | Requires specialized curing oven | Standard thermoplastic processing equipment |
| Risk of burns | High temperature risk in case of runaway reaction | Low |
| Heat resistance rating | 90℃ continuous, 250℃peak | 90℃ continuous, 200℃ peak |
| Cost considerations | Higher initial investment, but faster curing | Low capital investment, long processing cycle |
PE-Xa: Continuous operating temperature 90°C, short-circuit resistance temperature 250°C, crosslink density with gel content 70-80%, exhibiting extremely high creep resistance and thermal deformation resistance.
PE-Xb: Continuous operating temperature 90°C, peak temperature resistance 200–225°C, gel content 30–50%, moderate network rigidity. Compared to PE-Xa, it resists thermal aging and water trees, though slight creep may occur under prolonged stress.
PE-Xa: Maintains dielectric strength above 80% after 20 years of stress testing at 90°C. Exhibits strong resistance to partial discharge and water treeing, with stable dielectric constant and loss.
PE-Xb: Dielectric strength remains stable above 20kV/mm. Retains over 70% performance after aging. Silane crosslinking structure reduces charge trapping and ensures smooth magnetic field distribution in medium-voltage cables.
PE-Xa: Tensile strength >20 MPa, elongation at break >200%. High abrasion resistance but moderate flexibility, potentially limiting installation at small bending radii.
PE-Xb: Tensile strength 15–18 MPa, elongation at break >300%. Superior flexibility and impact resistance, facilitating easier installation in confined spaces.
| Properties | PE-Xa (peroxide-crosslinked) | PE-Xb (Silane crosslinked) |
| Gel content | 70–80% | 30–50% |
| Continuous temperature | 90℃ | 90℃ |
| Short-circuit resistance | 250℃ | 200℃ |
| Dielectric strength | >80% after 20 years of storage at 90℃ | >70% after similar aging treatment |
| Tensile strength | >20MPa | 15–18MPa |
| Elongation at break | >200% | >300% |
| Flexibility | Moderate | High |
When designing and manufacturing cables, cable manufacturers must select crosslinking materials based on the cable's specific characteristics.
Choosing a crosslinking method requires balancing performance, manufacturing efficiency, and cost. Key decision factors include voltage rating, operating environment, production scale, and budget.
High-voltage transmission: Prioritize peroxide crosslinking due to its high crosslink density, superior heat resistance, and strong fault tolerance.
Medium/Low-Voltage Distribution: Silane crosslinking offers better cost-effectiveness, lower equipment requirements, and reduced scorch risk.
Flexible or Thin-Wall Cables: Silane crosslinking or EB radiation crosslinking are suitable, providing high flexibility and low odor.
Specialty or Medical Cables: EB radiation crosslinking leaves no chemical residues, ensures a clean process, and allows precise control over crosslinking density.
Mass production: Silane crosslinking leverages conventional production lines for higher efficiency.
Cables with extreme performance requirements: Peroxide crosslinking or EB radiation crosslinking deliver optimal network density and performance assurance.
| Applications | Recommended methods: | Reasons: |
| High-voltage power transmission | Peroxide crosslinking | Highest heat/failure tolerance |
| Medium and low-voltage power distribution | Silane crosslinking | Low scorch marks, simple equipment, balanced cost |
| Flexible/thin-profile cables | Silane or EB | High flexibility, low odor |
| Specialized/medical applications | EB radiation | Clean, precise control, no residue |
| High-volume production | Silane | Thermoplastic production line, high output |
| High-performance requirements | Peroxide or EB | Maximum network density, superior performance |
Conclusion
The appropriate crosslinking method enables cables to deliver optimal performance across diverse applications.
For applications demanding extreme heat resistance and high-voltage reliability, peroxide crosslinking is the preferred choice.
When prioritizing cost, flexibility, and processing convenience, silane crosslinking offers an ideal solution.
In scenarios requiring stringent cleanliness and precision, EB radiation crosslinking stands as the optimal selection.
Through proper selection, cables can achieve the optimal balance between safety, longevity, and cost-effectiveness.
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