How does cross-linked polyolefin insulated wire improve the insulation performance and mechanical strength of conductors?
Release Time : 2026-02-18
In modern buildings, rail transportation, new energy, and fire protection power systems with extremely high requirements for safety and reliability, cross-linked polyolefin insulated wire is gradually replacing traditional PVC or ordinary polyethylene cables. Its core advantages lie not only in its environmentally friendly characteristics of being "halogen-free, low-smoke, and flame-retardant," but also in the significant improvement in the electrical performance and mechanical strength of the insulation layer through electron beam irradiation cross-linking technology.
1. Electron Beam Irradiation: A Structural Leap from Linear to Three-Dimensional Network
The basic raw material for cross-linked polyolefins is usually ethylene-propylene copolymer or other modified polyolefins, which initially have a linear polymer chain structure, easily softening under heat and having limited mechanical strength. During manufacturing, after the conductor is extruded, it enters the electron accelerator irradiation zone. The high-energy electron beam penetrates the insulation layer, generating a large number of free radicals. These free radicals rapidly recombine at room temperature, forming stable C–C covalent bonds between adjacent molecular chains, constructing a dense three-dimensional network cross-linked structure. This structural transformation fundamentally alters the material's physicochemical properties: the originally thermoplastic polyolefin becomes a thermosetting material, no longer melting and flowing, significantly improving its heat resistance while greatly enhancing tensile strength, abrasion resistance, and creep resistance.
2. Comprehensive Improvement in Insulation Performance: Voltage Resistance, Tracking Resistance, and Volume Resistivity
The cross-linked polyolefin molecular network is more uniform and dense, reducing micropores and impurity migration channels, thus effectively suppressing electric field concentration and partial discharge, far exceeding that of ordinary PVC. This means that leakage current is extremely low under the same voltage, resulting in higher insulation reliability. Furthermore, the cross-linked structure enhances the material's resistance to electrical treeing and water treeing—major causes of insulation failure under high voltage or humid environments. More importantly, under fire or high-temperature conditions, cross-linked polyolefins do not release corrosive gases like halogen-containing materials; the carbonized layer formed on its surface still possesses a certain degree of insulation, helping to maintain circuit integrity and meeting the stringent standard of "90 minutes of uninterrupted power supply" for fire-fighting circuits.
3. Synergistic Enhancement of Mechanical Strength: Tensile Strength, Impact Resistance, and Dimensional Stability
The three-dimensional cross-linked network acts like a "molecular steel mesh" within the material, significantly improving the tensile strength and elongation at break of the insulation layer. This makes it less prone to cracking or damage during laying bends, pipe pulling, or equipment vibration. Simultaneously, the cross-linked structure restricts molecular chain slippage, greatly reducing the material's coefficient of thermal expansion and cold flow tendency, ensuring dimensional stability across a wide temperature range of -40℃ to +125℃. This prevents delamination of the insulation layer from the conductor or stress concentration due to thermal expansion and contraction. Furthermore, the localized pressure generated during zinc alloy or metal sleeve crimping is less likely to cause crushing or permanent deformation of the cross-linked polyolefin insulation layer, ensuring end sealing and electrical safety.
4. Green Process Support: No Chemical Residue, Purer Performance
Compared to traditional peroxide chemical cross-linking, electron beam irradiation is a physical cross-linking process, eliminating the need for cross-linking agents, catalysts, or byproduct removal procedures. This not only avoids the potential degradation of insulation performance by chemical residues but also results in a purer material composition, further improving dielectric strength and long-term aging stability. Meanwhile, this process can be carried out at room temperature, is energy-efficient, and aligns with the concept of green manufacturing.
In summary, cross-linked polyolefin insulated wire, through electron beam irradiation-induced molecular cross-linking, achieves a dual leap in insulation performance and mechanical strength without sacrificing flexibility. This "structure determines performance" technological approach makes it an ideal choice for safe, reliable, and long-life operation in high-end buildings, emergency systems, and harsh industrial environments.
1. Electron Beam Irradiation: A Structural Leap from Linear to Three-Dimensional Network
The basic raw material for cross-linked polyolefins is usually ethylene-propylene copolymer or other modified polyolefins, which initially have a linear polymer chain structure, easily softening under heat and having limited mechanical strength. During manufacturing, after the conductor is extruded, it enters the electron accelerator irradiation zone. The high-energy electron beam penetrates the insulation layer, generating a large number of free radicals. These free radicals rapidly recombine at room temperature, forming stable C–C covalent bonds between adjacent molecular chains, constructing a dense three-dimensional network cross-linked structure. This structural transformation fundamentally alters the material's physicochemical properties: the originally thermoplastic polyolefin becomes a thermosetting material, no longer melting and flowing, significantly improving its heat resistance while greatly enhancing tensile strength, abrasion resistance, and creep resistance.
2. Comprehensive Improvement in Insulation Performance: Voltage Resistance, Tracking Resistance, and Volume Resistivity
The cross-linked polyolefin molecular network is more uniform and dense, reducing micropores and impurity migration channels, thus effectively suppressing electric field concentration and partial discharge, far exceeding that of ordinary PVC. This means that leakage current is extremely low under the same voltage, resulting in higher insulation reliability. Furthermore, the cross-linked structure enhances the material's resistance to electrical treeing and water treeing—major causes of insulation failure under high voltage or humid environments. More importantly, under fire or high-temperature conditions, cross-linked polyolefins do not release corrosive gases like halogen-containing materials; the carbonized layer formed on its surface still possesses a certain degree of insulation, helping to maintain circuit integrity and meeting the stringent standard of "90 minutes of uninterrupted power supply" for fire-fighting circuits.
3. Synergistic Enhancement of Mechanical Strength: Tensile Strength, Impact Resistance, and Dimensional Stability
The three-dimensional cross-linked network acts like a "molecular steel mesh" within the material, significantly improving the tensile strength and elongation at break of the insulation layer. This makes it less prone to cracking or damage during laying bends, pipe pulling, or equipment vibration. Simultaneously, the cross-linked structure restricts molecular chain slippage, greatly reducing the material's coefficient of thermal expansion and cold flow tendency, ensuring dimensional stability across a wide temperature range of -40℃ to +125℃. This prevents delamination of the insulation layer from the conductor or stress concentration due to thermal expansion and contraction. Furthermore, the localized pressure generated during zinc alloy or metal sleeve crimping is less likely to cause crushing or permanent deformation of the cross-linked polyolefin insulation layer, ensuring end sealing and electrical safety.
4. Green Process Support: No Chemical Residue, Purer Performance
Compared to traditional peroxide chemical cross-linking, electron beam irradiation is a physical cross-linking process, eliminating the need for cross-linking agents, catalysts, or byproduct removal procedures. This not only avoids the potential degradation of insulation performance by chemical residues but also results in a purer material composition, further improving dielectric strength and long-term aging stability. Meanwhile, this process can be carried out at room temperature, is energy-efficient, and aligns with the concept of green manufacturing.
In summary, cross-linked polyolefin insulated wire, through electron beam irradiation-induced molecular cross-linking, achieves a dual leap in insulation performance and mechanical strength without sacrificing flexibility. This "structure determines performance" technological approach makes it an ideal choice for safe, reliable, and long-life operation in high-end buildings, emergency systems, and harsh industrial environments.