(1) Cross-Linked Low Smoke Zero Halogen Polyethylene (XLPE) Insulation Material:
XLPE insulation material is produced by compounding polyethylene (PE) and ethylene vinyl acetate (EVA) as the base matrix, along with various additives such as halogen-free flame retardants, lubricants, antioxidants, etc., through a compounding and pelletizing process. After irradiation processing, PE transforms from a linear molecular structure into a three-dimensional structure, changing from a thermoplastic material to an insoluble thermosetting plastic.
XLPE insulation cables have several advantages compared to ordinary thermoplastic PE:
1. Improved resistance to thermal deformation, enhanced mechanical properties at high temperatures, and improved resistance to environmental stress cracking and thermal aging.
2. Enhanced chemical stability and solvent resistance, reduced cold flow, and maintained electrical properties. Long-term operating temperatures can reach 125°C to 150°C. After cross-linking processing, the short-circuit temperature of PE can be increased to 250°C, allowing for a significantly higher current-carrying capacity for cables of the same thickness.
3. XLPE-insulated cables also exhibit excellent mechanical, waterproof, and radiation-resistant properties, making them suitable for various applications, such as internal wiring in electrical appliances, motor leads, lighting leads, automotive low-voltage signal control wires, locomotive wires, subway cables, environmentally friendly mining cables, ship cables, 1E-grade cables for nuclear power plants, submersible pump cables, and power transmission cables.
The current directions in XLPE insulation material development include irradiation cross-linked PE power cable insulation materials, irradiation cross-linked PE aerial insulation materials, and irradiation cross-linked flame-retardant polyolefin sheathing materials.
(2) Cross-Linked Polypropylene (XL-PP) Insulation Material:
Polypropylene (PP), as a common plastic, has characteristics such as light weight, abundant raw material sources, cost-effectiveness, excellent chemical corrosion resistance, ease of molding, and recyclability. However, it has limitations such as low strength, poor heat resistance, significant shrinkage deformation, poor creep resistance, low-temperature brittleness, and poor resistance to heat and oxygen aging. These limitations have restricted its use in cable applications. Researchers have been working to modify polypropylene materials to improve their overall performance, and irradiation cross-linked modified polypropylene (XL-PP) has effectively overcome these limitations.
XL-PP insulated wires can meet UL VW-1 flame tests and UL-rated 150°C wire standards. In practical cable applications, EVA is often blended with PE, PVC, PP, and other materials to adjust the performance of the cable insulation layer.
One of the disadvantages of irradiation cross-linked PP is that it involves a competitive reaction between the formation of unsaturated end groups through degradation reactions and cross-linking reactions between stimulated molecules and large molecule free radicals. Studies have shown that the ratio of degradation to cross-linking reactions in PP irradiation cross-linking is approximately 0.8 when using gamma-ray irradiation. To achieve effective cross-linking reactions in PP, cross-linking promoters need to be added for irradiation cross-linking. Additionally, the effective cross-linking thickness is limited by the penetration capability of electron beams during irradiation. Irradiation leads to the production of gas and foaming, which is advantageous for the cross-linking of thin products but limits the use of thick-walled cables.
(3) Cross-Linked Ethylene-Vinyl Acetate Copolymer (XL-EVA) Insulation Material:
As the demand for cable safety increases, the development of halogen-free flame-retardant cross-linked cables has grown rapidly. Compared to PE, EVA, which introduces vinyl acetate monomers into the molecular chain, has lower crystallinity, resulting in improved flexibility, impact resistance, filler compatibility, and heat sealing properties. Generally, the properties of EVA resin depend on the content of vinyl acetate monomers in the molecular chain. Higher vinyl acetate content leads to increased transparency, flexibility, and toughness. EVA resin has excellent filler compatibility and cross-linkability, making it increasingly popular in halogen-free flame-retardant cross-linked cables.
EVA resin with a vinyl acetate content of approximately 12% to 24% is commonly used in wire and cable insulation. In actual cable applications, EVA is often blended with PE, PVC, PP, and other materials to adjust the performance of the cable insulation layer. EVA components can promote cross-linking, improving cable performance after cross-linking.
(4) Cross-Linked Ethylene-Propylene-Diene Monomer (XL-EPDM) Insulation Material:
XL-EPDM is a terpolymer composed of ethylene, propylene, and non-conjugated diene monomers, cross-linked through irradiation. XL-EPDM cables combine the advantages of polyolefin-insulated cables and common rubber-insulated cables:
1. Flexibility, resilience, non-adhesion at high temperatures, long-term aging resistance, and resistance to harsh climates (-60°C to 125°C).
2. Ozone resistance, UV resistance, electrical insulation performance, and resistance to chemical corrosion.
3. Resistance to oil and solvents comparable to general-purpose chloroprene rubber insulation. It can be produced using common hot extrusion processing equipment, making it cost-effective.
XL-EPDM-insulated cables have a wide range of applications, including but not limited to low-voltage power cables, ship cables, automotive ignition cables, control cables for refrigeration compressors, mining mobile cables, drilling equipment, and medical devices.
The main disadvantages of XL-EPDM cables include poor tear resistance and weak adhesive and self-adhesive properties, which can affect subsequent processing.
(5) Silicone Rubber Insulation Material
Silicone rubber possesses flexibility and excellent resistance to ozone, corona discharge, and flames, making it an ideal material for electrical insulation. Its primary application in the electrical industry is for wires and cables. Silicone rubber wires and cables are especially well-suited for use in high-temperature and demanding environments, with a significantly longer lifespan compared to standard cables. Common applications include high-temperature motors, transformers, generators, electronic and electrical equipment, ignition cables in transportation vehicles, and marine power and control cables.
Currently, silicone rubber-insulated cables are typically cross-linked using either atmospheric pressure with hot air or high-pressure steam. There is also ongoing research into using electron beam irradiation for cross-linking silicone rubber, although it has not yet become prevalent in the cable industry. With the recent advancements in irradiation cross-linking technology, it offers a lower-cost, more efficient, and environmentally friendly alternative for silicone rubber insulation materials. Through electron beam irradiation or other radiation sources, efficient cross-linking of silicone rubber insulation can be achieved while allowing control over the depth and degree of cross-linking to meet specific application requirements.
Hence, the application of irradiation cross-linking technology for silicone rubber insulation materials holds significant promise in the wire and cable industry. This technology is expected to reduce production costs, improve production efficiency, and contribute to reducing adverse environmental impacts. Future research and development efforts may further drive the use of irradiation cross-linking technology for silicone rubber insulation materials, making them more widely applicable for manufacturing high-temperature, high-performance wires and cables in the electrical industry. This will provide more reliable and durable solutions for various application areas.
Post time: Sep-28-2023