Analysis of the Applicability of XLPE and PVC Materials in Cable Insulation and Sheath Layers

2025-09-01 01:11:22

Excellent Electrical Insulation: XLPE has an extremely high volume resistivity (≥1×10¹⁴Ω·cm at 20℃), much higher than that of PVC (usually around 1×10¹²Ω·cm), enabling it to effectively block current leakage. Its dielectric loss tangent (tanδ) is extremely low (≤0.003 at 50Hz), resulting in minimal energy loss during current transmission and preventing insulation aging caused by dielectric loss heating. This makes it particularly suitable for scenarios requiring high power supply efficiency (such as residential power distribution and industrial Power Cables).

Strong Temperature Resistance and Wide Temperature Range Adaptability: XLPE has a long-term allowable operating temperature of up to 90℃, and can withstand an instantaneous high temperature of up to 250℃ (for a duration of no more than 5 seconds) in the event of a short circuit—far superior to PVC Insulation (long-term operating temperature ≤70℃, instantaneous short-circuit temperature ≤160℃). This property allows it to withstand the heat generated during cable operation (such as the instantaneous high temperature when high-power equipment starts), reducing the risk of insulation melting or breakdown. It is suitable for cable use in high-temperature environments (such as wiring around industrial ovens and cables in high-rise building shafts).

Outstanding Aging Resistance and Stability: The cross-linked three-dimensional molecular structure makes XLPE less susceptible to factors such as oxygen, ultraviolet radiation, and humidity. Its anti-aging service life can exceed 20 years, and its water absorption rate is ≤0.01%. Even in humid environments (such as bathrooms and underground garages), it can maintain stable insulation performance, avoiding a decrease in insulation resistance due to water absorption.

Mechanical Strength Meets Insulation Layer Requirements: XLPE has a tensile strength of ≥12MPa and an elongation at break of ≥200%. It can withstand slight bending stresses during cable installation and is not prone to cracking during long-term use, protecting the conductor from external environmental erosion. Although this strength is not as high as required for sheath layers, it fully meets the basic mechanical needs of insulation layers for "covering conductors and isolating current."

Adapting to Low-Smoke Halogen-Free Requirement Scenarios: Ordinary PVC Sheaths release toxic halogen gases (such as HCl) when burned, while modified XLPE (e.g., halogen-free low-smoke XLPE) produces low smoke density (light transmittance ≥70%) and no toxic gas emission. It can be used as a sheath layer for cables in densely populated areas such as hospitals, subways, and high-rise buildings, balancing mechanical protection with safety and environmental friendliness.

Temperature Resistance Meeting Sheath Requirements in High-Temperature Environments: In high-temperature industrial environments (such as metallurgical plants and glass factories), ordinary PVC sheaths are prone to softening and deformation, while XLPE sheaths can operate continuously at 90℃, protecting the internal structure of the cable from high-temperature damage.

Excellent Mechanical Protection Performance: PVC sheaths have a Shore A hardness of ≥85, with wear-resistant and impact-resistant surfaces. They can withstand collisions and scratches during cable transportation and installation (such as friction during cable tray wiring and ground dragging), protecting the internal insulation layer and conductor from damage. With a tensile strength of ≥10MPa and an elongation at break of ≥150%, they can resist slight extrusion (such as pressure from heavy objects during indoor decoration) and prevent sheath cracking.

Strong Weather and Corrosion Resistance: PVC itself has good weather resistance; after adding UV stabilizers, it can be used for a long time in outdoor environments with temperatures ranging from -20℃ to 60℃, and is not prone to cracking or softening due to ultraviolet radiation or temperature changes. At the same time, it can resist erosion from common acids and alkalis (such as rainwater and mild chemical pollutants), making it suitable for outdoor (such as community courtyard wiring), humid (such as kitchens), and slightly corrosive (such as basements) environments.

Significant Flame Retardancy and Cost Advantages: PVC itself has a certain degree of flame retardancy (oxygen index ≥28%), and can meet flame retardant standards such as GB/T 18380 without adding a large number of additional flame retardants, which can slow down flame spread. Additionally, PVC has low raw material costs and mature processing technology (easy extrusion molding), making it suitable for large-scale production and reducing the overall cost of cables. This advantage makes it the mainstream choice for cable sheaths in ordinary civil and industrial scenarios. For example, the "low-voltage YJV/YJV22 cables" mentioned earlier use PVC as the sheath layer.

Strong Processing Adaptability: The thermoplastic nature of PVC allows it to be easily made into sheath layers of different thicknesses and colors (such as black outdoor sheaths and colored indoor sheaths) through extrusion processes. It also has good adhesion to internal cable structures (such as shielding layers and armoring layers), preventing delamination and ensuring the integrity of the sheath.

Adapting to Low-Voltage and Small-Current Scenarios: In low-voltage lighting circuits (such as wiring for 220V desk lamps) and Internal Wiring of small household appliances (such as power cords for rice cookers), the current is small and heat generation is low. PVC insulation layers (with a volume resistivity of approximately 1×10¹²Ω·cm) can meet basic insulation needs, and their cost is only 1/2 to 2/3 of that of XLPE, making them suitable for low-cost civil products.

Convenient Processing Adapting to Small-Specification Cables: PVC has a low melting temperature (160℃-180℃) and can be easily extruded into thin insulation layers (such as 0.5mm-1.0mm), making it suitable for insulation coating of small cross-sectional area cables (such as 0.75mm² and 1.0mm² Control cables) with high production efficiency.

Poor Temperature Resistance: The long-term operating temperature is ≤70℃; exceeding this temperature will easily cause softening, a decrease in insulation resistance, and even the risk of electric leakage. It cannot be adapted to wiring for high-power equipment (such as air conditioners and electric water heaters) or in high-temperature environments.

Weak Aging Resistance and Stability: Plasticizers in PVC are prone to migration over time, causing the insulation layer to harden and crack (known as "aging hardening"). Its service life is usually only 5-10 years, and its water absorption rate (≤0.5%) is higher than that of XLPE, leading to easy attenuation of insulation performance in humid environments.

Low Combustion Safety: It releases toxic halogen gases and dense smoke when burned, failing to meet the safety requirements of densely populated places (such as hospitals and schools). Therefore, PVC insulation layers have gradually been replaced by XLPE in high-voltage, medium-voltage cables, or scenarios with high safety levels.