Selecting appropriate cable materials directly impacts the operational reliability, safety, and compliance of cables, electrical systems, and power transmission. If cable engineers choose insulation or sheathing materials that fail to meet application requirements, cables may experience premature failure, leading to downtime or safety hazards.
Cable material performance must be evaluated across five critical dimensions: electrical properties, thermal resistance, mechanical strength, flame retardancy and fire safety, chemical resistance, and environmental protection.
Each property must meet the specific requirements of the target application to ensure long-term stable operation and compliance with industry standards.
A cable's electrical performance determines its safety and stability during power and signal transmission. Insufficient insulation thickness or dielectric strength may cause leakage, short circuits, or insulation breakdown around conductors. Low insulation resistance increases energy loss and the risk of insulation failure.
Insulation Resistance: Measures an insulating material's ability to suppress leakage current. Higher insulation resistance minimizes leakage and energy loss under humid or aged conditions.
Dielectric Strength: This indicates the electric field strength per unit thickness that insulation can withstand before breakdown. For example, polytetrafluoroethylene (PTFE) typically has a dielectric strength of approximately 50–60 kV/mm, making it suitable for high-voltage or sensitive communication systems; polyvinyl chloride (PVC) typically has a value of about 14–18 kV/mm and is commonly used for general wiring.
Dielectric Constant: The dielectric constant determines a cable's capacitive properties. High-frequency signals experience greater capacitive coupling and loss in materials with high dielectric constants. Materials with low dielectric constants (e.g., PTFE at approximately 2.1) are better suited for RF and microwave applications; materials with higher dielectric constants (e.g., PVC at approximately 3.2–4.0) are more commonly used for low-frequency power or general wiring.
In electrical design, trade-offs must be made between insulation thickness (enhancing dielectric strength) and cable flexibility, outer diameter, and installation convenience: thicker insulation improves voltage resistance but increases cable stiffness and bulk.
| Material | Dielectric strength (kV/mm) | Dielectric constant | Typical Applications |
| PVC | 14–18 | 3.2–4.0 | General Wiring Cables |
| XLPE/XLPO | 20–30 | 2.3–2.6 | Power Cables, High-Voltage Cables |
| PTFE | 50–60 | 2.1 | RF and Aerospace |
| Rubber | 15–20 | 2.5–3.0 | Portable Cables |
| FEP | 45–55 | 2.1 | Data and Control |
Cables generate heat under electrical load and environmental influences. Insulation materials and sheaths must maintain mechanical and electrical integrity at specified operating temperatures. If a material's maximum heat resistance falls below the operating temperature, it will soften, degrade, or lose mechanical/electrical insulation properties, leading to failure or fire hazards.
Heat Resistance: Maximum long-term operating temperatures vary significantly across materials. Polyvinyl chloride (PVC) begins softening around 70 °C, making it unsuitable for sustained high loads; cross-linked polyethylene (XLPE) can operate long-term at 90–110 °C, suitable for power cables; fluoropolymers (e.g., PTFE) maintain performance at 200–250 °C.
Thermal Aging: Prolonged exposure to high temperatures degrades a material's mechanical strength and insulation properties. Accelerated thermal aging tests are commonly used in engineering to evaluate changes in elongation, tensile strength, and insulation resistance under sustained high temperatures, thereby determining service life.
A material's thermal properties critically influence the longevity and safety of cables in industrial, power, automotive, and aerospace applications.
| Material | MAX operating temperature(℃) | Thermal Aging Resistance | Typical Applications |
| PVC | 70–90 | Low | Residential Wiring |
| XLPE/XLPO | 90–150 | Medium | Power Cables |
| Rubeer | 90–120 | Medium | Flexible Cables |
| PTFE | 200–250 | High | Aerospace and Defense |
| Silicone Rubber | 180–200 | High | High-Temperature Work Zones |
Cables are subject to tension, bending, abrasion, and impact during installation, handling, and operation (e.g., in drag chains and robotics). If the material's tensile strength or fatigue resistance is insufficient, the cable may break, the insulation may crack, or the conductor may break during installation or repetitive movement.
Tensile strength: The ability of a material to resist failure under tensile load, typically expressed in MPa.
Elongation at break: The percentage of deformation a material can deform before breaking. A material with a higher elongation is more ductile and fracture-resistant. Rubber-based materials can achieve elongation of hundreds of percentage points, demonstrating excellent flexibility.
Flexibility/Bend Radius: Flexibility is often measured in terms of the minimum safe bend radius. A smaller bend radius makes the cable easier to route through confined spaces or use in dynamic applications.
For applications with high flex cycles or high wear (e.g. mining, robotics or drag chains), it is recommended to use sheath materials with high wear resistance and high cycle fatigue life (e.g. specialized thermoplastic polyurethanes or thermoplastic elastomers).
| Material | Tensile Strength(MPa) | Elongation(%) | Flexibility | Typical Applications |
| PVC | 15–25 | 100–250 | Moderate | Indoor Wiring |
| XLPE/XLPO | 20–25 | 150–300 | Moderate | Power Cables |
| Rubber | 15–20 | 300–400 | High | Portable Cables |
| TPU | 25–30 | 400–600 | High | Robotics, Cable Chains |
| PTFE | 20–30 | 200–300 | Low | Aerospace |
The combustion behavior of cables during a fire directly impacts evacuation and property protection. Inadequate flame retardancy in cable materials can accelerate fire spread and release large amounts of toxic smoke, significantly increasing casualties and equipment damage.
Smoke and Toxic Gases: For example, PVC releases dense smoke and corrosive hydrogen chloride gas when burning; low-smoke zero-halogen (LSZH/LS0H) materials produce significantly less smoke and toxic gases when burning. Fluoropolymers (such as PTFE and FEP) typically produce very low smoke and have good self-extinguishing properties.
Flame Retardancy Standards: Commonly used tests and standards include IEC 60332 (Cable Flame Spread), UL 94 (Plastic Flammability Ratings), and EN 50265 (Cable Flame Performance). The EU Construction Products Regulation (CPR) classifies the fire reaction of cables (e.g., B2ca, Cca, Dca), with different requirements depending on the application.
For buildings with high passenger flow, rail transit and public facilities, priority should be given to products that meet the requirements of low smoke and halogen-free and corresponding fire protection levels.
| Material | Smoke Emissions | Toxic gas release | Flame Retardancy | Standard Compliance |
| PVC | High | Yes | Moderate | IEC 60332 |
| XLPE/XLPO | Medium | Yes | High | UL 94 |
| LSZH | Low | No | High | EN 50265，CPR |
| Rubber | Medium | Yes | Moderate | IEC 60332 |
| Fluoropolymer | Very Low | No | Very High | UL 94 V-0 |
Cables in outdoor, marine, or chemical environments are exposed to UV rays, moisture, salt spray, oils, acids, and alkalis, among other chemicals. If the material lacks UV or chemical resistance, the insulation or jacket will degrade, crack, or swell, ultimately leading to conductor corrosion or insulation failure.
UV Impact: Prolonged sunlight exposure can cause polymer chains to break, leading to surface cracking. PVC and some rubbers experience significant degradation under prolonged outdoor exposure.
Moisture and Water Penetration: Moisture penetrating the insulation accelerates conductor oxidation and reduces insulation resistance. Cross-linked polyethylene (XLPE) generally offers excellent moisture resistance.
Chemical Resistance: Oils, fuels, and certain solvents can swell or soften common materials (such as PVC and ordinary rubber); fluoropolymers exhibit excellent resistance to most chemicals. Marine environments (salt spray) can accelerate corrosion of metal components and conductors, requiring specialized protective measures and materials.
Proper material selection can significantly reduce maintenance and replacement frequency, preventing environmentally-induced system failures.
Different markets and industries have specific requirements for cable performance and material composition. Products that fail to comply with local regulations may not be allowed into the market or may pose legal and safety risks during use.
UL: A commonly used US standard covering requirements for flammability, electrical safety, and other areas.
IEC: Provides internationally recognized test methods and performance benchmarks.
RoHS: Restricts the use of hazardous substances such as lead, cadmium, and mercury in electrical products.
REACH: Regulates the Registration, Evaluation, and Restriction of Chemicals, impacting the compliance of material composition.
When selecting a cable, consider the regulatory requirements of your target market (such as North America, the EU, and China), and maintain relevant test certificates and compliance documentation to ensure market access and long-term compliance.
Conclusion (Practical Takeaways)
When selecting cable materials, consider the project's critical operating conditions: voltage level and frequency, maximum and long-term operating temperatures, mechanical stress and bending requirements, fire safety rating requirements, and expected environmental exposure (UV, moisture, chemicals, salt spray, etc.). On this basis:
Prioritize meeting minimum requirements for electrical insulation strength and insulation resistance;
Select high-temperature-resistant materials (such as PTFE or silicone rubber) for high-temperature applications;
Use high-elongation and high-abrasion-resistant sheaths (such as TPU) for dynamic or high-cycle bending applications;
Prefer low-smoke, halogen-free, or high-flame-retardant cables for public spaces and transportation facilities;
Prefer materials with strong chemical and weather resistance (such as fluoropolymers) for chemical or marine exposure.
All selected materials must meet the regulatory and testing standards of the target market (UL, IEC, RoHS, REACH, etc.).
