Wire Harness Material Selection Guide

In the design and manufacture of wire harnesses, the choice of wire harness materials directly determines their reliability and service life in a specific environment. Only by reasonably matching the characteristics of the wire harness materials with environmental requirements can the wire harnesses be ensured to work stably during use. This article will analyze in detail the selection method of wire harness materials based on the environmental conditions encountered during wire harness use.

1. High temperature environment

High temperature environments (usually temperatures above 120°C) can cause many problems with wiring harness materials:

• The insulation layer ages and carbonizes when exposed to heat, losing its insulation properties.
• The conductor is easily oxidized, increasing the contact resistance.
• The heat-shrink tubing may soften and melt, losing its protective function. At the same time, high temperatures will accelerate the chemical decomposition of the material and shorten the service life of the wiring harness.

High-temperature resistant material selection

• Conductor material: Tinned copper or silver-plated copper is preferred. The coating prevents oxygen from contacting the copper and reduces oxidation. In extremely high temperature environments (over 200°C), nickel-chromium alloy conductors can be selected, which have excellent high-temperature oxidation resistance. 
• Insulation material: Cross-linked polyvinyl chloride (XLPE), polyimide (PI), and fluoroplastics (such as PTFE) are commonly used high-temperature insulation materials. XLPE has a temperature resistance of up to 135°C, PI can work for a long time at temperatures above 250°C, and PTFE has a temperature resistance of up to 260°C.
• Sheath material: Polyamide (PA) and fluororubber (FKM) exhibit good high-temperature resistance and aging resistance, making them suitable as sheath materials in high-temperature environments. Choose high-temperature resistant wire.
• FLRY series conductors: tinned copper core and cross-linked PVC insulation, temperature resistance of 135°C, widely used in high temperature areas such as automobile engine compartments. 
• Polyimide wrapped wire: PI film is used as the insulation layer, the conductor is mostly silver-plated copper, temperature resistance of up to 250°C, suitable for high temperature motors, aerospace equipment, and other fields. 
• PTFE insulated cable: The insulation layer is PTFE, the conductor is nickel-plated copper, temperature resistance of 260°C, and can be used in extremely high temperature environments such as industrial furnaces and high temperature testing equipment.

2. Low temperature environment

A low temperature environment (usually refers to a temperature below -40°C) will slow down the molecular movement of the wiring harness material, causing the material to harden, become brittle, and have reduced flexibility. When the wiring harness is subjected to external forces such as bending and vibration, the insulation layer and sheath are prone to cracking, exposing the conductor and causing short circuits and other faults. Low temperatures will also affect the conductivity of the conductor and increase signal transmission losses.

Low-temperature resistant material selection

• Conductor material: Soft oxygen-free copper has good low-temperature toughness, is not easily brittle, and can maintain good conductivity, making it the first choice for conductors in low-temperature environments.
• Insulation material: Cross-linked polyethylene (XLPE) and polyurethane (PU) still have certain flexibility at low temperatures, and have a low brittle temperature, making them suitable as insulation materials in low-temperature environments. 
• Sheath material: Thermoplastic polyurethane (TPU) and ethylene propylene diene monomer (EPDM) have excellent low-temperature elasticity and can maintain good flexibility and crack resistance below -40°C.
• AVSS series conductors: using soft oxygen-free copper core and PVC insulation containing cold-resistant plasticizer, the brittle temperature is lower than - 40℃, and is widely used in low-temperature and easy-to-bend parts such as car door lines and roof wiring harnesses.
• XLPE insulated TPU sheathed cable: the insulation layer is XLPE, the sheath is TPU, it has excellent low-temperature resistance, can work normally in an environment of - 50℃, and is suitable for polar scientific research equipment, cold chain logistics vehicles, etc.
• EPDM sheathed cable: the sheath is made of EPDM rubber, which has good low-temperature resistance and weather resistance, and is often used for power transmission in outdoor low-temperature environments.

3. Chemical Corrosion Environment

In a chemically corrosive environment, the wiring harness will be corroded by substances such as acid, alkali, salt spray, and oil. These substances react chemically with the wiring harness material, causing the insulation layer and sheath to swell, crack, age, and even corrode the conductor, affecting the electrical conductivity and mechanical strength of the wiring harness.

Selection of chemical-resistant materials

• Conductor material: Silver-plated copper and nickel-plated copper can effectively resist chemical corrosion and perform well in salt spray, acid, and alkali environments. Titanium alloy conductors can be selected in highly corrosive environments, but their cost is relatively high. 
• Insulation material: Polytetrafluoroethylene (PTFE) and ethylene-tetrafluoroethylene copolymer (ETFE) are extremely chemically inert and can withstand corrosion from most acids, alkalis, and organic solvents. 
• Sheath material: Fluororubber (FKM), chloroprene rubber (CR), and halogen-free low-smoke polyolefin (LSZH) have good tolerance to oil, salt spray, etc., and are suitable as sheath materials for chemically corrosive environments.
• PTFE insulated silver-plated copper cable: The insulation layer is PTFE, the conductor is silver-plated copper, it has excellent chemical corrosion resistance, and is suitable for chemical plants, laboratories, and other highly corrosive environments. 
• FKM sheathed cable: The sheath is made of FKM rubber, and the insulation layer is ETFE, which can effectively resist the erosion of oil and chemical solvents. It is often used in automobile engine compartments, gearboxes, and other parts in contact with oil. 
• LSZH sheathed nickel-plated copper cable: The sheath is LSZH polyolefin, the conductor is nickel-plated copper, it has good salt spray and weather resistance, and is suitable for coastal areas, ships, and other humid salt spray environments.

4. Mechanical application environment

Wire harnesses face three major challenges in mechanical application environments: 

1. High-frequency bending (such as robot drag chains and car door wires) can easily lead to conductor fatigue fracture and insulation wear. 
2. Wear (such as wire harnesses of mining machinery and construction equipment), which often rub against other objects and cause sheath damage; 
3. Vibration (such as wire harnesses of engines, machine tools, and other equipment), long-term vibration can cause connectors to loosen and conductors to break.

Selection of materials resistant to mechanical wear

• Conductor material: Ultra-fine stranded copper wire (diameter 0.05-0.1mm) is used to improve flexibility and fatigue resistance, and reduce damage caused by bending and vibration. 
• Insulation material: Silicone and polyurethane (PU) have good flexibility and wear resistance, and are suitable as insulation materials under mechanical stress environments. 
• Sheath material: Polyurethane (PUR) and polyamide (PA) have excellent wear resistance and tear resistance, and the aramid braided reinforced sheath can further improve the mechanical strength of the harness.
• Ultrafine stranded silicone insulated PUR sheathed cable: The conductor is ultrafine stranded copper wire, the insulation layer is silicone, and the sheath is PUR. It has excellent flexibility and wear resistance and is suitable for high-frequency bending scenarios such as industrial robot drag chains and automated production lines. 
• Aramid braided reinforced PA sheathed cable: The aramid braided layer is added to the PA sheath to improve the tensile and wear resistance. It is often used in environments with severe wear, such as mining machinery and construction equipment. 
• Vibration-resistant cable: The conductor adopts a multi-strand twisted structure, the insulation layer is PU, and the sheath is PUR. It has good vibration resistance and is suitable for vibration equipment such as engines and machine tools.

5. Electromagnetic interference environment

In an electromagnetic interference environment, the wiring harness will be interfered with by external electromagnetic waves, resulting in signal transmission distortion, increased bit error rate, and even inability to communicate normally. During use, the electromagnetic radiation generated by the wiring harness itself will also interfere with the operation of surrounding equipment.

Selection of anti-electromagnetic interference materials

• Conductor material: High-purity oxygen-free copper (OFC) has low resistance and good conductivity, which can reduce signal transmission loss and electromagnetic radiation.
• Insulation material: Foamed polyethylene (PE) and polytetrafluoroethylene (PTFE) have low dielectric constant and loss factor, which can reduce attenuation and distortion in signal transmission.
• Shielding material: Copper foil, aluminum foil, and copper wire braid are commonly used shielding materials, which can effectively block external electromagnetic wave interference and reduce the electromagnetic radiation of the harness itself.
• Copper foil + copper wire braided shielded cable: The conductor is high-purity oxygen-free copper, the insulation layer is foamed PE, and the shielding layer is composed of copper foil and copper wire braiding. The shielding efficiency is above 80dB, which is suitable for high-frequency signal transmission (such as USB4.0, automotive Ethernet, etc.). 
• Aluminum foil shielded low-smoke halogen-free cable: The shielding layer is aluminum foil, and the insulation and sheath are made of low-smoke halogen-free materials. It has good electromagnetic compatibility and environmental protection performance, and is often used in places sensitive to electromagnetic interference, such as office buildings and hospitals. 
• Double-shielded cable: The double-shielded structure with inner aluminum foil and outer copper wire braiding is adopted. The shielding efficiency is further improved, which is suitable for strong electromagnetic interference environments (such as substations, communication base stations, etc.).

6. Common combination application reference

1. High-temperature resistance:

• General application (120-150℃): tinned copper conductor + cross-linked PVC (XLPE) insulation + PA6 corrugated tube sheath.
• Upgraded application (>180℃): nickel-chromium alloy conductor (anti-oxidation temperature increased to 250℃) + polyimide (PI) film wrapping + PTFE coating (temperature resistance increased to 260℃) + fluororubber (FKM) sheath (with glass fiber braid reinforcement, tensile strength increased from 50MPa of PA6 to 100MPa of FKM).

2. Low-temperature resistance:

• General application (-30 to -40℃): soft oxygen-free copper conductor + cold-resistant PVC insulation (phthalate plasticizer added) + TPU sheath (Shore hardness A80).
• Upgraded application (<-40℃): ultra-fine soft oxygen-free copper (diameter reduced to 0.08mm, bending radius reduced from 8D to 5D) + silicone insulation (add cold-resistant silicone oil, low-temperature resistance up to - 60℃) + EPDM sheath (containing carbon black antifreeze agent, with aramid fiber braiding layer, tear strength increased from 15kN/m to 30kN/m).

3. Chemical corrosion resistance:

• General application (medium and low corrosion): nickel-plated copper conductor + ETFE insulation + LSZH sheath.
• Upgraded application (strong corrosion): titanium alloy conductor (TC4 material, resistant to aqua regia corrosion) + PTFE insulation (resistant to all concentrations of acid, alkali, and organic solvents) + FKM sheath (built-in 304 stainless steel armor layer).

4. Mechanical stress:

• General application (medium stress): multi-stranded copper + PU insulation (Shore hardness A75) + PUR sheath.
• Upgraded application (strong stress): ultra-fine stranded copper (200 strands) + silicone insulation (Shore hardness A60) + aramid braided reinforced PUR sheath (wear resistance increased by 3 times).

5. Anti-electromagnetic interference:

• General application (low-frequency interference): high-purity copper (99.95%) + foamed PE insulation (foaming degree 40%) + aluminum foil shielding + PVC sheath.
• Upgraded application (high-frequency strong interference): 7N oxygen-free copper (purity 99.99999%) + PTFE insulation (physical foaming, which increases the signal transmission rate from 1Gbps to 10Gbps) + copper foil (0.05mm) + tinned copper wire braiding (coverage 95%) double shielding + aluminum-plastic composite belt sheath.

Selecting the right material according to the application scenario can improve the reliability and service life of the wiring harness and reduce maintenance costs. Kaweei wiring harness customization factory can provide high-quality wiring harness solutions for complex environments. If you need customized wiring harnesses, please get in touch with us.