Polyolefin materials are widely used in industries demanding exceptional heat resistance, mechanical strength, and long-term stability, such as cables, automotive, and industrial manufacturing. This paper provides an in-depth analysis of two widely used polyolefin systems in the materials field: irradiated crosslinked polyolefin (XLPO) and thermoplastic polyolefin (TPO).
Polyolefins are a class of polymeric materials synthesized from olefin monomers, including polyethylene (PE), polypropylene (PP), and their modified systems. Their excellent corrosion resistance, stable physical properties, and processing convenience enable extensive applications in cables, automotive components, building materials, and consumer goods. XLPO and TPO represent two typical yet distinctly different materials within the polyolefin family.
XLPO is a crosslinked material formed by subjecting polyolefin to electron beam irradiation. Irradiation induces crosslinking reactions in polymer chains, generating a stable three-dimensional crosslinked network structure.
This structural transformation directly enhances heat resistance, mechanical strength, dimensional stability, and chemical resistance.
This process is particularly prevalent in the cable industry. For instance, irradiated crosslinked polyethylene (XLPE) and irradiated crosslinked polyolefin (XLPO) both belong to the same technological category.
1. Superior Thermal Stability
The melting point and heat deflection temperature of crosslinked materials are significantly enhanced, withstanding temperatures up to 150℃.
2. Exceptional Chemical Resistance
The crosslinked structure improves the material's resistance to permeation by oils, fuels, coolants, solvents, and other chemicals.
This makes it suitable for automotive wiring harnesses, industrial cables, and applications involving frequent chemical exposure.
3. Superior Mechanical Strength
XLPO demonstrates markedly higher tensile strength, tear resistance, and abrasion resistance compared to uncrosslinked polyolefins.
Standard XLPO typically maintains tensile strength within the stable range of 12–20MPa, exhibiting robust toughness.
TPO is a typical blend of PP (polypropylene) and elastomers (such as EPDM rubber), with fillers or additives incorporated to tailor properties.
Its core characteristics include:
Uncrosslinked, melt-processable, and reprocessable—a true thermoplastic material.
This confers distinct advantages in processing and recycling.
1. High Flexibility
The incorporation of a rubber phase in TPO significantly enhances the material's flexibility and impact resistance.
Certain automotive-grade TPOs can achieve notch impact strengths exceeding 20 kJ/m², making them suitable for complex structural components or parts requiring repeated bending.
2. Excellent Recyclability
As a thermoplastic material, TPO can be repeatedly melted and reprocessed, helping reduce manufacturing costs and aligning with sustainable production trends.
3. High Cost-Effectiveness
TPO's raw material and processing costs are generally lower than crosslinked systems, making it a preferred choice for many medium-to-low-load applications.
In the wire and cable industry, material selection directly impacts the safety, long-term stability, and service life of finished cables. As industry demands for weather resistance, chemical resistance, and mechanical strength continue to rise, XLPO and TPO—two representative polyolefin materials—exhibit distinct performance characteristics in cable insulation and sheathing applications.
XLPO (Irradiation-Crosslinked Polyolefin)
In insulation applications, XLPO offers the following advantages:
High dielectric strength: Crosslinking enhances dielectric stability, meeting insulation requirements for low- to medium-voltage applications (typical XLPO insulation materials achieve 18–30 kV/mm dielectric strength, depending on formulation).
Low Dielectric Loss: Cross-linking fixes molecular chain structures, reducing dielectric loss and making it suitable for high-current or long-distance transmission scenarios.
High Heat Resistance: Conventional XLPO insulation maintains long-term temperature resistance between 90–150℃, applicable to solar PV cables, industrial equipment cables, charging station cables, and high/low-voltage cables.
When used for insulation, TPO is typically employed in applications with lower electrical performance requirements, such as low-voltage wiring or general household wiring. Characteristics include:
Moderate dielectric properties: TPO's dielectric strength is generally lower than crosslinked systems, making it unsuitable for high-voltage insulation.
Relatively limited heat resistance: Typically suitable for long-term operating temperatures of 70–80℃.
Processing convenience: Easy melt processing with short forming times, suitable for cost-sensitive products.
Therefore, in insulation applications, XLPO is more suitable for scenarios with stringent electrical safety requirements, while TPO is commonly used in low-to-medium-demand low-voltage applications and cost-driven cables.
When used as sheath material, XLPO demonstrates distinct advantages, particularly in high-stress environments:
High abrasion and scratch resistance: Ideal for industrial drag chain cables, robotics cables, and other high-bend applications.
Superior oil resistance: Withstands corrosion from hydraulic fluids, lubricants, and fuels, suitable for factory, automotive, and machinery wiring.
Superior weather resistance: Resists UV radiation, ozone, and humid heat, making it suitable for long-term exposure in outdoor photovoltaic cables, marine cables, and similar environments.
More reliable flame retardancy: Many XLPO formulations meet VW-1, FT1, and other flame retardant standards, depending on the specific compounding.
TPO exhibits the following characteristics in sheathing applications:
Superior flexibility and bendability compared to unreinforced XLPO: Suitable for lightweight mobile cables, electronic wires, etc.
Moderate weather resistance: Not suitable for long-term outdoor use without UV additives.
Weaker oil resistance than XLPO: Generally not used in industrial environments with heavy oil exposure.
Lower cost: Offers significant cost advantages for high-volume cables with less stringent environmental requirements.
| Comparison Items | XLPO (Irradiation Crosslinked Polyolefin) | TPO (Thermoplastic Polyolefin) |
| Thermal Performance | High heat resistance rating, with long-term stability at 90–150℃; | Primarily used in environments of 70–80℃ |
| Chemical Resistance | Excellent resistance to oil, solvents, and corrosion | Not suitable for heavily oil-contaminated environments |
| Mechanical Strength | High tensile strength, abrasion resistance, and tear resistance | Offers good flexibility but inferior durability compared to XLPO |
| Weather Resistance | Outstanding UV, ozone, and moisture/heat resistance | Requires additives to enhance UV resistance |
| Flame Retardancy | Achieves flame retardant ratings such as VW-1 and FT1 | Requires additional flame retardant systems |
| Processability | Non-meltable for recycling; requires irradiation processing | Can be thermoplastically reprocessed |
| Environmental Friendliness | Not Recyclable | Recyclable and re-meltable |
| Typical Applications | Applications: Photovoltaic cables, automotive wiring harnesses, industrial cables | Applications: Indoor cables, automotive interiors, roofing membranes |
The choice between XLPO and TPO primarily depends on specific application requirements:
If the project demands high heat resistance, strong chemical resistance, and long-term durability → Prioritize XLPO
Examples: Cable insulation, automotive engine compartments, industrial equipment, etc.
If the project emphasizes flexibility, recyclability, and cost advantages→Prioritize TPO
Examples: Automotive interior and exterior components, consumer goods, building waterproofing materials, etc.
