The difference between polyvinyl chloride (PVC) and cross-linked polyethylene (XLPE) insulation materials

Polyvinyl chloride (PVC) and cross-linked polyethylene (XLPE) are two commonly used materials for cable insulation. They differ significantly in performance, application scenarios, and safety.

PVC is a thermoplastic material that can be formed through conventional extrusion processes, making it simple to process and low-cost. It exhibits excellent flame retardancy and self-extinguishes when removed from a fire source, making it widely used in general applications where fire protection requirements are not extreme. The long-term operating temperature of PVC cables is generally 70°C, with short-term overloads reaching up to 90°C. Beyond this temperature range, PVC tends to soften, deform, or even decompose, compromising its insulation effectiveness. Furthermore, PVC is brittle at low temperatures and prone to cracking below -15°C, making it unsuitable for use in cold regions or harsh outdoor environments. Another significant issue is that combustion of PVC releases toxic and corrosive gases such as hydrogen chloride, as well as large amounts of black smoke, posing a threat to human health and equipment safety, and hindering evacuation and rescue efforts in the event of a fire.

Cross-linked polyethylene, a thermoset material, is formed by physically or chemically cross-linking polyethylene molecular chains to form a three-dimensional network structure. This structure prevents it from melting under heat, resulting in superior overall performance. XLPE cable has a long-term operating temperature of 90°C, a short-term overload capacity of up to 130°C, and can withstand transient high temperatures of up to 250°C during a short circuit, making it ideal for high-load, high-current power transmission scenarios. It offers excellent electrical performance, including a low dielectric constant, low dielectric loss, high insulation resistance, and strong resistance to electrical aging, resulting in a service life of over 30 years. Mechanically, XLPE exhibits excellent flexibility, tensile strength, compressive strength, and abrasion resistance, maintaining excellent performance even at low temperatures and capable of stable operation in environments as low as -40°C. While XLPE itself is not flame-retardant, it can be made into environmentally friendly cables by adding flame retardants or using low-smoke, halogen-free sheathing. These cables produce less smoke and have lower toxicity during combustion, making them suitable for locations with stringent safety and environmental requirements, such as subways, hospitals, high-rise buildings, and data centers.

In terms of application, PVC-insulated cables are primarily used in low-voltage power distribution systems, such as BV cables in home renovations and RVV cables for equipment connections. They are suitable for fixed wiring with voltage levels of 450/750V and below. XLPE insulated cables are widely used in medium- and high-voltage power systems, such as 10kV, 35kV, and even higher voltage transmission and distribution lines. Common models include YJV and YJY, making them the preferred choice for critical infrastructure such as modern urban power grids, industrial plants, wind farms, and rail transit.

Overall, PVC offers low cost and excellent flame retardancy, making it suitable for general civilian and low-voltage applications. XLPE, on the other hand, outperforms PVC in terms of temperature resistance, electrical, mechanical, and environmental performance. Although more expensive, it is becoming the mainstream choice for mid- to high-end power projects due to its high reliability, long lifespan, and higher safety rating. As awareness of electrical safety and environmental protection grows, the application of XLPE cables continues to expand.

Polyvinyl chloride (PVC) and cross-linked polyethylene (XLPE) are two polymer materials widely used in wire and cable insulation. They differ significantly in performance, application scenarios, and cost. The following are the key differences:
1. Chemical Structure and Manufacturing Process
Polyvinyl chloride (PVC) is a thermoplastic formed by the polymerization of vinyl chloride monomer. The insulation layer is directly applied to the conductor via an extrusion process, then formed after cooling. It can be repeatedly heated to soften.

Cross-linked Polyethylene (XLPE)
Based on polyethylene (PE), the molecular chains are formed into a three-dimensional network structure through physical or chemical methods (such as peroxide crosslinking, silane crosslinking, and radiation crosslinking). It is a thermosetting material.

It cannot be remelted after processing, significantly improving its heat resistance and mechanical strength.

2. Temperature Resistance

PVC:

The long-term operating temperature is 70°C, with a short-term overload of up to 90°C.

PVC tends to soften and age at temperatures exceeding 70°C, affecting its insulation performance.

XLPE:

The long-term operating temperature is 90°C, with a short-term overload of up to 130°C. In emergency situations, it can withstand temperatures of 250°C (e.g., during a short circuit).

It has far superior heat resistance to PVC, making it suitable for high-load operating environments.

3. Electrical Performance

PVC:

Its dielectric strength is acceptable, but its high dielectric constant and dielectric loss make it unsuitable for high-frequency or high-voltage transmission. It is prone to electrical aging after long-term use.
XLPE:
It has excellent electrical properties, a low dielectric constant, low dielectric loss, and high insulation resistance, making it suitable for medium and high voltage power transmission.
It is highly resistant to electrical and water treeing, resulting in a longer service life.
4. Mechanical Properties
PVC:
It is a relatively rigid material that becomes brittle at low temperatures (below -15°C) and has poor impact and bending resistance.
Prolonged stress may cause creep or cracking.
XLPE:
It has excellent flexibility, high tensile strength, is resistant to abrasion and cracking, and offers strong mechanical protection.
It also has better low-temperature performance than PVC and can be used in environments as low as -40°C.
5. Flame Retardancy and Environmental Protection
PVC:
It is naturally self-extinguishing and has excellent flame retardancy (extinguishes immediately when away from flames).
However, combustion releases toxic and corrosive gases such as hydrogen chloride (HCl) and thick black smoke, which are harmful to people and equipment, and hinder evacuation and fire fighting.
XLPE:
It is not inherently flame retardant and requires the addition of flame retardants to achieve flame retardancy. It is halogen-free, produces little or no smoke when burned, and has low toxicity. It is an environmentally friendly material suitable for use in safety-critical locations such as subways, hospitals, and high-rise buildings.
6. Service Life
PVC:
Its design life is generally 15-25 years, but it ages more rapidly in high temperatures or harsh environments.
XLPE:
It has strong aging resistance, a design life of 30-40 years or even longer, and low maintenance costs.
7. Cost and Applications
PVC:
Its raw materials are inexpensive, processing is simple, and its cost is low.
It is widely used in low-voltage power distribution systems, such as building wiring (BV, RV), control circuits, and household appliances.
XLPE:
Its raw material and process costs are higher, but its overall performance is superior.
It is primarily used in medium- and high-voltage power systems (such as 10kV and 35kV cables), urban power grids, wind power plants, rail transit, industrial trunk lines, and other applications requiring high safety and reliability. 8. Typical Cable Model Examples
PVC Insulated Cables:
BV, BVR (Fixed Wiring)
RVV, KVV (Equipment and Control Lines)

XLPE Insulated Cables:
YJV, YJY (XLPE Insulated PVC/PE Sheathed Power Cables)
YJLV (Aluminum Core XLPE Cables)
High-voltage cables commonly use XLPE insulation.