Cable jacketing, sometimes called cable sheathing or cable extrusion, is an important stage in the cable manufacturing process. It provides the final protective layer that gives a cable its strength, stability, and resilience. Without it, even the best-engineered cable design would quickly fail under environmental or mechanical stress.
Whether you’re specifying a jacketed cable for industrial automation, ordering power and data lines for commercial buildings, or designing a custom cable for a highly regulated sector, every cable must be held together by a suitable jacket. The right cable jacketing material protects the inner structure, ensures electrical reliability, and helps the product meet safety and performance standards.
But how do you know which jacket material to choose? And how exactly is that outer layer created?
This guide explains everything you need to know about the purpose of cable jacketing, the extrusion process, the main types of jacket materials, and the key points to consider when selecting the right option for your environment.
Why is cable jacketing important?
The cable jacket (or outer sheath) is the visible outer layer surrounding the internal construction of a cable. It’s usually made from a thermoplastic or thermosetting compound such as PVC (polyvinyl chloride), PE (polyethylene), or LSZH (low smoke zero halogen), depending on where and how the cable will be used.
Inside that jacket are several core elements (conductors, shielding, fillers, and cable insulation) all of which require mechanical support and environmental protection. The jacket holds these parts firmly together and forms a barrier against physical, chemical, and electrical hazards.
Without a protective jacket, an unjacketed cable would leave its insulation and conductors exposed. That exposure would make it far more vulnerable to abrasion, water, oil, extreme temperatures, and oxidation. It could also create serious safety risks, such as electrical leakage or combustion if the insulation were to break down.
In short, the cable jacketing process is an essential part of cable construction. To ensure a cable meets its design life and complies with safety regulations, the jacket material must be selected and applied to match the environmental and mechanical conditions it will face. For this reason, cable jacketing forms one of the most important stages of cable extrusion and quality testing during manufacturing.
Understanding the layers with cable insulation vs cable jacketing
Cable insulation and jacketing are often mentioned together, but they serve very different roles.
- Cable insulation sits directly around each conductor inside the cable. Its main purpose is electrical – preventing current leakage and short circuits while maintaining signal integrity. Common insulation materials include XLPE (cross-linked polyethylene) and EPR (ethylene propylene rubber), both chosen for their dielectric strength and heat resistance.
- Cable jacketing, by contrast, covers the complete cable assembly. It protects all insulated conductors and fillers from the outside world: moisture, abrasion, sunlight, oils, and chemicals. In doing so, it ensures the cable’s overall mechanical strength, flexibility, and fire performance.
Think of insulation as the inner electrical defence, and jacketing as the outer mechanical armour. Both are indispensable, and together they allow the finished cable to perform safely under demanding conditions.
Properties and benefits of cable jackets
Because the jacket surrounds and seals the entire cable, it contributes a wide range of performance benefits. Below are the most significant properties. With each crucial to the long-term durability and compliance of jacketed cables across every sector from construction and medical to aerospace and marine.
1. Abrasion resistance
Abrasion occurs when a cable rubs against rough or uneven surfaces such as machinery housings, concrete floors, or rocky ground. Over time, this friction can wear away insulation or expose conductors. A high-quality cable jacket protects against such wear by providing a tough outer skin that absorbs the damage instead. This mechanical protection is particularly important for mobile equipment, factory environments, and trailing or retractable cables that experience frequent movement.
2. Chemical resistance
Many industrial and laboratory settings expose cables to oils, solvents, cleaning fluids, and corrosive substances. Chemical attacks can cause swelling, cracking, or brittleness in inferior jackets. Chemically resistant materials such as polyurethane (PUR) and fluoropolymers prevent this degradation, keeping the jacketed cable intact and preventing contamination or failure of the inner insulation.
3. Electrical insulation support
While the main electrical protection comes from the insulation layer, the jacket adds an additional barrier that helps maintain the cable’s dielectric integrity. By keeping moisture and conductive particles away from the insulation, the jacket minimises the risk of electrical faults or signal interference. This is vital for telecommunications, instrumentation, and data cables where signal quality directly affects system performance.
4. Temperature resistance
Cables may need to operate in freezing cold or near sources of intense heat. Without adequate temperature tolerance, the jacket can crack in low temperatures or soften and deform under heat, eventually compromising insulation and conductors. Selecting a jacket compound with the correct service temperature, from -0 °C for specialised PE or fluoropolymer jackets up to +200 °C for PTFE and PVDF, ensures the cable retains its shape and performance throughout its service life.
5. Low moisture absorption
Water is one of the most common causes of cable failure. A properly sealed jacket acts as a barrier to moisture, preventing corrosion and dielectric breakdown. Polyethylene and polyurethane jackets are particularly effective in this regard, making them popular for outdoor, underground, or marine installations where condensation and water ingress are frequent threats.
6. Flame resistance
Fire safety is a major factor in cable selection. Jacket compounds such as LSZH (Low Smoke Zero Halogen) are designed to resist ignition and limit flame spread. Even if they do burn, they emit minimal smoke and no halogen gases, reducing the risk of toxic fumes in enclosed spaces. Other materials, like polyvinyl chloride jackets, can be formulated to self-extinguish and provide cost-effective flame retardancy for general-purpose power and control cables.
7. UV resistance
Outdoor cables face constant exposure to sunlight and ultraviolet radiation. Over time, UV can cause conventional plastics to fade, embrittle, and eventually crack. UV-resistant jackets, often black or dark-pigmented for added stability, absorb harmful rays and convert them to heat, preventing degradation. This ensures the cable insulation inside remains protected, even after years of installation on rooftops or open sites.
8. Flexibility
Good flexibility allows a cable to bend and route easily without internal stress. Jacket flexibility depends on both the material and wall thickness: softer compounds such as PUR or rubber provide excellent bending performance for dynamic applications, while more rigid jackets like HDPE suit fixed installations. Balancing flexibility and toughness make installation easier and prevents premature failure at tight bend points.
9. Durability
All the properties above contribute to one key outcome: durability. A durable cable jacket withstands abrasion, chemicals, moisture, heat, UV, and mechanical stress without losing integrity. This durability reduces the need for replacements, minimises downtime, and ensures reliable operation across the cable’s full rated life.
10. Regulatory compliance
Many industries have strict standards governing the use of cables in specific environments. Fire-retardant, halogen-free, or oil-resistant jackets may be required to comply with British, European, or international standards (such as UL, CSA, or IEC specifications). Using certified materials and documented manufacturing controls during cable extrusion ensures that the finished jacketed cable meets every necessary regulation and safety approval.
11. Easy customisation
Cable jackets are also highly customisable. Manufacturers can adjust colour, surface texture, and wall thickness, or add printed markings and branding during the extrusion process. Colour coding and cable printing make installation and maintenance more efficient, while allowing OEMs and distributors to trace batches and display company information clearly on each jacketed cable.
Common cable jacket materials at a glance
Different cable applications require different jacket materials, each offering unique properties suited to specific mechanical, thermal, and environmental conditions. The right choice depends on whether flexibility, chemical resistance, temperature tolerance, or fire performance is most important to your installation.
The table below summarises the most common cable jacketing materials used across industries:
| Material | Temperature Range | Flame Resistance | Flexibility | Moisture Resistance | Common Applications |
|---|---|---|---|---|---|
| PVC (polyvinyl chloride) | –20 °C to +70 °C | Good | High | Good | Power, telecoms, construction, household wiring |
| PE (polyethylene) | –50 °C to +80 °C | Limited | Medium | Excellent | Outdoor and buried cables, automotive, control systems |
| XLPE (cross-linked polyethylene) | –50 °C to +90 °C | Excellent | Moderate | Excellent | Power distribution, high-voltage cables |
| LSZH (low smoke zero halogen) | –30 °C to +90 °C | Very high | High | Good | Public buildings, tunnels, transportation, marine |
| PUR (polyurethane) | –40 °C to +80 °C | Good | Very high | Excellent | Robotics, coiled/retractable cables, automation |
| EPR (ethylene propylene rubber) | –40 °C to +120 °C | Excellent | Very high | Excellent | Industrial, marine, and offshore power systems |
| Neoprene | –40 °C to +90 °C | Good | High | Excellent | Harsh environments, outdoor installations |
| Fluoropolymers (e.g. PVDF, PTFE) | –60 °C to +200 °C | Excellent | Moderate | Excellent | Aerospace, chemical processing, medical |
| XLPO (cross-linked polyolefin) | –40 °C to +105 °C | Very high | High | Excellent | LSZH alternatives, transportation, building management |
Each cable jacket material offers a balance between flexibility, strength, flame resistance, and moisture protection. Selecting the right compound depends on the environment, installation method, and regulatory standards.
Types of cable jacketing materials explained
The most widely used cable jacket materials vary by industry and application. Here’s how each performs in more detail.
PVC (polyvinyl chloride)
PVC remains the most common and cost-effective jacket compound. It provides excellent durability, chemical resistance, flexibility, and flame retardancy. Polyvinyl chloride jackets are suitable for most general-purpose cables, including power, instrumentation, and telecommunications. Special formulations such as SR-PVC (semi-rigid) and HR-PVC (heat resistant) can be used where added toughness or higher temperature tolerance is required. PVC can also be used as both insulation and jacket material, often within a single cable extrusion process.
PE (polyethylene)
PE is tougher and more moisture-resistant than PVC, making it ideal for outdoor, direct-burial, or automotive cables exposed to the elements. It offers excellent dielectric properties and low moisture absorption.
Low-density polyethylene (LDPE) is softer and more flexible, while medium- and high-density versions (MDPE, HDPE) are stiffer and more impact resistant. The main limitation of PE is its relatively poor flame resistance, so it’s best used where fire risk is minimal.
XLPE (cross-linked polyethylene)
XLPE is a thermosetting version of polyethylene where the polymer chains are chemically bonded, or “cross-linked,” to improve heat, chemical, and voltage resistance. This makes XLPE one of the preferred materials for power transmission and distribution cables.
It can operate at higher temperatures than PVC while maintaining dielectric strength and mechanical stability. However, because it’s thermoset, XLPE cannot be remelted or recycled. This is an important consideration for sustainability-focused projects.
LSZH (low smoke zero halogen)
LSZH jackets are designed for maximum safety in the event of fire. They resist ignition, limit flame propagation, and emit minimal smoke or toxic gases when exposed to heat. These properties make LSZH essential in environments with limited ventilation or high occupancy, such as public buildings, tunnels, transportation networks, and offshore platforms.
Because LSZH compounds can be slightly less flexible than PVC, careful selection during the jacketed cable design stage ensures proper bend radius and handling during installation.
Polyurethane (PUR)
PUR is one of the most versatile jacketing materials, combining exceptional abrasion resistance with flexibility and resilience. It performs well in dynamic applications, such as robotic arms, conveyors, and retractable cables that undergo constant motion.
PUR also resists oil, oxidation, and mechanical stress. One unique property is its “shape memory”: it naturally returns to its original form, helping prevent tangling or kinking. Which is why polyurethane jackets are widely used in coiled and spiral cable designs.
Neoprene
Neoprene is a synthetic rubber compound valued for its toughness and flexibility across a wide temperature range. It remains pliable in sub-zero conditions and resists deformation at high temperatures.
Neoprene also resists UV radiation, ozone, and oxidation, making it highly suitable for outdoor, marine, and industrial environments. Its durability under heavy mechanical stress means neoprene-jacketed cables are often found in power tools, mining, and shipboard systems.
EPR (ethylene propylene rubber)
EPR offers excellent dielectric strength, flexibility, and heat resistance. It’s often used as both cable insulation and jacketing material because of its balanced mechanical and electrical properties.
EPR withstands extreme temperature fluctuations and resists water absorption, oxidation, and abrasion. It’s commonly used in heavy-duty power cables, especially where flexibility at low temperatures is essential.
Fluoropolymers
Fluoropolymer materials, such as PTFE (polytetrafluoroethylene), FEP (fluorinated ethylene propylene), and PVDF (polyvinylidene fluoride), deliver outstanding chemical resistance and heat tolerance up to around 200 °C.
These materials remain stable under aggressive conditions, including exposure to acids, solvents, and high voltages, making them a go-to option for aerospace, defence, and chemical-processing environments. The trade-off is cost: fluoropolymers are among the most expensive jacketing compounds. They can also release toxic gases if overheated, so they’re used primarily in highly controlled industrial systems.
Cross-linked polyolefins (XLPO)
XLPO jackets combine the durability and fire safety of LSZH materials with the flexibility of polyethylene. They don’t emit halogen gases when burned, making them a safer alternative for transportation and building systems.
These jackets maintain excellent electrical properties, mechanical strength, and heat resistance, and are often used for cables requiring both flexibility and stringent fire performance.
How the cable extrusion process works
Once the appropriate jacket material has been chosen, the next step in cable manufacturing is cable extrusion. This is the process that forms and applies the protective jacket. It involves several precise stages to ensure consistent quality:
- Material preparation – The chosen jacket compound (PVC, PUR, LSZH, etc.) is blended with any required additives such as plasticisers, stabilisers, and colourants to achieve the correct mechanical and fire performance characteristics.
- Feeding and melting – The compound is fed into an extruder, where a rotating screw conveys it through a heated barrel. The material melts and becomes a homogeneous, flexible mass ready for forming.
- Die and sizing – The molten compound passes through a specially shaped die that defines the jacket’s wall thickness and overall diameter. This die ensures the jacket fits tightly over the insulated cores without gaps or weak points.
- Application and adhesion – The molten jacket material coats the cable core evenly as it exits the die. Correct pressure and temperature control ensure uniform adhesion between the jacket and the underlying insulation.
- Cooling and curing – The newly jacketed cable is cooled either by water immersion or air to solidify the jacket. For thermosetting compounds like XLPE, curing occurs under controlled heat to complete the cross-linking process.
- Printing and marking – At this stage, identification codes, safety markings, and branding can be applied to the outer surface of the jacket.
- Testing and inspection – Finally, the cable undergoes rigorous quality checks, including tensile strength, elongation, dimensional accuracy, dielectric testing, and visual inspection for surface defects.
This controlled extrusion process guarantees a consistent, long-lasting cable jacket that meets all mechanical and electrical requirements. Every stage is critical to ensuring the finished product achieves full compliance with British, European, and international standards.
What to consider when choosing a cable jacket
Selecting the right jacket compound is more than matching a material to a temperature rating. A number of interconnected factors should be assessed to ensure performance and compliance:
- Cost and lifecycle value – Compare material costs with expected service life and maintenance demands. A cheaper compound may need replacing more often.
- Environmental exposure – Consider the presence of oils, chemicals, moisture, or UV radiation. Use chemical- or water-resistant jackets for harsh conditions.
- Temperature extremes – Confirm the compound’s continuous and peak temperature ratings.
- Flexibility and movement – Choose softer materials like PUR or rubber for cables that bend or move frequently; opt for tougher compounds like HDPE for fixed installations.
- Fire safety – For enclosed spaces or public areas, LSZH jackets or cross-linked polyolefins are preferred to reduce smoke and toxic emissions.
- Industry standards and compliance – Check that your selected jacket material meets the relevant approvals (UL, CSA, ISO 9001, RoHS, REACH).
- Sustainability – Consider recyclability and environmental impact, particularly for large-scale projects or green building initiatives.
A well-chosen jacket balances performance, safety, and cost efficiency – ensuring your jacketed cables deliver reliable service throughout their operational life.
FAQs about cable jacketing
What’s the difference between cable insulation and jacketing?
Insulation surrounds each conductor to prevent electrical faults, while jacketing covers the whole assembly to protect against environmental and mechanical damage. Both are needed for safe and reliable cable performance.
Which jacket material is best for outdoor installations?
Polyethylene (PE), polyurethane (PUR), and neoprene offer excellent moisture, UV, and abrasion resistance, making them ideal for outdoor or buried cables.
Are LSZH jackets mandatory in certain environments?
Yes. Many public buildings, tunnels, and transport systems specify LSZH cables to improve fire safety and reduce toxic smoke. Always check local regulations and project specifications.
Can PVC jackets be buried underground?
They can, but a polyethylene or cross-linked polyethylene jacket generally performs better for long-term underground use due to its superior moisture and impact resistance.
How does cable extrusion affect jacket quality?
Uniform extrusion ensures the jacket maintains consistent thickness and adhesion. Poor extrusion can cause weak spots or voids that lead to premature cable failure.
Get expert help from CDC
Still deciding between polyvinyl chloride jackets, LSZH compounds, or cross-linked polyolefins for your next design?
Our team at Custom Designed Cables Ltd can assist with material selection, extrusion parameters, and compliance testing to ensure your jacketed cables perform exactly as required.
Contact us today for specialist advice or send us your cable specification for a detailed feasibility review.
