Cable jacketing, also known as cable sheathing or cable extrusion, is an essential step in the cable manufacturing process, providing a final layer of mechanical protection, environmental resistance, and electrical insulation for the cable.
Whether you’re looking for standard power cables or hoping to design custom cables for complex applications, your cables will need to be held together by an appropriate cable jacketing material. But how do you know what to choose, and how will the final product be created?
In this helpful guide to cable jacketing, we’ll discuss everything you need to know about the cable extrusion process, including the properties and benefits of cable jackets, the types of jacketing materials you can choose from, how these materials will be applied, and the key things you need to consider when choosing a cable jacket.
Why is cable jacketing important?
The cable jacket is the outer sheath of the cable, commonly made from a material like PVC (polyvinyl chloride). The cable jacket or sheath is applied over the internal components of the cable (including the insulation and conductors) to hold them together and protect them from damage.
Without a cable jacket, the delicate interior of the cable would be exposed to threats like abrasion, water, oil, chemicals, extreme temperatures and oxidation. Not only would this negatively impact the performance and lifespan of your cables, but it would also create a very serious hazard, as the cable would be much more susceptible to electrical leakage or combustion.
This is why cable jacketing is an absolutely essential part of the cable construction process. To ensure that your cables meet regulatory requirements in your industry, you must have cable jacketing made from a material that’s appropriate for the cable’s environment (more on this later).
Properties and benefits of cable jackets
To further demonstrate the utmost importance of cable jacketing, here are the general features and benefits you can expect from all standard forms of cable jackets:
1. Abrasion resistance
Abrasion refers to damage done to the cable when it moves across rough surfaces, such as factory floors or bare, rocky soil. Cable jackets protect the delicate cable conductors from abrasion damage, providing an essential layer of mechanical protection. These abrasion-resistant jackets can also help the cable resist crushing forces, rough handling, and other types of mechanical impact, ensuring the long-lasting efficiency and durability of the cable.
2. Chemical resistance
In addition to resisting abrasion, cable jackets help cables resist chemical damage by keeping these substances away from the internal components. Effective cable jackets are made from chemical-resistant materials that won’t degrade in contact with chemicals, even in challenging environments like laboratories, medical facilities, and manufacturing facilities.
3. Electrical insulation
By holding the internal components of the cable in place, cable jackets or cable sheaths provide additional electrical insulation by ensuring that the electrical integrity of the cable is maintained. This helps to reduce the risks of electrical faults and leakage, meaning that the cables will be both more effective and safer. This signal integrity is particularly important for telecommunications cables and instrumentation cables.
4. Temperature resistance
Depending on where the cable is installed, it must be able to withstand extreme heat, extreme cold, or frequent temperature fluctuations. Adequate cable jacketing will prevent the cable from cracking, warping, or sustaining other kinds of damage, even in difficult environments like industrial freezers.
5. Low moisture absorption
The cable jacket acts as a moisture barrier, preventing the ingress of water or even small amounts of moisture. This protects the internal components of the cable from corrosion and more serious electrical faults.
6. Flame resistance
By resisting high temperatures, cable jacketing materials reduce the risk of cable combustion and therefore improve safety, which is particularly important for cables used in public or residential areas. Plus, some cable jacket materials – like LSZH – are very flame-resistant and will not release toxic smoke if they do catch fire, making these cables very safe and reliable.
7. UV resistance
For cables used outdoors, consistent exposure to UV rays can lead to issues like insulation degradation and disintegrated sheath plastic, which could eventually cause the internal conductors to become dangerously exposed. However, UV-resistant cable jackets can be used to mitigate these issues. Even something as simple as using black cable jacketing can be helpful, as this enables the cable jacket to absorb UV rays and convert them into heat.
8. Flexibility
Cable jacketing ensures that cables can be adequately flexible whilst still holding their shape, making the installation process much safer, easier and more effective. Certain materials are more flexible than others, allowing you to choose a cable jacket material that accommodates the amount of flexing, bending, and confinement required in your environment.
9. Durability
By helping cables resist abrasion, chemicals, water, fire, rough handling, extreme temperatures, and consistent flexing, cable jacketing is absolutely key for a cable’s durability and longevity. Without adequate cable jacketing, you would need to replace damaged and dangerous cables much more frequently, which would be both time-consuming and expensive.
10. Regulatory compliance
Thanks to all of the amazing properties listed above, cable jackets can help your cables reach essential national or international standards in your industry. Regulatory requirements will often stipulate that cables will need a certain level of fire resistance, mechanical protection, or electrical safety in order to be used in particular settings, and the right cable jacket will help you comply with all necessary regulations.
11. Easy customisation
Cable jackets are incredibly customisable. First of all, you can choose from a wide variety of jacket materials to make sure you get the properties you need considering your cable applications, such as enhanced fire resistance or UV resistance – which we’ll discuss in more detail below. In addition to this, you can also customise the appearance of your cable jackets with cable printing services. This allows you to label all of your cables with company branding, or to add labels or colour codes to make it easier to identify, classify, and maintain your cables.
Types of cable jacketing
Depending on what you want to use your cable for and where it will be installed, you can choose from a range of materials that offer different properties and benefits. Let’s take a look at some of the most popular choices:
PVC
PVC is the most commonly used cable jacket material for applications such as telecommunications, construction, and household electrical wires. PVC is a low-cost material that offers excellent durability, chemical resistance, flexibility, UV resistance, and flame resistance, making it a safe and reliable option for most general cables. Because of its strength and abrasion resistance, PVC can also be used for cable extrusion and insulation in specialised applications like direct burial.
PE
PE (polyethylene) is more commonly used for direct burial, automotive cables, and other types of harsh environments and outdoor applications because of its greater strength compared to PVC. PE is extremely tough, durable, moisture-resistant, and temperature-resistant, but the downside is that they can be quite rigid and not as flame-resistant. Low-density PE (LDPE) is more flexible if that’s your main concern, but if you want a cable jacket that isn’t susceptible to softening and potentially starting a fire when it’s heated to its melting point, you should choose a different material.
XLPE
XLPE or cross-linked polyethylene is a thermosetting polymer that’s often used for power cables because of its resistance to heat, chemicals, moisture and high voltages. XLPE cables can also withstand higher temperatures than PVC ones. However, XLPE isn’t suitable for temperatures over around 90˚C, and it also isn’t recyclable because it’s a thermoset material that permanently cures. If you’re making an effort to improve sustainability in your operations, XLPE may not be the best choice.
LSZH
LSZH (Low Smoke Zero Halogen) is commonly used in areas where safety and fire resistance are paramount, such as in public and residential buildings. This is because LSZH is very flame-resistant, and if a fire does occur, it doesn’t release toxic smoke when burnt because halogen is not used in its construction.
Polyurethane (PUR)
Polyurethane (PUR) is a highly abrasion-resistant, oil-resistant, and oxidation-resistant material that also remains very flexible, allowing it to be used in confined spaces and difficult cable configurations. Plus, one of polyurethane’s major benefits is that it has excellent ‘memory’ of its shape and anti-kink properties, which means it’s often used for sheathing retractable cables.
Neoprene
Neoprene is a type of synthetic rubber that makes a highly flexible and durable cable jacket. This material is also very resistant to cracking at cold temperatures, deforming at hot temperatures, and degrading due to UV rays and oxidation, making this cable jacket material an excellent choice for very harsh and demanding environments that need flexible cable solutions.
Ethylene propylene rubber (EPR)
Ethylene propylene rubber or EPR is another type of synthetic rubber that offers fantastic temperature, oxidation, and abrasion resistance, whilst also providing plenty of flexibility. In addition to being used as a cable sheathing material, EPR is also often used as cable insulation because of its high dielectric strength.
Fluoropolymers
If you’re looking for very strong chemical resistance and the ability to withstand temperatures up to 200˚C, then you should consider fluoropolymers for your cable jacket material. However, these materials are expensive and can release toxic fumes if they overheat, although they’re generally quite flame-retardant.
Cross-linked polyolefins
Cross-linked polyolefins (XLPO) are insulating and jacketing materials that are very durable and reliable. Plus, they don’t produce toxic halogen smoke if they burn, so you’ll often find these materials being used with LSZH cables in industries like transportation and building management.
How is cable jacketing applied?
Once you’ve chosen the right cable jacketing material, we can get started with the cable extrusion process. This involves preparing the raw materials, which can include both the chosen jacket material and any necessary additives (such as plasticisers, stabilisers, and colourants), and then applying the materials onto the cable.
After this, the cable and jacketing materials are fed into an extruder, which applies heat and pressure to form the right jacket dimensions. Finally, the sheathed cable is cooled with water or an air cooling system to solidify the cable jacket onto the cable.
Once the cable jacket has been constructed, the customer can choose to have company branding, colour coding, product specifications, safety markings, or any other printing work added to the cable jacket to customise the final product. The finished cable can then be put through quality control and testing, which will involve visual inspections, tensile strength tests, elongation at break tests, general measurements, and so on.
What to consider when choosing a cable jacket
Before you choose your cable jacket material, dimensions, and properties, make sure you fully consider all of the relevant factors to ensure your custom cables will be fit for purpose. As we’ve explained throughout this article, different cable jackets will have very different properties, so not all jacket materials and designs will be suitable for all applications, industries, and environments.
If you’re currently designing custom cables or designing a new cable jacket for an existing cable, make sure you consider all of the points listed below before making your final decision:
- Cost – Is your chosen material within your budget? Considering the durability of your chosen cable jacket, will you be able to afford ongoing maintenance and potential replacements?
- Sustainability – If you’re concerned about your environmental impact, make sure you research the production process, recyclability, and potential toxicity of each material.
- Flexibility vs rigidity – There is often a compromise between flexibility and rigidity, with rigid materials providing stronger protection but being much harder to install and manoeuvre compared to flexible ones.
- Environment and applications – Is your chosen cable jacket material built to withstand the pressures of the environment it will be installed in? Is it suitable for its intended use? Consider the main challenges in your environment (e.g., chemical exposure, heat, abrasion) and make sure your cables are built to withstand them.
- Industry standards – Does your chosen jacket material comply with national or international industry standards?
Still struggling to choose the right cable jacket material for your custom cable design? Get in touch with us today for expert advice on custom cable construction, or check out our blog for more helpful guides on all things cable-related.
