Wire and cable compounds: PE, XLPE, HFFR/LSZH and EVA by cable layer

Insulation, jacket, semiconductive shield and bedding

A cable is built in layers, and each layer asks something different of the compound. Insulation is about electrical properties and heat rating. The jacket (sheath) is about abrasion, sunlight, chemicals and the fire test. Shields only appear on medium- and high-voltage cable. Get the layer right before you compare grades.

Typical choices, not rules. The cable standard and the customer specification decide what each layer must pass.

PE jackets and insulation: LDPE, LLDPE, MDPE and HDPE

• LDPE. Soft and easy to process. Used for some insulation, including foamed or solid PE in data and coaxial cable, and in blends. Low stress-crack resistance makes it a weaker choice for jackets on its own.
• LLDPE. A common general-purpose jacket. Tougher and more stress-crack resistant than LDPE at the same density. See LLDPE.
• MDPE. A middle ground of stiffness, abrasion resistance and flexibility. Common on fiber optic and telecom cable jackets.
• HDPE. The hardest and most abrasion resistant PE jacket, used on direct-burial and duct-pulled cable. Stiffer to bend, and it needs good stress-crack resistance. See polyethylene.
• Carbon black for UV. Natural PE breaks down in sunlight. Outdoor jackets are black because a well-dispersed, fine carbon black is the most effective UV screen for PE. Black jacket compounds often carry about 2.5% carbon black (one producer’s black masterbatch is let down to give 2.6% in the finished jacket), and the cable specification sets the level. ASTM D3349 measures the absorption coefficient, which shows how well the black screens UV. Colored outdoor jackets need a UV stabilizer package instead, and they seldom last as long. See plastics for outdoor UV.
• Specs. ASTM D1248 is the specification for polyethylene extrusion materials for wire and cable. Many buyers also work to an ICEA jacket requirement. Melt index is at 190°C / 374°F and 2.16 kg (ASTM D1238), and density by ASTM D1505 or D792. Black compound density is higher than the base resin, so say which one you mean.

XLPE: silane (Sioplas and Monosil), peroxide and e-beam

Crosslinking ties PE chains together so the insulation will not melt and flow when the conductor runs hot. ASTM D2656, the specification for XLPE insulation on power cable rated 2,001 to 35,000 V, rates it for 90°C / 194°F continuous, 130°C / 266°F emergency overload and 250°C / 482°F short circuit. In low-voltage building wire, UL 44 rates XHHW-2 at 90°C / 194°F wet or dry. The rating belongs to the cable type and its standard, so check yours. There are three main ways to crosslink.

Sioplas and Monosil began as trade names and are widely used for the two silane processes. Mix ratios, cure conditions and shelf life vary by system, so follow the producer’s sheet for the exact pair you run.

HFFR and LSZH: EVA or POE loaded with ATH or MDH

HFFR (halogen-free flame retardant), LSZH or LS0H (low smoke zero halogen) and ZHFR describe the same family: compounds that burn with little smoke and give off no halogen acid gas. They are used where people need to escape and electronics must survive a fire, such as transit, tunnels, data centers, ships and public buildings.

• The recipe. A polymer that accepts a lot of filler, most often EVA, sometimes POE or a PE blend, loaded with a mineral flame retardant at roughly 55–70% by weight, often more than 60%. The mineral releases water when heated, which cools the flame and dilutes the gas. A coupling agent, often a maleic anhydride-grafted polymer, or a surface-treated filler, ties the mineral to the polymer so the compound keeps some elongation.
• ATH or MDH. Aluminum trihydroxide (ATH) starts to release water at about 180–200°C / 356–392°F, so ATH compounds are mixed and extruded below about 200°C / 392°F, which suits EVA and PE. Magnesium hydroxide (MDH) holds to about 300–320°C / 572–608°F, so it suits hotter processing, such as polypropylene-based compounds. Synthetic MDH often costs more than ATH.
• EVA for wire and cable. EVA base grades for HFFR and semiconductive compounds often run in the mid-20s to low-30s % VA, with 26–28% common, at a melt index of a few g/10 min (190°C / 374°F, 2.16 kg). Higher VA takes more filler and adds char, but softens the compound and lowers its heat resistance. Many recipes blend EVA with PE or POE to balance cost, toughness and filler acceptance. See EVA and EVA by vinyl acetate content.
• What it costs you. At that filler level, HFFR compounds are dense, less flexible and lower in elongation than PE or PVC. They run slower, can drool at the die, and pick up moisture, which shows as porosity. A grade swap changes all of that, so trial on the line, not just in the lab.
• HFFR is not automatically fire-rated. A compound can be halogen-free and still fail a flame test. The rating belongs to the cable construction, conductor size and wall, so a compound sheet often says a test result is expected at a stated wire gauge or larger.

PVC, TPE and TPU for building wire and flexible cords

• PVC. Still the workhorse for building wire insulation (THHN and THWN have a PVC layer under a nylon skin), cord jackets and many appliance wires. It is low in cost and flame resistant on its own, but it gives off hydrogen chloride and dense smoke in a fire, which is why HFFR exists. Plasticizer type matters for cold bend, migration and regulatory statements. See PVC.
• TPE. Styrenic TPE, TPO and TPV compounds make soft, colorable cord jackets and some insulation. In North American cord type letters, E means a thermoplastic elastomer, T a thermoplastic, and O an oil-resistant jacket (OO adds oil-resistant insulation), as in SJEOOW. Flame-retardant and halogen-free TPE grades exist. See TPE and TPV.
• TPU. The tough choice for cords that are dragged, flexed and cut: robotics, power tools, mining, and industrial control cable. Polyether TPU for wet and outdoor service, polyester TPU for oil. TPU must be dried before extrusion. See TPU and TPE vs. TPU.
• CPE and thermoset rubber. Some heavy-duty cords and mining cables use chlorinated PE, neoprene or EPDM jackets. These are compounded and cured by specialist rubber compounders.

Standards and fire tests on cable specs

Titles and scopes summarized from the standards’ published scopes. Editions change, so check the edition your customer names. Pass and fail limits sit in the product or customer spec, and the cable passes these tests, not the compound alone.

Moisture, storage and shelf life

• Silane-grafted resin. It starts to crosslink as soon as it meets moisture, and slowly even in the bag. One producer gives its graft resins an approximate shelf life of 6 months from the production date. Store sealed, dry and cool, use first in, first out, and do not open bags until you are ready to run. Old or damp material shows as gels, rough surface and high extruder pressure.
• Catalyst masterbatch. Keep it apart from the grafted resin until the extruder. Once mixed, the blend has a very short life, so mix only what the line will use.
• HFFR compounds. The high mineral load picks up moisture, which shows as porosity and a rough jacket. Follow the compound sheet: many need drying, and opened bags should be resealed.
• EVA pellets. Higher-VA EVA can block (stick together) in a hot warehouse. Store it cool and use it in order. See EVA.
• Everything else. PE and PVC compounds are tolerant, but outdoor, flame-retardant and crosslinkable grades depend on additives you cannot see. See resin shelf life and storage and moisture.

Compounding your own vs. buying ready compound, and what a UL file means for a switch

• Buying ready compound. Most cable makers buy finished insulation and jacket compounds. The compounder controls the recipe, the flame and smoke results, and the documents. You buy a known quantity tied to your UL file.
• Compounding your own. Larger cable makers and custom compounders mix their own HFFR, PVC or black PE. Then you buy the base resins (EVA, POE, LLDPE, HDPE), fillers, coupling agents and stabilizers, and you own the testing. See base resin for compounders and custom compounding.
• The UL file names the compound. A wire listed under UL 44, UL 83 or UL 62 was tested with specific compounds, and the wire maker’s file often identifies them by compounder and grade. A substitute compound, even one with the same data sheet values, often needs UL review and some retesting, such as flame, aging and physical tests, before the listed wire can use it. Plan for that in the timeline.
• Halogen-free claims. Ask how the claim is defined. Some compounds carry a UL halogen-free certification under UL 2885; ask for the certificate and the limits it applies. One compounder reports a limit of 1,000 ppm for each of fluorine, chlorine, bromine and iodine. Others are tested to IEC 60754. See compliance documents.
• Where we fit. We quote base resins for compounders and cable makers. Ready insulation and jacket compounds we quote and source through our supply partners case by case, where a compounder’s grade is available in gaylord to truckload volumes; we do not stock them. We do not supply medium-voltage cable compounds (peroxide or tree-retardant XLPE insulation, EPR, or semiconductive shields), which are bought direct from their producers under qualification.

What to put on the RFQ

• Layer and cable type. Insulation, jacket, shield or bedding, and the wire or cable type (for example XHHW-2, THHN, SJOOW, tray cable, fiber optic).
• The standard and fire test. UL 44, UL 83, UL 62, VW-1, IEC 60332-1-2 or -3, IEC 61034, IEC 60754, or the ICEA or customer spec.
• The compound you run now. Grade name and data sheet, and whether it is named in your UL file.
• Polymer and form. For base resins: PE type, melt index (190°C / 374°F, 2.16 kg) and density, or EVA VA % and melt index. For silane systems: the graft resin or copolymer and the catalyst masterbatch, as a pair.
• Color and outdoor use. Black with carbon black level, or a color with a UV package.
• Halogen-free definition, if it applies, and the RoHS and REACH statements you need.
• Packaging and storage. Moisture-barrier bags for silane and HFFR compounds, and your monthly usage so the lot is not sitting past its shelf life.
• Quantity and ship-to city. Trial gaylords or a production release, and yearly volume.

Common questions

If your grade is not listed, tell us what you run. We source commodity, engineering and specialty resins.